Itaru Adachi

Iodine-123 metaiodobenzylguanidine myocardial scintigraphy for prediction of response to β-blocker therapy in patients with dilated cardiomyopathy

This study was performed to evaluate whether iodine-123 metaiodobenzylguanidine (MIBG) myocardial scintigraphy could predict the response to beta-blocker therapy in patients with nonischemic dilated cardiomyopathy (DCM). Beta-Blocker therapy is effective in some patients with DCM. MIBG myocardial scintigraphy has also been suggested to be useful in evaluating the severity of myocardial damage in DCM. However, no data exist on whether MIBG imaging can be used to predict which patients with DCM will respond to beta-blocker therapy. We prospectively evaluated whether MIBG myocardial imaging was useful in predicting responses to beta-blocker therapy in patients with DCM. MIBG imaging was performed in 45 patients with DCM (35 men, 10 women, aged 13 to 68 years) before the start of bisoprolol. The heart to mediastinum (H/M) MIBG uptake ratio was evaluated on initial and delayed images, and the percent washout rate of myocardial MIBG was also obtained from these data. Of the 45 patients, 30 (67%) responded to beta-blocker therapy, whereas 2 were resistant and 13 showed progression of heart failure or died of heart failure. By logistic regression analysis, the H/M uptake ratio on delayed images was seen to be a good predictor of the response to beta-blocker therapy with a threshold of 1.7 (sensitivity = 91%, specificity = 92%, accuracy = 91%, positive and negative predictive value = 97% and 80%, respectively). These results indicate that an H/M ratio > 1.7 on the delayed MIBG myocardial scintigraphic images provides a useful indication of whether patients with DCM will respond to beta-blocker therapy.

Tc-99m sestamibi uptake by malignant lymphoma and slow washout

Tc-99m sestamibi has been used to detect primary brain tumors, lung tumors, and breast cancers. The authors report a patient who had superior vena cava (SVC) syndrome and underwent Tc-99m sestamibi and TI-201 SPECT to differentiate the tumor from thrombus in the mediastinum because of an abnormal mass lesion on a contrast enhanced CT scan. An abnormal area of increased Tc-99m sestamibi uptake in the supra azygos area was demonstrated on early and delayed SPECT imaging. The washout of tumor uptake was slow. The removed tumor was confirmed to be malignant lymphoma.

Gated blood pool SPECT improves reproducibility of right and left ventricular Fourier phase analysis in radionuclide angiography

Objectives: The ventricular phase angle, a parametric method applied to Fourier phase analysis (FPA) in radionuclide ventriculography, allows the quantitative analysis of ventricular contractile synchrony. However, FPA reproducibility using gated blood pool SPECT (GBPS) has not been fully evaluated. The present study evaluates whether by using GBPS, the reproducibility of FPA could be improved over that in planar radionuclide angiography (PRNA).Methods: Forty-three subjects underwent both GBPS and PRNA, of which 10 subjects were normal controls, 25 had dilated cardiomyopathy, and 8 had various heart diseases. Interventricular contractile synchrony was measured as the absolute difference in RV and LV mean ventricular phase angle as deltaø (RV- LV). Intraventricular contractile synchrony was measured as the standard deviation of the mean phase angle for the RV and LV blood pools (RVSDø, LVSDø). Two nuclear physicians processed the same phase images of GBPS to evaluate the interobserver reproducibility of the phase angles using data from the 43 study participants. Phase images acquired from PRNA were processed in the same manner.Results: Excellent reproducibility of deltaø (RV - LV) was obtained with both GBPS (Y = -3.10 + 0.89 X; r = 0.901) and PRNA (Y = -4.51 + 0.81 -X; r = 0.834). In regard to RVSDø reproducibility was not adequate with PRNA (Y = 18.56 + 0.35.X; r = 0.424), while it was acceptable with GBPS (Y = 5.22 + 0.85.X; r = 0.864). LVSDø reproducibility was superior using both GBPS (Y = 4.15 + 0.97.X; r = 0.965) and PRNA (Y = -0.55 + 0.98.X; r = 0.910).Conclusion: Our results demonstrate FPA obtained using GBPS to be highly reproducible for evaluating deltaø (RV - LV), RVSDø and LVSDø, in comparison with the PRNA method. We thus consider GBPS appropriate for evaluating ventricular contractile synchrony.

Tc-99m PMT whole-body scintigraphy for evaluation of therapeutic effect and for monitoring bone metastasis in a patient with hepatocellular carcinoma

Detection of metastatic lesions by bone scintigraphy is highly sensitive but has a low rate of specificity. Often bone metastases from hepatocellular carcinoma are not detected by bone scintigraphy because of low uptake or a photopenic area in the tumor. In contrast, Tc-99m Sn-N-pyridoxy-5-methyltryptophan (Tc-99m PMT) whole-body scintigraphy reflects tumor viability, and the specificity of detection is so high that tumor structure can be shown well. Tc-99m PMT whole-body scintigraphy was helpful for evaluating the response to therapy and monitoring the course of the patient described here with bone metastasis from hepatocellular carcinoma.

