Science topic

PET Imaging - Science topic

Explore the latest questions and answers in PET Imaging, and find PET Imaging experts.
Questions related to PET Imaging
  • asked a question related to PET Imaging
Question
6 answers
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?
Relevant answer
Answer
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 (!)
  • asked a question related to PET Imaging
Question
3 answers
I have found lots of MRI repositories so no need for this, thank you.
Relevant answer
Answer
Take a look in our database in our new free medical imaging question and answer forum ( www.imagingQA.com ). You can filter on 'ct' and 'spect' as needed at the link below:
Feel free to sign up too, and join the growing community.
If you can't find what you're looking for, please feel free to open a new topic at the link below :
  • asked a question related to PET Imaging
Question
3 answers
I have 9 positron emission tomography (PET) images of a patient, taken at different times. I want to calculate total disintegration (cumulated activity) but I don't know where to begin.
Has anyone came across this topic before? Is there a practical reference or step-by-step guide to it? What tools do I need?
Thank you for your time and attention.
Regards
Relevant answer
Answer
Hi Sara,
To begin with you have to build the time activity curve (TAC) from all 9 points of your data. An x axis for time/ duration while y axis as measured PET data. From there, just integrate the TAC and the total integrate result will be your cumulated activity in activity.time (example; MBq.s). If you devide your cumulated activity with your administered activity, you will get the residence time (for this example in sec). Hope this helps.
Best Regards,
Syahir
  • asked a question related to PET Imaging
Question
3 answers
I know that in List mode data the scintillating events are stored along with the time stamps of the event. I have a doubt regarding image reconstruction from the list mode data.
Is each (x,y coordinate of) photon count binned into an image matrix or are the photon counts integrated in certain time interval and treated with Anger algorithm or MLEM algorithm then binned into a image matrix? If the latter is the case then what is the value of the time interval?
If my question is not clear or wrong can anybody suggest some sources which will help me in understanding this ?
Relevant answer
Answer
Can someone refer to any text or website that provides a step by step guide for image reconstruction in PET using list-mode data
  • asked a question related to PET Imaging
Question
2 answers
Hello.
I am going to perform a longitudinal study in mice involving a radiotracer that is eluted in Ethanol in its formulation, [11C] Raclopride. The amount of Ethanol in the final product is no higher than 10%. I am planning to inject this very solution in the animal via i.v. and flush with a saline solution, but I am concerned with the final concentration of Ethanol in the organism being high enough to hinder the animal, or giving me some long-term effect on dopaminergic neurons that are undesirable in a longitudinal study.
Is there anyone that looked into this specific matter, or that can give me some references on it?
Thank you very much.
Relevant answer
Answer
make it more dilute,
make stock in 5% ethanol
further dilute prepare fresh working stock with 0.1% ethanol.
  • asked a question related to PET Imaging
Question
2 answers
I guess we need the optical part of GATE. But how do I modify / set the physics to simulate this effect (because geant4 seems to have it already)?
Relevant answer
Answer
Following
  • asked a question related to PET Imaging
Question
2 answers
Ideally the software would adjust the PET signal by tissue type and provide some normative values from healthy individuals.
Relevant answer
Answer
Just an add-on software from the previous answer could be the Analyze by the Biomedical Imaging Resource (BIR) at Mayo Clinic.
The only disadvantage is that it accepts images where the format has to be in Analize (.img and the respective .hdr).
Plus you have to create an object map of the brain for GM and WM in order to get concentration values.
  • asked a question related to PET Imaging
Question
7 answers
 I see at least 8-9 methods for doing the correction, and papers that compare their merits, but none of these papers discusses the specifics of how they did it, only mathematical formulas and algorithms. My lab already uses FSL, Freesurfer and AFNI if anyone knows an approach that would work with minimal new coding. Thanks.
Relevant answer
Answer
There is this toolbox that I use which has all the existing PVC methods and a combination of those.
Attached is the link to download it and the respective published article.
  • asked a question related to PET Imaging
Question
4 answers
There are different types of diagnostic tests for Alzheimer's disease. as far as I know, one of them is positron emission tomography (PET) scanning. what exactly does cause the sign of the disease on a PET image? what percentage of Alzheimer's disease can be diagnosed by this procedure? do prescription drugs affect these signs after we take the test again?
Relevant answer
Answer
Hi,
Currently, International Working Group (IWG) and National Institute on Aging Alzheimer's Association (NIA-AA) has proposed several biomarkers as diagnostic criteria which includes cerebro spinal fluid (CSF) amyloid beta (Aβ) and tau, atrophy on MRI, glucose metabolism on [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) and fibrillar Aβ burden on amyloid PET.
