[en] We assessed the usefulness of positron emission tomography (PET)/CT images to determine the target volume in radiotherapy planning by evaluating the standardized uptake value (SUV). We evaluated the imaging conditions and image-reconstruction conditions of PET/CT useful for treatment planning by collecting ¹⁸F-fluorodeoxyglucose (FDG) images of acrylic spheres (10-48 mm in diameter) in a phantom. The ¹⁸F-FDG concentration in the spheres was 10-fold higher than that of the phantom. The contours were delineated according to the SUV by the threshold and regions of interest (ROI) methods. Comparisons of two- and three-dimensional (2D and 3D) acquisition images indicated that the sharpness and quantitative qualifies of the sphere boundaries were better in the former than in the latter. In the extraction of outlines using the SUV, outlines obtained at an SUV of 40-50% of the maximum agreed well with the actual acrylic sphere size. 2D acquisition images are more suitable for delineating target volume contours, although 3D acquisition images are more popular in diagnostic imaging. An SUV of 40-50% of the maximum is suggested to be appropriate for gross tumor volume (GTV) contouring of sphere tumors with homogenously distributed ¹⁸F-FDG. (author)

[en] To evaluate the effects of radiation on various types of EMS (expandable metallic stent) that differ in shape and the quality of the material, we performed external irradiation and intraluminal irradiation using 5 types (Spiral Z stent: SZ, Wallstent: Wall, NT stent: NT, ZA stent: ZA, Accuflex: Acc.) of EMS for the biliary tract, and measured back scatter on the EMS interface and absorption due to shielding using TL (thermoluminescent) sheets. TL sheets can be wound around the external side of the EMS in water, allowing phantom experiments close to the in vivo state for the measurement of dose perturbation of radiation near the EMS. Images of the relative dose in a small area near the EMS were obtained using a spatial read-out system using a cooled CCD camera. In external irradiation, an 8.2±0.53% increase in back scatter was observed in SZ with a wire diameter of 260 μm and 7.9±1.2% and 4.5±0.62% decreases in absorption due to shielding in SZ and Wall, respectively. In intraluminal irradiation, a 7.7±0.85% decrease in absorption was observed in SZ alone. Therefore, in both external and intraluminal irradiation on various types of EMS that differ in shape and the quality of the material, the dose perturbation near the EMS is 8.2% or less, which presents no clinical problem. (author)

[en] In radiation therapy of the lung, it is difficult to decide an accurate tumor dose when only correcting for the density of the lung tissue. Many investigators have studied the correction of tumor dose in the lung. In this report, the mean density of the lung was measured by the transit dose and we calculated using the correction formula for tumor dose of the lung, devised by Burlin, Batho, and Dutreix, applied to the mean density of the lung. We compared these calculation results with a correction factor derived by measuring the lung phantom. It was proved that the method devised by Batho which calculates the correction factor on the basis on the tissue/air ratio, seems to be relatively accurate. (author)

[en] Since the doses around sources in intracavitary radiation therapy changed rapidly with distance from sources, measurement of the dose distribution is very difficult. A thermoluminescence [TL] sheet and its spatial readout system used measurement of cosmic rays has been applied for dosimetry of the intracavitary radiation therapy. The TL sheet, which is composed of teflon mixed with BaSO₄: Eu powder, has a linear response with a very wide dynamic range from at least 0.002 cGy to 5000 cGy for ⁶⁰Co-γ rays. In this study, the characteristics of annealing, measurement of the high dose rate distribution around ⁶⁰Co sources and the method for measuring the dose distribution using TL emission at the normal temperature (25 degC) were shown. The TL sheet was suggested to provide a convenient means of measuring the dose distribution around sources in intracavitary radiation therapy. (author)

[en] Current practices for patient safety control in radiological diagnosis may involve problems. For solving of these problems, we have to bear in mind that the mental and physical capacity of patients tend to be limited during radiological testing. When radiography is performed using a general X-ray device at a source table distance (STD) of 100 cm, the patient's head can touch the X-ray tube housing during position adjustment on the stand (up and down adjustment) or the patient is made to take an unnatural posture during body positioning. With this in mind, we carried out a questionnaire survey about source image receptor distance (SID). This survey disclosed that more than 92% of the institutions have adapted 100 cm STD. We then conducted a three-dimensional analysis of a patient's posture and motion by video taping patients during positioning on a roentgenographic table. This analysis revealed that the adoption of the 120 cm STD resulted in less contact between the patient's head and X-ray tube housing, less of unnatural body position and less time required for positioning adjustment when compared to those at 100 cm STD. These results indicate that the current STD (100 cm) is not suitable for safe and smooth adjustment of the positioning of a patient's body of a roentgenographic table. We examined the optimun STD, taking into consideration the dimensions of patient's movement and posture during an X-ray examination. (author)

