Jonathan Sachs

SPECT/CT hybrid imaging with 111In-pentetreotide in assessment of neuroendocrine tumours.

objective  Somatostatin receptor scintigraphy (SRS) of neuroendocrine (NE) tumours is often challenging because of minute lesion size and poor anatomic delineation. This study evaluates the impact of sequentially performed single‐photon emission computed tomography (SPECT)/CT fusion on SRS study interpretation and clinical management of these tumours.

Correction of Heart Motion Due to Respiration in Clinical Myocardial Perfusion SPECT Scans Using Respiratory Gating

Several studies have described nonuniform blurring of myocardial perfusion imaging (MPI) due to respiration. This article describes a technique for correcting the respiration effect and assesses its effectiveness in clinical studies. Methods: Simulated phantoms, physical phantoms, and patient scans were used in this study. A heart phantom, which oscillated back and forth, was used to simulate respiration. The motion was measured on a γ-camera supporting list-mode functionality synchronized with an external respiratory strap or resistor sensor. Eight clinical scans were performed using a 1-d 99mTc-sestamibi protocol while recording the respiratory signal. The list-mode capability along with the strap or sensor signals was used to generate respiratory bin projection sets. A segmentation process was used to detect the shift between the respiratory bins. This shift was further projected to the acquired projection images for correction of the respiratory motion. The process was applied to the phantom and patient studies, and the rate of success of the correction was assessed using the conventional bulls eye maps. Results: The algorithm provided a good correction for the phantom studies. The shift after the correction, measured by a fitted ellipsoid, was <1 mm in the axial direction. The average motion due to respiration in the clinical studies was 9.1 mm in the axial direction. The average shift between the respiratory phases was reduced to 0.5 mm after correction. The maximal change in the bulls eye map for the clinical scans after the correction was 6%, with a mean of 3.75%. The postcorrection clinical summed perfusion images were more uniform, consistent, and, for some patients, clinically significant when compared with the images before correction for respiration. Conclusion: Myocardial motion generated by respiration during MPI SPECT affects perfusion image quality and accuracy. Motion introduced by respiration can be corrected using the proposed method. The degree of correction depends on the patient respiratory pattern and can be of clinical significance in certain cases.

Reduction in SPECT bone imaging scan times through collimator design and accurate system modeling

The current conventional bone scan protocol involves a 15-minute whole-body planar scan followed by one or more tomographic acquisitions focused on a region of interest lasting 15 minutes or more per bed position. Through a detailed simulation study, we investigated methods for reducing the SPECT acquisition scan time while preserving lesion detection performance. We evaluated different collimator choices providing a range of sensitivity versus resolution trade-offs. We also evaluated the improvements obtained by improved system modeling (point spread function and attenuation correction) within the OSEM framework. Lesion detection performance was measured through LROC curves for a non-prewhitening matched filter (NPWMF) observer with location uncertainty. We also performed a subjective visual assessment of image quality. Our results demonstrate that acquisition times can be reduced by a factor of two over the current protocol by using an LEHR collimator pair in conjunction with attenuation correction and point spread function modeling.