Toshiki Takei

Myocardial imaging with 18F-fluoro-2-deoxyglucose positron emission tomography and magnetic resonance imaging in sarcoidosis

PurposeDespite accumulating reports on the clinical value of 18F-fluoro-2-deoxyglucose positron emission tomography (18F-FDG PET) and magnetic resonance imaging (MRI) in the assessment of cardiac sarcoidosis, no studies have systematically compared the images of these modalities.MethodsTwenty-one consecutive patients with suspected cardiac sarcoidosis underwent cardiac examinations that included 18F-FDG PET and MRI. The association of 18F-FDG PET and MRI findings with blood sampling data such as serum angiotensin converting enzyme levels was also evaluated.ResultsEight of 21 patients were diagnosed as having cardiac sarcoidosis according to the Japanese Ministry of Health and Welfare Guidelines for Diagnosing Cardiac Sarcoidosis. Sensitivity and specificity for diagnosing cardiac sarcoidosis were 87.5 and 38.5%, respectively, for 18F-FDG PET, and 75 and 76.9%, respectively, for MRI. When the 18F-FDG PET and MRI images were compared, 16 of 21 patients showed positive findings in one (n = 8) or both (n = 8) of the two modalities. In eight patients with positive findings on both images, the distribution of the findings differed among all eight cases. The presence of positive findings on 18F-FDG PET was associated with elevated serum angiotensin-converting enzyme levels; this association was not demonstrated on MRI.ConclusionsBoth 18F-FDG PET and MRI provided high sensitivity for diagnosing cardiac sarcoidosis in patients with suspected cardiac involvement, but the specificity of 18F-FDG PET was not as high as previously reported. The different distributions of the findings in the two modalities suggest the potential of 18F-FDG PET and MRI in detecting different pathological processes in the heart.

18p-FDG PET is superior to67Ga SPECT in the staging of non-Hodgkin’s lymphoma

ObjectiveOur study aims to compare diagnostic accuracy between18F-FDG PET and67Ga SPECT in the staging of non-Hodgkin’s lymphoma.MethodsTwenty-eight patients with non-Hodgkin’s lymphoma, underwent18F-FDG PET,67Ga SPECT and CT for the pretreatment staging of malignant lymphoma between August 1999 and March 2002.18F-FDG PET imaging was obtained 60 minutes after the intravenous administration of 185 MBq of18F-FDG.67Ga SPECT imaging was obtained 2 days after the intravenous administration of 148 MBq of67Ga.18F-FDG PET and 67Ga SPECT were performed within one month. Both imagings were performed on the area from the neck to the pelvis. The18F-FDG PET and67Ga SPECT findings were compared with the CT findings and the clinical course.ResultsSixty-six nodal lesions were clinically confirmed. Of these, 32 were identified by both18F-FDG PET and67Ga SPECT. The remaining 34 lesions were identified only by18F-FDG PET. The mean (± SD) sizes of the nodes were 34.7 ± 32.4 mm for18F-FDG-positive and67Ga-positive lesions and 15.7 ± 8.3 mm for18F-FDG-positive and67Ga-negative lesions (p >; 0.001). Of the 23 extranodal lesions, 12 were identified by both18F-FDG PET and67Ga SPECT, whereas 6 lesions were identified by only18F-FDG PET. Five lesions were not identified by either technique. No18F-FDG-negative but67Ga-positive nodal or extranodal lesions were observed. The difference in findings between the two studies is related to the difference in the size but not in the histology or site of the lesions.Conclusion18F-FDG PET detected significantly more lesions particularly small lesions than67Ga SPECT. Thus,18F-FDG PET is considered to be superior to67Ga SPECT in the staging of non-Hodgkin’s lymphoma.

A case of multimodality multiparametric 11C-choline PET/MR for biopsy targeting in prior biopsy-negative primary prostate cancer.

We introduce the case of a 70-years-old man with an elevated level of prostate-specific antigen and prior negative biopsy. For targeting rebiopsy, the patient underwent C-choline PET/CT and subsequent PET/MR. Both the high uptake in PET and the abnormal findings in MR gave strong evidence for prostate cancer at the ventral periphery of the right apex. This location is sometimes not covered by routine sextant biopsy. The following targeted rebiopsy was positive for prostate cancer. This case indicates the potential role of PET/MR for identifying primary prostate cancer because of its high soft tissue contrast and the possibility of a multimodality approach.

