Shielding effect of radiation dose reduction fiber during the use of C-arm fluoroscopy: a phantom study.

This study evaluated the shielding effect of a newly developed dose-reduction fiber (DRF) made from barium sulfate, in terms of radiation doses delivered to patients' radiosensitive organs and operator during C-arm fluoroscopy and its impact on the quality of images. A C-arm fluoroscopy unit was placed beside a whole-body phantom. Radiophotoluminescent glass dosimeters were attached to the back and front of the whole-body phantom at 20 cm intervals. Radiation doses were measured without DRF and with it applied to the back (position 1), front (position 2) or both sides (position 3) of the phantom. To investigate the impact of DRF on the quality of fluoroscopic images, step-wedge and modulation transfer function phantoms were used. The absorbed radiation doses to the back of the phantom significantly decreased by 25.3-88.8% after applying DRF to positions 1 and 3. The absorbed radiation doses to the front of the phantom significantly decreased by 55.3-93.6% after applying DRF to positions 2 and 3. The contrast resolution values for each adjacent step area fell in the range 0.0119-0.0209, 0.0128-0.0271, 0.0135-0.0339 and 0.0152-0.0339 without and with DRF applied to positions 1, 2 and 3, respectively. The investigated DRF effectively reduces absorbed radiation doses to patients and operators without decreasing the quality of C-arm fluoroscopic images. Therefore, routine clinical use of the DRF is recommended during the use of C-arm fluoroscopy.

Effect of metallic tools on scattered radiation dose during the use of C-arm fluoroscopy in orthopaedic surgery.

This study investigated the effect of metallic tools on the scattered radiation dose delivered to surgeons' radiosensitive organs while simulating hip surgery using C-arm fluoroscopy. Two phantoms, a pelvis and a Rando phantom, were used to simulate a patient and a surgeon in this study. Photoluminescence dosimeters were inserted into the Rando phantom in the positions of the eye, thyroid and gonad. A drill was positioned above the hip of the pelvis phantom or beside the pelvis phantom of the same height. For each drill location, the scattered radiation dose was measured when the angle to the operator phantom was 45°; this was repeated when the angle was 90°. The scattered radiation doses to the eye, thyroid and gonad when the drill was placed beside the pelvis phantom with 90° angulation to the operator phantom were significantly lower than the reference values and those when the drill was placed beside the pelvis phantom at a 45° angulation to the operator phantom. The scattered radiation doses to the eye and thyroid when the drill was placed above the hip were significantly lower than the references values. Of the four different scenarios, the scattered radiation doses to the eye, thyroid and gonad were lowest when the drill was placed beside the pelvis phantom with 90° angulation. This study showed that the scattered radiation doses to radiosensitive organs were affected by the location and angle of the metallic tools in relation to the operator. Therefore, orthopedic surgeons should consider the effect of metallic tools on the scattered radiation dose during intraoperative use of C-arm fluoroscopy.

Simulation study of a novel target oriented SPECT design using a variable pinhole collimator.

PURPOSE: In the past decade, demands for organ specific (target oriented) single-photon emission computed tomography (SPECT) is increasing, and several groups have conducted studies on developing clinical dedicated SPECT with pinhole collimator to improve the spatial resolution. However, acceptance angle of the collimator cannot be adjusted to fit the different ROIs of target objects because the shape of pinhole could not be changed, and the magnifying factor cannot be maximized as the collimator-to-detector distance is fixed. Furthermore, those dedicated pinhole SPECTs are typically made for a single purpose and therefore possess a drawback in that it cannot be utilized for any other purpose. In this study, we propose a novel SPECT system using variable pinhole collimator (VP SPECT) whose parameters are flexible. METHODS: The proposed variable pinhole collimator is modeled on conventional pinhole by piling several tungsten layers of different apertures. Depending on the combination of the holes in each layer, a variety of hole diameters and acceptance angles of the pinhole can be made. In addition, VP SPECT system allows attaching the collimator to the object as close as possible to maximize the sensitivity and adjust the distance of the pinhole from the scintillation detector to optimize the system resolution for each rotation angle, automatically. For quantitative measurement, we compared the sensitivity and spatial resolution of VP SPECT with those of conventional pinhole SPECT. To determine the possibility of the clinical and preclinical use of proposed system, a digital mouse whole-body (MOBY) phantom is used for simulating the live mouse model. RESULTS: The result of simulation using ultra-micro hot spot phantom shows that the sensitivity of the proposed VP SPECT system is about 297% of that of the conventional system. While hot rods of diameter 0.6 mm can be distinguished in the image with the proposed VP SPECT system, 1.2-mm hot rods are barely discernible in the conventional pinhole SPECT image. According to the result of MOBY phantom simulation, heart walls separated by 3 mm were not distinguished in conventional pinhole SPECT images, but were clearly discerned in VP SPECT images. CONCLUSIONS: In this study, we designed a novel pinhole collimator for SPECT and presented preliminary results of target oriented imaging with a simulation study. Currently, we are pursuing strategies to realize the proposed system, with the goal to apply the technology into a high-sensitivity and high-resolution preclinical SPECT. Should VP SPECT be applied to the clinical setting, we anticipate a high-sensitivity, high-resolution system for applications such as heart dedicated SPECT or related fields.

Performances of a protector against scattered radiation during intraoperative use of a C-arm fluoroscope.

The scattered radiation protector for mobile x-ray systems, Creative Valuable Protector-2, has been recently developed. However, there have been no studies investigating the effects of this device. We aim to investigate the effects of the scattered radiation protector on the equivalent doses from scattered radiation delivered to radiosensitive organs while simulating spine surgery using a C-arm fluoroscope. Chest and rando phantoms were used to simulate a patient and a surgeon in this study. The equivalent dose from scattered radiation to radiosensitive organs was measured in four different situations according to the use of the scattered radiation protector and the C-arm configuration. To compare the quality of the images with and without the scattered radiation protector, an acryl step phantom with five steps was used, and the contrast resolution of each step was calculated. The equivalent dose from the scattered radiation to the surgeon's eye, thyroid, and gonad decreased significantly by using the scattered radiation protector for both the Posteroanterior (PA) (p < 0.001) and Anteroposterior (AP) (p < 0.001) C-arm configurations. The installation of the scattered radiation protector also reduced the direct radiation dose to the chest phantom. A scattered map showed that scattered radiation doses decreased by approximately 50% for the PA configuration and 75% for the AP configuration by using the scattered radiation protector. Before and after installation of the scattered radiation protector, the contrast resolution of each adjacent step area was 0.025-0.404 and 0.216-0.421. The scattered radiation protector was effective in reducing not only the equivalent dose from scattered radiation to the surgeon's radiosensitive organs, but also the direct radiation dose to the patient. This was all achieved without decreasing the quality of the C-arm fluoroscopic images.