Clinical use of nuclear cardiology in the assessment of heart failure

A nuclear cardiology test is the most commonly performed non-invasive cardiac imaging test in patients with heart failure, and it plays a pivotal role in their assessment and management. Quantitative gated single positron emission computed tomography (QGS) is used to assess quantitatively cardiac volume, left ventricular ejection fraction (LVEF), stroke volume, and cardiac diastolic function. Resting and stress myocardial perfusion imaging, with exercise or pharmacologic stress, plays a fundamental role in distinguishing ischemic from non-ischemic etiology of heart failure, and in demonstrating myocardial viability. Diastolic heart failure also termed as heart failure with a preserved LVEF is readily identified by nuclear cardiology techniques and can accurately be estimated by peak filling rate (PFR) and time to PFR. Movement of the left ventricle can also be readily assessed by QGS, with newer techniques such as three-dimensional, wall thickening evaluation aiding its assessment. Myocardial perfusion imaging is also commonly used to identify candidates for implantable cardiac defibrillator and cardiac resynchronization therapies. Neurotransmitter imaging using (123)I-metaiodobenzylguanidine offers prognostic information in patients with heart failure. Metabolism and function in the heart are closely related, and energy substrate metabolism is a potential target of medical therapies to improve cardiac function in patients with heart failure. Cardiac metabolic imaging using (123)I-15-(p-iodophenyl)3-R, S-methylpentadecacoic acid is a commonly used tracer in clinical studies to diagnose metabolic heart failure. Nuclear cardiology tests, including neurotransmitter imaging and metabolic imaging, are now easily preformed with new tracers to refine heart failure diagnosis. Nuclear cardiology studies contribute significantly to guiding management decisions for identifying cardiac risk in patients with heart failure.

Dynamic expression of tenascin-C after myocardial ischemia and reperfusion: assessment by 125I-anti-tenascin-C antibody imaging

Tenascin-C, an extracellular matrix glycoprotein, appears only in the early stages of embryonic development. It is not normally expressed in the adult heart but does reappear transiently in distinct areas in association with active tissue remodeling. The aim of this study was to explore serial changes in the expression of tenascin-C after myocardial ischemia and reperfusion, using (125)I-labeled anti-tenascin-C antibody ((125)I-TNC-Ab) in a rat model of acute ischemia and reperfusion.

METHODS

The left coronary artery was occluded for 20 or 30 min, followed by reperfusion for 1, 3, or 7 d in rats with 20 min of ischemia and for 1, 3, 7, 14, or 28 d in rats with 30 min of ischemia. At the time of the study, (125)I-TNC-Ab (1.0-2.5 MBq) was injected. Three to 5 h later, to verify the area at risk, (99m)Tc-methoxyisobutylisonitrile (100-200 MBq) was injected intravenously just after the left coronary artery reocclusion and the rats were sacrificed 1 min later. Dual-tracer autoradiography was performed to assess (125)I-TNC-Ab uptake and the area at risk.

RESULTS

In rats with 20 min of ischemia, (125)I-TNC-Ab uptake peaked at 3 d after reperfusion, followed by faint uptake after 7 d (uptake ratios at 1, 3, and 7 d after reperfusion were 1.81 +/- 0.53, 2.46 +/- 0.79, and 1.23 +/- 0.17, respectively [P < 0.05 vs. 3 d]). In rats with 30 min of ischemia, uptake was high at 1 and 3 d after reperfusion (2.99 +/- 0.90 and 2.71 +/- 0.80, respectively), decreased at 7 and 14 d (1.94 +/- 0.23 and 2.06 +/- 0.37, respectively), and was weak at 28 d (1.47 +/- 0.27, P < 0.005 vs. 1 d, P < 0.05 vs. 3 d).

CONCLUSION

These data indicate that (125)I-TNC-Ab imaging may be a way to monitor myocardial injury and its repair process after ischemia and reperfusion by visualizing tenascin-C expression.

