Clinical evaluation of the effect of attenuation correction technique on 18F-fluoride PET images.

OBJECTIVE: The purpose of this study is to evaluate effect of attenuation correction technique on 18F-fluoride positron emission tomography (PET). METHODS: We performed PET scans after the injection of 185 MBq 18F-fluoride on 32 patients from October 20th, 2004 to April 13th, 2005. We calculated bone-to-muscle ratios for the images with and without attenuation correction. We placed regions of interest (ROIs) on normal bone accumulation in 22 patients. The exclusion criteria were bone metastasis, Paget's disease, and rheumatoid arthritis. Several regions were chosen for ROI placement: skull, cervical vertebra, mandible, scapula, thoracic vertebra, rib, humerus, lumbar vertebra, radius, ulna, pelvis, femoral head, femoral shaft, tibia, and fibula. The count ratios of normal bones to gluteus muscle were calculated as bone-to-muscle ratios. The count ratios of abnormal skeletal lesions to gluteus muscles were calculated as bone-to-muscle ratios, while the count ratios of abnormal skeletal lesions to normal bones were calculated as bone-to-bone ratios. RESULTS: PET images without attenuation correction showed significantly higher mean bone-to-muscle ratios than those with attenuation correction (p < 0.05) for all normal bones except the femoral head and lumbar vertebrae. For abnormal bones, bone-to-muscle ratios without attenuation correction were significantly higher than those with attenuation correction (p < 0.005). The same statistical significance was found for bone-to-bone ratios (p < 0.005). CONCLUSIONS: The attenuation correction technique is not necessary to conduct the visual interpretation of 18F-fluoride PET images. The bone-to-muscle ratio analysis without attenuation correction may be of use to differentiate malignant from benign disease processes.

Investigating the functionality of diamond-like carbon films on an artificial heart diaphragm.

In this study, the authors used diamond-like carbon film to coat the ellipsoidal diaphragm (polyurethane elastomer) of artificial hearts. The purpose of such coatings is to prevent the penetration of hydraulic silicone oil and blood through the diaphragm. To attach diamond-like carbon film uniformly on the diaphragm, the authors developed a special electrode. In estimating the uniformity of the diamond-like carbon film, the thickness was measured using a scanning electron microscope, and the characteristics of the diamond-like carbon film was investigated using infrared spectroscopy, Ar-laser Raman spectrophotometer, and x-ray photoelectron spectrometer. Also, to estimate the penetration of silicone oil through the diaphragm, in vitro testing was operated by alternating the pressure of silicone oil for 20 days. The authors were able to successfully attach uniform deposition of diamond-like carbon film on the ellipsoidal diaphragm. In this in vitro test, diamond-like carbon film was proven to have good stability. The amount of silicone oil penetration was improved by one-third using the diamond-like carbon film coating compared with an uncoated diaphragm. It is expected that through the use of the diamond-like carbon film, the dynamic compatibility of an artificial heart diaphragm will increase.