[Questionnaire Survey on IVR Dose Management in Tokai Region].

PURPOSE: National diagnostic reference levels in Japan 2020 (DRLs 2020) have been published. In the field of angiography, in addition to the fluoroscopic dose rate, incident air kerma at the patient entrance reference point displayed on the equipment (Ka,r: mGy) and air kerma-area product displayed on the equipment (PKA: Gycm2) were set. A questionnaire survey was conducted at each facility in the Tokai region to confirm the status of medical radiation dose control in the region. METHOD: A questionnaire survey was conducted at each facility in the Tokai region. The items were fluoroscopic dose rate in each area (head and neck, cardiac, chest and abdomen, and limbs), DA and DSA dose rates, and dose area product meter (Ka,r, PKA) for the main procedures in each area. RESULT: The median values in this study were lower than those in the DRLs 2020, indicating that appropriate dose control is being implemented in the Tokai region. The trends of fluoroscopic and radiographic dose rates were different in each area, and there was some variation among the facilities. CONCLUSION: We believe that the incorporation of fluoroscopic and radiographic dose rates by area into the DRLs will facilitate more appropriate dose control at each facility in the future.

Examination of Dose Reduction Using Image Noise Reduction Technology in Cardiovascular X-ray Systems.

The aim of this study is to establish radiation exposure dose reduction protocols during cardiac intervention by decreasing the entrance dose at flat panel detector (FPD) with image quality evaluations. For measuring entrance surface dose (ESD), we have used a Radical 9015 dosimeter (6 cc ion chamber) placed under 20 cm thick acrylic plates at the patient's entrance reference point. We performed an image quality assessment based on quantitative as well as visual evaluation of the images obtained via current and dose reduction protocols. The visual evaluation was performed by measuring the signal to noise ratio and contrast using a cine/digital angiography cardiac phantom. The quantitative evaluation was performed by cardiologists and radiological technologists using the five-point scale method. For the dose reduction protocol, we used an image noise reduction technique to prevent the deterioration of image quality. The ESDs for the fluoroscopy and digital cine in the dose reduction protocol were 18.0 mGy/min and 0.18 mGy/frame, respectively, which corresponded to 81% and 49% of the ESD in the current protocol. Our results reveal that the ESD for fluoroscopy was lower than the diagnostic reference level (20 mGy/min) for interventional radiology. We recommend a lower dose setting and the maintenance of image quality using noise reduction techniques. This will ensure use of a lower FPD entrance dose compared to the initial dose setting currently recommended by manufacturers.

Evaluation of Entrance Skin Dose during Catheter Ablation Procedures by Use of Reference Air-Kerma Displayed on Angiography Systems.

BACKGROUND: Our aim in this study was to estimate entrance skin doses (ESDs) to patients who underwent catheter ablation procedures, by using a reference air-kerma (RAK) displayed on the monitor of an angiography system (displayed RAK). METHODS: The displayed RAK was calibrated with use of an air-kerma value measured on a 20-cm-thick acrylic plate at the interventional reference point for the inclusion of backscattered x-rays (calibrated RAK). The ESD evaluated from the calibrated RAK (evaluated ESD) was verified through direct ESD measurements on an anthropomorphic phantom. The values of the evaluated ESD agreed with those of the measured ESD within a statistical error of 10% for both fluoroscopy and digital cine. The patient population included 356 consecutive patients (108 female and 248 male) who underwent catheter ablation procedures in the catheter laboratory of the Nagoya Daini Red-Cross Hospital from January 2013 to February 2014, where ablation procedures were performed for seven types of arrhythmias, i.e., atrial fibrillation (AF), atrial flutter (AFL), atrial tachycardia (AT), atrioventricular nodal reentrant tachycardia (AVNRT), ventricular premature contraction (VPC), ventricular tachycardia (VT), and Wolff-Parkinson-White syndrome (WPW). RESULTS: Patients who had arrhythmias that received the highest evaluated ESD were those for AF, followed by those for VPC, AT, WPW, AFL, VT, and AVNRT. CONCLUSIONS: Despite extremely long fluoroscopy times of up to 66.6 minutes in left anterior oblique projection, only one patient was considered to exceed a threshold dose of 2 Gy for the onset of radiation-induced skin injuries.