Respiratory Motion Detection and Correction in ECG-Gated SPECT: a New Approach

OBJECTIVE: Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function. MATERIALS AND METHODS: Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest (99m)Tc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals. RESULTS: A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 +/- 2.9 mm) and 7.8-11.8 mm (mean, 9.5 +/- 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography. CONCLUSION: Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases.

potential value of F-18 FDG PET in comparison to CT in early prediction of response to imatinib [STI571] therapy in patients with gastrointestinal stromal tumors

Gastrointestinal stromal tumors [GISTs] are the most common mesenchymal neoplasms of the gastrointestinal tract. GIST has been shown to over-express c-KIT [CD117], the receptor tyrosine kinase. Imatinib [STI571 or Glivec] is a new type of tyrosine kinase inhibitor that selectively inhibits various tyrosine kinases and has been successfully used to treat GIST. In this study we have compared the results of F-18 FDG PET with those of CT in patients with GIST before and early after the treatment with Imatinib. The performance of CT and FDG PET imaging in the staging and follow-up of GIST lesion was retrospectively evaluated and compared in 15 patients with 67 suspicious lesions. All patients were examined before and after treatment with Imatinib. Findings of CT and FDG PET were compared on both patient-and lesion-based basis for the whole group and for anatomic locations. Overall 67 lesions were detected in both pre-therapeutic FDG PET and CT imaging. In the pre-treatment studies there was no significant difference between detected lesions on FDG PET and CT [p=0.19]. However, after treatment with Imatinib [follow-up interval of 30+16 days], FDG PET predicted response to therapy earlier than CT in 18% of lesions and 14% of patients, respectively. There was no significant difference in the density of malignant lesions by means of Hounsfield unit [HU] in the baseline PET in comparison to the early post-therapeutic investigations [93+16 vs. 90+22]. For treatment monitoring of Imatinib in GIST patients, FDG PET gives more precise information of active state of disease compared with CT