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Explore the latest questions and answers in Medical Physics, and find Medical Physics experts.
Questions related to Medical Physics
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Greetings!
I am new to x-ray radiology, and working on a project where I am supposed to compute the thickness of the subject being examined. I found a technical paper published by Fuji inc. ("Improvement in Image Quality and Workflow of X-Ray Examinations using a New Image Processing Method, Virtual Grid Technology"), where it is shown that the thickness can be calculated using the x-ray dose absorbance (figure 5 of the paper). My idea is to apply the Beer-Lambert law on 2D images that I capture before-and-after placing the subject; and to solve the natural logarithm at each corresponding pixel location to obtain a 2D thickness image. I would be very grateful if you could advise whether this is the correct way of computing the thickness. Thank you in advance!!
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Dr. Gerhard Martens, Thank you for your prompt response regarding the matter. It seems like I still need to do more individual research related to x-ray. Thank you!
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Brain Tumor Imaging Protocol will reduce variability and increase accuracy in determining progression and response of investigational therapies.
In the pictures below, with the FFT and DFT methods and the PCA phase recovery, which is common in optical microscopes, I obtained the magnetic resonance imaging (MRI) phase of the human brain tumor and the phase obtained.
Can the process be performed on MRI without prescribing Jumpstarting Drugs (JBTDDC)?
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سلام عقیل عزیز
ایمیل بنده در قسمت نام کاربری موجود است
آرزوی موفقیت
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Hi, has somebody the IPEM report no 32 part 7: Measurement of the Performance Characteristics of Diagnostic X - Ray Systems, Digital Imaging Systems in PDF. I would be very grateful if somebody could suggest where I can find this report?
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Hello, please have you gotten the IPEM report? if yes kindly share with me. Thank you so much
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As all the world is busy in discovering cure for COVID-19, so why not radiation? COVID-19 has been reported to effect the human's lungs and liver (specific tissues), So, what if those parts are exposed to radiation for the rapid recovery of the patients? Is it possible? Or, is there any possibility for radiotherapy of COVID-19?
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Positron emission tomography generally shows imaging of the physiology of the tumor as well as its anatomy, which is superior. It is unique compared to other cross-sectional imaging such as computed tomography or computed tomography (CT) or computed tomography. CT scans or MRIs often can not detect changes at the cellular level if the PET scan is capable of immediate changes. Identify in patient cells.
In order to image the tumor using PET or other methods, differences in basic features established in physiological and Metabolic of tumors and normal tissues. These differences include tumor surface antigens compared to cell tissues. Generally grow and DNA precursors such as thymidine and the rate of protein synthesis in tumors often increase compared to normal tissues. transport and Mixing of various amino acids, as well as anaerobic and aerobic glucose levels, are observed in tumor cells. In a wide range of Tumor types Glucose intake increases significantly compared to healthy tissues. In a typical PET system they are separated by a lead or tungsten blade detection of random photons in one shot Match with photons detected in other shots. In the diagram below, I plotted the average positron emitted energy from several desired radionuclides. Which of these radionuclides is best for our purposes?
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The question you mention is very broad! As for which is so-called "better", it really depends what type of tumour you are testing for or evaluating. As we know, different types of tumours are better analysed with different types of PET scans and I know my colleagues generally think they (PET scans) are all the same but you and I know that is not true. Most commonly, they expect if someone is said to have had a PET scan, it most commonly refers to using F18-FDG and clinicians are often surprised when it turned out to be something else (!)
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I am asking about the effectiveness and accuracy of using the film badge dosemeters to record and measure the exposure for the medical staff nowadays as it is a very old way, but it cost nothing to make such a system for developing the films and read it by a densitometer
and the only guidelines that I have to implement such a system is the (IAEA) Safety series NO.8 Vienna 1962 but it is a very old one and can't get any other new versions or similar guidelines, so is there any such recent guidelines
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To date, there are no newer safety guidelines (IAEA) series No. 8 Vienna, 1962. But you can still use such dosimeters.
Dosimeters with film badges for recording and measuring exposure have been replaced in many laboratories by more modern thermoluminescent dosimeters.
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Or anything related with shielding materials and dosimetry for medical application. I need topics that can be researched on and suitable for undergraduate research work.
Thank you.
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In my opinion, you could expand and search for "luminescence methods for radiation dosimetry applications". Or you may be interested in the topic "Armoring of rooms containing radionuclide in hospitals using shielding materials". Of course, you can enrich and restrict these titles by considering your major university and research opportunities.
Best wishes
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Hi everyone
Could you share your research and/ or other researches related to the application of magnetic fields in biophysics and Medical physics?
Thanks
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Also, one can mention this although rather exotic technique https://en.wikipedia.org/wiki/Magnetoencephalography
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Dear Sirs,
I did not find this material on the internet. There are only mechanical models of some aspects of self-replication. Full mechanical model is absent. Of course it is enourmous problem if one precisely build it. But maybe there are simple and simultaneously more complete mechanical models? I prefer purely mechanical self-replicating machine but self-replicating robots are also good.
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The first mechanistic model of self-replication was given by John von Neumann by his self-replicating cellular automaton. He was followed by others: Langdon, Reggia, ...
It would be interesting to study this research stream as it provides great insights into creation of mechanistic description of certain properties of living structures.
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I am currently developing a mammography phantom that has an MTF edge portion. The MTF portion is used to test the resolution of the digital mammography unit. My MTF is made of stainless steel with a thickness of 0.8mm and a dimension of 40mm x 40mm.
After exposing the phantom, I have an image of the MTF (a square object with very high attenuation compared to the background). I don't know what the next step is, analyze it or determine the MTF from that image. I just know that you need to put the ROI between the edge and the background. Is there a way I can manually determine the MTF edge of the system? Can you provide me an article or steps on how to do so. Or do I really need software to do determine the MTF? What software can I use to determine the MTF edge? Can you suggest software and the steps on how to determine the MTF from that software.
