Ichiro Higuchi

18F-FDG PET/MRI fusion in characterizing pancreatic tumors: comparison to PET/CT

ObjectiveTo demonstrate that positron emission tomography (PET)/magnetic resonance imaging (MRI) fusion was feasible in characterizing pancreatic tumors (PTs), comparing MRI and computed tomography (CT) as mapping images for fusion with PET as well as fused PET/MRI and PET/CT.MethodsWe retrospectively reviewed 47 sets of 18F-fluorodeoxyglucose (18F -FDG) PET/CT and MRI examinations to evaluate suspected or known pancreatic cancer. To assess the ability of mapping images for fusion with PET, CT (of PET/CT), T1- and T2-weighted (w) MR images (all non-contrast) were graded regarding the visibility of PT (5-point confidence scale). Fused PET/CT, PET/T1-w or T2-w MR images of the upper abdomen were evaluated to determine whether mapping images provided additional diagnostic information to PET alone (3-point scale). The overall quality of PET/CT or PET/MRI sets in diagnosis was also assessed (3-point scale). These PET/MRI-related scores were compared to PET/CT-related scores and the accuracy in characterizing PTs was compared.ResultsForty-three PTs were visualized on CT or MRI, including 30 with abnormal FDG uptake and 13 without. The confidence score for the visibility of PT was significantly higher on T1-w MRI than CT. The scores for additional diagnostic information to PET and overall quality of each image set in diagnosis were significantly higher on the PET/T1-w MRI set than the PET/CT set. The diagnostic accuracy was higher on PET/T1-w or PET/T2-w MRI (93.0 and 90.7%, respectively) than PET/CT (88.4%), but statistical significance was not obtained.ConclusionPET/MRI fusion, especially PET with T1-w MRI, was demonstrated to be superior to PET/CT in characterizing PTs, offering better mapping and fusion image quality.

Fusion Image of Positron Emission Tomography and Computed Tomography for the Diagnosis of Local Recurrence of Rectal Cancer

BackgroundThe aim of this study was to evaluate the clinical and therapeutic value of digital fusion image (FI) of positron emission tomography (PET) using 18F-fluorodeoxy glucose and computed tomography (CT) in patients who were suspected of having a local recurrence of rectal cancer.MethodsForty-two patients (32 men and 10 women; mean age, 61.4 years, range, 40–79 years) with a suspicion of local recurrence after curative resection of rectal cancer were prospectively recruited and underwent 18F-fluorodeoxy glucose-PET and CT. The FI was reconstructed with a commercially available digital software program, T-B Fusion. Wilcoxon signed rank test was used to compare FI with CT alone or PET alone.ResultsFI yielded a correct diagnosis in 39 (93%) of 42 patients, whereas CT alone and PET alone did so in 33 (79%) and 37 (88%) patients, respectively. FI had better diagnostic accuracy than CT alone (P = .0138) and PET alone (P = .0156). Overall, FI altered patient management in 11 (26.2%) patients on the basis of additional information, including differentiation of the tumor from the postoperative scar in 6 patients, exact anatomical location in 3 patients, and both in 2 patients.ConclusionsFI has a potential clinical value in the treatment of suspected local recurrence of rectal cancer.

Diagnostic performance of fluorodeoxyglucose positron emission tomography/magnetic resonance imaging fusion images of gynecological malignant tumors: comparison with positron emission tomography/computed tomography.

PurposeWe compared the diagnostic accuracy of fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) and PET/magnetic resonance imaging (MRI) fusion images for gynecological malignancies.Materials and methodsA total of 31 patients with gynecological malignancies were enrolled. FDG-PET images were fused to CT, T1- and T2-weighted images (T1WI, T2WI). PET-MRI fusion was performed semiautomatically. We performed three types of evaluation to demonstrate the usefulness of PET/MRI fusion images in comparison with that of inline PET/CT as follows: depiction of the uterus and the ovarian lesions on CT or MRI mapping images (first evaluation); additional information for lesion localization with PET and mapping images (second evaluation); and the image quality of fusion on interpretation (third evaluation).ResultsFor the first evaluation, the score for T2WI (4.68 ± 0.65) was significantly higher than that for CT (3.54 ± 1.02) or T1WI (3.71 ± 0.97) (P < 0.01). For the second evaluation, the scores for the localization of FDG accumulation showing that T2WI (2.74 ± 0.57) provided significantly more additional information for the identification of anatomical sites of FDG accumulation than did CT (2.06 ± 0.68) or T1WI (2.23 ± 0.61) (P < 0.01). For the third evaluation, the three-point rating scale for the patient group as a whole demonstrated that PET/T2WI (2.72 ± 0.54) localized the lesion significantly more convincingly than PET/CT (2.23 ± 0.50) or PET/T1WI (2.29 ± 0.53) (P < 0.01).ConclusionPET/T2WI fusion images are superior for the detection and localization of gynecological malignancies.