Iodine-123 metaiodobenzylguanidine imaging and carbon-11 hydroxyephedrine positron emission tomography compared in patients with left ventricular dysfunction

BACKGROUND

Although both (123)I-metaiodobenzylguanidine ((123)I-MIBG) imaging and (11)C-hydroxyephedrine ((11)C-HED) positron emission tomography (PET) are used for assessing cardiac sympathetic innervation, their relationship remains unknown. The aims were to determine whether (123)I-MIBG parameters such as heart-to-mediastinum ratio (H/M) are associated with quantitative measures by (11)C-HED PET and to compare image quality, defect size, and location between (123)I-MIBG single-photon emission computed tomography (SPECT) and (11)C-HED PET.

METHODS AND RESULTS

Twenty-one patients (mean left ventricular ejection fraction, 39 ± 15%) underwent (123)I-MIBG imaging and (11)C-HED PET. Early (15-minute), late (3-hour) H/M, and washout rate (WR) were calculated for (123)I-MIBG. Myocardial retention and WR was calculated for (11)C-HED. Using a polar map approach, defect was defined as the area with relative activity <60% of the maximum. Both the early (r=0.76) and late (r=0.84) (123)I-MIBG H/M were correlated with (11)C-HED retention. (123)I-MIBG WR was correlated with (11)C-HED WR (r=0.57). Defect size could not be measured in 3 patients because of poor quality (123)I-MIBG SPECT, whereas (11)C-HED defect was measurable in all patients. Although defect size measured by early or late (123)I-MIBG SPECT was closely correlated with that by (11)C-HED PET (early: r=0.94; late: r=0.88), the late (123)I-MIBG overestimated defect size particularly in the inferior and septal regions.

CONCLUSIONS

(123)I-MIBG H/M gives a reliable estimate of cardiac sympathetic innervation as measured by (11)C-HED PET. Furthermore, despite the close correlation in defect size, (11)C-HED PET appears to be more suitable for assessing regional abnormalities than does (123)I-MIBG SPECT.

Biodistribution of humanized anti-VEGF monoclonal antibody/bevacizumab on peritoneal metastatic models with subcutaneous xenograft of gastric cancer in mice

PURPOSE

Vascular endothelial growth factor (VEGF) is correlated with peritoneal metastasis of gastric cancer, increasing vascular permeability accompanied by accumulation of ascites. The aim of the current study is to investigate the biodistribution of bevacizumab in a peritoneal metastatic model of gastric cancer and to clarify which is more suited to treatment of peritoneal metastasis, systemic or regional therapy.

METHODS

A highly peritoneal-seeding cell line of gastric cancer, OCUM-2MD3, which exhibited high production and release of VEGF was used in this study. The biodistribution of bevacizumab was investigated using peritoneal metastatic models together with subcutaneous xenografts, and (125)I-radiolabelled bevacizumab was administrated to these models subcutaneously (s.c.) or intraperitoneally (i.p.), respectively. In addition, the anti-tumor response of bevacizumab and paclitaxel was assessed as single agents or in combination using peritoneal metastatic models.

RESULTS

In the analysis of biodistribution, (125)I-bevacizumab administrated i.p. indicated low peritoneal clearance. On the other hand, s.c. administration of (125)I-bevacizumab showed preferential accumulation in subcutaneous tumors and peritoneal nodules, with a high blood concentration. In peritoneal metastatic models, the effects of bevacizumab were found for both the growth inhibition of peritoneal nodules (P < 0.01) and the reduction of ascites (P < 0.05). These effects were more prominent by s.c. administration compared with i.p. administration and were increased in combination with i.p. paclitaxel.

CONCLUSION

Bevacizumab should be administrated systemically compared to regionally, and the combination with i.p. paclitaxel has a potential to be useful for patients with peritoneal metastasis of gastric cancer.