My alternative way of measuring the MTF of the system is to use a high attenuating material and bar pattern materials. So this MTF is made of a copper sheet (0.2-mm thick), a copper wire that forms 2lp/mm and 4lp/mm, and a transparent area (PMMA). I got this from IEC, and the method of determining the MTF is easy. But this kind of configuration is not used in any commercialized mammography phantom. Most commercialized mammography phantoms used MTF edge. That's why I prefer the 1st MTF configuration.
Do you know the difference between MTF edge and MTF bar pattern?
I really appreciate any help you can provide. Thank you!
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Dear Neil
To calcultad the MTF from edges or slits method you can use some available free softwares. I suggest the following:
(PDF) Free software for performing physical analysis of systems for digital radiography and mammography (DOI: 10.1118/1.4870955)
Best, Alessandra
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Since technology has seemed to extensively pervade virtually every facet of medicine, do you feel that students of medicine (MD or MBBS) should be better equipped with knowledge and skills in mathematics, physics, biomedical image processing (to better process medical images for diagnostics and surgical planning), biomedical signal processing (for better analysis of bioelectrical signals, e.g. EEG, EKG, EMG), and basic computer science?
Care to discuss?
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Myles Joshua Toledo Tan dear, I don't think medical students need to study math or physics as they already has to acquire a good basics on them to qualify for the admission test. In MBBS level they have to cover a vast and extensive curriculum. If you want to add something to them you can add--English language, Behavioral science and Psychology.
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What is the logic or significance for using the inverse square factor for calibration of in vivo dosimeters (placed on surface) to the dose measured by ion chamber at dmax?
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Nazia Toor I do understand your point now, thanks for elucidating your thoughts.
While the addition of ISF in the dose calibration formulae may lack significance due to the cancellation during the calculation. However, I think the ISF further acts as a factor to correct for any (if at all) change during setup.
Also, I tried to find relevant articles that have evaluated the ISF effect in in-vivo dosimetry calibrations but to no avail. This may suggest again that both accuracy and precision are needed during calibration procedures.
I hope this helps!
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Hi i am a Medical Physics PhD student, im interested in Radiolysis and production of free radicals, i am very curious is to collect information is there any possibility to measure the free radicals, singlet oxygen in vivo and vitro. My idea is to measure the spectral changes.I would appreciate suggestions or possibilities if any.
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You can use some chemical probes such as APF (aminophenyl fluorescein) or SOSG (singlet oxygen sensor green). You measure probes' fluorescence before and at the end of the irradiation. Fluorescence enhancement will indicate ROS or signlet oxygen generation.
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Hi
I am trying to calculate PDD using Geant4
I divided a water phantom to voxels (2 mm x 2mm x 2 mm) by G4NestedParameterisation and i have created a class derived from Sensitive Detector class using Hit (I am not sure that this sensitive detector must be used)
How can I calculate the dose at each voxel?
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Dear @Keyvan Tabaei,
To calculate PDD using a voxelized geometry, you need first to create you own SensitiveDetector class derived from the Geant4 class G4VSensitiveDetector, and assign this object to your geometry. In this class (SensitiveDetector) you have a virtual method called ProcessHits(G4Step*, G4TouchableHistory* ) in which you can accumulate the dose deposition (dE/dm).
I suggest you to see in details the source code of the project medical_linac in your geant4 example folder ($Geant4-install-folder/share/Geant4-vx.x/examples/advanced/medical_linac/).
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I am working on Ultrasound Contrast Micro bubbles. I am from Medical background with little Knowledge of Medical Physics. kindly Guide me to some book or video lectures regarding Theoretical Models for estimation of Bubble dynamics ....
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Dear Ramish,
It may be worth linking direcrly with the corresponding authors of the papers you read, so that they will give you specific guidelines on their mathematical models and logic behind them.
Very good luck,
Giorgos
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I am using Eclipse Treatment System (Version 13.6) on VARIAN CLINAC and I want to know what are the principal differences between another planning systems using the same lineal accelerator.
I want to know what are the differences in the commissioning in the same LINAC.
Is there a significant differences? Is the same?
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Thank you, Pablo.
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I am modelling a Phototopic eye system, which includes five wavelengths with different weights, in Zemax.
This system should have defocus of -0.5 diopter (D).
I want to know in a multi-wave system how the defocus is calculated?
Defocus is the average defocus of all five wavelengths?
Or
Defocus is the weighted average defocus of these five wavelengths (weighted based on the weight of the waves)?
Or
Defocus is calculated in a reference wavelength for example 555 nm?
Thanks.
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Dear Elmira,
Assuming that you are working with a centered eye model, I suggest you look at the "Chromatic Shift" curve, and locate what wavelength has your expected defocus. Usually, the curve has a zero chromatic shift for the primary wavelength you have defined in ZEMAX, and, obviously, this can be changed.
However, I guess you are working with a complete, and realistic, model eye (non-centered). So, I suggest here that you use the expression corresponding to the equivalent defocus in terms of the Zernike defocus coefficient. This means that you have to calculate (take into account the pupil diameter ! ) the Zernike defocus for each wavelength, and check your expected result for defocus.
I hope this helps.
José Antonio
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I have been trying to download this dataset for a few weeks now but the download consistently crashes. USC's servers seem to be very slow and the download is trickling at best. Even downloading the data in 5 or 10 file segments, it crashes.
Is there any other website where this data is downloadable from?
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Shafagat Mahmudova Thanks for the links. The servers for the website seem to be very slow. Downloads keep failing.
I eventually stopped using Chrome, and Firefox, and installed a browser called Brave. Using this, it seemed to download fine, but still very slowly. But finally after months of trying, it works.
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In telecommunications, a transmission system is a system which transmits a signal from one place to another. The signal can be an electrical, optical or radio signal.
