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James R Galt

Publications and source records attributed to James R Galt.

12 recordsLinked to original sources
PubMed2006

Improved quantification in 123I cardiac SPECT imaging with deconvolution of septal penetration.

OBJECTIVES: (123)I is becoming an important radionuclide for cardiac imaging. Multiple, low-abundance, high-energy photons associated with (123)I imaging can cause septal penetration in the collimators and degrade quantification of the (123)I cardiac uptake. This study presents a method for the deconvolution of septal penetration (DSP) for improving quantification in (123)I cardiac single photon emission computed tomography (SPECT). METHODS: Distance-dependent point spread functions were measured for low-energy high-resolution collimators on a dual-head SPECT system. The measured point spread functions were used in two-dimensional (2-D) and three-dimensional (3-D) models of the collimator response, respectively. 2-D DSP and 3-D DSP were then developed and implemented using iterative reconstruction. A cardiac torso phantom with an internal calibration source was designed with various heart-to-calibration ratios (HCRs) simulating different levels of a patient's uptake. SPECT acquisitions of the phantom were performed using optimized acquisition and processing parameters for (123)I cardiac SPECT. HCRs were calculated using planar projection and tomographic reconstructions. The paired t-test and regression analysis were used to compare the HCRs given by different calculation methods. RESULTS: SPECT produced more accurate HCRs than planar imaging. The slopes of the regression lines for SPECT using filtered back-projection were statistically significantly higher than those for planar imaging (0.2118 +/- 0.0297 vs. 0.0819 +/- 0.0070, P = 0.0001). 2-D DSP and 3-D DSP yielded similar HCRs that were close to the true HCR. The slopes of the regression lines for 2-D DSP and 3-D DSP were 0.9203 +/- 0.0523 and 0.9101 +/- 0.0304, respectively. The DSP HCRs were significantly more accurate than those calculated without DSP (P < 0.0001). CONCLUSION: DSP significantly improves quantification in (123)I cardiac SPECT imaging. 2-D DSP with its less computational burden shows promise for implementation in clinical practice so as to allow the use of the widely available low-energy, high-resolution collimators for quantitative I cardiac SPECT imaging.

Algorithms↗
PubMed2006

Apical hypertrophy caused by glycogen storage disease creating artifacts in myocardial perfusion imaging.

A 46-year-old man with atrial fibrillation and coronary artery disease was referred for myocardial perfusion imaging for the evaluation of chest pain. The patient underwent adenosine stress and rest dual-isotope myocardial perfusion imaging. There was no adenosine-induced chest pain or EKG changes specific for ischemia. Myocardial perfusion images demonstrated an apical "hot spot" and decreased tracer activity in the base of the heart. The polar plots showed a bright center with a rim of significant (>2.5 SD) defect around the base of the myocardium. Ischemia in the base of the heart, with the apex of the heart seemingly normal, was rather puzzling and correlation with magnetic resonance images (MRI) showed apical hypertrophy. Examination of the history revealed that the patient was diagnosed with restrictive cardiomyopathy 2 years ago and endocardial biopsy showed intramyocardial glycogen on electron microscopy, suggesting glycogen storage disease. The case illustrates a "hot spot" resulting from apical hypertrophy creating artifactual fixed defects in myocardial perfusion images and in polar maps.

Atrial Fibrillation↗
PubMedDate not supplied

Optimized acquisition and processing protocols for I-123 cardiac SPECT imaging.

BACKGROUND: Deconvolution of septal penetration (DSP) has been developed to improve quantification so as to allow the use of low-energy high-resolution collimators for iodine 123 cardiac single photon emission computed tomography (SPECT) imaging. The purpose of this study is to optimize its acquisition and processing protocols. METHODS AND RESULTS: Planar images of a 9-compartment phantom loaded with variable radioactive concentrations were acquired to derive optimal scatter compensation scaling factors for 20% and 15% photopeak energy window configurations, respectively. A cardiac phantom, loaded with high and low heart-to-calibration ratios (HCRs), respectively, was imaged with both configurations. Repeated acquisitions were done for medium-energy all-purpose collimators for comparison. Critical frequencies for Butterworth filtering were optimized by use of defect contrast and normal short-axis uniformity as selection indices. HCRs were calculated with planar projection and different reconstruction methods, respectively, and then compared with the true HCRs. SPECT produced more accurate HCRs than planar imaging. With the optimized parameters for scatter compensation and filtering, the 2 energy window configurations yielded similar results. Iterative reconstructions with DSP yielded more accurate HCRs than other reconstructions without DSP. CONCLUSION: The optimized protocols based on DSP show promise that quantification of I-123 cardiac SPECT imaging can be achieved with the widely available low-energy high-resolution collimators.

Algorithms↗
PubMedDate not supplied

Quantitative Tc-99m sestamibi attenuation-corrected SPECT: development and multicenter trial validation of myocardial perfusion stress gender-independent normal database in an obese population.