The role of CT and 18F-FDG PET in managing the neck in node-positive head and neck cancer after chemoradiotherapy

Conclusion. Patients showing a complete response on computed tomography (CT) can be spared from neck dissection. Objective. To determine whether CT or fluorine-18-fluorodeoxyglucose positron emission tomography (18F-FDG PET) is superior in the evaluation of persistent nodal disease after chemoradiotherapy in patients with node-positive head and neck squamous cell carcinoma (HNSCC). Patients and methods. Study entry criteria included node-positive HNSCC treated with definitive chemoradiotherapy, a local complete response, and post-treatment CT and 18F-FDG PET studies 7 weeks after chemoradiotherapy. Forty-eight patients with 60 node-positive necks were eligible. Nodes larger than 1 cm, or with central necrosis on CT, or any visually hypermetabolic nodes on 18F-FDG PET were considered positive. Regardless of PET findings, necks with positive CT were subjected to neck dissection, whereas those with negative CT were observed without neck dissection. Results. Twenty-two necks showed positive CT, 20 and 2 of which underwent neck dissection and fine needle aspiration cytology, respectively, resulting in pathologic evidence of persistent nodal disease in 13 necks. Five of 38 necks with negative CT developed regional recurrence. Diagnostic accuracy was equivalent between CT and 18F-FDG PET. There was no difference in 3-year cause-specific survival between patients with positive and negative CT (79% and 81%, respectively).

Mucosa-associated lymphoid tissue lymphoma studied with FDG-PET: a comparison with CT and endoscopic findings

ObjectiveWe investigated the accumulation of 2-deoxy-2-[18F] fluoro-d-glucose positron emission tomography (FDG-PET) in patients with mucosa-associated lymphoid tissue (MALT) lymphoma patients as compared with computerized tomography (CT) and endoscopic imaging.MethodsFDG-PET was performed on 13 untreated patients with MALT lymphoma. CT scanning of the affected areas was performed in all the patients to compare with the FDG-PET images. In five patients with gastric MALT lymphoma, comparison was also made with the endoscopic findings.ResultsOf the 13 untreated MALT lymphoma patients, all 8 non-gastric MALT lymphoma patients exhibited abnormal accumulation of FDG. However, in the five gastric MALT lymphoma patients, no abnormal FDG accumulation was observed. Although lesions could be confirmed on CT images from the patients other than those with gastric MALT lymphoma, the mucosal lesions of gastric MALT lymphoma could be observed only by endoscopy.ConclusionsFDG-PET can be used to detect MALT lymphoma when it forms mass lesions, whereas it is difficult to detect non-massive MALT lymphoma of gastrointestinal origin.

Evaluation of delayed18F-FDG PET in differential diagnosis for malignant soft-tissue tumors

