Eriko Tsukamoto

Image fusion between 18FDG-PET and MRI/CT for radiotherapy planning of oropharyngeal and nasopharyngeal carcinomas

PURPOSE Accurate diagnosis of tumor extent is important in three-dimensional conformal radiotherapy. This study reports the use of image fusion between (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG-PET) and magnetic resonance imaging/computed tomography (MRI/CT) for better targets delineation in radiotherapy planning of head-and-neck cancers. METHODS AND MATERIALS The subjects consisted of 12 patients with oropharyngeal carcinoma and 9 patients with nasopharyngeal carcinoma (NPC) who were treated with radical radiotherapy between July 1999 and February 2001. Image fusion between 18FDG-PET and MRI/CT was performed using an automatic multimodality image registration algorithm, which used the brain as an internal reference for registration. Gross tumor volume (GTV) was determined based on clinical examination and 18FDG uptake on the fusion images. Clinical target volume (CTV) was determined following the usual pattern of lymph node spread for each disease entity along with the clinical presentation of each patient. RESULTS Except for 3 cases with superficial tumors, all the other primary tumors were detected by 18FDG-PET. The GTV volumes for primary tumors were not changed by image fusion in 19 cases (89%), increased by 49% in one NPC, and decreased by 45% in another NPC. Normal tissue sparing was more easily performed based on clearer GTV and CTV determination on the fusion images. In particular, parotid sparing became possible in 15 patients (71%) whose upper neck areas near the parotid glands were tumor-free by 18FDG-PET. Within a mean follow-up period of 18 months, no recurrence occurred in the areas defined as CTV, which was treated prophylactically, except for 1 patient who experienced nodal recurrence in the CTV and simultaneous primary site recurrence. CONCLUSION This preliminary study showed that image fusion between 18FDG-PET and MRI/CT was useful in GTV and CTV determination in conformal RT, thus sparing normal tissues.

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.

Significance of reduced uptake of iodinated fatty acid analogue for the evaluation of patients with acute chest pain

OBJECTIVES To assess whether 15-(p-[iodine-123] iodophenyl)-3-(R,S) methylpentadecanoic acid (BMIPP) imaging can identify previous ischemic areas, BMIPP SPECT was performed in patients with acute chest pain to compare its findings with those of technetium-99m-tetrofosmin (tetrofosmin) SPECT and coronary angiography. BACKGROUND Basic studies indicate that BMIPP can identify previous ischemia as reduced tracer uptake. METHODS This study prospectively enrolled 111 consecutive patients with acute chest pain without myocardial infarction. Tetrofosmin SPECT was performed at rest within 24 h after the last episode of chest pain. Coronary angiography and BMIPP SPECT were also performed on the following day. RESULTS Sixty-four of the 87 patients with coronary stenosis or spasm showed BMIPP abnormalities corresponding to the areas of coronary abnormalities (sensitivity 74%), whereas only 33 of them showed perfusion abnormalities (sensitivity 38%) (p < 0.001). Of 24 patients [corrected] without coronary stenosis or spasm, 22 showed normal BMIPP SPECT (specificity = 92%) [corrected] and 23 showed normal tetrofosmin SPECT (sensitivity = 96%) [corrected]. Coronary stenosis was more often seen in the group with abnormal tetrofosmin/abnormal BMIPP (82%) and with normal tetrofosmin/abnormal BMIPP (69%) than in the group with normal tetrofosmin/normal BMIPP (36%) (p < 0.05). Coronary spasm was observed more often in the group with abnormal tetrofosmin/abnormal BMIPP (83%) and with normal tetrofosmin/abnormal BMIPP (90%) than in the group with normal tetrofosmin/normal BMIPP (27%) (p < 0.05). The extent and severity scores of tetrofosmin and BMIPP in the patients with organic stenosis were significantly higher than those of patients with no organic stenosis or spasm (p < 0.0001). CONCLUSIONS These data indicate that BMIPP SPECT may specifically identify previous ischemic lesions due to coronary stenosis or spasm in patients with acute chest pain.

Abnormal neuronal network in anorexia nervosa studied with I-123-IMP SPECT.

Single photon emission computed tomography was used to study 14 female patients with anorexia nervosa and 8 female normal comparison subjects. Automatic voxel-based analysis of the images was carried out using statistical parametric mapping (SPM) software. Statistics across the entire brain were displayed as Z scores (threshold: P<0.05). Compared with the normal comparison subjects, the anorectic patients were characterized by hypoperfusion in the medial prefrontal cortex and the anterior cingulate gyrus, and hyperperfusion in the thalamus and the amygdala-hippocampus complex. These results suggest that a dysfunction in neuronal circuitry may be related to anorexia nervosa.