BACKGROUND: A gender-independent stress normal database and criteria for abnormality for attenuation-corrected rest-stress technetium 99m sestamibi same-day myocardial perfusion imaging were developed by evaluation of 112 patients, validated against an obese population of 95 patients from four different clinical sites, and compared with conventional gender-matched database quantification of non-attenuation-corrected studies. METHODS AND RESULTS: These 95 validation patients (63 men) were used for prospective quantitative evaluation (mean weight, 213 +/- 57 lb; mean body mass index, 32 +/- 9 kg/m(2)). This group included 21 patients (12 men) with a lower than 5% likelihood of coronary artery disease (mean weight, 226 +/- 72 lb; mean body mass index, 34 +/- 13 kg/m(2)) and 74 who underwent cardiac catheterization within 2 months (35 with normal coronaries or coronary lesions <70%). These studies were processed twice, once by use of conventional reconstruction and gender-specific database quantification and a second time by use of attenuation correction and a single gender-independent attenuation-corrected normal database. The attenuation-corrected normal database and criteria for abnormality were developed by evaluation of 48 and 78 patients, respectively. No statistically significant differences were found when comparing attenuation-corrected perfusion distributions of normal men and women, whereas significant differences were found in the same uncorrected studies. Compared with quantitative analysis of the uncorrected studies, quantitative analysis of the attenuation-corrected studies by use of a gender-independent normal database demonstrated a significant improvement in normalcy rate (90% vs 52%, P =.006) and specificity (57% vs 29%, P =.015) in this obese population at no significant loss in sensitivity (90% vs 97%, P = not significant). CONCLUSION: Attenuation-corrected studies can be quantified with a single gender-independent normal database and a single criterion for abnormality without loss of sensitivity and with significantly better specificity and normalcy rate.

Coronary Artery Disease↗
PubMedDate not supplied

Clinical value of attenuation correction in stress-only Tc-99m sestamibi SPECT imaging.

BACKGROUND: Attenuation artifact remains a substantial limitation to confident interpretation of images and reduces laboratory efficiency by requiring comparison of stress and rest image sets. Attenuation-corrected stress-only imaging has the potential to ameliorate these limitations. METHODS AND RESULTS: Ten experienced nuclear cardiologists independently interpreted 90 stress-only electrocardiography (ECG)-gated technetium 99m sestamibi images in a sequential fashion: myocardial perfusion imaging (MPI) alone, MPI plus ECG-gated data, and attenuation-corrected MPI with ECG-gated data. Images were interpreted for diagnostic certainty (normal, probably normal, equivocal, probably abnormal, abnormal, and perceived need for rest imaging). With stress MPI data alone, only 37% of studies were interpreted as definitely normal or abnormal, with a very high perceived need for rest imaging (77%). The addition of gated data did not alter the interpretations. However, attenuation-corrected data significantly increased the number of studies characterized as definitely normal or abnormal (84%, P <.005) and significantly reduced the perceived need for rest imaging (43%, P <.005). These results were confirmed by use of a nonsequential consensus interpretation of three readers. CONCLUSION: Attenuation correction applied to studies with stress-only Tc-99m ECG-gated single photon emission computed tomography images significantly increases the ability to interpret studies as definitely normal or abnormal and reduces the need for rest imaging. These findings may improve laboratory efficiency and diagnostic accuracy.

Adult↗
PubMedDate not supplied

Transmission scan truncation with small-field-of-view dedicated cardiac SPECT systems: impact and automated quality control.

BACKGROUND: Small-field-of-view (FOV) dedicated cardiac single photon emission computed tomography (SPECT) systems will frequently exhibit severe transmission scan truncation that may degrade attenuation correction (AC). This study evaluated the impact of transmission scan truncation on AC and developed automated transmission scan truncation quality control (ATSTQC) for small-FOV systems. METHODS AND RESULTS: Small-FOV data were simulated from the data of 10 patients acquired by a full-FOV Philips Vertex system. AC images of the full- and small-FOV data were compared by mean and maximum absolute differences of myocardial counts, and differences in stress and rest severity scores were calculated by use of the Emory Cardiac Toolbox.small-FOV systems. ATSTQC was developed to identify critical truncation that significantly increased these indices and then tested with 18 independent patients. Left-side truncation resulted in significant distortion of the quantitative indices. ATSTQC, developed on the condition that left-side truncation is critical, showed high concordance with the qualitative assessment in identification of critical truncation. CONCLUSIONS: Identification of left-side truncation as critical truncation is necessary to judge whether accurate AC can be obtained. The developed ATSTQC can accurately detect critical truncation and will help clinicians decide whether to use AC in a particular study.

Artifacts↗
PubMedDate not supplied

Automated quality control of emission-transmission misalignment for attenuation correction in myocardial perfusion imaging with SPECT-CT systems.

BACKGROUND: Emission-transmission misalignment with single-photon emission computed tomography (SPECT)-computed tomography (CT) systems can impair attenuation correction (AC) in myocardial perfusion imaging. This study was performed to develop automated quality control (Auto-QC) to detect critical misalignment that can significantly impact AC. METHODS AND RESULTS: Auto-QC was developed to segment myocardium and mediastinum from emission and transmission reconstructions, respectively. Myocardium-mediastinum mismatch was used as the quality-control index (QCI). The QCI threshold for acceptable AC was determined with NCAT (NURBS [nonuniform rational B-spline]-based cardiac torso phantom) simulation and verified with 2 patients with minimal misalignment. Compromised data sets, generated by shifting the attenuation maps by 0.5, 1.0, 1.5, and 2.0 pixels along left-right, up-down, and head-foot directions, respectively, were qualitatively and quantitatively compared with the unshifted data sets. Auto-QC was tested with the 2 verification patients and 41 additional patients. Shifts by more than 1 pixel along any direction compromised AC. Auto-QC with the QCI threshold (3%) had highly concordant results with manual quality control in the detection of critical misalignment (sensitivity of 88% and 90% and specificity of 93% and 95% for the tests by use of the 2 verification patients and 41 additional patients, respectively). CONCLUSION: QCI quantitatively represented the severity of misalignment. Auto-QC can help clinicians be aware of critical misalignment and can assist in realignment of SPECT and CT images.

Algorithms↗