Paul E. Christian

Non-uniform attenuation correction using simultaneous transmission and emission converging tomography

Photon attenuation in cardiac single photon emission computed tomography (SPECT) is a major factor contributing to the quantitative inaccuracy and the decrease in sensitivity of lesion detection. A measured map of the attenuation distribution is used in combination with iterative reconstruction algorithms to accurately compensate for the variable attenuation in the chest. The transmission and emission data are acquired simultaneously using a multidetector, fan beam collimated SPECT system with a precisely aligned transmission line source (Tc-99m) at a different energy than the emission source (Tl-201). The contamination of transmission and emission data due to scatter and multiple photopeaks is removed based on measurements from the detectors acquiring only the emission data. The quantitative accuracy of cardiac SPECT is significantly improved using simultaneously acquired transmission and emission data which are obtained in clinically acceptable patient scanning times.<<ETX>>

Gastric emptying of varying meal weight and composition in man. Evaluation by dual liquid- and solid-phase isotopic method.

Ten subjects were given self-selected filling meals (mean weight=1692 g) and meals of 900 and 300 g. The three meals varied in composition and total kcal. Solid and liquid phase gastric emptying was evaluated using99mTc-sulfur colloid-labeled chicken liver and [111In]DTPA, and emptying was quantitated using the geometric mean of the anterior and posterior counts. Emptying of the solid-phase marker was linear; mean half-emptying times were 277 min, 146 min, and 77 min for the filling, 900-g, and 300-g meals, respectively. Emptying of the liquid-phase marker was curvilinear, mean half-emptying times were 178 min, 81 min, and 40 min, for the filling, 900-g, and 300-g meals, respectively. Thus, meals of larger weight and kcal content were associated with longer emptying times for both solids and liquids.

Effect of age on gastric emptying of liquid-solid meals in man

A dual radioisotopic method was employed to study the rate of gastric emptying of meals in ten males with an average age of 31 years and 10 elderly males with an average age ot 76.4 years. All study subjects were fed a standardized 900-g meal labeled with a liquid (111indium-DTPA) and solid (99mtechnetium-tagged liver) phase isotopic marker. There were no significant differences in solid food emptying rates between the young and aged men. A delay in liquid emptying, however, was observed in the aged men. The clinical significance of this observation is unknown.

EANM/SNMMI Guideline for 18F-FDG Use in Inflammation and Infection

1Department of Nuclear Medicine, Universite Catholique de Louvain, Brussels, Belgium; 2Department of Nuclear Medicine, Cambridge Biomedical Campus, Cambridge, United Kingdom; 3Nuclear Medicine, Istituto Clinico Humanitas, Milan, Italy; 4Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah; 5Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee; 6Department of Nuclear Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; 7Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; 8Nuclear Medicine Department, Hospital Universitario de Bellvitge, Barcelona, Spain; and 9Nuclear Medicine Unit, Faculty of Medicine and Psychology, University “Sapienza,” Rome, Italy

Review of convergent beam tomography in single photon emission computed tomography

Investigation of convergent-beam single photon emission computed tomography (SPECT) is actively being pursued to evaluate its clinical potentials. Fan-beam, cone-beam, pin-hole and astigmatic collimators are being used with rotating gamma cameras having large crystal areas, to increase the sensitivity for emission and transmission computed tomography of small organs such as the thyroid, brain or heart. With new multi-detector SPECT systems, convergent-beam geometry offers the ability to simultaneously obtain emission and transmission data necessary to quantify uptake of radiopharmaceutical distributions in the heart. The development of convergent-beam geometry in SPECT requires the integration of hardware and software. In considering hardware, the optimum detector system for cone-beam tomography is a system that satisfies the data sufficiency condition for which the scanning trajectory intersects any plane passing through the reconstructed region of interest. However, the major development of algorithms has been for the data insufficient case of single planar orbit acquisitions. The development of these algorithms have made possible the preliminary evaluation of this technology and the imaging of brain and heart are showing significant potential for the clinical application of cone-beam tomography. Presently, significant research activity is pursuing the development of algorithms for data acquisitions that satisfy the data sufficiency condition and that can be implemented easily and inexpensively on clinical SPECT systems.

Influence of meal weight and caloric content on gastric emptying of meals in man.