[The role of / 18FDG PET/CT for the initial staging and therapy in primary breast cancer]

PURPOSE

To evaluate the utility of / 18F-FDG PET/CT in the initial staging and predicting response to neoadjuvant chemotherapy ( NAC) for primary breast cancer.

METHODS

One hundred fourteen patients with primary breast cancer were preoperatively evaluated with PET/CT. The diagnostic value of PET/CT was compared in the final histopathology following surgery. Twenty patients also underwent PET/CT at baseline and after 4 and 8 courses of NAC. Changes (deltaSUV)in the maximum standard uptake value (SUVmax) between baseline study and after 4 or 8 courses of NAC were compared with the pathological response.

RESULTS

In the detection of primary breast cancer, PET/CT was 80. 7% sensitive, and especially, less sensitive in the detection of tumor size less than 10mm (66. 7%), low tumor grade (61. 3%), and ductal carcinoma in situ (50%). For axillary staging, PET/CT was 51. 9% sensitive and 95. 3% specific; in particular, it was less sensitive for small (<10mm) axillary lymph nodes (29. 4%) and could not detect micrometastasis. A cut-off deltaSUV value of 91. 9% was determined between baseline and after 4 courses of NAC differentiated responders(pathological CR)and non-responders, with a sensitivity of 80%, and a specificity of 78. 6% (p=0. 038).

CONCLUSION

Although PET/CT may have limited diagnostic value for detecting primary tumor and axillary staging, it is a valuable modality for monitoring the response to therapy.

Preparation and evaluation of 186/188Re-labeled antibody (A7) for radioimmunotherapy with rhenium(I) tricarbonyl core as a chelate site

OBJECTIVE

Rhenium is one of the most valuable elements for internal radiotherapy because (186)Re and (188)Re have favorable physical characteristics. However, there are problems when proteins such as antibodies are used as carriers of (186/188)Re. Labeling methods that use bifunctional chelating agents such as MAG3 require the conjugation of the (186/188)Re complex to protein after radiolabeling with the bifunctional chelating agent. These processes are complicated. Therefore, we planned the preparation by a simple method and evaluation of a stable (186/188)Re-labeled antibody. For this purpose, we selected (186/188)Re(I) tricarbonyl complex as a chelating site. In this study, A7 (an IgG1 murine monoclonal antibody) was used as a model protein. (186/188)Re-labeled A7 was prepared by directly reacting a (186/188)Re(I) tricarbonyl precursor, [(186/188)Re(CO)(3)(H(2)O)(3)](+), with A7. We then compared the biodistribution of (186/188)Re-labeled A7 in tumor-bearing mice with (125)I-labeled A7.

METHODS

For labeling A7, [(186/188)Re(CO)(3)(H(2)O)(3)](+) was prepared according to a published procedure. (186/188)Re-labeled A7 ((186/188)Re-(CO)(3)-A7) was prepared by reacting [(186/188)Re(CO)(3)(H(2)O)(3)](+) with A7 at 43 degrees C for 2 h. Biodistribution experiments were performed by the intravenous administration of (186/188)Re-(CO)(3)-A7 solution into tumor-bearing mice.

RESULTS

(186)Re-(CO)(3)-A7 and (188)Re-(CO)(3)-A7 were prepared with radiochemical yields of 23 and 28%, respectively. After purification with a PD-10 column, (186/188)Re-(CO)(3)-A7 showed a radiochemical purity of over 95%. In biodistribution experiments, 13.1 and 13.2% of the injected dose/g of (186)Re-(CO)(3)-A7 and (188)Re-(CO)(3)-A7, respectively, accumulated in the tumor at 24-h postinjection, and the tumor-to-blood ratios were over 2.0 at the same time point. Meanwhile, uptake of (125)I-A7 in the tumor was almost the same as that of (186/188)Re-(CO)(3)-A7 at 24-h postinjection. Blood clearances of (186/188)Re-(CO)(3)-A7 were faster than those of (125)I-A7.

