Single- vs. dual-head SPECT for detection of myocardial ischemia and viability in a large study population.

BACKGROUND: As single-head data acquisition for thallium-201 myocardial SPECT is a frequently used method mainly in the outpatient medical care as well as in smaller hospitals, comparison to dual-head data collection is a still discussed issue mainly with regard to quality control and -assurance. METHODS: A total of 1334 patients undergoing thallium-201 myocardial SPECT for diagnosis of myocardial ischemia and/or viability have been retrospectively analyzed. In 554 patients, a single-head gamma camera (360 degrees rotation) has been applied, whereas a dual-head gamma camera (180 degrees rotation) has been used in 780 patients. Four hundred twenty-six patients received both myocardial SPECT as well as coronary angiography. The diagnostic value of both applied acquisition techniques has been analyzed. RESULTS: Regarding myocardial viability, positive predictive value for the diagnosis of myocardial scar tissue was significantly higher for dual-head- as compared to single-head acquisition. Among the 426 patients undergoing diagnosis of myocardial ischemia, significant differences have only been found with regard to specificity being higher in the single-head acquisition. Diagnosis of myocardial ischemia related to a distinct myocardial perfusion region showed a significantly higher sensitivity of dual-head acquisition for the left anterior descending perfusion area, whereas specificity was significantly higher for single-head acquisition. CONCLUSIONS: Our results indicate a beneficial effect of dual-head data collection with regard to sensitivity of the diagnosis of myocardial ischemia. In contrast, single-head data acquisition was superior with regard to specificity. However, it is justified to preferably apply dual-head data collection in clinical routine due to the shorter acquisition time leading to an evident time benefit of this acquisition technique.

Myocardial uptake characteristics of three 99mTc-labeled tracers for myocardial perfusion imaging one hour after rest injection.

OBJECTIVE: 99mTc-tetrofosmin and 99mTc-sestamibi are approved tracers for myocardial perfusion studies. Recently, a 99mTc-MIBI preparation from a different manufacturer (99mTc-cardiospect-MIBI) has been introduced to the market. Therefore, the aim of this study was the evaluation of 99mTc-tetrofosmin as well as of two different 99mTc-labeled MIBI tracers with regard to differences in imaging quality under resting conditions. METHODS: Sixty patients (mean age 63.8 years +/- 1.25) with known or suspected coronary artery disease but without evidence of rest-ischemia were included. Twenty patients in each group were examined by a two-day-rest-stress protocol using the three 99mTc-labeled tracers. Visual analysis of all images was performed by two experienced physicians blinded with regard to the applied tracer. Regions of interest (ROI) were defined over the heart, lung and whole body only in the rest imaging in order to calculate heart-to-lung, lung-to-whole body-, and heart-to-whole body-ratios. RESULTS: The heart-to-lung ratio was statistically significant higher for 99mTc-cardiospect-MIBI as compared to 99mTc-sestamibi as well as to 99mTc-tetrofosmin. Furthermore, a significantly higher heart-to-lung ratio was found for 99mTc-sestamibi as compared to 99mTc-tetrofosmin. The heart-to-whole body-ratio and the lung-to-whole body-ratio were equivalent between all tracers. Visual analysis revealed only slight differences regarding image quality between all tracers. CONCLUSIONS: ROI analysis surprisingly revealed a significant higher myocardial uptake and consequently a higher heart-to-lung ratio for 99mTc-cardiospect-MIBI. Whether this leads to a better visual image quality has to be evaluated in future studies with larger study populations as well as semiquantitative segmental analysis of the myocardial perfusion images.

Dose selection for radioiodine therapy of borderline hyperthyroid patients with multifocal and disseminated autonomy on the basis of 99mTc-pertechnetate thyroid uptake.

The aim of this study was to optimise radioiodine therapy of diffuse and nodular toxic goitre by calculation of the radiation dose delivered to the thyroid on the basis of the pretreatment technetium-99m pertechnetate thyroid uptake under thyrotropin suppression (TcTU(s)). The TcTU(s) value serves as a substitute for the non-suppressible iodine turnover and the functional autonomous mass. Marinelli's formula was used to calculate tissue absorbed doses of 150 Gy, 200 Gy, 250 Gy and 300 Gy to the thyroids of 438 patients with multifocal and disseminated autonomy. The mean age of patients was 70+/-9 years, and the mean thyroid volume was 54+/-26 ml. Two hundred and sixty-one of the patients had at least one documented previous episode of overt hyperthyroidism. Tissue absorbed doses were adapted to the pretreatment TcTU(s): 150 Gy for a TcTU(s) of 1.5%-2.49%, 200 Gy for a TcTU(s) of 2.5%-3.49%, 250 Gy for a TcTU(s) of 3.5%-4.49% and 300 Gy for a TcTU(s) of > or =4.5%. Normalisation of TcTU(s) and thyrotropin (TSH), thyroid volume reduction and frequency of hypothyroidism and recurrent hyperthyroidism were evaluated 1 year after a single radioiodine therapy. The presented dose strategy resulted in normalisation of TcTU(s) in 96% and an increase in TSH to the normal range in 92%. Recurrent hyperthyroidism was observed in only five patients. Thyroid volume decreased from 54+/-26 before treatment to 34+/-20 ml, a mean reduction of 37%. The frequency of hypothyroidism, at 0.9%, was encouragingly low. Dose selection in accordance with pretreatment TcTU(s) can be recommended for elimination of functional autonomous tissue with a single radioiodine therapy in patients of advanced age with enlarged thyroid glands and relevant autonomous masses who are at risk of developing iodine-induced hyperthyroidism.