Characterizing the contribution of cardiac and hepatic uptake in dedicated breast SPECT using tilted trajectories

Perez, Kristy L.; Cutler, Spencer J.; Madhav, Priti; Tornai, Martin P.

doi:10.1088/0031-9155/55/16/007

Cited by 8 publications

(7 citation statements)

References 35 publications

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“…The tracer uptake that we assumed in different organs is listed in table 1. These are typical numbers found in practice if 925 MBq 99m Tc-Sestamibi is injected to the patient (Wackers et al 1989, Maublant et al 1996, Brzymialkiewicz et al 2005, Hruska and O'Connor 2008a, 2008b, Perez et al 2010.…”

Section: Projection Image Comparisonmentioning

confidence: 86%

Voxelized ray-tracing simulation dedicated to multi-pinhole molecular breast tomosynthesis

Wang

Roosmalen

Piët

et al. 2017

Biomed. Phys. Eng. Express

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Accurate gamma photon transport simulations of emission tomography systems are important to optimise system geometries and for iterative image reconstruction. Monte Carlo simulation (MCS) is widely established for this purpose but has the disadvantage of being prohibitively slow. Voxelized ray tracing (VRT) can be used as an alternative but the accuracy of VRT needs to be assessed for each simulation task at hand. The aim of this work is to propose and validate a dedicated VRT code for a novel radionuclide-based multi-pinhole molecular breast tomosynthesis (MP-MBT) scanner. The MP-MBT system images radionuclide distributions in a mildly compressed breast using two opposing gamma cameras, each equipped with a focusing multi-pinhole collimator, that slide along opposite sides of the breast. VRT simulates gamma photon transport by tracing rays efficiently through the voxelized phantom, collimator, and detector volumes using Siddon's raytracing algorithm, accelerated by dual-grid methods. To assess its accuracy, we compare point spread functions (PSFs) calculated with VRT for different voxel sizes with those generated by the established MCS toolkit GATE. Furthermore, VRT and MCS-simulated projections of realistic anthropomorphic XCAT phantoms with different compressed breast sizes are compared, as well as reconstructed images obtained from these projections. With VRT, PSFs for MP-MBT can be simulated accurately when the fine voxel size of the VRT's dual-grid is 1/8 mm. Reaching a similar deviation from noiseless PSFs takes 29 300 times longer with full MCS than with VRT. Furthermore, XCAT phantom simulations show that VRT-generated projections are very close to MCS-generated low-noise projections when these are corrected for scatter by the triple energy window method. However, we also find that primary gamma photons from the torso may in some cases reach the detector, meaning that torso activity should not be neglected in VRT. Finally, reconstructed images obtained from projections generated by VRT and MCS are visually very similar and have no significant difference in contrast and noise characteristics. We conclude that VRT can accurately and efficiently simulate MP-MBT even though it neglects scattered photons originating from the torso.

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Section: Projection Image Comparisonmentioning

confidence: 86%

Voxelized ray-tracing simulation dedicated to multi-pinhole molecular breast tomosynthesis

Wang

Roosmalen

Piët

et al. 2017

Biomed. Phys. Eng. Express

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“…The k value was calculated at each position for five simulated trajectories (Fig. 4): 0 deg, 15 deg, 30 deg, and 45 deg fixed tilt trajectories, as well as a variable tilt trajectory that minimizes direct views of the heart and liver, 27 and is currently used in all clinical studies with our system. 35 Figure 11 shows plots of the measured k values at each detector position for the simulated trajectories.…”

Section: Resultsmentioning

confidence: 99%

“…These organs are important to include due to the preferential clinical uptake of MIBI in these organs (Table 1) and their proximity to the breast. 10,27 The torso, liver, and heart tissues were modeled as tissue-equivalent materials. 28 For the breast, a symmetric hemiellipsoid with semimajor and semiminor axis lengths of 10 and 6 cm, comparable to the average observed pendant breast size, 29 was placed at the center of rotation, excluding the volume of the ellipsoid intersecting the torso.…”

