Absolute quantitation of a spherical I-131 activity distribution using a high-resolution rotating collimator: a phantom study

Trotter, D. E. González; Bowsher, J.E.; Jaszczak, R.J.

doi:10.1109/23.910834

Cited by 10 publications

(6 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…are not modeled within image reconstruction, approximately the same results are obtained using the summed data of Figure C2(b) as using the ideally spatially invariant projections of Figure C2(c). Hence these results are consistent with those in [7][8][9], where good image quality was obtained using summed rotating collimator projections together with standard filtered back-projection (FBP) and iterative reconstruction methods that do not model the thick septa. Figures C3 and C4 show superior spatial resolution recovery when the projections of Figure C2(a) and the projections for the corresponding 120-and 240-degree rotations are left unsummed and the thick septa are modeled within image reconstruction.…”

Section: De-fg02-96er62150supporting

confidence: 88%

Final Progress Report: SPECT Assay of Radiolabeled Monoclonal Antibodies

Jaszczak¹

2004

View full text Add to dashboard Cite

Section: De-fg02-96er62150supporting

confidence: 88%

Final Progress Report: SPECT Assay of Radiolabeled Monoclonal Antibodies

Jaszczak¹

2004

View full text Add to dashboard Cite

“…Single-photon emission tomography (SPET) imaging is often used to quantify iodine-131 tumor uptake in patients following radiopharmaceutical therapy [1,2,3,4]. SPET quantification accuracy is affected by many factors, including attenuation, scatter, and finite spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo evaluation of object shape effects in iodine-131 SPET tumor activity quantification

2001

View full text Add to dashboard Cite

In our clinical iodine-131 single-photon emission tomography (SPET) quantification for radioimmunotherapy, calibration and partial volume correction are based on measurements with phantoms containing spheres to simulate patient tumors even though real tumors are frequently nonspherical. In this study, Monte Carlo simulation was used to evaluate how object shape influences "spill-out" and "spill-in", which are major sources of quantification error associated with the poor spatial resolution of 131 I SPET. Objects that varied in shape (spheres, cylinders, and an irregular structure) but were identical in activity and volume were simulated. Iterative reconstruction employed both attenuation and triple-energy-window scatter compensation. VOIs were defined in the reconstructed images both using physical boundaries and using expanded boundaries to allow for the limited resolution. When physical boundaries were used, both spill-out and spill-in were more significant for nonspherical structures than for spherical structures. Over the range of object volumes (50-200 ml) and at all background levels, VOI counts in cylinders were lower than VOI counts in spheres. This underestimation increased with decrease in object size (for the cold background −18% at 200 ml and −39% at 50 ml). It also decreased with increase in background activity because spillin partially compensated for spill-out. It was shown that with a VOI larger than physical size, the results are independent of object shape and size only in the case of cold background. Activity quantification was carried out using a procedure similar to that used in our clinic. Quantification of nonspherical objects was improved by simple sphere-based partial volume correction, but the error was still large in some cases (for example, −39% for a 50-ml cylinder in a cold background and −35% for a 200-ml irregular structure defined on the basis of a typical tumor outlined on an X-ray computed tomography scan of a patient with non-Hodgkin's lymphoma). Partial volume correction by patientspecific Monte Carlo simulation may provide better quantification accuracy.

show abstract

“…Deconvolution scatter subtraction also has the effect of correcting for the geometric response of the collimator [37], which further decreases count density. Geometric response includes septal penetration, which increases with energy and, in the case of 131 I imaged with a medium-energy collimator, can lead to a 10-40% overestimation of reconstructed activity [38]. Conversely, attenuation correction increased count density, especially for lower energy gamma rays due to the energy dependence of attenuation coefficients.…”

Section: Discussionmentioning

confidence: 98%