There are few regions, which acts as definite Hallmark regions for AD. You could refer to below attached papers.
(11)C-PIB-PET for the early diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI)
Structural MRI and Amyloid PET Imaging for Prediction of Conversion to Alzheimer's Disease in Patients with Mild Cognitive Impairment: A Meta-Analysis
18F-FDG PET for the early diagnosis of Alzheimer’s disease dementia and other dementias in people with mild cognitive impairment (MCI)
FDG-PET for Prediction of AD Dementia in Mild Cognitive Impairment. A Review of the State of the Art with Particular Emphasis on the Comparison with Other Neuroimaging Modalities (MRI and Perfusion SPECT)
Biomarker-based prediction of progression in MCI: Comparison of AD signature and hippocampal volume with spinal fluid amyloid-β and tau
Biomarker-based prediction of progression in MCI: Comparison of AD signature and hippocampal volume with spinal fluid amyloid-β and tau
I hope these article will help you.
Further, regarding the medication you could look into these articles
Drugs for Alzheimer’s Disease: Are They Effective?
Pharmacogenomics and therapeutic prospects in Alzheimer's disease
Cholinesterase inhibitors for Alzheimer's disease
Gud Luck !!!!
  • asked a question related to PET Imaging
Question
3 answers
We have injected a radiolabeled small protein (10 kDa) to an animal model bearing positive and negative tumors. During submission process, reviewers asked for the concentration of accumulated protein in the positive tumor and... I really don't know how to do this.
I've tried with the "binding potential" formula, but we aren't in the good experimental conditions (the concentration of radiolabeled protein is too low and we have only one time point). Help!
What we know :
- Number of receptors of interest per cell : 5 × 10^5 EGFR per cell (5x10^6 cells were injected in each mouse).
- Effective specific activity of the injected proteins (mixture of labeled and unlabeled proteins): 37.0 – 53.6 MBq/nmol
- Total quantity of injected proteins: 10 nmol
- Uptake in the positive tumor 2.5h p.i. : 1.42 ± 0.18 %ID/g 
- Uptake in the negative tumor 2.5h p.i. : 0.56 ± 0.10 %ID/g 
- In vitro affinity of the protein for the receptor : Kd = 27 nM
Relevant answer
Answer
Hi Marine,
Calculating the protein quantity in the tumor is very straight forward when radioactively labeled.
Let's assume an average specific activity of 45MBq/nmol which means an injected dose of 450MBq and 10 nmoles. The %ID/g for the positive tumor is 1.42 which means you have 6.4MBq and 0.142 nmole (which with a Mw of 10kDa is 1.42ug) of protein in the tumor per gram of tumor. You can check my numbers and calculate the same for the antigen negative tumor. Hopefully, you have the tumor sizes from a cut&count study or a CT scan of the animals.
Take into account that:
1) I didn't decay correct the numbers so depending on whether you wrote decay corrected numbers or not, this may need to be accounted for
2) We're assuming all the radioactivity is associated with the antibody (stability studies might hint whether this is a valid approximation)
Good luck,
Ohad
  • asked a question related to PET Imaging
Question
2 answers
hi everyone,
I try to quantify the biodistribution via pet/ct images but I have some problems, for example I am not sure that is that ok if I apply any filter such as 3D Gaussian on SPECT or PET images? 
I am working with p-mod  software.
Relevant answer
Answer
There is always a resolution/noise tradeoff when using filtering. If you use larger kernels, you will reduce more noise but small structures will loose contrast. If you are trying to quantify organ level distributions, then filtering is ok and won´t change your results. On the other hand, if you are quantifying small lesions, your measurements will get lower as you increase the filter size due to partial volume effects. 
  • asked a question related to PET Imaging
Question
3 answers
Hello all,
My question is whether positron emission tomography measures the binding of the radioligand to a receptor that is specifically located at the cytoplasmic membrane or to all receptors regardless where they are located in the cell. I guess it depends on the tracer physiochemical characteristics, whether it penetrates the cellular membrane or not, and on the binding site within the protein. I just need a confirmation from an expert. 
Thanks
Relevant answer
Answer
Furthermore, due to the resolution of PET you could not differentiate the binding site in a cell........
  • asked a question related to PET Imaging
Question
6 answers
I am looking for an appropriate FDG PET SUVmax threshold to use. Can anybody provide me with some ideas?
Thank You. 
Relevant answer
Answer
SUV of 2.5 and for that matter any other value cannot be adopted as a threshold for distinguishing malignant lesions from benign abnormalities,  this is a terrible misconception and should be ignored completely, the size of the lesion and respiratory motion are very important factors in such measurements and the proponents of this threshold were totally misinformed about the physics of PET and their ignorance has resulted in mishandling many patients with cancer all over the world.    This has been a tragic addition to the literature and it is about time to abandon it for good,  we won't miss it for a second!!!