Tumors of the Liver and Biliary Tract

Hepatoma or hepatocellular carcinoma (HCC), a tumor arising from hepatocytes, is one of the most common tumors worldwide, with approximately one million new cases diagnosed/year. Five-year survival ranges from 70% for stage I to <20% for stage III. HCC is often associated with cirrhosis and chronic hepatitis. The tumor is staged using the AJCC TNM classification, which considers tumor size, vascular invasion, lymph node status, and metastatic disease. The tumor is usually advanced at the time of diagnosis. CT and MRI are usually used for staging used for this purpose. Several reports indicated low sensitivity of [18F]FDG for detecting HCC due to a relatively low [18F]FDG uptake within the tumor, due to the presence of glucose-6-phosphatase (G-6-Pase), an enzyme present in normal liver, which converts [18F]FDG-6-P to [18F]FDG, allowing the tracer to diffuse out of tumor cells. [18F]FDG-PET has clinical value for identifying distant metastases and identifying poorly differentiated HCC in patients with multiple lesions, since these lesions show higher [18F]FDG uptake.

Molecular imaging of apoptosis with radio-labeled Annexin A5 focused on the evaluation of tumor response to chemotherapy.

Apoptosis, or programmed cell death, is activated in the course of successful anti-neoplastic therapy. Determining baseline levels of apoptosis and the increment of apoptosis induced by therapy can serve as useful prognostic markers. Thus, non-invasive assessment of apoptosis would be desirable to provide clinicians with information on therapeutic efficacy as well as for the development and testing of new anticancer drugs. In these regards, apoptosis detecting radio-probes (radiopharmaceuticals) have been extensively studied. Annexin A5 (annexin V) is an endogenous protein that binds with high affinity and specificity to phosphatidylserine, which is presented on the cell surface in an early process of apoptosis. Accordingly, apoptotic cells can be detected in vivo using annexin A5 labeled with radionuclides, such as 99mTc and 18F. To date, several annexin A5 radio-probes have been developed. Among these, 99mTc-HYNIC-annexin A5 is the best candidate for apoptosis imaging. The apoptosis imaging using radio-labeled annexin A5 has been applied for detecting apoptosis in vivo in the experimental and clinical evaluation of the tumor response to chemotherapy or radiotherapy. The present review describes apoptosis imaging with annexin A5 radio-probes, focusing on its application to the evaluation of the tumor response to chemotherapy. First, principles of apoptosis imaging with annexin A5 radio-probes are described. Next, experimental results with radio-labeled annexin A5 in the evaluation of therapeutic efficacy are discussed. Finally, clinical application of apoptosis imaging with radio-labeled annexin A5 is addressed.

FDG PET/CT in a patient with spontaneous remission of methotrexate-associated lymphoproliferative disorders after interruption of methotrexate.

We report a case that fluorodeoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) depicted systemically multiple lesions of methotrexate (MTX)-associated lymphoproliferative disorders. A 70-year-old man receiving MTX for rheumatoid arthritis complained of neck swelling. FDG PET/CT revealed multiple FDG-avid lesions in lymph nodes, lungs, bones, and muscles. Lesions in bones and muscles were not detected on X-CT. Final diagnosis of cervical node was confirmed as MTX-associated lymphoproliferative disorders. FDG PET/CT performed 148 days after discontinuing MTX demonstrated complete remission.

Molecular Imaging for the Assessment of Tumor Malignancy and Response to Therapy

Fluorine-18-2-deoxy-2-lluoro-d-glucose (18F-FDG) is a useful positron emission tomography (PET) probe for differentiating tumors from benign lesions and for evaluating therapeutic effects. However, limitations of FDG-PET have recently been noted and the development of post-FDG molecular probes is strongly required. Here, we describe our basic studies on post-FDG molecular probes for the assessment of tumor malignancy and response to therapy, focusing on cell proliferation and apoptosis.