Toshikazu Nambu

Early detection of osteochondritis dissecans of the capitellum in young baseball players : Report of three cases

The prevalence of osteochondritis dissecans is high among individuals who have played baseball actively since childhood1,19, and repetitive throwing is considered to be one of the main etiological factors of this disease1,4,5,10,25. During the acceleration phase of throwing, the elbow joint may be stressed into a valgus position17,38,47,49 and the capitellum may be subjected to compression and shear forces4,20,21,44,48,50. However, little is known about the primary changes leading to osteochondritis dissecans. We attempted to detect these changes by examining the elbows of players on youth baseball teams with magnetic resonance imaging and ultrasonography. Forty-four young baseball players who were ten to twelve years old and had not had a previous examination of the elbow were selected for this study. Magnetic resonance imaging was performed with a 1.5-tesla magnet (Magnetom H15; Siemens Medical Systems, Erlangen, Germany), and coronal and sagittal T1-weighted spin-echo images and sagittal T2-weighted gradient-echo images were made. Anterior and posterior longitudinal ultrasonograms of the capitellum were made with a real-time linear-array scanner (Aloka SSDF-650, Tokyo, Japan) that was equipped with a 7.5-megahertz transducer27,45 (Figs. 1-A and 1-B). Figs. 1-A through 1-D: Illustration and ultrasonograms of the capitellum. Fig. 1-A: Line drawing showing the relationship of the humerus and the radial head to the ultrasonographic scanner. Fig. 1-B: Anterior longitudinal ultrasonogram of a normal capitellum, showing the subchondral bone of the capitellum as a high-signal-intensity round area (white arrows) and the articular cartilage as a low-signal-intensity round area (black arrows) over the subchondral bone. Three of the forty-four boys were found to have an abnormality of the capitellum. The T1-weighted images of …

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.

Wavelet compression on detection of brain lesions with magnetic resonance imaging.

The purpose of this report is to assess clinically acceptable compression ratios on the detection of brain lesions at magnetic resonance imaging (MRI). Four consecutive T2-weighted and the corresponding T1-weighted images obtained in 20 patients were studied for 109 anatomic sites including 50 with lesions and 59 without lesions. The images were obtained on a 1.5-T MR unit with a pixel size of 0.9 to 1.2×0.47 mm and a section thickness of 5 mm. The image data were compressed by wavelet-based algorithm at ratios of 20∶1, 40∶1, and 60∶1. Three radiologists reviewed these images on an interactive workstation and rated the presence or absence of a lesion with a 50 point scale for each anatomic site. The authors also evaluated the influence of pixel size on the quality of image compression. At receiver operating characteristic (ROC) analysis, no statistically significant difference was detected at a compression ratio of 20∶1. A significant difference was observed with 40∶1 compressed images for one reader (P=.023), and with 60∶1 for all readers (P=.001 to .012). A root mean squared error (RMSE) was higher in 0.94-×0.94-mm pixel size images than in 0.94-×0.47-mm pixel size images at any compression ratio, indicating compression tolerance is lower for the larger pixel size images. The RMSE, subjective image quality, and error images of 10∶1 compressed 0.94-×0.94-mm pixel size images were comparable with those of 20∶1 compressed 0.94-×0.47-mm pixel size images. Wavelet compression can be acceptable clinically at ratios as high as 20∶1 for brain MR images when a pixel size at image acquisition is around 1.0×0.5 mm, and as high as 10∶1 for those with a pixel size around 1.0×1.0 mm.

Computed Tomography and Magnetic Resonance Imaging of Retroperitoneal and Mesenteric Tumor

Because retroperitoneal and mesenteric tumors may not be found until they become huge, speculating about the site of origin of a tumor is sometimes difficult. Computed tomography and magnetic resonance imaging are the primary modalities for evaluating the spread of tumor and the location of the tumo

MR Imaging of the Fetus

This article describes the indications, safety, and technique of fetal MR imaging, as well as the MR findings of the abnormal fetus, placenta, and surrounding tissues. MR imaging is not routinely recommended and is usually performed when obstetric ultrasound does not suffice. Single-shot sequences h

Elucidation of accuracy in calibration of MR signal intensity based on transmission amplitude method

To calibrate magnetic resonance (MR) signal intensity that depends on radio frequency (RF) coil loading, the transmission amplitude (TRA) for the excitation in the transmit-receive RF coil has been used as a good index in the so-called TRA method. As this TRA method needs neither an internal reference nor an additional external reference for the calibration, its accuracy is free from reference measurements. This study elucidated the calibration accuracy of MR signal intensities based on the TRA method. A cylindrical gel phantom was used for accuracy measurements with a 1.5-T MRI unit with conventional TI imaging as a simple pulse sequence for various loading conditions. The brain parenchyma of eight healthy volunteers also showed calibrated MR signal deviations. The error of the phantom calibration measurements was 2.18% (S.D.%). The background noise intensity of images was theoretically derived to correlate with the impedance mismatching of the RF coil, which is inevitable for fixed tuning, even for automatic tuning that is not always exact. Taking into account this noise intensity, the calibration method was modified to reduce its error to 1.50%. The standard deviations of the calibrated values in the thalamus and frontal white matter were 2.9 and 3.8%. respectively. We suggest that the modified TRA method is a practical and reliable technique to obtain clinical numeric evidence.