  • asked a question related to PET Imaging
Question
3 answers
Is there an MRI package that allows you to swap out different templates for brain segmentation (using template from 17 vs 22 year old person)? brain extraction software
Relevant answer
Answer
Hi
Have a look at FMRIB FSL. There is also a large amount of atlases registered on MNI template.
Good luck.
  • asked a question related to PET Imaging
Question
5 answers
As you may know we can use FDG-PET scans for evaluating tumor metabolism. There is a parameter named SUV for PET images that can be used as a measure for metabolic energy evaluations. I wonder if we can use SPECT scans instead? If yes, is there any measure like SUV for SPECT as well?
Relevant answer
Answer
Dear Dr. Ramakrishnan  and dear Dr. Bradshaw
Thanks for your answers. Dr. Ramakrishnan is right, I am looking for a metric to find metabolic energy distribution (metabolic map) in the  tumor. So I need a tracer that is involved in metabolic process of tumor cells. But I only have Tl and Tc SPECT :(
  • asked a question related to PET Imaging
Question
3 answers
does anyone have experiences with the direct influence of the reconstruction matrix on the SUV in µPET? should one correct for that?
Relevant answer
Answer
The larger the reconstruction matrix, the lesser the so-called tissue-fraction effect will be. Indeed this phenomenon is due to the fact that each image pixel may represent the contribution of different tissue, and is more pronounced with larger pixels / voxels. The only interest in going for a smaller reconstruction matrix is to reduce pixel noise level, but this will be at the expense of increased resolution (i.e., partial volume) effects, hence  potentially leading to lesser SUV values. It all comes down to that infamous accuracy / precision trade-off.
  • asked a question related to PET Imaging
Question
5 answers
A couple of radiotracers we developed (C-11 and F-18 labeled) undergo extensive metabolism (less than 10 % intact tracer after 30 min pi). However, the radiometabolites didn't cross the BBB (hence no effect on the image acquired). In biodistributions study, we were also able to block 70 % to 90 % of the binding of the radiotracers in the target organ at 30 min pi with a structurally unrelated/different and validated compound. Hence, this rules out the contribution (significant) radiometabolites on the observed retention of radioactivity in the target organs. 
Here is the problem. Can this be considered a significant drawback of the radiotracers as a potential PET tracers? Could anyone give me a feedback on this (including citation will be a plus).
Any help is greatly appreciated. 
Relevant answer
You would need to establish how the metabolite formation is influenced by other factors.
I have worked on a tracer (11C-SA4503) which has low (but not as low as in your case) intact parent at 90min, and the metabolite does not cross BBB. The metabolite formation was influenced, at least preclinically, by various factors- age, treatment, species under consideration etc. This meant that kinetic modelling and metabolite correction was required for every study, which is not ideal as you can imagine. Metabolite correction is not exactly something you would want to do regularly in clinic, but if there are no better tracers for that particular purpose it will be used anyway. If another tracer comes along that does not require metabolite correction, but is otherwise similar, that would be preferred. 
  • asked a question related to PET Imaging
Question
4 answers
hello. We want to measure the radiation dose with Nipam gel. As an imaging modality CT scan offered good results. Now there is some problems with image quality and linearity with absorbed dose when we take the image with C-arm device. dose anyone have the same experience about feasibility of using C-arm? please inform me. Thank you .
Relevant answer
Answer
i appreciate your considerations.
  • asked a question related to PET Imaging
Question
8 answers
I found an equation that reads: SUV(t) = Activity concentration (t) / (Injected activity / Body weight ), which implies that the activity concentration is not decay corrected, is this true?
Relevant answer
Answer
Look at the Decay Correction flag in the DICOM header (0054,1102). 
NONE = no decay correction
START= acquisition start time
ADMIN = radiopharmaceutical administration time
  • asked a question related to PET Imaging
Question
5 answers
I do not have experience working with PET scanners for patients so I don't know if the software automatically corrects for the branching ratio of the nuclide. Most of the conventional nuclides have positron branching ratios close to 100% (18F, 11C, 68Ga) so the branching ratio does not affect the computation significantly. However, since the positron branching ratio of 64Cu is 17.6%, 5.5 mCi of 64Cu emit the same amount of 511 keV gammas as 1 mCi of 18F and in this case the computation could be off by a factor of 17.6/96.7 = 0.18. For instance if a subject is injected with 5.5 mCi of 64Cu and a lesion captures 100 %ID, the software could potentially assume that the lesion captured only 1 mCi (assuming it is 18F) and since the injected activity is 5.5 mCi 64Cu the software could assume that the %ID was 18% instead of 100%. I ask this because it seems to me that the SUV values for 64Cu and 89Zr reported in the literature are low, as if the positron branching ratio is not being considered.