Section: Methodsmentioning

confidence: 99%

Characterization of simulated incident scatter and the impact on quantification in dedicated breast single-photon emission computed tomography

Mann

Tornai

2015

J. Med. Imag

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Abstract. The objective was to characterize the changes seen from incident Monte Carlo-based scatter distributions in dedicated three-dimensional (3-D) breast single-photon emission computed tomography, with emphasis on the impact of scatter correction using the dual-energy window (DEW) method. Changes in scatter distributions with 3-D detector position were investigated for prone breast imaging with an ideal detector. Energy spectra within a high-energy scatter window measured from simulations were linearly fit, and the slope was used to characterize scatter distributions. The impact of detector position on the measured scatter fraction within various photopeak windows and the k value (ratio of scatter within the photopeak and scatter energy windows) useful for scatter correction was determined. Results indicate that application of a single k value with the DEW method in the presence of anisotropic object scatter distribution is not appropriate for trajectories including the heart and liver. The scatter spectra's slope demonstrates a strong correlation to measured k values. Reconstructions of fixed-tilt 3-D acquisition trajectories with a single k value show quantification errors up to 5% compared to primary-only reconstructions. However, a variable-tilt trajectory provides improved sampling and minimizes quantification errors, and thus allows for a single k value to be used with the DEW method leading to more accurate quantification.

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“…However when imaging the irregularly shaped breast, the TPB trajectory yielded the well-known, distorted data that was not as accurately quantified as the VAOR and PROJSINE trajectories. Less extreme tilt for the TPB trajectory has indeed shown less distortion [14], which could lead to better quantification with that trajectory. Moreover, use of attenuation or scatter correction in such a clearly distorted reconstructed volume doesn’t make sense.…”

Section: Discussionmentioning

confidence: 99%

Towards Quantification of Functional Breast Images Using Dedicated SPECT With Non-Traditional Acquisition Trajectories

Perez

Cutler

Madhav

et al. 2011

IEEE Trans. Nucl. Sci.

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Quantification of radiotracer uptake in breast lesions can provide valuable information to physicians in deciding patient care or determining treatment efficacy. Physical processes (e.g., scatter, attenuation), detector/collimator characteristics, sampling and acquisition trajectories, and reconstruction artifacts contribute to an incorrect measurement of absolute tracer activity and distribution. For these experiments, a cylinder with three syringes of varying radioactivity concentration, and a fillable 800 mL breast with two lesion phantoms containing aqueous 99mTc pertechnetate were imaged using the SPECT sub-system of the dual-modality SPECT-CT dedicated breast scanner. SPECT images were collected using a compact CZT camera with various 3D acquisitions including vertical axis of rotation, 30° tilted, and complex sinusoidal trajectories. Different energy windows around the photopeak were quantitatively compared, along with appropriate scatter energy windows, to determine the best quantification accuracy after attenuation and dual-window scatter correction. Measured activity concentrations in the reconstructed images for syringes with greater than 10 µCi /mL corresponded to within 10% of the actual dose calibrator measured activity concentration for ±4% and ±8% photopeak energy windows. The same energy windows yielded lesion quantification results within 10% in the breast phantom as well. Results for the more complete complex sinsusoidal trajectory are similar to the simple vertical axis acquisition, and additionally allows both anterior chest wall sampling, no image distortion, and reasonably accurate quantification.

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Characterizing the contribution of cardiac and hepatic uptake in dedicated breast SPECT using tilted trajectories

Cited by 8 publications

References 35 publications

Voxelized ray-tracing simulation dedicated to multi-pinhole molecular breast tomosynthesis

Voxelized ray-tracing simulation dedicated to multi-pinhole molecular breast tomosynthesis

Characterization of simulated incident scatter and the impact on quantification in dedicated breast single-photon emission computed tomography

Towards Quantification of Functional Breast Images Using Dedicated SPECT With Non-Traditional Acquisition Trajectories

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