# Medical Physics

How does to calculate treatment time of Cobalt-60 Teletherapy unit ?

How does to calculate treatment time of Cobalt-60 Teletherapy unit ?

Mohammad Ali Shafaei · University of Yazd

Hi, I send 2 attachment for improve your information abuot Radiation treatment.

Is there a novel area in physics emerging that could be called "Physics of Cancer" and how would you define this area?
Recently a discussion has started to what extent physics can contribute to cancer research. Is there a specific contribution of physics or can physics just provide novel techniques?
Sousan Abolhassani · Paul Scherrer Institut
The issues of Transport of materials and their modeling was subject of a Workshop in 2010 organized by SSOM.
I expected at that time that in the future some aspects discussed in that Workshop will become new fields of research and I agree that in the field of cancer, this should already get established.
http://lnm.web.psi.ch/transpore2010/
Is there a method (paper or website) to convert radiation meter readings (like:Geiger counter) from human organ or material to absorbed dose?
I am looking to convert Geiger counter readings to absorbed dose.
David Christopher Medich · Worcester Polytechnic Institute
I would like to build on Hanno's great reply. A GM could be calibrated so that the number of detected events from photon irradiation (which is directly related to the photon fluence rate that the detector is exposed to) can be related to absorbed dose to some material (such as tissue or water) if charged particle equilibrium (CPE) exists at the location of measurement. Under conditions of CPE, absorbed dose is equal to the photon fluence multiplied by the photon energy multiplied by the mass energy absorption coefficient (I won't derive this relationship - please check a text book such as Turner's Atoms Radiation and Radiation Protection).

Here's the practical part. Photons in the range of about 300 keV to a few MeV predominately interact by Compton Scatter. Since Compton scatter is relatively energy independent in this energy range, you could calibrate a GM to, for example, Cs-137 to absorbed dose (satisfying the CPE equation I gave above) and, within an error of a few percent, could use this conversion constant to also predict a GM's absorbed dose from photons at other photon energies also between 300 keV to a few MeV.

That is, a GM calibrated to convert the rate of detected events from a Cs-137 source into absorbed dose to some material (usually water) can be used to predict the absorbed dose to that material from another isotope such as Co-60 (to within a few percent). the important thing to keep in mind is that this rule of thumb falls apart below 300 keV where photoelectric absorption (which is highly energy and material dependent) and above a few MeV due to increased pair-production probability.

You'll notice that I reference photons and not beta's (or other charged particles). You didn't specify any specific type of radiation, but without going into Cavity theory (please see Attix for an excellent explanation), the approach above is not applicable for measurements of charged particles made in air.
Diffusion equation solution
Hi. I need a book or an article about diffiusion equation solution for laser (EM wave) not for dynamic flue.
Ana-Maria Ciobotaru · University of Bucharest
Hy, look on this paper.
Water content in normal and neoplastic tissues?
There is an indication (J. H. Ali, W. B. Wang, M. Zevallos and R. R. Alfano, "Near infrared spectroscopy and imaging to probe differences in water content in normal and cancer human prostate tissues," Technol. Cancer Res. Treat. 3, 491-497 (2004)) that cancer tissues may have lower water content in vitro. I'm wondering if somebody done similar studies (in vitro, ex vivo, in vivo). While the prostate is of the main interest, any other organs and tissues would do it as well!
Parisa Farzam · ICFO Institute of Photonic Sciences
You may find the water content of tissue in the following publications:

White, D. R., Widdowson, E. M., Woodard, H. Q., & Dickerson, J. W. (1991). The composition of body tissues (II). Fetus to young adult. The British Journal of Radiology, 64(758), 149–59. Retrieved from http://bjr.birjournals.org/content/59/708/1209.short