Can we consider some of the human body systems as transmission systems and then model it using telecommunications' concepts for better understanding?
If we do, can someone please provides some examples of these systems and determines their basic elements(message, transmitter, medium and receiver)?
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Dear Mahdi,
This question is an interesting one as it invokes the analogy between the electrical communication systems and the signal transmission in the human body.
Any communications system consists of information sources, transmitters, transmission medium receiver and communication destination.
At first i would like to speak about the signal transmission medium in the human body. The main medium of the transmission in the human body is the water.
Water is a dipolar material and serves as a solvent for the substances supplied to the human body. It solves the slats including sodium chloride and forms an electrolyte capable to conduct electricity by its positive sodium ions and negative chlor ions. So, the electricity conduction is an ionic conduction. The generation of electrical signals is by electrochemical effect.
The system responsible for the sensation is the nervous systems where it generates the electrical signals in form of electrical pulses and transfer it from the a part of the body to the brain or from the brain to an intended part of the body. The brain is responsible for processing, taking actions and storing the signal in its memory cells. Th humans tried to mimic the function of the nervous system by introducing the so called Neural network.
The information is generated by sensors at skin of the human body. It is generated also by the ears and eyes. All of these sensors work as transducers converting the nonelectrical signals int electrical signals conducted by the Nerves to the central spinal cord then to the brain and back from the brain to the different organs to control them.
So the brain can be considered a source an destination of the information. It also stores and process the information to take decisions.
Signals also are generated by the transducers and some of them work as a destination. The communication system can be considered wire line one transmitting base band signals directly through conducting wires.
Best wishes
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I am Ph.D. student in medical physics. My research topic entitled (assessment of fetal biometry in low-risk pregnant).
I adopted a cross-sectional design in this study. Please I have several questions about my study and hope to find feedback from you.
- Regarding the sample technique I would like to know what is the most appropriate technique for my study? What I did in this regard, the pregnant come to their appointments randomly and the one who meets the criteria of this study would be participated after getting their consent.
- How can I apply the validity and reliability in this study?
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Good luck with your PhD study. It is really interesting question. I hope we will find answer soon.
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Does Dmax (Depth of dose maximum) depend on chamber? If we measured Dmax (Depth of dose maximum)using cylindrical chamber for specific electron energy (10 MeV) with field size (10x10) and then using parallel plate chamber, does Dmax differ?
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The smaller the cylindrical chamber the better. Electron beams are easily perturbed. 10 MeV electrons will have Dmax between 2 and 3 cm. The accuracy will be affected by the total geometry. Wall thickness, central electrode, probe size and material. Multiple measurements with small increments in position and orientation can indicate geometry effects and location of Dmax.
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Would be possible to implant a prostate PC-3 tumor cell in a gluteus of a mice (or rat) so that it will grow somewhat laterally respect to the animal normal contour?
If that would be possible, a Radiotherapy 6 MV highly collimated single beam could hit the tumor (of about 1 cm3 size) but not vital organs of the animal. If that would be a wrong way, is there a better localization of the tumor Xenograft to obtain the desired result ? Thanks in advance for the help!
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We inject PC-3 cells into the hind flank of mice when doing xenografts (http://altogenlabs.com/xenograft-models/prostate-cancer-xenograft/pc-3-xenograft-model/). Based on your experimental conditions I think you could also do such an injection and proceed with the radiation protocol as you've stated it. If you're trying to not damage vital organs then the hind flank is one of the more "distant" locations from such organs.
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I know how to calculate the MU time but not sure how to get the cumulative dose. I have gone through the Radiation Physics book by Faiz. However no clear cut approach is shown for getting the cumulative dose? So my question is 1) Is there any approach by which cumulative dose can be calculated? or it is prescribed by the radiologist? 2) Do we need to optimize the dose distribution for telecobalt therapy?
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Francisco is correct in his comments. I will add a few as well.
Calculating MU/time and calculating dose are the inverse of one another. You need to be given MU to calculate dose, or you need prescribed dose to calculate MU. Typically one is tasked with calculating MU or time after the dose is prescribed by the Radiation Oncologist. In simple calculations the dose would be prescribed to a point in the body and the field apertures shaped to conform to the local anatomy, followed by normalizing to an isodose line that covers the desired area. All of this goes into the calculation of MU or time needed to get the prescribed dose. Modern techiniques involve the use of inverse planning utilizing arcs, dynamic MLC's, etc. It is always important to optimize the dose distribution, whether in linac based therapy or cobalt teletherapy. The ability to optimize the dose distribution is tied to the imaging available (2D, 3D, 4D, PET, MRI, etc.) the technology contained in the treatment planning system, and the skill of the planner.
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Hi all,
I'm trying to simulate the photon decay spectrum of Eu155 in Geant4. I'm not using the decay file provided by Geant4 because the energies and intensities listed are incorrect. I've changed/added values to match trusted literature, ensuring that the syntax is the same and the intensity column sums to 100.
The resulting spectra however is not right. There are too few photons per decay for most energies. I'm confident I'm collecting all the photons. I've attached my decay file and the resulting plot. The picture also has a 2nd plot of what the spectra should approximately look like for comparison.
I want to know what the intensity column is actually doing and how to adjust it such that the photons per decay match the values I've placed in the intensity column (noting that it's as a percentage there).
Any help is greatly appreciated
Thanks,
- Giuseppe
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Hi Giuseppe,
According to my knowledge, the intensity of every line of gamma emission from Eu155 does not have to sum 100, the Intensity could mean Relative Intensity of Absolute Intensity.
On the one hand, relative intensity means that 100 is assigned to the most intense gamma from a given initial level, and other gammas relative intensities are referred to that. This is not usually used.