This study was designed to assess the relative influence of meal weight and caloric content on gastric emptying of liquid and solid meals in man. A dual radioisotopic method which permits noninvasive and simultaneous measurement of liquid-and solid-phase emptying by external gamma camera techniques was employed. Nine healthy volunteer subjects ingested 50-,300-, and 900-g lettuce and water meals adjusted to either 68, 208, or 633 kcal with added salad oil. The following observations were made: (1) absolute emptying rates (grams of solid food emptied from the stomach per minute) increased directly and significantly with meal weight; (2) increasing meal total caloric content significantly slowed solid food gastric emptying but did not overcome the enhancing effect of meal weight; and (3) liquid emptying rates were uninfluenced by meal total kcal amount.

Variability of gastric emptying measurements in man employing standardized radiolabeled meals

Radiolabeled liquid and solid portions of standardized 300-g meals were administered on four different study days to eight healthy subjects in an attempt to define the range of inter- and intrasubject variability in gastric emptying. Meal half emptying times, analysis of variance, and intraclass correlations were computed and compared within and between subjects. The mean solid half emptying time was 58±17 min (range 29–92), while the mean liquid half emptying time was 24±8 min (range 12–37). A nested random effects analysis of variance showed moderate intrasubject variability for solid emptying and high intrasubject variability for liquid emptying. The variability of solid and liquid emptying was comparable and relatively large when compared with other reports in the literature. The isotopic method for measuring gastric emptying is a valuable tool for investigating problems in gastric pathophysiology, particularly when differences between groups of subjects are sought. However, meal emptying time is a variable phenomenon in healthy subjects with significant inter- and intraindividual day-to-day differences. These day-to-day variations in gastric emptying must be considered in interpreting individual study results.

Comparison of Whole-Body PET/CT, Dedicated High-Resolution Head and Neck PET/CT, and Contrast-Enhanced CT in Preoperative Staging of Clinically M0 Squamous Cell Carcinoma of the Head and Neck

The purpose of this study was to compare optimized whole-body (WB) and dedicated high-resolution contrast-enhanced PET/CT protocols and contrast enhanced CT in the preoperative staging of primary squamous cell carcinoma of the head and neck. Methods: A total of 44 patients with clinically M0 squamous cell carcinoma of the head and neck underwent primary tumor resection and neck dissection within 6 wk of diagnostic imaging. Imaging consisted of a standard WB PET/CT protocol without intravenous contrast enhancement, followed by a high-resolution dedicated head and neck (HN) PET/CT protocol, which included diagnostic-quality contrast-enhanced CT (CECT). Imaging results were compared with histopathology. A 5-point scale was used to designate primary tumor localization and the presence of lymph node metastasis on a per-patient and per-level basis. For cervical nodes, receiver-operating-characteristic curves were generated to determine the differences in performance between the WB and HN PET/CT protocols and CECT. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for primary tumor and cervical nodes. Results: No statistical difference was observed between WB and HN PET/CT protocols, both of which significantly outperformed CECT, in the evaluation of the primary tumor. The performance of the HN PET/CT protocol was superior to that of the WB PET/CT in the detection of cervical node metastases, achieving statistical significance on a per-level basis and approaching significance on a per-patient basis, with the greatest advantage in the detection of small positive lymph nodes (<15 mm). No significant difference was observed between the WB PET/CT protocol and CECT in nodal staging, either on a per-patient or on a per-level basis. Conclusion: The primary advantage of the dedicated HN PET/CT protocol over the WB protocol or CECT in the staging of head and neck cancer is in the detection of small lymph node metastases.

Effect of body posture on radionuclide measurements of gastric emptying

The purpose of this investigation was to compare the effect of body posture on gastric emptying measurements of radiolabeled meals. Eight healthy male subjects were studied on four separate days. During each study subjects were fed a standardized meal of beef stew labeled with technetium-99m sulfur colloid, and orange juice. Measurements of solid-phase gastric emptying rates were obtained by a gamma camera. Subjects were studied in the lying, sitting, standing, or combined sitting-standing postures. The results demonstrated that the lying position significantly slowed gastric emptying compared to all other positions. Conversely, a decrease in emptying times of 51% and 35% occurred in the combined sitting-standing position compared to the lying and sitting position. These results support a marked effect of body posture on the radionuclide measurement of gastric emptying.

Effects of Carvedilol on Right Ventricular Function in Chronic Heart Failure

This study investigated the effects of carvedilol on right ventricular (RV) volume and systolic function in chronic heart failure patients. Carvedilol treatment resulted in a significant improvement of RV ejection fraction and systolic performance, which paralleled the improvement of systolic function demonstrated in the left ventricle.