Relevant answer
Answer
PET scanners in our centre (GE Discovery 710, Siemens mMR) will correct for the positron branching ratio. When you select the isotope, the overall calibration factor of the scanner is adjusted by the branching ratio. Older scanners might not have these presets, but you could verify this for yourself on your system if you scan a phantom with a known activity concentration and see what you get in the images. 
  • asked a question related to PET Imaging
Question
6 answers
I have a FDG18 brain PET data set. In order to better visualize and quantify the FDG uptake in different regions, I want to perform a statistical parametric mapping. But it seems that the SPM package requires control group to formulate the template. After searching online, it seems that neurostat/3d-ssp does not require the user defined template. But somehow, it cannot be downloaded now.  So I want to know which packages you guys use to perform statistical parametric mapping without control group. 
Thanks very much.
Relevant answer
Answer
MedINRIA is great to normalize PET data on a given template. In addition, this one is free : https://med.inria.fr/
  • asked a question related to PET Imaging
Question
9 answers
I have these set of images:
  1. MRI images and MRI-ac attenuation maps
  2. CT images and CT-ac attenuation maps
  3. PET reconstructed with attenuation correction maps from CT (PET-CTac)
  4. PET reconstructed without attenuation correction maps from CT or uncorrected PET
The images were acquired with:
PET/CT GEMINI TF TOF 16, Philips
MRI TrioTrim 3T, Siemens
The MRI-ac and CT-ac sets are co-registered to the PET images.
I want to reconstruct the PET images using the attenuation correction maps formed from the MRI images (MRI-ac). The attenuation maps from the MRI were obtained by segmenting the MRI images and assigning to the different classes/tissues their known attenuation coefficients values.
The goal is to compare both reconstructed PET images: PET-CTac and PET-MRac.
I naively changed the pixel data of the CT-ac images with those from the MRI-ac (the header files were kept identical, dicom images) and I tried to make the reconstruction using the proprietary software of the PET/CT scanner. The idea was to use the same parameters that were used to perform the reconstruction of the PET-CTac images and to have a valid point of comparison, but it did not work. The scanner does not accept these new images (MRI-ac).
So, I was wondering if someone could tell me how to perform the reconstruction of the PET images using the MRI-ac attenuation maps and the proprietary software of the PET/CT scanner or with another method/software/libraries?
Or perhaps, is there a simple method to perform attenuation correction on the uncorrected PET images using only the MRI-ac maps without making the whole process of reconstruction again?
Any insight will be helpful,
Thanks.
Relevant answer
Answer
Dear Jorge,
it did these kind of reconstruction with the Philips Ingenuity PET/MR (using external attenuation images). I used a special recon protocol provided by Philips (EXAC reconstruction protocol). EXAC stands for external attenuation. This protocol allows you to use externally genererated attenuation images.
I think the best way would be to ask Philips about this recon protocol.
Georg
  • asked a question related to PET Imaging
Question
26 answers
Are you a family physician or pediatrician? if yes, what would be your main reasons to request an advanced imaging test in pediatric patients?
(Please consider orthopedic cases only)
Thank you!
Relevant answer
Answer
this is so easy to answer in hindsight with the retrospectoscope. Or even better on a desk running analysis on a population based retrospective study....however in real life where physicians must decide, in broad day light or night alike; some times under time pressure, some times biased by a recent case, sometimes afraid of medicolegal implications ....it becomes harder to only order the best exam
off course there will be overuse, how else can one be sure that all necessary examinations have been carried out... 
and yes it is frustrating that we have examinations and time and effort spend when in hindsight it could have been done without... however ...better safe than sorry and first don't harm are still relevant 
  • asked a question related to PET Imaging
Question
1 answer
Professor Dr. Carala
Relevant answer
Answer
I do not think it is pretreated
  • asked a question related to PET Imaging
Question
3 answers
Is PET scan of any good in this?
As this is not an animal trial, I would be happy to know whether any non-invasive sensitive tool is available?
Thank you 
Relevant answer
Answer
The only approach that one uses with human beings is based on beta cells/islet response to insulin secretory stimuli (primarily glucose). This method has its limitations because of obvious reasons where altered secretion or function of insulin for any reason will effect the secreted insulin levels and given that there is considerable reserves of insulin, in a typical test duration, it is difficult to reliably link the insulin levels (are under the curve etc.) to a specific number of beta cells.