White, D. R., Woodard, H. Q., & Hammond, S. M. (1987). Average soft-tissue and bone models for use in radiation dosimetry. The British Journal of Radiology, 60(717), 907–13. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/3664185
Which dosimeter can we use in radiotherapy for a radiation dose measurement up to 150 Gy?
In routine radiation therapy, we deliver a dose of 1.8Gy up to 3Gy, which depends upon the site and the stage of the disease. For Functional Radio-surgery, like trigeminal neuralgia, parkinson's disease, we need to deliver a radiation dose around 50Gy to 140Gy. So how can we do the dosimetry for this?
Is there anybody doing this radiosurgery on a Medical Linear Accelerator?
Radu A. Vasilache · Canberra Packard CE GmbH
Do you need to do absolute dosimetry (beam calibration) or TP verification? In the first case, you can use a PTW Unidos Webline with a MicroDiamond detector (the electrometer has a high range going to 2.5 microamps and the detector withstands 50 Gy/min without problem. For TP verification you can use the Octavius 1000 SRS detector, which has 1000 liquid filled ion chambers.
You can get more data from www.ptw,de
What is the best Monte Carlo software for a shielding calculation of spectrum of neutrons? And also its price?
We want to generate an external beam of neutrons from a Synchrotron for experiments.
R. M Gunasingha · Duke University Medical Center
Fluka: http://www.fluka.org is one of the code you can use and its free.
What type of of dosimeter can I use with rando phantom rather than TLD?
In order to calculate CBCT dose to Rando phantom.
Hanno Krieger · retired from Justus-Liebig-Universität Gießen
@Jerry, thanks for the photo and tzhe calibration infos.
Where might I find references on the optical properties of thermally coagulated muscle tissues?
I couldn't find much (or anything) on reports of spectrally resolved optical properties (absorption and scattering) of thermally coagulated muscle tissue. So, please share your knowledge on the topic. Human, bovine, porcine, canine - anything would be useful. Any group of muscles will do. Single-wavelength measurements will be useful as well.
Daniel Tsegay Berhe · University of Copenhagen
The thesis is very useful. Thank you Mehra.
Are there any vendor sequences for Arterial Spin Labeling (ASL)?
Arterial Spin Labeling sequences are widely spread in the research community. Nevertheless, to become a clinical standard it is crucial that vendors provide sequences that can be used for diagnostic purposes. Furthermore, these sequences should be easy and fast to use.
Thorsten Feiweier · Siemens
Regarding the ASL product software currently provided by Siemens, you might want to have a look here: https://www.healthcare.siemens.com/magnetic-resonance-imaging/options-and-upgrades/clinical-applications/asl
• Are the other vendors like Hitachi, Toshiba, Bruker, United Imaging providing Arterial Spin Labeling sequences too?
I only know about SIEMENS, Phillips and GE
How can we check suitability of radiology room shielding with a Geiger counter?
What is the safe reading in term of microSv/h?
Dear Peofessor Jim Malone
Very nice opinion, I read and understand a lot of things from the given web links.
What is a statistical range of total hemoglobin (oxy- and deoxy-) and water concentration for canine prostate? How does it compare with the human?
If somebody can provide numbers for in vitro and in vivo, it would be great!
Serge Grabtchak · University of Prince Edward Island
We have some numbers now on concentrations of Hb, HbO2 and H2O in a canine prostate ex vivo. We could only compare our data with those for a human prostate since we couldn't find similar data for a canine prostate.

Does anyone knows about the current status of High intensity focussed ultrasound.
HIFU is used in treating cancer. I am interested in a project involving Ultrasound as therapy unit and imaging devices. Does anyone has a suggestion.
Giovanni Borasi · National Research Council
A very complete and objective description of the HIFU present status and perspectives can be found in the attached paper from Schlesinger et al.
What accessories
What accessories
Guy A. Storme · University Hospital Brussels
Please look to the publication of Gevaert Thierry
What materials in accelerator?
...........
Lindsay Tremethick · Radiation Oncology Victoria
Yes Hanno quite correct, my apologies, I didn't add that "head of linac" actually means primary collimator.
I'm looking for data on spectrally-resolved optical properties (absorption and scatering coefficients etc) of porcine muscles.
I'd appreciate any references on the subject. Range: 650-900 nm
Serge Grabtchak · University of Prince Edward Island
This publication contains our recent data on optical absorption and scattering properties of bulk porcine muscles, Longissimus dorsi (the loin) and Psoas major (the tenderloin):
Does anyone know a setup to generate 10 Volume per average respiratory motion in MRI?
I am using MRI symphony TIM Siemens.
The lungs, esophagus, liver, pancreas, breast, prostate, and kidneys, among other organs, are known to move with breathing. The degradation of image quality due to this motion and subsequent effects on radiotherapy dose planning and delivery have prompted medical physicists and clinicians to study the motion using a variety of imaging modalities.
How do you react to the recent publication from Australia in the BMJ that indicates an increase in cancers arising from paediatric CT scans?
The publication can be accessed in the link below. This is how the publication is summarised in an ESR Newsletter: This cancer risk assessment in an Australian study cohort showed that overall cancer incidence was 24% higher for children and adolescents exposed to low dose ionising radiation from computed tomography (CT) than for patients who were not exposed. Australian Medicare records from 1985–2005 were analysed for this study, and although radiation doses from current CT scans are likely to be lower, a slight increase in cancer risk due to exposure is still possible.
Alan Futivić · General Hospital Zabok
Exactly. We need to know at least roughly what we want to prove with examination. Then we can do a search in the patient's best interests. Optimal protocol with less radiation.
Thanks
How do I measure Organ doses by gamma counter?
I have measured Counts from a γ-counter for different organs (lungs, liver, spleen, stomach, brain, kidney and heart) after 3.5 hours of intravenous injection with 80 MBq initial dose of Technetium labeled with Glycol Chitosan Palmitoylated quaternary ammonium (GCPQ). Now I want to convert these counts in to organ injected doses. Please can any person guide me how to do this?
Andrew Chicco · Liverpool Hospital
Hi Rafique,
As mentioned above you do require the activity within each of the different organs at several points in time (i.e. you need to have data from several rabbits, each sacrificed at these times).

