title: Overlap of radiation field and radiation field shape in cardiac catheterization.
abstract: The radiation field shape for cardiac catheterization has changed from being circular to being rectangular with the spread of flat-panel detector systems. A rectangular radiation field provides a wide fluoroscopy field to the four corners of a subject area; however, in cardiac catheterization, there is not much usable information around the four corners at several angles, and this tends to be regarded as a meaningless radiation exposure. Hence, overlap of radiation fields has been of concern recently. The authors changed field sizes/fluoroscopy angles and examined entrance dose rates to study radiation field shapes and configurations of radiation exposure to patients, and they discussed a radiation exposure reduction method. In measurements of phantom entrance dose rates, we considered right anterior oblique (RAO) directions, cranial (CRA) directions and RAO-CRA directions and found that entrance dose rates rose considerably, particularly at the RAO-CRA. In the study of radiation field overlap, we discuss radiation field shapes (rectangular/circular) as well as angles. In the RAO-CRA directions, differences occurred in angles of non-overlapping radiation field by differences in radiation field shapes. For RAO-CRA, compared with the RAO and CRA directions, entrance dose rates increased with an increase in angle. When convenience in clinics is considered, the utilization frequency of the four corners of a rectangular field is low. When one considers the increases in radiation exposure caused by radiation field overlap, it is more effective to use circular radiation fields.
authors.affiliation: Department of Radiology, Showa University Hospital, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8666, Japan. tnkjm@cmed.showa-u.ac.jp
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Nakajima
authors.forename: Toshio
authors.initials: T
authors.lastname: Take
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Sumi
authors.forename: Hideki
authors.initials: H
authors.lastname: Ishida
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakazawa
mesh_terms: D006328:Cardiac Catheterization / Q000295:instrumentation*; D004781:Environmental Exposure / Q000517:prevention & control; D005471:Fluoroscopy / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012886:Skull / Q000528:radiation effects
references.citation: Radiology. 2002 Nov;225(2):329-36
references.pmid: 12409563