Even if invasive procedures procedures could be contemplated, needle biopsy is not very likely to give an overall picture due to difference in composition of islet cells between head a tail of pancreas. 
As you alluded to, in experimental animals PET has been used for estimates islet mass by loading the animals with labeled compound (dihydrotetrabenazine and fluoropropyl analogue -  DTBZ) that target vesicular monoamine transporter in beta cells. I do recall a clinical trial by Columbia U but I am not sure about the outcome. Perhaps you could search through NIH website.
You may want to give the following review a quick read:
Estimation of -Cell Mass by Metabolic Tests
Necessary, but How Sufficient?
  • asked a question related to PET Imaging
Question
1 answer
I used a general protocol using multiple regression (treshold masking 0.8, no global calculation,..). Moreover, I get the same (whole brain) cluster when I perform correlations with other behavioral tests. Has any of you experienced the same problem and found a solution to the problem?
Relevant answer
Answer
Dear Melissa,
I had the same problem for fMRI analysis in the SPM. They are probably two problems; i.e. estimation parameters in the preprocessing stages, and standard brain masks and templates in SPM. I found useful information in the following paper for my case (fMRI). Further, I think that the last version of SPM (version 12) is more trustable than the old one for processing the brain data sets.
I wish that my information will be useful for you. 
Best Regards,
Tony.
P.S. Paper: Michal Mikla, Radek Mareček, Petr Hluštík, Martina Pavlicová, Aleš Drastich, Pavel Chlebus, Milan Brázdil, Petr Krupa: Effects of spatial smoothing on fMRI group inferences. Magnetic Resonance Imaging 26 (2008) 490–503.
  • asked a question related to PET Imaging
Question
7 answers
I want to correct a FDG-PET image by using the corresponding MRI information. I tried this software SFSRR developed by Miho Shidahara et al. But it failed in the last step. The output image contained only NaN values. Anyone has an idea about this problem? Do you know any other convenient software that can do this job? Thank you in advance!
Relevant answer
Answer
PVELab was developed specifically for partial volume correction (PVC). It is free, but it needs  Matlab environment.
PMOD offers same PVC algorithms as PVELab, although minor differences may exist (for instance, PMOD offers more options for estimating the intensity value of white matter). By the way, PMOD requires licence fee.
I also tried the SFSRR package, unfortunately, I can hardly complete the whole procedure.
  • asked a question related to PET Imaging
Question
3 answers
I am wondering if anyone could suggest standard databases for PET images with ground truth showing inside and outside the lesions (e.g contour or coordinate). 
Are there any CT and PET dataset together with ground truth?
Thanks!
Relevant answer
Answer
  • asked a question related to PET Imaging
Question
2 answers
Does anyone happen to have (or know of) data on both features and exemplars for a particular concept combination and also for its two constituents? (e.g. feature and exemplar data on PET, feature and exemplar data on FISH, and feature and exemplar data on PET FISH?) There is lots of partial data but we are looking for a complete data set of this kind. 
 
Many thanks in advance. 
Liane
Relevant answer
Answer
James Hampton (City university of London) has done a lot on the conceptual combination issue.
Or Geert Storms in Leuven Belgium. I think that Geert has some norms on this. It sounds familiar.
  • asked a question related to PET Imaging
Question
2 answers
In the context of MCI and Alzheimer's research.
Relevant answer
Answer
Hi Roberto,
The biggest pro of florbetapir is the longer half-life. F18 compounds are for many sites the only choice. As a consequence, F18 compounds are the standard in clinical trails. Thus. for now, PiB might still be used in most publications, but this might already be old news and is sure to change in the near future.
As mentioned, the biggest pro of PiB is that has been used the longest. It might have slightly beter sensitivty, but this is not the biggest issue when measuring patients with MCI and AD. (See http://www.ncbi.nlm.nih.gov/pubmed/23166389). Yet, when you are interested in cognitively normal older adults and working in "grey-zone" between Amyloid +/-, I would prefer PiB over florbetapir. See supplemental materials http://www.ncbi.nlm.nih.gov/pubmed/24748674
The more difficult issue is that there are many other F18 compound and some of them are better than others. These other compounds also differ in off-target binding, but I know very little about that.
Good luck - and love to hear what you are planning.
Willem
  • asked a question related to PET Imaging
Question
2 answers
Any experience in T2* sequence of thalassaemia for detection of iron overload on the heart on toshiba MRI machine ??
Relevant answer
Answer
Hi Rasha, I know Heart Institute (INCOR) from Sao Paulo, Brazil, has that machine. Try to find some researchers from that institution, the most well known is Carlos Rochitte and also Cesar Nomura. They have profiles in ResearchGate. Best of luck.