CONCLUSION

(186/188)Re-labeled A7 showed high uptakes in the tumor. However, further modification of the labeling method would be necessary to improve radiochemical yields and their biodistribution.

Evaluation of radioiodinated vesamicol analogs for sigma receptor imaging in tumor and radionuclide receptor therapy

It has been reported that sigma receptors are highly expressed in a variety of human tumors. In this study, we selected (+)-2-[4-(4-iodophenyl)piperidino] cyclohexanol [(+)-pIV] as a sigma receptor ligand and evaluated the potential of radioiodinated (+)-pIV for tumor imaging and therapy. (+)-[(125/131)I]pIV was prepared by an iododestannylation reaction under no-carrier-added conditions with radiochemical purity over 99% after HPLC purification. Biodistribution experiments were performed by the intravenous injection of (+)-[(125)I]pIV into mice bearing human prostate tumors (DU-145). Blocking studies were performed by intravenous injection of (+)-[(125)I]pIV mixed with an excess amount of unlabeled sigma ligand into DU-145 tumor-bearing mice. For therapeutic study, (+)-[(131)I]pIV was injected at a dose of 7.4 MBq followed by measurement of the tumor size. In biodistribution experiments, (+)-[(125)I]pIV showed high uptake and long residence in the tumor. High tumor to blood and muscle ratios were achieved because the radioactivity levels of blood and muscle were low. However, the accumulations of radioactivity in non-target tissues, such as liver and kidney, were high. The radioactivity in the non-target tissues slowly decreased over time. Co-injection of (+)-[(125)I]pIV with an excess amount of unlabeled sigma ligand resulted in a significant decrease in the tumor/blood ratio, indicating sigma receptor-mediated tumor uptake. In therapeutic study, tumor growth in mice treated with (+)-[(131)I]pIV was significantly inhibited compared to that of an untreated group. These results indicate that radioiodinated (+)-pIV has a high potential for sigma receptor imaging in tumor and radionuclide receptor therapy.

Clinical usefulness of novel cardiac MDCT/SPECT fusion image

BACKGROUND

We evaluated the relationship between computed tomography angiography (CTA) and SPECT, and assessed to determine the clinical usefulness of the fusion image using CTA and myocardial perfusion imaging (MPI).

METHODS

Forty-one consecutive patients [after coronary artery bypass operation (n = 13) and suspected stenosis (n = 28)] underwent MPI and CTA. SPECT/CTA fused images were generated.

RESULTS

In total, 687 segments including bypass graft in 164 coronary arteries were analyzed. Myocardial ischemia on MPI was observed in 11 patients among 28 with CTA abnormalities, one had both ischemia and infarction, and 7 had only infarction. Segment-based analysis showed that ischemia was found in 14 segments (24%) among 59 stenoses on CTA. Forty stenotic segments (69%) were not associated with perfusion abnormality. The rest 5 stenotic segments were considered equivocal (8%). A fusion image made it possible to associate perfusion defects with its corresponding coronary artery in 4 out of 5 equivocal lesions on side-by-side analysis. Patients with incremental diagnostic information on SPECT/CTA fusion (n = 4) had significant smaller coronary diameter than that of not-improved coronary vessels (2.0 +/- 0.4 vs. 3.9 +/- 0.4 mm, p = 0.001).

CONCLUSION

Cardiac fusion imaging accurately diagnosed functionally relevant coronary stenosis. SPECT/CTA fusion images in coronary artery disease may provide added diagnostic information on functional relevance of coronary artery disease.

The importance of population-specific normal database for quantification of myocardial ischemia: comparison between Japanese 360 and 180-degree databases and a US database

OBJECTIVES

We aimed to develop a Japanese normal database for specific acquisition conditions, to compare US and Japanese normal populations, and to examine effects of camera rotation angle range on the normal limits.