On the other hand, absolute intensity is "like" the probability of emission. Look at the Co60 spectrum, the two most intense gamma lines have ~99.9%. It means that every time the Co60 decays, the photon has a probability of 99.9826% of having 1332.492 keV and 99.85% of having 1173 keV, and the probability of a photon to have 1332 or 1173 keV is almost equal so you will see two peaks of the same heigh.
Using the utility GPS (general particle source) in Geant4 offers you a great control over the particles which you are interested. You can use something like:
/gps/source/add 1
/gps/particle ion
/gps/ion <Z><A> #atomic number and atomic mass number
Best regards,
Jose A.
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Hello
I am working on a DICOM file generated using a medical CT scanner (GE Brightspeed 16). I need to know what is the point spread function of this CT scanner. What information do I need to determine the PSF? can anyone help?
Mohammad
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Hi;
PSF can be measured using various techniques. The straightforward way is to measure it using a pinhole phantom. The hole needs to be smaller than the detector pitch size. Usually with this technique, alignment is the issue. Another way is to use a tungsten wire. Experimentally, it is not difficult and the in plane (xy) reconstructed images will yield those PSF from tungsten wire. Then, you can employ the oversampling method to estimate the LSF and MTF etc. If you are interested to measure the focal spot, then you have to use the pinhole camera for accurate findings of FWHM.
Best of Luck
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In order to protect the patients and workers, How to deal with a radioactive emergency in the first instant
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Generally speaking, each hospital has at least one person responsible for radiation protection. As part of risk management, procedures must be in place at each facility to ensure that those affected by the incident know immediately what to do in a particular type of emergency. It all depends on the type of facilities, the type of treatment performed (nuclear medicine, radiotherapy, etc.).
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ICRP-118-2011) Published new version decreased dose limit for occupational workers from 150 mSv to 20 mSv but i did not find any publication concerning any change in eye lens dose limit for public. 
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Situations should be different among countries each with different national regulation and policy, but all people who enter radiation control area (regardless of whether routinely or occasionally) should wear dosimeter.
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Hello, I wanted to know what is wrong with my CT (CAT scan) image. when I do medical imaging everything look normal and clear but after Multi Planar Reformation picture in sagittal and coronal part have low resolution. How can I resolve this problem? do you have any suggestion? thank you
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Stefan, I don't practice medical CT and I can hardly understand details of this technique. Based on the common sense, I would recommend you check these things: 1) is the voxel isotropic? 2) are some filters applied during the reformation?
Or you can contact me directly via this site or e-mail batranin_at_gmail_com
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 I need this book or any  recent copy of  it, or any reference have the relation   of calculating  the  absorbed gamma dose  (D= Γ x A /d2) or any other dose.
the book: F. H. Attix, "Introduction to Radiological Physics and Radiation Dosimetry," New York, John Willy & Sons, (1986).
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impact CT patient DOSIMETRY CALCULATOR  software
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Every software for calculating organ dose has laid down etiquette and procedures. Carefully go through the procedures or request directly from the manufacturers.
Thank you.
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This is a link to the instrument in question:
J Trauma. 2001 Oct;51(4):740-6.
Development of a brief version of the Burn Specific Health Scale (BSHS-B).
Kildal M1, Andersson G, Fugl-Meyer AR, Lannerstam K, Gerdin B.
Author information
1
Burn Unit, Department of Plastic Surgery, University Hospital, Uppsala, Sweden
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Carole,
The Burn Specific Health Scale (BSHS) is an outcome scale designed specifically for burn patients.
The original scale is composed of 114 items across six domains of health.  Since the original scale it has been revised (BSHS-R) and shorter versions have been proposed, one of which you referenced, which used a factor analytic approach to further improve the scale for clinical use.
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PDD is one of the important parameters in dose assessment at a given point. I want to know is there any way to assess this parameter using MCNPx code? Is there any tally or command helping to calculate this parameter? 
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You can also read the attached useful paper.
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I need to perform Monte Carlo simulations of a imaging device (dental) with static anode x-ray tube.  Can you provide me one or point out a reference/paper/article? Thanks in advance!
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I'm not sure, if someone can provide measured data as gamma (photon) spectroscopy for such X-ray tubes is hard to perform. Scintillator-based detectors mostly have a too rough energy resolution for this purpose. Semiconductor-based detectors are mostly too sensitive resulting in dead time problems. One can increase the distance to the X-ray tube or use collimation to decrease the photon flux photon, but then you will loose low energy photons which would otherwise contribute to your spectrum. In addition, low energy photons are also absorbed inside the cover of the detector (stainless steel cap for cooling).
But maybe you are lucky and someone solved these problems :-)
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Is the risk of necrosis on the helix cartilage of the auricle high? With 50 Gy in 20 fractions and electrons?
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As you know that IMRT is delivered with multi-leaf collimators (MLCs). However, the use of MLCs is not mandatory.
Can potentially deliver IMRT plans with the use of collimator jaws?
Is anyone here? doing Jaws s only IMRT
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Dear Dương Thanh Tai,
there are some publications on that topic (thanks to Giovanni), but in practice, I think that this technique is rarely used since using the MLC leaves for IMRT mostly has some important advantages:
- more flexibility in field shaping,
- higher speed of leaf motion compared to jaw motion,
- smaller penumbra of leaves compared to jaws.
However, jaw motion during IMRT application (using MLC leave motion) plays an important role mainly to reduce the leakage through the MLC.
There is also a technique called "virtual wedge" that can be applied using Siemens  medical linear accelerators. Thereby, continous jaws motion is used instead of a real wedge to create an angled dose distribution. The advantages are, that arbitrary angles are achievable (not only 15/30/45/60° of real wedge) and that the dose rate is not reduced due to additional material of the real wedge. The disadvantage is, that jaw motion direction is only perpendicular to the leaf motion direction. This technique is not, what is usually subsumed under IMRT, but it is indeed a kind of intensity modulation.