There is a very good book published by Dr. Michael Stabin: "Fundamentals of Nuclear Medicine Dosimetry" (Springer, 2008). It has several case studies included (i.e. fuly worked examples), and also discusses the issues involved in translating animal dosimetry to human. I most thoroughly recommend it.

There is also freely available MIRD Pamphlet 16 (published by the Society of Nuclear Medicine, available online), which discusses the experimental design for what you are attempting to do (please correct me if I am wrong).

Good luck,
Andrew.
Does the shape of dosimeter influences the position of TL main peak?
Should I get the same peak position if i use TLD-100 chip shape and TLD-100 rod shape?
Alawiah Ariffin · University of Science Malaysia
Thanks Anuj for sharing the paper...
• Abhijit Mandal asked a question:
Can someone advise on the use of an implantable biocompatible in vivo dosimeter?
I have found some articles on DVS Dosimetry system from Sicel technologies and am seeking to learn more.
Is it possible to introduce magnetic flux density (B) in the radiative transfer equation?
i like to quantify the magnetic field (B) from the fluence rate from radiative transport equation. Since light is an electromagnetic wave, i guess there should be a place for B(x,t).
Michael Dada · Federal University of Technology Minna
Thanks Dr. Patyk. Your response is very insightful indeed!
Could anyone suggest a reasonable dose range for calculating gamma pass rate in radiation therapy?
When we evaluate the difference between the measured and calculated dose distribution values, gamma index can serve as a good quantitative method. But what is the reasonable dose range when we calculate the pass rage? Generally, for clinic radiation therapy, dose range 60%-100% is what we are concerned with, right? So we can just calculate the dose range from 60% to 100%? I asked another medical physicist, but he said there is no exact answer for this question. Could anyone give me a suggestion? Thank you very much.
Peer Koltermann · P2P MPI
Just some general thoughts added: As said above the gamma index is not a fixed equation. Vendors "adapt" the gamma pass rate as their devices need it. There are many ways to name a gamma index. So you can not even compare 2 gamma pass rate without lots of background information. Sayings like "we just treat with pass rates above 98%" don't give you any information, it just sounds nice.
We are working on common "baselines" so medical physicists can compare worldwide exactly for this reason.
Can anyone recommend a medical physics expert willing to travel to London, UK?
We have a DXA scanner than requires a MPE to approve any protocols before we can commence testing. If anyone could suggest a MPE near London that would be much appreciated.
Peer Koltermann · P2P MPI
we work with medical physicists worldwide. Email to support@p2pmpi.com and we can help.
How can I find a good fiber-optical thermocouple?
I need a good thermometer for measuring temperature of nanoparticles and mouse skin in a AC magnetic field. I need the available models with moderate price for temperature range: 25-70 centigrade degree
Samuel Ojo · University of Birmingham
I will suggest the use of small diameter optical fibre (SDOF) as we once developed a novel method for measuring light intensity at different temperature. This can measure up to 180 degree celcius. This probably allay the fear of high costs you raised as the diameter of SDOF ranges between 12-20 microns.
Does anyone know the average life span of Varian Clinac's klystron tube?
Klystron tube damage
Martins Piksis · Riga Technical University
Thanks, Marcel!