METHODS AND RESULTS

Stress-rest (99m)Tc myocardial perfusion databases for 360 degrees (Jp360) and 180 degrees (Jp180) acquisitions were created by the working group activity of the Japanese Society of Nuclear Medicine using Japanese patients. A standard 180 degrees database (US180) had been previously generated by the Cedars Sinai Medical Center based on American patients. Additionally, 90 Japanese patients underwent coronary arteriography and stress-rest (99m)Tc perfusion study with 360 degrees acquisition for validation purposes, and quantitative evaluation was performed by QPS software using the above three normal database sets. Major differences between US180 and Jp360 databases were found in the apex and in the anterior wall in females and in the inferior wall in males. When the diagnostic performance was evaluated by receiver-operating characteristic analysis, area under the curve was the highest for Jp360 (0.842), followed by Jp180 (0.758) and US180 (0.728) databases (P = .019, Jp360 vs US180; P = .035, Jp360 vs Jp180). The coronary territory score at stress was highest with the Jp360 database in male patients with right coronary artery stenosis (n = 26, Jp360: 4.92 +/- 4.61 [mean +/- SD], Jp180: 4.23 +/- 4.29, US180: 2.92 +/- 3.53; P < .0001 between Jp360 and US180) and in female patients with left anterior descending artery stenosis (n = 12, Jp360: 6.33 +/- 4.76, Jp180: 5.25 +/- 4.83, US180: 4.50 +/- 4.15; P = .0076 between Jp360 and US180).

CONCLUSION

Because of the differences between US and Japanese normal databases, it is essential to use population- and acquisition-specific databases when using quantitative perfusion SPECT software.

Potential usefulness of D2R reporter gene imaging by IBF as gene therapy monitoring for cerebellar neurodegenerative diseases

We investigated a gene expression imaging method to examine the level of therapeutic gene expression in the cerebellum. Using a human immunodeficiency virus derived lentivial vector, we expressed the dopamine D(2) receptor (D(2)R) as a reporter protein to mouse cerebellar Purkinje cells. Biodistribution and ex vivo autoradiography studies were performed by giving [(125)I]5-iodo-7-N-[(1-ethyl-2-pyrrolidinyl)methyl]carboxamide-2,3-dihydrobenzofuran ([(125)I]IBF) (1.85 MBq), as a radioactive D(2)R ligand, to model mice expressing the D(2)R with an HA tag (HA-D(2)R) in the cerebellum. In this study, [(125)I]IBF was bound to the D(2)R expressed in the cerebellum of the model mice selectively. Immunostaining was performed to confirm the HA-D(2)R expression in the cerebellum of the model mice. A significant correlation (r=0.900, P<0.001) between areas that expressed HA-D(2)R by immunostaining and areas in which [(125)I]IBF accumulated by the ex vivo autoradiograms was found. These results indicated that radioiodinated IBF is useful as a reporter probe to detect D(2)R reporter gene expression, which can be used for monitoring therapeutic gene expression in the cerebellum.

Iodine-123-MIBG sympathetic imaging in Lewy-body diseases and related movement disorders

Iodine-123-labeled metaiodobenzylguanidine (MIBG) has a history of over 20 years as a marker of myocardial sympathetic activity in Japan and has been used for various cardiac diseases. Aside from conventional utilities in patients with cardiac diseases, including ischemic heart diseases, cardiomyopathy, heart failure and diabetes, neurological disorders have recently been drawing special attention. The [(123)I]MIBG study showed markedly decreased myocardial uptake in Parkinson's disease, dementia with Lewy bodies and pure autonomic failure, which is a common feature of Lewy-body diseases. The MIBG study can be used for differentiating patients with extrapyramidal signs and dementia. The unique application of MIBG in movement disorders and related neurological diseases is one of its most common uses in Japan, and further studies are expected worldwide.