Best regards
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Hi,
I'm looking for a tool able to extract a single slice from a 3D DICOM volume and save it in DICOM format in order to be loaded by the QUART DVT_TEC v2.5.1 analysis software. Someone who know if exist something like that? Also an ImageJ macro will be ok.
Thanks a lot!
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Dear Turco,
your welcome.
best regards,
parvaneh darkhor
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I am working with MCNP. The set-up is simply trying to carry out a radiotherapy simulation where I can use a point source of gamma photons to destroy cancerous cells.
My Problem: I am losing particles so the run is terminated.
Geometry: A cylinder is the skull in it there is a sphere>>>Tumor. I put them into a big rectangular box. My point source is another sphere inside the box.
I need help. Am I going the right way?
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 Thank you guys for your assistance
I am actually new to MCNP but I am catching up quickly. I think.
I checked my problem on MCNP X and I found out that Cell 3 in my problem is actually not showing and my results on MCNP 6 shows that I am losing particles because it cannot detect that same cell.
Please Check the 1)code 2) the 3d diagram 3) the crossection*
*When i check all crossections: XY XZ YZ and all I dont see cell 3. 
How can I solve it?
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Dear Dr. Sheikh-Bagheri
Greetings and respect
I am a medical physics PhD student from Iran.I have questions about .3ddose Files from DOSXYZnrc.
My question is how can I 35 different *.3ddose files (about 35 segments in IMRT) will be together and convert it to a Single *.3ddose file. I respectfully ask you to guide me in solving this problem. I am waiting for your mail.
Sincerely
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Hi Dear Gadir Ahmadov
I apologize for the delay in response.
Unfortunately I missed the perfect solution.
Two examples will send you a file. (If you did not upload the file because the file size is high. If so, please send your email to me.)
I'd be happy to give tips.
Please schedule it (script, etc.) also send me.
My E-mail is here:
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i want use the tld with rando phanton in the chest and abdomen 
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A short tip to tld in randso. Drill small cylindrical holes, enough to put a small cylindrical pmma tube with a central hole for cylindrical tlds. You will get commercial hints by PTW in germany Freiburg.
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Hello!
I am a field physicist and I perform QA measurements of various types of X-ray units. Due to recent changes in legal requirements in my country, we have to provide the radiation output value for each unit/tube measured (in mGy/mA.s at 1 meter from focal spot) at filtration of 2,5 mm Al equivalent. This unfortunately cannot be directly achieved for interventional radiology units, some CTs and occasionally other types of X-ray inits.
My question is: how can one calculate the dose at filtration of 2.5 mm Al equivalent from the measured dose at other filtration, assuming HF generators and 0% ripple?
For example: GE Innova 2100 interventional radiography unit, dose rate at 83 kVp and 165,5 mA (single shot) is 14,47 mGy/s and total filtration is 8,33 mm Al equivalent (actual filtration is combination of Al and Cu filters, but I do not have the precise values of both of these).
Thank you very much!
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Regarding ref 3. in my previous posting. It has been taken down! If you still want a copy. Contact me.
I also add this more recent paper on the subject of Anode roughness:
"Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation". https://www.ncbi.nlm.nih.gov/pubmed/20229884
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use tandem and ovoid applicator.
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This is also a good review on the topic:
American Brachytherapy Society consensus guidelines for locally advanced carcinoma of the cervix. Part II: high-dose-rate brachytherapy. Brachytherapy. 2012 Jan-Feb;11(1):47-52.
Free to read in PMC
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Dear Experts
I am looking for companies working in the field of medical radioisotopes production using electron LINAC. I have searched the web, but I could not find major companies using this accelerator for this purpose.
I want to find out if it is possible to produce radioisotopes, such as F-18, using electron linac (instead of cyclotron).
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 i want to calculate the number of neutrons producing by an electron linac but i don't find the proper physics reference that can do this:(
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I don't know with GEANT4 but similar simulations were performed using MCNP in the work below.
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How to estimate risk of stochastic effects mainly cancer for a given population exposed to low doses (5-10) mGy per year prevalent in High Background Radiation Areas without using the concept of collective dose as well as ICRP's accepted risk factor of ~5%/Sv?
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Different lifestyles in different populations would indeed be important.
ERR in each study is obtained after consideration of various lifestyle factors and other confounders, but the background incidence of disease varies among countries and also within the country.
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Hi,
Is anyone able to point me in the direction of where i can buy large volumes of monodisperse silca (SiO2) microspheres, preferably in dry form? I am trying to make a fairly large volume set of phanoms using these spheres and i am struggling to find a supplier that provides more than a few grams which is frustrating?
Ideally somewhere that supplies in at least 50g, although closer to 100-200g would be much more useful. 
If anyone knows of any companies then please let me know.
Thank you
Charlotte
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From kV and mAs values and without the use of any detectors, how can you find the dose delivered to patients? When using an X-ray, for diagnosis purposes, if you know only the two values of mAs and kV, can you determine the dose or maybe even estimate the dose delivered to the patient? Without the use of any modern detectors. 
I have portable 30mA X ray machine with the following specifications:
Output     30mA at 52 KV
                20mA at 68 KV
                15mA at 85 KV
Timer        0.06mA to 6.0
                 23 Steps
Tube         1.5 mm sq. Focal Spot X-Ray tube
Input          230V, 15 Amps
L. V. Compensation     210 to 250V
Beam Limination Cone with Centering Device
Weight        15 Kgs.
Dimension (mm)   250x175x250
Can somebody guide me to calculate the dose in gray (Gy)?
Thanking you in anticipation.
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Mr Sandeep Mittal
I am working out below two independent methods to arrive at the output of x-rays for a given combination of kV and mA. Please note that both these are only approximate but they do indicate the different approaches to the answers. Let us take the distance from the x-ray tube target to the point at which the output is required as 100 cm.