Mediastinal Lymph Node Staging by FDG-PET in Patients with Non-Small Cell Lung Cancer: Analysis of False-Positive FDG-PET Findings

Background: Accurate staging of mediastinal and hilar lymph nodes is a critical factor determining operability in patients with non-small cell lung cancer (NSCLC). Positron emission tomography with 2-[18F] fluoro-2-deoxy-D-glucose as a tracer (FDG-PET) has recently been reported to be more effective in detecting tumor involvement in mediastinal and hilar lymph nodes than computed tomography (CT). Objective: In this study, we analyzed the accuracy of FDG-PET in mediastinal and hilar lymph node staging in patients with NSCLC and the factors associated with false-positive or false-negative FDG-PET findings in mediastinal and hilar lymph node staging. Methods: Fifty-four patients with NSCLC who underwent preoperative analysis including chest CT and whole-body FDG-PET were evaluated retrospectively. Using FDG-PET, lesions were considered to be positive if a definite, localized area of higher uptake, excluding physiologic uptake, than in surrounding normal tissue was present. On CT findings, lymph nodes were considered to be positive if they were >10 mm in short-axis diameter, except subcarinal lymph nodes (#7), which were considered to be positive if they were >15 mm in short-axis diameter. All patients underwent surgical resection of primary tumors and mediastinal and hilar lymph nodes between 1999 and 2001 in our institute. Resected lymph nodes were histologically examined for the existence of tumor cells. Results: A total of 306 lymph nodes were resected and used for analysis. The sensitivity, specificity, positive predictive value and negative predictive value of FDG-PET were 73, 98, 70 and 98%, while those of CT were 55, 96, 55 and 96%, respectively. When pre-operative nodal staging was compared with post-operative histopathological staging, 44 patients (81%) were correctly staged, 7 (13%) were overstaged and 3 (6%) were understaged by FDG-PET, while 39 patients (72%) were correctly staged, 8 (15%) were overstaged and 7 (13%) were understaged by CT. All 7 overstaged patients by FDG-PET had other pulmonary complications, including interstitial pneumonitis (n = 2), previous pulmonary tuberculosis (n = 3), silicosis (n = 1) and emphysema (n = 1), although they were not in the active stage. In 3 understaged patients by FDG-PET, lymph nodes were also undetectable by CT. Conclusion: FDG-PET is superior to CT in mediastinal and hilar lymph node staging of patients with NSCLC. However, care should be taken in lymph node staging for patients who have other pulmonary complications, including interstitial pneumonitis, previous pulmonary tuberculosis and silicosis.

Clinical role of 18 F-FDG PET for initial staging of patients with extrahepatic bile duct cancer

Abstract. In extrahepatic bile duct cancer, preoperative evaluation is important because only surgical excision of all detectable tumours is associated with improvement in 5-year survival. However, morphological imaging techniques, including computed tomography (CT), are still insufficient for accurate staging. The purpose of this study was to assess the additional value, in relation to CT, of 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) for the evaluation of extrahepatic bile duct cancer. Thirty patients with extrahepatic bile duct cancer underwent both 18F-FDG PET and CT for initial staging. The results of the two modalities for evaluation of primary tumours and regional lymph nodes were compared with the final diagnoses based on pathological or clinical findings. The primary tumours were interpreted as malignant on the basis of CT in 24 (80%) of the patients, while 18F-FDG PET revealed increased 18F-FDG uptake in 18 (60%) of them. On the other hand, 18F-FDG PET showed focal accumulation of 18F-FDG in the bile duct in three of the six patients with equivocal findings on CT. The sensitivity, specificity and accuracy of CT for regional lymph node metastases were 54%, 59% and 57%, while those of 18F-FDG PET were 38%, 100% and 73%, respectively. The specificity of 18F-FDG PET for regional lymph node metastases was significantly higher than that of CT (P<0.01). Of 14 patients with N1 or N2 disease diagnosed by CT, only seven (50%) had a final diagnosis of regional lymph node metastasis. In these 14 patients, 18F-FDG PET accurately evaluated the N component of the disease in 12 patients (86%). In conclusion, in the initial staging of patients with extrahepatic bile duct cancer, 18F-FDG PET offers additional value in relation to CT in evaluating both the primary tumour and regional lymph nodes.

Lung tumors evaluated with FDG-PET and dynamic CT: the relationship between vascular density and glucose metabolism.