[Assessment for the image interpretation of 111In-ibritumomab tiuxetan in the phase II study of 90Y-ibritumomab tiuxetan in patients with relapsed or refractory indolent B-cell lymphoma]

Prior to the 90Y-ibritumomab tiuxetan (Y2B8) therapy, imaging is performed to verify the expected biodistribution of 111In-ibritumomab tiuxetan (In2B8). In order to determine the indication of radioimmunotherapy with Y2B8, the interpretation criteria for altered biodistribution of In2B8 was established. A phase II study of Y2B8 in patients with relapsed or refractory indolent B-cell lymphoma was performed in nine institutions in Japan. After the completion of the rituximab infusion at 250 mg/m2, 130 MBq of In2B8 was administered intravenously over 10 minutes. Gamma-camera imaging was performed at 2-24 hrs, 48-72 hrs, and 90-144 hrs. Images were interpreted by two investigators including a nuclear physician at the individual institution according to the protocol defined criteria to determine the indication of the radioimmunotherapy. Forty-seven cases were enrolled in the study, and 45 cases underwent In2B8 scintigraphy. After the completion of the study, central assessment of the scintigram was performed by three nuclear physicians according to both the criteria of the phase II study and the latest version of the package insert of Zevalin in the United States of America. Two cases were judged as altered biodistribution based on both criteria. They demonstrated diffusely increased bone marrow uptake. The protocol defined criteria revealed additional two cases with altered biodistribution. They showed increased splenic uptake with facilitated blood clearance without increase in the bone marrow uptake. They received Y2B8 and no increment in the adverse event was noted as compared with cases with expected biodistribution. Then this type of biodistribution was not considered altered biodistribution. Increased focal bone marrow uptake was noted in other two cases. They were also considered within the limit of expected biodistribution. The present study recommends the following criteria for altered biodistribution of In2B8. 1) Diffusely increased bone marrow uptake simulating the super scan on bone scintigraphy, 2) Prominent uptake in all of the liver, spleen, and bone marrow, 3) Uptake in the lung, kidney, and intestine without lymphoma higher than the liver.

[Guideline draft of appropriate use of 131I-MIBG for internal radiotherapy of neuroendocrine tumors]

I3I-MIBG has been used for therapy of unresectable neuroendocrine tumors including malignant pheochromocytomas and neuroblastomas in foreign countries since the '80s when its clinical therapeutic trials were initiated. In Japan, 131I-MIBG for therapy has not been approved by Health and Labor Ministry, however, personally imported 131I-MIBG is now available in limited institutions for therapeutic purpose. This guideline draft was made to provide the information about 131I-MIBG radiotherapy including related side effects for doctors, nurses, patients and their families, to prevent the adverse effects of this therapy and to protect radiation injuries from this tracer. The appendices were also attached concerning practical guidance for attending physicians, patient management and referring physicians for their conveniences.

Cardiac scintigraphic findings of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes: A case report

A 49-year-old woman was admitted to hospital because of heart failure. She was diagnosed as having mitochondrial cardiomyopathy and diabetes mellitus. Echocardiography revealed a hypertrophic and poorly contracting left ventricle. A diagnosis of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes was established by muscle biopsy. She underwent technetium-99m-sestamibi ((99m)Tc-MIBI) and beta-methyl-p-(123)I-iodophenyl-pentadecanoic acid ((123)I-BMIPP) scintigraphic examinations. (99m)Tc-MIBI single-photon emission computed tomography revealed reduced tracer uptake in the hypertrophic left ventricular inferior wall. In contrast, there was an increase in (123)I-BMIPP uptake in the in the region of reduced (99m)Tc-MIBI uptake ((99m)Tc-MIBI/(123)I-BMIPP mismatch). There was rapid washout of (99m)Tc-MIBI from the myocardium (washout rate increased by 30%). Decreased (99m)Tc-MIBI and increased (123)I-BMIPP uptake ((99m)Tc-MIBI/(123)I-BMIPP mismatch) were the characteristics of cardiac involvement in mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes.