Method 1:
Let us assume kV = 60 and mA = 10; then power dissipated on the x-ray target is:
60 x 10 watts or 600 joules/sec = 600 x 107 ergs/sec ……….(1)
The fraction of electron energy converted to bremmstralung (f) is given approximately by:
f = Ee x Z x 10-6 (Z is the atomic number of target = 74 for tungsten; Ee is the electron energy in keV)(from medical physics literature).
Since the average energy of the unfiltered x-ray photon energy is one-third of the electron energy from Kramer’s equation, the photon energy available as bremmstralung therefore is:
Hence f = (60/3) x 74 x 10-6 = 0.148% …………………………..(2)
Therefore the x-ray energy output at the target = (1) x (2) above = 0.888  x 107 ergs/sec …… (3)
Assuming the x-ray distribution from the target is isotropic (valid for a thick target), the energy output at 100 cm is: [(3) above] / 4π (1002) = 0.0705 x 103  ergs/sec/cm2 ………………(4)
Assuming the total (inherent + added) filtration in the tube is 3 mm:
For 60kV, 3mm filtration offers 2HVLs, since the first HVL is 1mm and the homogeneity coefficient is 0.5 (obtained from literature); Hence the attenuation offered by 3 mm Al = ¼ (0.25)
This leads to an output after filtration = [(4) above]/4  = 0.0176 x 103 ergs/sec/cm2 ……….(5)
To get the output air in R/sec at 1 meter, we have to multiply (5) above by the mass energy absorption coefficient of air for 60 kV with 3 mm filtration. For an unfiltered x-ray beam, Kramer’s Law gives an average energy of one-third kV; for a filtered(hardened) beam, let us assume the average energy as 30 keV (this is a valid approximation). The mass energy absorption coefficient µen /ρ for 30 keV x-rays = 0.1501 cm2 /gm [From Hubbel’s 1982 revised 2012 data]…………….(6)
Therefore the output at 1m = [(5) x (6)]/ 87.7 [1 R = 87.7 ergs/gm of air] = 0.0301 R/sec  = 1.81 R/min…..(7)
This can be converted to air kerma in rads/sec by multiplying by 0.877
It may be noted the above derivation involves a number of approximations. Moreover, the values of  (µen /ρ) vary widely over the low keV region.
 Method II
This  method uses the RadPro calculator available free on-line. Here you have to enter the values of kV (60), mA (10), filtration(3 mm Al) and distance(100 cm) from the target to the point of measurement. This calculation then yields a value of 1.8719 x 108 µR/hr = 187.19 R/hr = 187.19/3600 R/sec = 0.052 R/sec = 3.12 R/min ………………………….(8)
It may be noted that these values (7) and (8) above are obtained by altogether two different approaches and both involve approximations. Both these denote typical outputs of a fluoroscopic unit.
Please consult any radiation physics text or website for references cited above.
Hope this helps.Good Luck.
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In calculation of the absorbed dose in radionuclide scintigraphy, the absorbed dose in tissue T from radionuclide  in a single source organ S is given by:
D(T <-- S)= As x S (T <-- S)
where As is the cumulated activity. 
I want to calculate the absorbed dose of the kidney in renal scintigraphy using 99mTc-DMSA. I have measured the activity of the rat's kidney using dose calibrator. for calculation of the absorbed dose in a period of time, I need the S-value for rat's kidney and 99mTc-DMSA.
How can I find or calculate it?
Or:
Is there another way to calculate the absorbed dose in rat's kidney from measured activity?
Thanks
Kaveh
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Is it possible to rotate the current spin states of electrons of cancer cells with some kind of  non-elastic collision via high intensity photon particles to stop cancer progression in last stage.
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Spin is an intrinsic angular momentum of electron or an associated magnetic moment. Spin quantum number of electron can only be +1/2 and -1/2 and in one orbital there cannot be two electrons with the same spin (Pauli exclusion principle). As a result, if two electrons are in the same orbital, their spin quantum numbers cannot be changed without moving electron to another orbital, which is essentially changing its energetic state. So your question can be understood as treating advanced cancers by changing energy states of atoms (this re-phrasing would be more specific in terms of physics). This would actually cover a spectrum of existing therapies from laser therapy to radiotherapy. As mentioned in previous answers, this is often helpful for local or loco-regional control of the disease, and I would also add pre-cancerous lesions in case of laser therapy, but not in advanced stages with distant metastases. There is also photodynamic therapy, which employs singlet oxygen (an excited electron state of molecular oxygen that also differs in electron spins from ground state of molecular oxygen) to kill malignant cells. Again, all these processes are primarily energy-state related with excitation or ionization leading to higher reactivity and subsequent damage to critical biomolecules. It has no direct connection to spin as an inherent and quantized electron property. It is my personal observation that speculations about quantum physics/chemistry and cancer do not come from people who have developed insight in these disciplines.
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What is the best method to assess the absorbed dose by the target organs in nuclear medecine examinations?
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An excellent reference would be George Sgouros papers. I am assuming by best you mean most reliable (accurate and precise). Your question has multiple aspects, including what is the best software tool to perform dosimetry, or what is the best way to provide inputs from the patients (e.g. radiotracer uptake) to these software tools. For the latter, several methods are available, such as imaging, blood samples, etc., and finding out which method is the best is an area of active research. Perhaps you might be interested in the following publication: https://www.ncbi.nlm.nih.gov/pubmed/26982626
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Quelle est la meilleure mmethod to assess the absorbed dose by target organs in nuclear medecine examinations ? 
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Since  direct measurement of the absorbed dose to target organs   from nuclear medicine procedures is rarely possible,  most estimates rely on the  Monte Carlo simulation or numerical calculation based on indirect measurements/radiopharmaceutical data.