ObjectivePositron emission tomography (PET) with 2-deoxy-2-[18F]fiuoro-D-glucose (18F-FDG) has been used for the evaluation of soft-tissue tumors. However, the range of accumulation of18F-FDG for malignant soft-tissue lesions overlaps with that of benign lesions. The aim of this study is to investigate the usefulness of delayed18F-FDG PET imaging in the differentiation between malignant and benign soft-tissue tumors.MethodsFifty-six patients with soft-tissue tumors underwent whole body18F-FDG PET scan at 1 hour (early scan) and additional scan at 2 hours after injection (delayed scan). The standardized uptake value (SUVmax) of the tumor was determined, and the retention index (RI) was defined as the ratio of the increase in SUVmax between early and delayed scans to the SUVmax in the early scan. Surgical resection with histopathologic analysis confirmed the diagnosis.ResultsHistological examination proved 19 of 56 patients to have malignant soft-tissue tumors and the rest benign ones. In the scans of all 56 patients, there was a statistically significant difference in the SUVmax between malignant and benign lesions in the early scan (5.50 ± 5.32 and 3.10 ± 2.64, respectively, p < 0.05) and in the delayed scan (5.95 ± 6.40 and 3.23 ± 3.20, respectively, p < 0.05). The mean RI was not significantly different between malignant and benign soft-tissue tumors (0.94 ± 23.04 and -2.03 ± 25.33, respectively).ConclusionsIn the current patient population, no significant difference in the RI was found between malignant and benign soft-tissue lesions. Although the mean SUVmax in the delayed scan for malignant soft-tissue tumors was significantly higher than that for benign ones, there was a marked overlap. The delayed18F-FDG PET scan may have limited capability to differentiate malignant soft-tissue tumors from benign ones.

18F-FDG PET for the evaluation of thymic epithelial tumors: Correlation with the World Health Organization classification in addition to dual-time-point imaging

PurposeOur aim was to determine dual-phase 18F-FDG PET imaging features for various subtypes of thymic epithelial tumors based on the World Health Organization classification.MethodsForty-six patients with histologically verified thymic epithelial tumors [23 with low-risk tumors (4 with type A, 16 with AB, and 3 with B1) and 23 with high-risk tumors (7 with B2, 5 with B3, and 11 with thymic carcinoma] were enrolled in this study. All patients were injected with 18F-FDG.; after 1 h, they underwent scanning; after 3 h, 23 patients underwent an additional scanning. The maximum standard uptake value (SUVmax) and the retention index (RI%) of the lesions were determined.ResultsThe early and delayed SUVmax values in the patients with high-risk tumors [early SUVmax (mean: 6.0) and delayed SUVmax (mean: 7.4)] were both significantly larger than those in patients with low-risk tumors [early SUVmax (mean: 3.2) and delayed SUVmax (mean: 3.4)] (P < 0.05). Early SUVmax values of greater than 7.1 differentiated thymic carcinomas from other types of tumors. For the histological differentiation between high-risk tumors and low-risk tumors, an early SUVmax value of 4.5 was used as the cutoff. The sensitivity, specificity, and accuracy were 78.3, 91.3, and 84.8%, respectively.ConclusionHigh SUV values (early SUV > 4.5) suggest the presence of high-risk tumors. A very high SUV value (early SUV > 7.1) is useful for the differentiation of thymic carcinomas from other types of tumors. The delayed SUV values were higher than the early SUV values in all types of tumors.

18F-FDG-PET of musculoskeletal tumors: a correlation with the expression of glucose transporter 1 and hexokinase II

ObjectiveIt remains controversial whether positron emission tomography (PET) with 2-deoxy-2-[F-18]fluoro-d-glucose (F-18-FDG) can differentiate between benign and malignant musculoskeletal tumors. To uncover the mechanism of F-18-FDG accumulations, we analyzed the correlation between the F-18-FDG accumulation and the expression of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in benign and malignant musculoskeletal tumors.MethodsThe maximum standardized uptake values (SUVmax) of F-18-FDG in 24 benign and 26 malignant musculoskeletal tumors were compared with the histologic malignancies, and the expression of Glut-1 and HK-II was analyzed by immunohistochemistry.ResultsThe SUVmax for malignant tumors (6.33 ± 4.79) was significantly higher than those with benign tumors (3.47 ± 3.12, P < 0.01). The expression of Glut-1 was high in 12 patients (all malignant) and low in 38 patients (24 benign and 14 malignant), and the expression of HK-II was high in 36 patients (11 benign and 25 malignant) and low in 14 patients (13 benign and 1 malignant). Cases with high expression of Glut-1 and HK-II at immunohistochemistry showed a higher SUVmax than those with low expression (Glut-1 8.03 ± 5.10 and 3.98 ± 3.53, P < 0.01; HK-II 5.73 ± 4.49 and 2.99 ± 3.02, P < 0.01). No significant dividing threshold of the SUVmax of F-18 FDG was found for the differential diagnosis between benign and malignant tumors or for the expression of Glut-1 and HK-II.ConclusionsThe limited capability of F-18 FDG-PET in the differential diagnosis of musculoskeletal tumors is owing partly to the various levels of Glut-1 and HK-II expression in individual tumors.