A change of in vivo characteristics depending on specific activity of radioiodinated (+)-2-[4-(4-iodophenyl)piperidino]cyclohexanol [(+)-pIV] as a ligand for sigma receptor imaging

The radioiodinated (+)-p-iodovesamicol [(+)-pIV], which shows a high binding affinity for sigma-1 (sigma-1) receptors, is prepared by an exchange reaction. The specific activity (SA) is fairly low and therefore is insufficient for clinical use. In this study, we prepared (+)-[(125)I]pIV with a high SA from tributylstannyl precursor and compared the in vivo characteristics between high and low SA by imaging sigma-1 receptors in the central nervous system. In the biodistribution study, a difference in brain accumulation was observed between the two methods. At 30 min postinjection, the brain accumulation (1.58%ID/g) of low SA [0.6-1.1 TBq/mmol (16-30 Ci/mmol)] (+)-[(125)I]pIV was higher than that (1.34%ID/g) of high SA [>88.8 TBq/mmol (>2400 Ci/mmol)] (+)-[(125)I]pIV. In the blocking study, the brain uptake of high SA (+)-[(125)I]pIV was reduced more significantly by the coadministration of sigma ligands such as pentazocine, haloperidol or SA4503 than that of low SA (+)-[(125)I]pIV. These results showed that nonspecific binding of high SA (+)-[(125)I]pIV in the brain was lower than that of low SA (+)-[(125)I]pIV, and high SA (+)-[(125)I]pIV bound more specifically to sigma-1 receptors in the brain than low SA (+)-[(125)I]pIV. In contrast, in the blood-binding study, high SA (+)-[(125)I]pIV (58.4%) bound to blood cells with higher affinity than low SA (+)-[(125)I]pIV (46.0%). In metabolite studies, blood metabolites of high SA (+)-[(125)I]pIV (57.3+/-3.5%) were higher than those of low SA (+)-[(125)I]pIV (45.5+/-4.1%) at 30 min postinjection. Higher SA may be apt to bind to blood cells with higher affinity and to be metabolized faster.

Airway complication occurring during radioiodine treatment for Graves' disease

Airway complications rarely occur in 131I radioiodine therapy for Graves' disease. This study presents two cases in which 131I therapy caused this acute complication. The patients complained of the symptom 6 h and 33 h after administration of 131I. A histamine H1 receptor antagonist and hydrocortisone rapidly resolved symptoms in both cases. These two cases remind physicians that 131I therapy for Graves' disease may cause potentially life-threatening complications.

In vivo characterization of radioiodinated (+)-2-[4-(4-iodophenyl) piperidino] cyclohexanol as a potential sigma-1 receptor imaging agent

In this study, the (+)-enantiomer of radioiodinated 2-[4-(4-iodophenyl)piperidino]cyclohexanol [(+)-[(125)I]-p-iodovesamicol] [(+)-[(125)I]pIV], which is reported to bind with high affinity to sigma-1 receptors in vitro, was tested for its usefulness in imaging sigma-1 receptors in the central nervous system (CNS) in vivo. In biodistribution studies, significant amounts (approximately 3% of the injected dose) of (+)-[(125)I]pIV accumulated in rat brain, and its retention was prolonged. In blocking studies, the accumulation of (+)-[(125)I]pIV in the rat brain was significantly reduced by the coadministration of sigma-ligands such as pentazocine (5.0 micromol), haloperidol (0.5 micromol) or SA4503 (0.5 micromol). The blocking effect of pentazocine (selective sigma-1 ligand) was similar to the blocking effects of SA4503 and haloperidol [nonselective sigma (sigma-1 and sigma-2) ligands]. Ex vivo autoradiography of the rat brain at 45 min following intravenous injection of (+)-[(125)I]pIV showed high localization in brain areas rich in sigma-1 receptors. Thus, the distribution of (+)-[(125)I]pIV was thought to bind to sigma-1 receptors in the CNS in vivo. These results indicate that radioiodinated (+)-pIV may have the potential to image sigma-1 receptors in vivo.

