Evaluation of radioiodine therapy in differentiated thyroid cancer subjects with elevated serum thyroglobulin and negative whole body scan using 131I with emphasize on the thallium scintigraphy in these subgroups.

OBJECTIVE: Negative diagnostic 131I whole body scans with elevated serum thyroglobulin (Tg) levels are found in 20% of patients with differentiated thyroid cancer (DTC). Empirical radioiodine treatment has been advocated by some researchers, but has had with controversial outcomes. This anterospective study was performed to examine this dilemma and also to determine the capability of thallium (201TI) scintigraphy in these patients. MATERIALS AND METHODS: A total of 21 patients who had a history of DTC and elevated serum Tg levels, together with a negative diagnostic 131I whole body scans (WBS), were included in the study. All patients underwent posttreatment 131I WBS. Patients with negative posttreatment 131I WBS then underwent 201TI scintigraphy. RESULTS: The 21 included patients (9 women and 12 men) had a mean age of 53 +/- 14.17 years. The mean pretreatment and posttreatment Tg levels were 227.23 +/- 208.50 ng/ml and 163.43 +/- 282.57 ng/ml, respectively (p value <0.05). Eleven cases showed at least a 50% decrease in Tg value (remission group), 6 patients revealed less than a 50% decrease in Tg value (stable group), while 4 subjects demonstrated an increment in posttreatment Tg relative to pretreatment Tg value (progression group). The cumulative and last 131I doses in the remission, stable, and progression groups were not significantly different (p value >0.05). In the posttreatment 131I WBS, 10 patients showed abnormal findings in their images. In a follow-up scan after 201TI treatment, 7 out of 11 patients had positive scans. CONCLUSION: The study indicates a positive effect of RAI therapy in DTC patients with elevated Tg and negative 131I WBS. In addition, 201TI scintigraphy can be useful as an alternative modality to improve tumoral detection in this situation and when access to a PET system is limited.

Initial and delayed stress phase imaging in a single-injection double-acquisition SPECT. The potential value of early 99mTc-MIBI redistribution in assessment of myocardial perfusion reversibility in patients with coronary artery disease.

UNLABELLED: Some studies reported that 99mTc-MIBI may redistribute in ischaemic myocardium and this phenomenon may have potential role for better assessment of viability by delayed 99mTc-MIBI imaging. Some studies also suggested that infusion of low dose dobutamine during delayed imaging may enhance the value of 99mTc-MIBI imaging for evaluation of viability. The aim of this study is to determine whether the observed changes of perfusion defects on delayed images are caused by early radiotracer redistribution or as a result of reversal partial volume effect secondary to inotropic stimulation. PATIENTS, METHODS: 89 patients with angiographically proven coronary artery disease (CAD) were enrolled in this randomized clinical trial study. In all cases, gated-SPECT images were obtained 60 minutes after stress with dipyridamole injection. Subsequently the patients were randomly allocated in two groups and the second imaging was performed at 120th minute during low dose dobutamine (dobutamine group; 45 cases) or placebo infusion (placebo group; 44 cases). Difference between summed stress score of the first (SSS1) and second (SSS2) stress images (DeltaSSS) was considered as a marker of reversibility in single-injection double-acquisition (SIDA) protocol. Also summed difference score (SDS) was recorded as a marker of reversibility in standard stress/rest, double-injection double-acquisition (DIDA) protocol. DeltaSSS of the two studied groups were compared. Also the correlation and agreement between DeltaSSS and SDS were analyzed. RESULTS: A significant difference was found between SSS1 (median 15, range 0-48) and SSS2 (median 11, range 0-42) in total patients (p < 0.0001). A significant correlation was noted between DeltaSSS and SDS in dobutamine group (r = 0.58, p = 0.002) as well as in placebo group (r = 0.57, p < 0.0001). Considering DIDA protocol as a standard reference method, the influence of dobutamine infusion was not shown to be significantly different from the placebo effect on the magnitude of fixed or reversible perfusion defects in SIDA protocol. CONCLUSION: The changes in the magnitude of the perfusion defects may occur in the first hours of 99mTc-MIBI injection in the stress phase imaging. These changes correlate well and are in agreement with perfusion improvement on the rest images. This phenomenon may be independent of improvement in myocardial function, in more delayed imaging or following inotropic augmentation, and thus is likely due to 99mTc-MIBI redistribution. This may open new technical and clinical aspects and potentials for 99mTc-MIBI imaging.

Platelet-based MPLE denoising of SPECT images: phantom and patient study.

In this study the evaluation of a Platelet-based Maximum Penalized Likelihood Estimation (MPLE) for denoising SPECT images was performed and compared with other denoising methods such as Wavelets or Butterworth filteration. Platelet-based MPLE factorization as a multiscale decomposition approach has been already proposed for better edges and surfaces representation due to Poisson noise and inherent smoothness of this kind of images. We applied this approach on both simulated and real SPECT images. For NEMA phantom images, the measured noise levels before (M(b)) and after (M(a)) denoising with Platelet-based MPLE approach were M(b)=2.1732, M(a)=0.1399. In patient study for 32 cardiac SPECT images, the difference between noise level and SNR before and after the approach were (M(b)=3.7607, SNR(b)=9.7762, M(a)=0.7374, SNR(a)=41.0848) respectively. Thus the Coefficient Variance (C.V) of SNR values for denoised images with this algorithm as compared with Butterworth filter, (145/33%) was found. For 32 brain SPECT images the Coefficient Variance of SNR values, (196/17%) was obtained. Our results shows that Platelet-based MPLE is a useful method for denoising SPECT images considering better homogenous image, improvements in SNR, better radioactive uptake in target organ and reduction of interfering activity from background radiation to compare to that of other conventional denoising methods.