Single-photon emission tomographic quantification in spherical objects: effects of object size and background

Zito, Felicia; Gilardi, Maria Carla; Magnani, Patrizia; Fazio, Ferruccio

doi:10.1007/bf00837624

Cited by 19 publications

(18 citation statements)

References 16 publications

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“…The RC depends not only on tumor volume but also on image sampling. The RC can be calculated by assuming no surrounding activity, and the uptake surrounding the tumor, which has to be estimated to compensate for spilling in, can be accounted for subsequently by use of a simple formula when the RC is applied (17)(18)(19)(20)(21).…”

Section: Correction Methods Applied At Regional Levelmentioning

confidence: 99%

Partial-Volume Effect in PET Tumor Imaging

Soret¹,

Bacharach²,

Buvat³

2007

Journal of Nuclear Medicine

1,303

953

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PET has the invaluable advantage of being intrinsically quantitative, enabling accurate measurements of tracer concentrations in vivo. In PET tumor imaging, indices characterizing tumor uptake, such as standardized uptake values, are becoming increasingly important, especially in the context of monitoring the response to therapy. However, when tracer uptake in small tumors is measured, large biases can be introduced by the partialvolume effect (PVE). The purposes of this article are to explain what PVE is and to describe its consequences in PET tumor imaging. The parameters on which PVE depends are reviewed. Actions that can be taken to reduce the errors attributable to PVE are described. Various PVE correction schemes are presented, and their applicability to PET tumor imaging is discussed.

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Section: Correction Methods Applied At Regional Levelmentioning

confidence: 99%

Partial-Volume Effect in PET Tumor Imaging

Soret¹,

Bacharach²,

Buvat³

2007

Journal of Nuclear Medicine

1,303

953

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“…However, studies addressing the magnitude of the problem in SPET activity quantification are limited, particularly with respect to object shape and nontarget activity. In addition to the work by our group with 131 I [5,6], there have been two recent studies on effects of object size on technetium-99m quantification and the use of recovery coefficients (RCs) in SPET [7,8]. In these two studies the partial volume correction models proposed by Hoffman et al [9] and Kessler et al [10] for position emmission tomography (PET) were assessed for SPET quantification of spherical objects.…”

Section: Introductionmentioning

confidence: 99%

“…Hot spot RCs (to correct for spill-out) and cold spot RCs (to correct for spill-in) were determined in calibration experiments using spheres of different sizes. Zito et al used these RCs to correct measured radioactivity concentrations in spheres for a range of object sizes and showed good agreement with the true radioactivity concentration [8]. On the other hand the work of Geworski et al demonstrated that while partial volume correction based on physical phantom studies is feasible in PET, it is subject to serious difficulties in the case of SPET [7].…”

Section: Introductionmentioning

confidence: 99%

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

2001

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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.

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“…Countbased methods [12,13,29,30] use only the maximum of the profile. They are very susceptible to background noise, and applying the recovery coefficient correction was cumbersome [12,13,31]. Geometry-based methods attempted to locate the endo-and epicardial borders by edge detection using the first [9] or second derivative [32], thresholding [1] or deconvolution [33].…”

Section: Discussionmentioning

confidence: 99%

The Effect of Finite Spatial Resolution on the Measurement of Cardiac Phantom Wall Thickness in Single Photon Emission Computerized Tomographic Imaging

Ballani

Dougherty²

2004

Med Princ Pract

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Objective: To devise and validate a method of estimating accurately myocardial wall thickness from cardiac images acquired with single photon emission tomography (SPECT). Materials and Methods: We simulated the imaging process by convolving a spatial resolution function, experimentally determined for a clinical SPECT system, with rectangular profiles mimicking the myocardial walls for different thicknesses and separations. Wall thicknesses were estimated by fitting the resulting profiles to a linear superposition of two offset Gaussians. The method was validated by extensive computer simulation and by testing on real phantom images. Results: Accurate estimates of the wall thickness of SPECT phantoms were obtained when the estimated thickness (using fitting to Gaussians) was deconvolved with the point spread function (PSF) of the imaging system using a look-up table. Conclusions: This method is a novel method of estimating wall thickness from cardiac images. It is particularly useful for small separations (e.g. at end systole and/or towards the apex of the heart) of walls that are narrow compared to the PSF of the imaging system.

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Single-photon emission tomographic quantification in spherical objects: effects of object size and background

Cited by 19 publications

References 16 publications

Partial-Volume Effect in PET Tumor Imaging

Partial-Volume Effect in PET Tumor Imaging

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

The Effect of Finite Spatial Resolution on the Measurement of Cardiac Phantom Wall Thickness in Single Photon Emission Computerized Tomographic Imaging

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