Effect of Postconditioning on Myocardial 99mTc-Annexin-V Uptake: Comparison with Ischemic Preconditioning and Caspase Inhibitor Treatment

99mTc-annexin-V imaging has been proved to be feasible to detect phosphatidylserine, which externalizes on the outer cell membrane early in the process of apoptosis. To determine whether postconditioning suppresses myocardial cell damage or apoptosis, we evaluated the intensity and distribution of 99mTc-annexin-V uptake after postconditioning in a rat model of ischemia and reperfusion and compared the effect to that of ischemic preconditioning and pretreatment with caspase inhibitor.

METHODS

In control rats (n = 13), after thoracotomy the left coronary artery was occluded for 20 min followed by reperfusion for 30 or 90 min and injection of 99mTc-annexin-V (80-150 MBq). One hour later, to verify the area at risk, 201Tl (0.74 MBq) was injected intravenously just beyond the left coronary artery reocclusion, and the rats were sacrificed 1 min later. In the groups of rats with various interventions, postconditioning (n = 11) was performed just after the reperfusion, and preconditioning (n = 11) and caspase inhibitor treatment (n = 11) were performed before ischemia. Dual-tracer autoradiography was performed to assess 99mTc-annexin-V uptake and area at risk.

RESULTS

In all control rats, intense 99mTc-annexin-V uptake was observed in the area at risk (uptake ratios at 30 or 90 min after reperfusion, 4.15 +/- 1.89 and 3.70 +/- 1.41, respectively). Postconditioning suppressed 99mTc-annexin-V uptake (uptake ratios at 30 or 90 min after reperfusion, 2.09 +/- 0.56, P < 0.05, and 1.88 +/- 0.69, P < 0.05, respectively). Preconditioning also suppressed uptake (uptake ratios at 30 and 90 min after reperfusion, 1.17 +/- 0.29, P < 0.005, and 1.33 +/- 0.74, P < 0.01, respectively), as did caspase inhibitor (uptake ratios at 30 and 90 min after reperfusion, 2.08 +/- 0.50, P < 0.05, and 1.27 +/- 0.24, P < 0.005, respectively). In all interventions, the percentage of cells positive on deoxyuride-5'-triphosphate biotin nick end labeling and histologic changes with myocardial cell degeneration and cell infiltrations were suppressed markedly.

CONCLUSION

These data indicate that 99mTc-annexin-V imaging may be a way to monitor myocardial injury and its response to novel therapeutic interventions including postconditioning, preconditioning, and antiapoptotic therapy.

Changes in the Levels of CD4+ and CD8+ T-Lymphocytes After Strontium-89 Chloride Therapy for Painful Bone Metastases in Patients Correlate with Treatment Efficacy

The aim of this study was to evaluate changes in the peripheral blood CD(4)(+) and CD(8)(+) T-lymphocyte populations following strontium-89 chloride ((89)SrCl(2)) therapy for painful bone metastases and to relate these changes to a therapeutic response. Forty-two (42) patients with painful bone metastases were treated with 148 MBq (4 mCi) of (89)SrCl(2). Blood samples were drawn before and monthly for 6 months after the treatment. CD(4)(+) and CD(8)(+) T-lymphocyte levels were measured using flow cytometry. The number of bone metastases and the pain score were used to assess the effect of therapy. Before the administration of (89)SrCl(2), the ratio of CD(4)(+) to CD(8)(+) T-lymphocytes was lower in patients with bone metastases than in the control subjects (p < 0.01); after therapy, the ratio increased up to the fourth month and then gradually declined to pretreatment levels. Responders had higher post-therapeutic ratios of CD(4)(+) to CD(8)(+) than nonresponders. There was a good correlation between the ratio of CD(4)(+) to CD(8)(+) and both the number of bone metastases and the pain score. The ratio of CD(4)(+) to CD(8)(+) T-lymphocytes correlated strongly with the response of bone metastases to (89)SrCl(2), and therefore, may be used as an indicator of (89)SrCl(2) efficacy.