Here in the  US MIRD method  has been  developed by Medical Internal Radiation Dose Committee (http://www.snmmi.org/AboutSNMMI/CommitteeContent.aspx?ItemNumber=12475)  that allows the calculation of dose to target organs, see e.g. http://ozradonc.wikidot.com/methods-of-dose-estimation,
you can find more references on the MIRD webpage under MIRD publications.
Dedicated MIRDose software is developed by M.G. Stabin that simplifies the calculations.
(M.G. Stabin, and G.D. Flux. "Internal Dosimetry as a Tool for Radiation Protection of the Patient in Nuclear Medicine". Biomedical Imaging and Intervention Journal, 2007; 3(2) 28)
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I'm using a Catphan phantom with an small bead to generate a MTF of a CT scan, so as I understand the matrix of CT numbers of the image of the impulsive signal is my PSF, right?
How do I get rid of the background signal? Do I make an average of the CT numbers in the matrix that apparently do not belong to the impulsive signal and subtract it element by element? when I try to do this I do not obtain the characteristic MTF so there must be another way. 
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You have to get rid of the background and make it closer to zero as you will not be able to compute the MTF curves correctly. The way that I approach this problem is by using curve fitting techniques and average mean subtraction of 20 pixels of the tail from the PSF curve. The oversampled curve has those issues as it concatenates several lines (N) for the computation. The later steps involves the normalization of the curve to 1 and the abs FFT.   
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buildup factors
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Thank u sir
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Rencently, I have been doing some experiments on temperature measurement of Argon plasma. I used the boltzmann plot method. I found that the fitting error is about (+-)1000 K. How can I decrease the error from experiment? 
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Hello, I'm building a ALD reactor in lab scale and I have a few questions referring to the security of operation. As known, most of ALD precursors such as TMA are pyrophoric, but how dangerous can it be, when an exhaust gas composed of small amounts of TMA diluted in nitrogen come in contact with oxigen? what is the best way to deal with exhaust gases of this kind of precursors when discharging at the atmosphere?
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I think, that the best way to eliminate the bad effects of TMA, TMG and similar precursors, when discharging at the atmosphere, is to flame 
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To measure grass alpha and beta by Low level Counter (gas proportional counter made by THERMO company) for meat and vegetable samples, the first, we prepare samples in format of ash, now the question is: what temperature must be selected to make ashes of these samples so that for example Cs-137 (as beta emitter) to be reminded in samples.
What temperature and why?
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Read pages 23-31 of document in attachment. It is IAEA guide for gamma emitters but you have general examples for Cs-137 (temperature must be below 400 C).
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Dear colleagues
This question is a continuation of the considerations set out in the previous question:
My new question is:
How to decrease the resistance of transmission WiFi in a strong EM field from the MV line  (60Hz)?
Is the direction of WiFi antenna affects the transmission of data from sensors in the vicinity of the MV line?
What physical phenomena are accompanying the data transmition of WiFi antenna in the strong magnetic field of 60 Hz?
Whether any standards are available in this matter in USA and EU?
I would be gratefull for your sugestions and giving me sample papers on related problems.
Best Regards,
Piotr
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Hi Piotr,
First, a bit on the earlier question (which I could not attempt then, simply because I had not joined RG at that time !!):
  • Since the Wi-Fi operates at very high frequency, only high frequency harmonics from the MV line can interfere, if at all ! 
  • A common power frequency line will simply not have such frequencies unless power electronic equipment are connected to it, and are injecting harmonics into the MV line. So check for such equipment connected to the line.
  • The interference (if at all !!) will be largely through inductive-capacitive coupling, of the similar type as erstwhile telephone line interference faced due to proximity to HVDC links (you can read about this from any good book on HVDC - you can also get standards under IEEE).
Now for your present question:
Since the Wi Fi frequency is very high, as I said capacitive-inductive coupling will dominate. Resistive effects in the coupling medium can practically taken to be negligible !! That is, the interference (if any) can be assumed to be lossless...
 With best wishes.
-Sanjay
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We want to generate an external beam of neutrons from a Synchrotron for experiments.
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MCNP is certainly one option, however it has export controls from the U.S. government because it is also useful for reactors/weapons development.  Fluka and Geant are not under U.S. government control and can do the same thing.  They all have the learning curves.  Most people stick with whatever they learned first because they all do a good job so their is no incentive to learn something new once you have something that works.  GATE and TOPAS are essentially wrappers for GEANT4 to make it more user friendly, so they could be explored as well.
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Physics experts in gamma and beta radiation detection.
Medical Physics.
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You could measure the distribution of beta+ emitters (e.g. I-123 or Sr-83) with positron emmission tomography (PET) and re-calculate the absorbed dose for I-131 and Sr-90. This would even work in an actual patient, if you tracer your therapeutic substance with the PET nuclides. Or am I missing a point? 
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For my project, I need to take FFT of MRI image and for that, I am planning to start with taking the FFT of a dipole corresponding to the sample. My question is, how to identify the dipole in the MRI image ?
I have the data in the form of a 3D array and using MATLAB for programming. My assumption is that first I need to convert this array into k-space matrix. Any suggestions ?
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To answer your question, we need to know what kind of 3D images do you have (real or complex)? what pulse sequence you used for the images?
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Hi Dear friends
I want to work with CR39 films for neutron dosimetry for the first time. I need help for knowing about 1) the interaction between films and neutron or other particle (which is produced by high energy photons like 15Mev) which make track on films, etching procedure and reading the track.
Do they record the fast or thermal neutron or both of them?
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Beyond vendor-specific definitions, what is the theoretical difference between FISP (fast imaging with steady-state precession) and bSSFP (balanced, steady-state free precession)?
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What is the number of bunches per MU and what is the delay between them?
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Regardless the energy of the electron beam, in medical linear accelerator the electron source is usually thermionic type which is considered to be a source of continuous electron beam which its duration equals to the duration of the applied voltage signal on the electron gun,  but the final electron bunch length does not equal to that signal length.
