Tsuyoshi Suga

Comparative study of FDG PET/CT and conventional imaging in the staging of rhabdomyosarcoma

ObjectiveThe current study was conducted to compare the diagnostic accuracy between 18F-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET)/computed tomography (CT), and conventional imaging (CI) for the staging and re-staging of patients with rhabdomyosarcomas.MethodsThirty-five patients who underwent FDG PET/CT prior to treatment were evaluated retrospectively. CI methods consisted of 99mTc-hydroxymethylene diphosphonate bone scintigraphy, chest radiograph, whole body CT, and magnetic resonance imaging of the primary site. The images were reviewed and two boardcertified radiologists reached a diagnostic consensus. Tumor stage was confirmed by histological examination and/or follow-up examinations.ResultsInterpretation on the basis of FDG PET/CT, and CI, diagnostic accuracies of the T and N stages were similar. Using FDG PET/CT, the M stage was correctly assigned in 31 patients (89%), whereas the accuracy of CI in M stage was 63%. TNM stage was correctly assessed with FDG PET/CT in 30 of 35 patients (86%) and with CI in 19 of 35 patients (54%). The overall TNM staging and M staging accuracies of FDG PET/CT were significantly higher than that of CI (P < 0.01).ConclusionsFDG PET/CT is more accurate than CI regarding clinical staging and re-staging of patients with rhabdomyosarcomas.

Clinical Value of Image Fusion from MR and PET in Patients with Head and Neck Cancer

PurposeThis study aimed to evaluate the clinical value of image fusion from magnetic resonance (MR) combined with positron emission tomography (PET) imaging, using 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) in head and neck cancer.MethodsSixty-five consecutive patients underwent MR and FDG-PET scans before or after the treatment of known or suspected head and neck cancer. T1-weighted and T2-weighted images were first assessed by MR interpretation, and then, the fused images of T2-weighted images from MR and PET were evaluated in a blind manner. Diagnostic performance was compared.ProceduresFor initial staging, in 48 patients, malignant tumors were histologically confirmed in 45 patients. The interpretation sensitivities of MR alone and fused images for primary tumors were 98% and 100%, respectively. For lymph node metastasis, the sensitivity and specificity of both methods were 85% and 92%, respectively. Of 15 patients with suspected recurrence, ten patients had recurrent tumors, three patients developed second malignant tumors, and two patients had no recurrence. For these patients, the overall sensitivity of MR alone was 67%, whereas that of the fused images was 92%. Eight additional lesions were accurately diagnosed by image fusion only. In two patients with lymph node metastasis from unknown origin, the primary site was not detected in one patient, while tonsilar cancer was identified only by image fusion interpretation.ConclusionImage fusion from MR with PET might be useful in evaluating head and neck cancer, especially in suspected recurrent cases rather than in fresh cases.

11C-Methionine PET/CT for multiple myeloma

A 57-year-old woman with 6-year history of IgA-k myeloma experienced an increase of serum IgA level from 331 to 683 mg/dl during maintenance therapy with thalidomide after autologous peripheral blood stem cell transplantation followed by allogeneic mini-transplantation. Bone marrow aspiration revealed no sign of relapse of the myeloma. We conducted positron emission tomography/computed tomography (PET/CT) scans using C-methionine (MET) and F-fluorodeoxyglucose (FDG). In MET-PET/CT, there were multiple abnormal hypermetabolic lesions, while FDG uptake in these lesions was faint (Fig. 1). After four courses of bortezomib therapy, MET-PET/CT revealed no abnormal uptake of MET, with decreased serum IgA level (25.3 mg/dl), indicating that MET uptake was correlated with the clinical course, as denoted by IgA level. C-Methionine is a radiolabelled PET tracer that is clinically used for brain tumor. An earlier study reported that MET-PET depicted active myeloma clearly, which might reflect the increased metabolism of amino acids in myeloma cells for producing abundant immunoglobulin [1]. In the present case, MET-PET/CT was very useful for determining the precise localization of the myelomatous lesions and evaluating therapeutic effects. Although FDGPET/CT is reported to have higher sensitivity for localized myelomatous lesions than other imaging modalities, our case suggests the possibility that MET-PET/CT detects myelomatous lesions more clearly than FDG-PET/CT. Considering that in myeloma patients higher FDG uptake or a larger number of FDG-avid lesions is reported to be associated with inferior overall survival and event-free survival, the lower FDG uptake in this patient is possibly related to the slowly progressive nature of her myeloma. In addition, in 30% of myeloma patients, FDG-PET/CT reportedly failed to show the abnormal findings in the spine and pelvis; this may account for the lower FDG uptake in these lesions. Although many imaging modalities, including FDGPET/CT are now widely available, the findings of the present case suggest that MET-PET/CT can provide valuable information for patients with myeloma and has a potential to become an important imaging test. However, further investigation to compare the MET-PET/CT with FDG-PET/CT or other imaging modalities are needed to confirm the diagnostic efficiency and the clinical feasibility of MET-PET/CT for multiple myeloma.

Clinical value of FDG-PET for preoperative evaluation of endometrial cancer

ObjectiveWhole body positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) has been widely used in various malignancies, but the clinical value of FDG-PET for endometrial cancer has not been fully investigated. The purpose of this study was to evaluate the usefulness of FDG-PET for preoperative evaluation of endometrial cancer.MethodsForty female patients suspected of having endometrial cancer were included in this study. All patients underwent an FDG-PET or PET/CT scan, and images were interpreted visually. The diagnostic performance in detecting the primary tumor, regional nodal status, and distant metastasis was determined. In addition, the usefulness of PET was assessed in terms of additional information and clinical impact for therapeutic management.ResultsOf 40 patients, 30 were histologically confirmed to have endometrial cancer. The patient-based sensitivity and specificity of FDG-PET for primary tumors were 83 and 100%, respectively, and 100 and 100%, respectively, for nodal metastases. There were 12 distant metastases in 6 patients and two second primary cancers in two patients, which were all accurately diagnosed by PET on a patient-basis. PET yielded 12 additional findings in 10 patients, and had a bearing on the therapeutic management of four patients, including one patient with recurrent breast cancer.ConclusionsFDG-PET had a reasonably high diagnostic accuracy in endometrial cancer. Although the number of cases with clinical impact was limited, additional information by PET was obtained in one-third of the cases.

Inhomogeneous bone marrow uptake caused by G-CSF mimics multiple bone metastases on FDG-PET.

Administration of granulocyte colony stimulating factor can cause homogeneous hypermetabolic activity of bone marrow in positron emission tomography using F-18-fluorodeoxyglucose. We report a case in which positron emission tomography demonstrated multiple foci of hypermetabolic activity in the bone marrow, which was considered an early effect of granulocyte colony stimulating factor, and not multiple osseous metastases.