  • asked a question related to PET Imaging
Question
12 answers
Some molecules are secreted from the gastro-intestinal mucosa to the gastro-intestinal lumen, and eventually ends up in the feces. Some positron emission tomography (PET) tracers may be secreted into the GI-lumen in this fashion, and therefore potentially confound the use of these tracers for imaging cancers and other pathology in  the GI-tract. I would appreciate some good references for papers or book chapters, which describe the principles and mechanisms of this type of secretion. Thanks. 
Relevant answer
Answer
  • asked a question related to PET Imaging
Question
3 answers
68Ga is a PET radioisotope used to label antibodies, DOTA, etc.
Relevant answer
Answer
Thank you. Please be aware the Eckert Ziegler has filed a Drug Master File with USFDA for their Ge68/Ga68 Generator
  • asked a question related to PET Imaging
Question
7 answers
Our centre using GE Discovery ST scanner with an 8-slice CT unit for PET/CT - 3D acquisition; and Philips Brightview XCT for SPECT/CT. Our images was grainy and full of scattered photon. 
Relevant answer
Answer
There are several approaches to retrieve good images. Thirst question is what do you really need/expect? You won't get any SUV from PET/CT until you made your own calibrations and very time consuming scans. To get nice images we use 25-30 min per bed position (about 18 cm with Philips Gemini TF and Time of Flight) for patients. I know that Philips was working on a calibration factor so that you can easily choose Y-90 like F-18 or Ga-68 in the acquisition protocol. I'm not sure if they succeeded or if such a calibration factor is available from GE. Maybe you've to contact GE Service. SPECT/CT is well described in several papers. One method is to use medium energy collimators and a wide energy window (20-30%) @75 keV to use Bremsstrahlung for imaging. This works fine for our Siemens Symbia T6 with 60 Frames over 360 degree with 15s per frame, continuous acquisition mode and auto contour. Reconstruction is 3DOSEM 8 iterations and 8 subsets and no filtering. It is necessary to perform scatter and attenuation correction. Maybe you have to set the energy to 75 keV for scatter and attenuation correction as well in your recon protocoll. I want to make clear that this is for routine use in patients, not for quantifying activity concentrations. There you may have to add more frames and more time per frame and play a little with reconstruction parameters. Hope this helps.  
  • asked a question related to PET Imaging
Question
9 answers
other than FDG.
Relevant answer
Answer
PBR28 compound of either [18F]fluoromethyl-PBR28 or [11C]PBR28 have been used to study Parkinson's disease. A recent study described its use to image a biomarker translocator protein (TSPO): Bioconjugate Chem., 2014, 25: 442-450.
  • asked a question related to PET Imaging
Question
3 answers
Hi all,
I'm working my way through the evidence base on decision making theory in clinical reasoning. There's obviously a myriad of models. Is anyone familiar with where current thinking lies? I'm particularly interested in making decisions using medical imaging.
Any thoughts or recommend articles would be appreciated.
Mark
Relevant answer
Answer
Hi Rabin,
Thanks for your really detailed response I've been doing some reading around dual process theory (Pat Croskerry has written a couple of nice articles), but haven't come across the naturalistic model, so I'll look that up thanks.
I'm working up an observational study investigating how clinical staff review images and make clinical/patient management decisions in the oncology setting.
I'll check out those references thanks and would appreciate any other thoughts you have.
Good luck with the publication
Best wishes
Mark
  • asked a question related to PET Imaging
Question
5 answers
It is very much operator dependent and has an impact on quantitative measurement.
Relevant answer
Answer
The ground truth is always pathology. The sensitivity and specificity of an agent is always measured against the ground truth. Brain surgery after PET imaging is often done and helps prove the utility of certain agents. Though MRI is the gold standard for brain tumors, the contrast enhanced MRI does not specifically image brain tumor cells but the result of infiltrated tissue ie. Build up of fluid 
  • asked a question related to PET Imaging
Question
1 answer
I would like to know if spleen, liver, salivary glands, adrenals etc take up the tracer - i.e. if the human tracer has cross-species affinity
Relevant answer
Answer
Not 90% sure; but I think so. Take a look at: Nuclear Medicine and Biology 30 (2003) 253–260, P. Bernhardt et al
  • asked a question related to PET Imaging
Question
3 answers
I am trying to do a multimodal registration. For that I am in need of CT and PET images of brain tumors. Can someone send me a list of websites where I can get them from?
Thanks in advance..
Relevant answer
Answer
How  would  you  be  able  to  effectively  use  images  which  parameters  for  generating  them  you  might  not  know? Shouldn't  it  be  better  for you  to  generate  some  yourself  and  use  them  as  guide/standards?