Medical linac usually operates at S-band frequency (2856 MHz or 3 GHz). To accelerate the electron bunch the linac should be energized by RF power which its signal length equals to 3-4 microseconds and that RF signal length determine the final length of the accelerated electron bunch.
However, since the electron bunch is accelerated in RF structure, hence each electron bunch composed of sub micro bunches. such micro bunches initiated under the effect of  periodic polarity of the RF signal. In other words, some parts of electron bunch are accelerated along the RF cavities with positive voltage while other parts are decelerated along RF cavities with negative voltage. This means that some electrons are pushed forward while other electrons are pushed back and this in consequence produces what is called micro bunches. the length of each micro bunch is order pico seconds.
The number of micro bunches even depends on the type of linac used and on the phase it operates with. For example the number of micro bunches in 2pi/3 traveling wave linac are greater than the number of micro bunches in pi/2 standing wave accelerator. This is because in traveling wave linac there are 3 cavities per RF signal while there are 2 RF cavities per RF signal in case of standing wave linac.
I hope that this answers your question about the details of the electron bunch length macroscopically and microscopically.
However. in medical linear accelerator the such fine details is not of great interest in contrast to the linacs used in 3rd generation (synchrotron)  and 4th generation (FEL) light sources.
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I expect such a dose distribution because of the mixture of high and low energy electrons. I have problems to imagine a clinical target volume to be irradiated. It should have a broad volume near the entrance and diminuish in the depth, possibly like a cone shaped tumor volume.
I´m interested to see such a dose distribution from your simulations.
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Hi,
I am irradiating some mammalian cells comparing both X-rays and protons. I know what dose I am exposing my cells to using X-rays, for example 4Gy, but if I want to radiate with protons how can I work out the equivalent dose in protons?
Thank you for any guidance
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If you want to calculate the proton dose you will find an established protocol in IAEA 398. I attend this report for you.
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Dear all,
When scanning  breast (size:13cm x 12cm x 6cm) in prone position by SIEMENS Symbia E gamma camera, 120 projections need to be collected. the problem is how to choose the zoom factor to get proper pixel size which means a bigger pixel size would degrade the image and a smaller pixel size would introduce more noise.
the following is the specifications for SIEMENS Symbia E gamma camera:
Detector Specifications:
Crystal dimention: 59.1 x 44.5 cm (23.25 x 17.5 in)
Field of View (FOV) 53.3 x 38.7 cm (21 x 15.25 in)
Radius of rotation: 15cm
Thank you!
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Dear All,
The best is to use so called optimal pixelsize, where resolution and noise level can be optimized by relatively easy way.
        PSopt~FWH/3, where PSopt is the optimal pixelsize, FWH is the system (currently the SPECT system resolution including both the detector resolution and the selected collimator resolution). If you follow this approximation you can be optimized any SPECT study.
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Our team is looking for evidence that muscle recruitment patterns are altered following ACL reconstructive surgery which may effect scores on tests such as the Bunkie test, outlined by de Witt and Venter in the attached publication.
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The author Greg Myer I am sure will know and has a lot of references about that topic. 
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Has anyone tried using 2 180 degrees arcs vs one full arc for lung VMAT SBRT? Can anyone see any advantage? I have heard in some discussions that it might confer some benefits but I am trying to wrap my head around it and cant see it immediately.
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hi read this article i think will be useful for you
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Is there a clear advantage with regards to DCAT in reducing lung dose relative to VMAT SBRT?
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Hello Shahin,
   My Msc thesis was also about comparing DCAT and VMAT techniques according to RTOG 0915 protocol.  I worked with 20 patients and I observed V20Gy lung percentage. According to my data avarage V20Gy for VMAT %3.88 for DCAT %4.02 also VMAT has statistical significance  to DCAT. (p=0,001).
   On the other hand I agree with Mr. Fitzgeralds undertsandings. Treatment time depends on MU and DCAT has way  more lower MU than  VMAT.  DCAT reduceses interplay effect but VMAT has sharp high and intermediate dose gradients.
Best regards
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It will be used for x-ray absorption studies in the human body as well as the dose fall off with depth.
I am using a PMMA container volume 35x38x40
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Darrion, you can find here an example of pelvic cavity phantom: http://www.cirsinc.com/file/Products/002PRA/002PRA_DS_070113.pdf
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I am interested by some connections between cosmology, gravity etc with life sciences, biophysics or whatever. I will be appreciative if you can give me some initial starting points with articles, textbooks etc dedicated to my interests.
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see arXiv 1311.6328 quant-ph.
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I'm looking for studies that investigate the spectral characteristics of sickle hemoglobin. I imagine that with structural differences, there should be a significant difference in the spectral characteristic of sickle hemoglobin.
Characterization of either absorption or extinction coefficient would be greatly appreciated!
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ultraviolet rays to detect the difference in shape and surface area between the normal blood cells and the sickle cells
This paper is clearly detected in their absorption pattern beyond 500nm. Specifically, HbS shows a higher absorption pattern than normal HbA, especially at the range between 700nm and 900nm, which lies in the near-infrared region.
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Why electron cut off energy is intended 500 keV?
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The determination of the electron cut-off  should be done after a criterious analysis of the problem. The higher of the cut-off corresponds to the higher time consuming. However sometimes the physics of the problem requires a higher cut-off.  Is a value that deppends of the problem. If the electrons are not relevant for the problem you can suppress the transport of the electrons. If the electrons are relevant you shouls analyse the problem and is assign the value are low as possible.
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anybody has experience about research in osteoporosis?
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Hi,
Yes, my professor do have experience in phantom based research experience.
Regards,
Dr.Giri
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I would like to fabricate micro needles in the dimension of 2 micro meter  width and 20 micro meter length, Can any one help me how to prepare MASK layout and mask preparation.             
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