Purpose The aim of the current study was to evaluate the relationship between FDG-PET and dynamic CT in lung tumors. Method Forty consecutive patients with pulmonary tumors underwent whole-body FDG-PET and contrast-enhanced dynamic CT. The size of tumors was 2.6 ± 0.2 cm (mean ± SD) at the largest diameter. The standardized uptake value (SUV) of FDG-PET, peak attenuation (APA), and relative flow (RF) of dynamic CT were evaluated. All patients underwent surgery, and tissue samples were available to be studied. The intratumoral microvessel densities (MVDs) were counted and compared with the radiologic parameters. The duration between radiologic examinations and surgery was within 2 weeks in all patients. Results The mean SUV, APA, and RF of lung cancers were significantly higher than those of benign lesions (p < 0.05). The mean APA and RF of lung cancers correlated with mean SUV (APA: r = 0.665, p < 0.0001; RF:r = 0.848, p < 0.05) and mean MVD (APA:r = 0.801, p < 0.0001; RF:r = 0.723, p < 0.05). The mean SUV of lung cancers correlated with the mean MVD (r = 0.612, p < 0.001). No correlation was found between the mean APA, RF, SUV, and MVD in benign tumors. Conclusion The APA and RF of dynamic CT correlated with the SUV of FDG-PET imaging in lung cancer. The APA and RF of dynamic CT as an index of blood pooling may be related to increased glucose metabolism in lung cancer.

PET/CT today: System and its impact on cancer diagnosis

Over the past six years, PET/CT has spread rapidly and replaced conventional PET. Although PET/ CT is a combination of PET for functional information and CT for morphological information, their combination is synergistic. PET/CT fusion images result in higher diagnostic accuracy with fewer equivocal findings. This results in a greater impact on cancer diagnosis. With attenuation correction performed by the CT component, PET/CT can provide higher quality images over shorter examination times than conventional PET. As with all modalities, PET/CT has several characteristic artifacts such as misregistration due to respiration, overattenuation correction due to metals, etc. Awareness of these pitfalls will help the imaging physician use PET/CT effectively in daily practice.

Fluorodeoxyglucose uptake and glucose transporter expression in experimental inflammatory lesions and malignant tumours: effects of insulin and glucose loading.

The expression of glucose transporters (GLUTs) and its relationship to fluorodeoxyglucose accumulation in malignant tumours have been well investigated, while such a relation has not been studied in inflammatory lesions. The aim of the present study was to investigate the effects of insulin and glucose loading on the expression of GLUTs in inflammatory lesions and compare them with those in malignant tumours in relation to fluorodeoxyglucose accumulation. All tissue specimens used in this study were obtained in our previous study, in which rats were inoculated with allogenic hepatoma cells (KDH-8), Staphylococcus aureus, or turpentine oil into the left calf muscle and divided into three subgroups: insulin loaded, glucose loaded, and control groups. The expression of glucose transporters (GLUT-1 to GLUT-5) was investigated by immunostaining the lesions (n = 5-6, for each group). In all control groups, the expression levels of GLUT-1 and GLUT-3 were significantly higher than those of GLUT-2, GLUT-4 and GLUT-5. Insulin loading did not significantly affect the expression levels of GLUT-1 and GLUT-3 in these lesions except for a significant but slight decrease in the GLUT-1 expression level in the inflammatory lesion of non-infectious origin (89% of the control value). Glucose loading significantly decreased the expression level of GLUT-1 in the inflammatory lesion of non-infectious origin (70% of the control value, P<0.01), and that of GLUT-3 in the inflammatory lesion of infectious origin (70% of the control value, P<0.05), while the expression levels of GLUT-1 and GLUT-3 in the tumour were not significantly affected. These results demonstrate the effects of insulin and glucose loading on the expression level of a molecule (GLUT proteins). The decreased GLUT-1 and GLUT-3 expression levels induced by glucose loading may partly explain the impaired FDG uptake observed in our previous study.

Use of 123I-BMIPP single-photon emission tomography to estimate areas at risk following successful revascularization in patients with acute myocardial infarction

Abstract. Previous studies have indicated that iodine-123 labelled β-methyliodophenyl pentadecanoic acid (BMIPP), an iodinated fatty acid analogue, can identify persistent alteration of fatty acid metabolism after restoration of blood flow. To assess whether fatty acid imaging can delineate areas at risk following successful revascularization in patients with acute myocardial infarction (AMI), BMIPP findings at 1 week post AMI were compared with perfusion imaging before and after revascularization therapy. Sixty-five patients with AMI underwent technetium-99m tetrofosmin single-photon emission tomography (SPET) before m (TF0) and 1 week (TF1) after successful revascularization therapy. BMIPP SPET was also performed under a fasting state at 1 week (BM1) post AMI. The extent scores were calculated from the defect scores in 20 segments. The BM1 score (7.7±3.9) was similar to the TF0 score (8.8±4.2) (r=0.86, P<0.0001), but significantly higher than the TF1 score (5.8±3.9) (P<0.0001). A significant correlation was observed between the BM1 score and TF0 score (r=0.86, P<0.0001). Among a total of 1300 segments, the BM1 score was identical to the TF0 score in 1156 (88.9%). These data indicate that the ability of BMIPP imaging at 1 week post AMI to identify areas at risk is similar to that of tetrofosmin perfusion imaging in the acute phase. This may be due to the impairment of fatty acid uptake and metabolism reflecting prior severe ischaemic insult which persists at least 1 week after recovery of perfusion in the acute phase of AMI.