  • asked a question related to PET Imaging
Question
10 answers
As far as I know, within several min after injection activity absorption would be in the highest value possible. What is "the" value in (Mbq/ml or mCi/ml) ?
Relevant answer
Answer
Quantification in terms of Bq/ml is usually only performed by a solid state camera (rotating heads are not fast enough to pick up the dynamics involved). Using a DSPECT system with 99mTc-MIBI, peak myocardial activity concentration is on the order of 5 Bq/ml (with injection of 800 MBq), while of course the input function from the ventricle should be much higher. These numbers are patient-dependent, but are certainly on the order of Bq/ml for SPECT (only 2% of MIBI is taken up in the myocardium), even in PET studies a maximum of few hundred kBq/ml are to be expected (depending on tracer of course)
A recent paper from UCL in London explains myocardial perfusion quantification in SPECT further:
Hope it helps
  • asked a question related to PET Imaging
Question
10 answers
In some papers they say dynamic SPECT provides a better contrast between normal and decreased flow regions than can be obtained from static imaging. what are the other advantages,if any?
Relevant answer
Answer
Well, in recents papers (such as Glenn Wells et al. 10.2967/jnumed.114.139782) the potential of fast cardiac SPECT cameras to acquire in a dynamic way to "track" the delivery  and uptake of perfusion agents is investigated (i.e. the tracer is injected while the patient is sitting/lying in/under the camera). Based on such data, quantification of absolute myocardial blood flow similar to PET would be possible. Theoretically this allows - amongst others advantages - the detection of balanced three vessel disease as the stress flow is reduced in absolute terms (ml/min/gram) but the (static) images look almost normal. The problem, however, is that conventional SPECT tracers are much less extracted by the myocardium as typical PET agents - thus this quantification is much less reliable.
  • asked a question related to PET Imaging
Question
6 answers
In PET imaging, anatomical expertise is essential because images are so fuzzy. I'm involved in a project where we want to automatically detect cancer lesion (for instance, lymphoma nodes) using PET/CT imaging. Lesions typically don't show up in the CT but the CT could be used for registering an anatomical model, for instance using the skeleton information, which would then be used to weed out false positives based on the location. For instance, the heart and liver show up prominently in the PET result, but there isn't any lymph nodes in either. Is there any work where an anatomical model is used in such a context? Thanks for any pointers.
Relevant answer
Answer
Thanks for all the good answers. We cannot rescan the patients in an MRI, we only have an anonymized database of PET+CT exams. This is true that the CT is mostly used for the attenuation but clinicians do use it for anatomical reference as well.
  • asked a question related to PET Imaging
Question
2 answers
K1 and k2 are cardiac kinetic parameters which define wash-in and wash-out rate in a compartmental model of the cardiac muscle. j1 and j2 are two coefficients which are related to K1 and k2. using equation Count=-C1.exp(-j1.t)+C2.exp(-j2.t) time-acitivity curve for myocardium can be plotted which shows washin and washout rate of myocardium, but as far as I know K1 and k2 are somehow different from j1 and j2.
Relevant answer
Answer
Dear Etienne,
as far as I know in a one compartment model, input function must be convolved with K1.exp(-k2.t) which is transfer function of the model.
how many TACs are there in a one compartment model of myocardium? I think in this model there is just one TAC which can be described by the equation C1.exp(-j1.t)+C2.exp(-j2.t)
also,the shape of input function is the way that it can be plotted using this equation. so maybe to have myocardium TAC the equation C1.exp(-j1.t)+C2.exp(-j2.t) must be convolved with the transfer function.
I would be glad if you let me know what you think about it.
M.Reza
  • asked a question related to PET Imaging
Question
8 answers
We are comparing MR, 99mTc-tetrofosmin, and FDG in assessing viability in a day protocol.
Relevant answer
Answer
Hi,
this might serve as a starting point:
Effect of diabetes mellitus on myocardial 18F-FDG SPECT using acipimox for the assessment of myocardial viability. Schinkel AF, Bax JJ, Valkema R, Elhendy A, van Domburg RT, Vourvouri EC, Bountioukos MA, Krenning EP, Roelandt JR, Poldermans D.
J Nucl Med. 2003 Jun;44(6):877-83.
We do a hyperglycemic clamp in order to maximally standardize the measurement; but I would not say that this is simple ;)
Best regards
Stephan
  • asked a question related to PET Imaging
Question
9 answers
If different isotopes (11-C, 89-Zr, 64Cu) are used to label different antibodies, can they all be used at the same time during PET imaging? Or because all of them undergo Beta+ decay and produce Gamma rays, is it not possible to distinguish between signals coming from the different probes?