Use of 18F-fluorodeoxyglucose-positron emission tomography to evaluate responses to neo-adjuvant chemotherapy for primary tumor and lymph node metastasis in esophageal squamous cell carcinoma

BACKGROUND Neoadjuvant chemotherapy (NACT) targets lymph node metastasis (LN), as well as the primary tumor (PT) in esophageal squamous cell carcinomas (ESCC). (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) reflects viable tumor volume and may be more useful for evaluating NACT responses than conventional radiography. Moreover, FDG-PET may elucidate the clinical significance of NACT responses for LN, which is not always identical to those for PT. PATIENTS AND METHODS We retrospectively investigated prognostic factors in 38 node-positive ESCC patients who had undergone NACT (5-fluorouracil, adriamycin, and cisplatin) and surgical resection. The NACT response was evaluated separately by both PET and computed tomography (CT) for each PT and LN. RESULTS Although NACT effect for PT and LN was similar by PET evaluation (SUVmax reduction; average 70.58% vs 71.57%), they did not show significant correlation, revealing discordance for 13 (34.2%) patients when SUVmax reduction of more than 70% was classified as a PET responder. An opposite relationship existed in that the pre-NACT SUVmax of PT was significantly lower in PET responders than in PET non-responders (9.92 +/- 4.3 vs 12.96 +/- 3.8, P = .032), while that of LN tended to be higher in responders than in non-responders (5.70 +/- 3.2 vs 3.77 +/- 0.9, P = .072). Multivariate analysis identified the number of PET-positive LN (P = .018, HR = 5.464) and PET response for PT (P = .015, HR = 4.620) and for LN (P = .028, HR = 3.854) as independent prognostic predictors. The NACT response for PT or LN on CT evaluation was not a significant prognostic predictor. CONCLUSION PET is superior to CT for evaluating the NACT response from the viewpoint of survival analysis. The NACT response should be evaluated for both LN and PT because of their different behaviors during chemotherapy. Further studies of larger sample number should be conducted in the future.

Utility of response evaluation to neo-adjuvant chemotherapy by 18F-fluorodeoxyglucose-positron emission tomography in locally advanced esophageal squamous cell carcinoma

BACKGROUND Neoadjuvant chemotherapy (NACT) has been frequently used for locally advanced esophageal squamous cell cancer (ESCC). It is therefore important to establish criteria for evaluating the response to NACT based on survival analysis. METHODS This study analyzed 100 patients with ESCC (cT1, 2/3/4:25/57/18, cN0/1/M1lym: 5/59/36) who received NACT (5-fluorouracil, adriamycin, and cisplatin) followed by surgical resection. NACT response was monitored using (18)F-fluorodeoxyglucose-positron emission tomography (PET) and computed tomography by measuring pre- and post-NACT maximal standardized uptake value (SUVmax) and area of primary tumor, respectively. The associations between NACT and clinicopathological factors including prognosis were analyzed. RESULTS The mean ± SEM values of pre- and post-NACT SUVmax were 12.23 ± 4.62 and 6.31 ± 5.41, respectively, and the mean/median SUVmax reduction was 59.50%/73.45%. The most significant difference in survival between responders and non-responders was at 70% of cutoff value based on every 10% stepwise cutoff analysis (2-year progression-free survival [PFS]: 57.7% vs 25.1%; hazard ratio [HR] = 2.864; P = .0004). Univariate analysis indicated a correlation between PFS and number of cN before NACT, SUVmax reduction, decrease in tumor area, pT, and number of pN, while cT before NACT and pathological response to NACT showed no association. Multivariate analysis identified number of cN before NACT (HR = 2.537; P = .0092), SUVmax reduction (HR = 3.202; P = .0072), and number of pN (HR = 2.226; P = .0146) as independent prognostic predictors. CONCLUSION By determining the optimal cutoff value based on survival analysis, we evaluated patient responses to NACT using PET. Such evaluation could be valuable in formulating treatment strategies for ESCC.