[en] To evaluate whether simultaneous metallic stent (MS) placement and radiotherapy are feasible, phantom and animal experiments were performed. The interface dose by external irradiation (EI) or intracavity irradiation (II) to 5 kinds of MS was measured using the charge-coupled device (CCD) camera with a thermoluminescent (TL) sheet, and backscatter and absorption were evaluated using composite method. Lineac 10 MV X-ray irradiated the MS in close contact with the TL sheet. II was performed using ¹⁹²Ir, and the irradiation dose transmitted through the MS was measured using the TL sheet. The ratio of the CCD value of the MS wire region to that of the MS non-wire region was defined as the dose perturbation factor (DPF). Furthermore, the effects of a combination of ⁶⁰Co gamma-ray EI and MS placement in the normal common bile duct were histopathologically evaluated in dogs. In the phantom experiments of EI, in backscatter by the MS, the DPF was 1.09 for CZ, and 1.03 for Pal, but no backscatter was detected in the remaining 3 MS. In absorption by the MS. the DPF was 0.92, 0.97, 0.97, and 0.98 for CZ, Wall, Pal, and Vel, respectively, but no absorption was detected in U. Flex. In those of II, the DPF of absorption was 0.91, 0.98, and 0.98 for CZ, U. Flex, and Wall, respectively, but no absorption was detected in Pal and Vel. The animal experiments showed infiltration of inflammatory cells and fibrosis in the case of both MS placement and EI. These changes were marked in EI treating after MS placement, but neither severe ulcer nor perforation was found. In conclusion, these results suggested that the effect of MS should be considered carefully when simultaneous MS placement and EI is performed clinically. (author)

[en] The effectiveness of postoperative irradiation depends on exposing the affected part of the body to a sufficient radiation dose and minimizing the exposure of other parts. The possibility of meeting this requirement in irradiation of the breast wall was improved by the development of the tangential pendulum irradiation method. However the cylinder model used in this method differs greatly from the human chest wall in shape. So we improved this method further by representing the wall with parts of two cylinders and by setting different swivel and pendulum angles for each axis of the cylinders. (author)

[en] A new system of radiation protection for angiographers was developed and its effect evaluated. The system consists of two components for radiation protection; one to protect the abdominal area and the other to protect the head and neck area. The first is composed of a lead curtain attached beneath the tissue table and a movable lead barrier next to the patient's trunk. The second is brim-shaped leaded rubber attached to the image intensifier. In abdominal angiography, the radiation protection system reduced X-ray scatter to 1% of the non-protective condition for the angiographer's abdominal area and to 50% for the head and neck area. This new system reduced X-ray scatter from the patient and enhanced the safety of the angiographer. (author)

[en] We have classified liver tumors on dynamic MRI by analyzing their enhanced patterns, and examined how useful it is for the differential diagnosis of hepatic tumors. We have analyzed the staining patterns and sequential changes of 211 nodules of 184 cases on MRI with the contrast media Gadopentetate gimegulmin (hereafter Gd-DTPA) injection. By analyzing the staining patterns of tumors on MRI, we found that diseases each have characteristic staining patterns. In conclusion, it can be said that dynamic MRI with Gd-DTPA injected has made more accurate qualitative diagnosis possible and has improved the existential diagnosis of diseases of minimal change, identifying the expanse of lesions and the degree of infiltration into tissues and organs. (author)

[en] We analyzed the data for 53 patients with histologically proven primary squamous cell carcinoma of the head and neck treated with radiotherapy between February 2006 and August 2009. All patients underwent contrast-enhanced (CE)-CT and ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) before radiation therapy planning (RTP) to define the gross tumor volume (GTV). The PET-based GTV (PET-GTV) for RTP was defined using both CE-CT images and FDG-PET images. The CE-CT tumor volume corresponding to a FDG-PET image was regarded as the PET-GTV. The CE-CT-based GTV (CT-GTV) for RTP was defined using CE-CT images alone. Additionally, CT-GTV delineation and PET-GTV delineation were performed by four radiation oncologists independently in 19 cases. All four oncologists did both methods. Of these, PET-GTV delineation was successfully performed in all 19 cases, but CT-GTV delineation was not performed in 4 cases. In the other 15 cases, the mean CT-GTV was larger than the PET-GTV in 10 cases, and the standard deviation of the CT-GTV was larger than that of the PET-GTV in 10 cases. Sensitivity of PET-GTV for identifying the primary tumor was 96%, but that of CT-GTV was 81% (P<0.01). In patients with oropharyngeal cancer and tongue cancer, the sensitivity of CT-GTV was 63% and 71%, respectively. When both the primary lesions and the lymph nodes were evaluated for RTP, PET-GTV differed from CT-GTV in 19 cases (36%). These results suggested that FDG-PET is effective for defining GTV in RTP for squamous cell carcinoma of the head and neck, and PET-GTV evaluated by both CE-CT and FDG-PET images is preferable to CT-GTV by CE-CT alone. (author)