[Relationship between Quantitativeness of Iodine and Accuracy of Virtual Non-contrast Image in Dual-energy Computed Tomography].

Dual-energy computed tomography (DE-CT) is the promising technology, such as enabling material decomposition, generation of the virtual monochromatic image, and measurement of effective atomic numbers. There are reports that utilization of the virtual non-contrast (VNC) image, the iodine map image, and the virtual monochromatic image can contribute to the improvement of lesion detection and its characterization, compared with conventional contrast CT by single-energy computed tomography (SE-CT). In addition, acquisition of the VNC images makes it possible to skip scanning of true non-contrast CT, which is also expected to reduce exposure. However, a reliable evaluation of the accuracy of the VNC image has not been established, and only a few reports have verified their accuracy. In this study, we evaluated the relationship between the quantitativeness of iodine and the CT value of VNC image. As a result of our study, when the iodine volume was overestimated, the CT value of the VNC image was lower than the reference value, and when the iodine volume was underestimated, the CT value was upper than the reference value. Moreover, we clarified that the CT value of the VNC image greatly diverges as the iodine volume increases.

Physician-received scatter radiation with angiography systems used for interventional radiology: comparison among many X-ray systems.

Radiation protection for interventional radiology (IR) physicians is very important. Current IR X-ray systems tend to use flat-panel detectors (FPDs) rather than image intensifiers (IIs). The purpose of this study is to test the hypothesis that there is no difference in physician-received scatter radiation (PRSR) between FPD systems and II systems. This study examined 20 X-ray systems in 15 cardiac catheterisation laboratories (11 used a FPD and 9 used an II). The PRSR with digital cineangiography and fluoroscopy were compared among the 20 X-ray systems using a phantom and a solid-state-detector electronic pocket dosemeter. The maximum PRSR exceeded the minimum PRSR by ~12-fold for cineangiography and ~9-fold for fluoroscopy. For both fluoroscopy and digital cineangiography, the PRSR had a statistically significant positive correlation with the entrance surface dose (fluoroscopy, r = 0.87; cineangiography, r = 0.86). There was no statistically significant difference between the average PRSR of FPDs and IIs during either digital cineangiography or fluoroscopy. There is a wide range of PRSR among the radiography systems evaluated. The PRSR correlated well with the entrance surface dose of the phantom in 20 X-ray units used for IR. Hence, decreasing the dose to the patient will also decrease the dose to staff.

Clarifying and visualizing sources of staff-received scattered radiation in interventional procedures.

OBJECTIVE: Interventional radiology tends to involve long procedures (i.e., long fluoroscopic times). Therefore, radiation protection for interventional radiology physicians and staff is an important issue. We examine and identify sources of staff-received scattered radiation in an interventional radiology system using a pinhole camera method. CONCLUSION: Physicians and staff are exposed primarily to two sources of scattered radiation: radiation scattered from the patient and radiation from the cover of the x-ray beam collimating device. Those who stand close to the patient and the x-ray beam collimating device, where scattered radiation is higher, have higher radiation doses. Thus, radiation protection during interventional radiology procedures is an important problem.

Comparison of the radiation dose in a cardiac IVR X-ray system.

In this study, the entrance surface dose rates received by a phantom during cineangiography and fluoroscopy were compared. The X-ray conditions used in the measurements were those normally used in facilities performing percutaneous coronary intervention. Although, today, the entrance surface doses (cineangiography and fluoroscopy) of X-ray equipment used for cardiac interventional radiology (IVR) tends to be lower than they were previously, some equipment produces a high radiation dose. Therefore, the X-ray equipment used for cardiac IVR procedures must be maintained in good repair and must be carefully calibrated. In addition, periodic measurement of the radiation dose from the X-ray equipment used for both cineangiography and fluoroscopy for cardiac IVR is necessary. If the radiation dose of the X-ray system in use is too high, the IVR staff should determine the reason and make an effort to reduce it. Hence, the IVR staff must be adequately trained in radiation protection.