Relevant answer
Answer
It might be possible to distinguish the contribution of the two radioisotopes to the images on the basis of their kinetics in the brain. If you have two ligands with well characterised kinetic profiles, then your tissue concentration of ligand build-up will be comprised of a sum of these two profiles. If sufficiently different, you could model this mathematically: the impulse response in the tissue would be a sum of two exponentials rather than one. Non-linear least squares algorithms are best suited for this sort of component analysis. Spectral analysis and principle component analysis of time-activity curves is already being used to look at PET ligand binding to two separate subtypes of the GABA receptor, so it is doable!
In this kind of analysis, the difference in isotope is not important, just the difference in brain behaviour. In fact, doing it with two different isotopes would make things harder: you could do the ligand comparison, but quantification would be hard given your problem with decay-correction.
  • asked a question related to PET Imaging
Question
33 answers
When searching for a method to compare two medical images, e.g. to determine how similar they are or how much and where they differ, I came across several proposals. A simple subtraction image + width of histogram or entropy, crosscorrelation or joint histograms to name some of them. Nevertheless, I wonder if there is something like a standard method? And if not, it might be worth to discuss what could be a sensible approach.
Relevant answer
Answer
There are a few ways with which you may compare similarity of images:
The stuctural similarity index (SSIN) is a good method proposed by Bovik et al. There are also other traditional metrics such the MSE, SNR, PSNR and many more.
You may find a complete analysis of all these metrics in a recent publication from our group:
C.P. Loizou, C. Theofanous, M. Pantziaris, T. Kasparis, “Despeckle filtering software toolbox for ultrasound imaging of the common carotid artery”, Comput. Meth. & Progr. Biomed., vol. 114, pp. 109-124, 2014. Best paper, editor’s choice.
There is also a software available to download with which you can perform analysis and get similarity meausres between images. You may download this from the researchgate.
  • asked a question related to PET Imaging
Question
2 answers
If so, what is the most common method for denoising?
Relevant answer
Answer
If you do a post filtering or not depends on what you want. Modern PSF reconstructions will enhance your contrast and special resolution (at least they are told to) but it is known that they are more infulenced by noise (e.g. gibbs artefacts). No post filter is good for sharp images but if you use the maximal pixel value (SUVmax) it will be less reproducible than with post filtering. For quantitative measurements post filtering could help. If you do not want post filtering you could use the mean pixel value of an threshold segmentet area or the mean of a fixed area around the max pixel. These values are more stable concerning noise.
TOF reconstructions should reduce noice, but I can't quantivy that reduction.
A common setting for post filtering is a Gaussian filter with 5mm FWHM
In Siemens PET/CTs nowadays monstly the TrueX algorithm (PSF) is used with no post filtering (Allpass). If the "Iterativ" algorithm (without PSF) is used mostly a 5mm FWHM Gaussian filter is used.
GE is using VUE POINT HD or TF(meaning TOF) and you can switch the PSF on and off (SHARP IR on/off). GE uses a Gaussian post filter. I think the recommended FWHM is 6.3mm (entered in the field Cut Off). The Z-Axis filter is a Axial 1:N:1 filter with N=2 (Heavy), N=4 (Standard), N=6 (Light).
For Philips i don't know a common setting. I didn't solve the mysteries of the examination cards till now but i am looking forward that i will somewhen.
The question post filtering or not can't be answert.
The importent thing is that post filtering is changing your measurements. You should be always aware that every change in recon setting or filter setting will influence the outcome. Therefor the choice of settings should be made in accordance with the things (measurements) you want to compare to.
E.g. if you want to monitor therapy response, you must not change the settings between the two studies because you would get values which are not comparable.
greetings
Ivo
  • asked a question related to PET Imaging
Question
7 answers
A 46 yr old presented with a 3x2 cm lump in the upper outer quadrant, with just palpable axillary lymph nodes. PET scan done suggests a hot lesion in the breast with non FDG avid nodes in axilla, but the mediastinum has two hot nodes (1cm ) with a SUV of 5. Is this stage IV?
Relevant answer
Answer
I agree that biopsy from mediastinal LN is needed. However, If the mediastinal LN are involved, I doubt that there is a benefit of treating her with curative intent. In most studies that investigated surgical resection of oligometastatic sites, mediastinal LN involvement was associated with significantly inferior prognosis, this applies to variety of carcinomas that metastasize to mediastinal LN.
  • asked a question related to PET Imaging
Question
8 answers
(not necessarily the best)
Relevant answer
Answer
The most used algorithm in emission tomography is the ML-EM (Maximum Likelihood Expectation Maximization) (Shepp and Vardi, 1982) and it's accelerated version OS-EM (Hudson and Larkin, 1994).