Evaluation of uptake and release of technetium-99m MIBI SPECT of pulmonary and mediastinal lesions

We evaluated the uptake and release of Tc-99m MIBI in 7 benign and 30 malignant pulmonary and mediastinal lesions. Of the 37 patients, 13 underwent surgery; malignant involvement was examined in 21 mediastinal lymph nodes. Tl-201 SPECT was also performed in 10 patients. Tc-99m MIBI SPECT studies were performed on transverse SPECT images acquired 30 minutes and 3 hours after intravenous injection of 600 MBq of Tc-99m MIBI with three gamma camera detectors (GCA-9300A). Regions of interest were set in the area of abnormal uptake of Tc-99m MIBI and in an area of normal tissue in the contralateral lung. The uptake ratio of the lesion in the contralateral normal lung was obtained on the early image (early ratio; ER) as well as the delayed image (delayed ratio; DR). The benign lesions showed significantly lower ER (1.6 ± 0.3) and DR (1.4 ± 0.4) than the malignant lesions (1.9 ± 0.5 and 1.8 ± 0.5, respectively; both p < 0.05). There was no significant difference in the retention index (RI), calculated as RI = (DR − ER)/ER × 100. The DR obtained with Tl-201 SPECT images was significantly higher than that obtained with Tc-99m MIBI SPECT (p < 0.05). For the detection of mediastinal lymph node metastases, the early images showed sensitivity, specificity, and accuracy of 85.7%, 100%, and 95.2%, respectively, for the delayed images these values were 85.7%, 92.9%, and 90.5%, respectively. These results suggest that the uptake ratio of Tc-99m MIBI is a useful index in assessing benign or malignant pulmonary and mediastinal lesions.

Evaluation of breath-hold201Tl SPECT in the differential diagnosis of solitary pulmonary nodules

The aim of this study was to evaluate the usefulness of deep inspiration breath-hold SPECT (BrST, a method for201T1 SPECT) in the diagnosis of solitary pulmonary nodules (SPN).Methods: Ten patients with malignant lesions and five with benign lesions were enrolled in this study. Early SPECT acquisition was performed 15 min after injection of201T1, while delayed SPECT images were acquired 3 h after injection. The first 15-sec acquisition was done using the BrST technique, and the second with the conventional free breathing (FB) method. We performed this technique alternately, and therefore, the odd data were from BrST and the even data were from FB. We referred to the T/N ratio of the early images as the ER and to the T/N ratio of the delayed images as the DR. To semi-quantitatively evaluate the degree of retention in the lesion, the retention index (RI) was calculated.Results: The RI of BrST indicated greater accuracy than that of FB in the differential diagnosis of SPN. For the benign and malignant lesions, the RI of BrST was -3.07 ± 31.51 and 29.86 ± 25.01, respectively (p < 0.05). The sensitivity, specificity, and accuracy of BrST (80%, 80%, and 80%, respectively) were significantly higher than those of FB (p < 0.05).Conclusion: The BrST method is more accurate than that of the conventional FB method in the differential diagnosis of SPN.

Do repolarization abnormalities in hypertrophic cardiomyopathy represent impaired fatty acid utilization?: An observation with QRST isointegral maps

To identify the clinical significance of the isointegral body surface map of the QRST interval (QRST map) and the occurrence of repolarization abnormalities in patients with hypertrophic cardiomyopathy (HCM), the QRST map and signal-averaged electrocardiogram were evaluated in 50 patients with HCM, in 33 of whom the results were compared with nuclear images both for radioiodine-labeled fatty acid metabolism and for radiothallium perfusion. The QRST departure map was used to determine two parameters of difference between patient and control recordings: the subnormal area (the number of lead points at which the departure index values were negative and lay more than 2 SDs from the mean of the normal control group) and the subnormal minimum (the absolute value of the minimum in the departure map). Late potentials were detected in 6 (12%) of the 50 patients; they were observed in 3 of the 5 patients with dilated-phase HCM but in only 3 (7%) of the other 45 patients. The subnormal area and minimum values were lower in nonobstructive HCM than in dilated-phase HCM. Of the 33 patients examined by myocardial imaging, 28 (33%) had a filling defect or decreased uptake, as shown on fatty acid metabolic images, and 10 of the 28 also showed abnormal myocardial perfusion images, while the 18 others showed normal perfusion images. These 28 patients showed significantly larger values of the subnormal area and minimum than patients with normal results in both image tests, regardless of whether or not myocardial perfusion imaging abnormalities were present. The localization of filling defects or of decreased uptake presented in fatty acid metabolic images corresponded to the position of the minimum on the QRST departure map. These results suggest that the QRST map is useful for detection of repolarization abnormalities in HCM and that these abnormalities are highly related to impaired fatty acid utilization of the myocardium.