A handheld portable dental intraoral x-ray system is available in the United States and elsewhere. The system is designed to minimize the user's radiation dose. It includes specially designed shielding of the x-ray tube housing and an integral radiation shield to minimize backscatter. Personnel radiation dose records were obtained from 18 dental facilities using both the handheld system and a wall mounted dental x-ray system, providing 661 individual dose measurements. Dental staff doses were also compared for the handheld and conventional systems using both film and digital imaging for the same facilities and staff members. The results indicate that the doses for the handheld systems are significantly less than for wall-mounted systems. The average monthly dose for the handheld systems was 0.28 μSv vs. 7.86 μSv (deep dose equivalent) for the wall-mounted systems, a difference that is statistically significant at the p = 0.01 level. Consequently, there should be no concern about the use of this handheld dental intraoral x-ray system. Additional shielding efforts, (e.g., wearing a lead apron) will not provide significant benefit nor reduce staff radiation dose.

The U.S. National Council on Radiation Protection and Measurements and United Nations Scientific Committee on Effects of Atomic Radiation each conducted respective assessments of all radiation sources in the United States and worldwide. The goal of this article is to summarize and combine the results of these two publicly available surveys and to compare the results with historical information. In the United States in 2006, about 377 million diagnostic and interventional radiologic examinations and 18 million nuclear medicine examinations were performed. The United States accounts for about 12% of radiologic procedures and about one-half of nuclear medicine procedures performed worldwide. In the United States, the frequency of diagnostic radiologic examinations has increased almost 10-fold (1950-2006). The U.S. per-capita annual effective dose from medical procedures has increased about sixfold (0.5 mSv [1980] to 3.0 mSv [2006]). Worldwide estimates for 2000-2007 indicate that 3.6 billion medical procedures with ionizing radiation (3.1 billion diagnostic radiologic, 0.5 billion dental, and 37 million nuclear medicine examinations) are performed annually. Worldwide, the average annual per-capita effective dose from medicine (about 0.6 mSv of the total 3.0 mSv received from all sources) has approximately doubled in the past 10-15 years.

Medical radiation exposure of the U.S. population has not been systematically evaluated for almost 25 y. In 1982, the per capita dose was estimated to be 0.54 mSv and the collective dose 124,000 person-Sv. The preliminary estimates of the NCRP Scientific Committee 6-2 medical subgroup are that, in 2006, the per capita dose from medical exposure (not including dental or radiotherapy) had increased almost 600% to about 3.0 mSv and the collective dose had increased over 700% to about 900,000 person-Sv. The largest contributions and increases have come primarily from CT scanning and nuclear medicine. The 62 million CT procedures accounted for 15% of the total number procedures (excluding dental) and over half of the collective dose. Nuclear medicine accounted for about 4% of all procedures but 26% of the total collective dose. Medical radiation exposure is now approximately equal to natural background radiation.

Reference values (RVs) are recommended by the American Association of Physicists in Medicine for four radiographic projections, computed tomography, fluoroscopy, and dental radiography. RVs are used to compare radiation doses from individual pieces of radiographic equipment with doses from similar equipment assessed in national surveys. RVs recommended by the American Association of Physicists in Medicine have been developed from the Nationwide Evaluation of X-ray Trends survey performed by the state radiation protection agencies with the cooperation and support of the U.S. Food and Drug Administration, the Conference of Radiation Control Program Directors, and the American College of Radiology. The RVs selected by the American Association of Physicists in Medicine represent, approximately, the 80th percentile of the survey distributions. Consequently, equipment exceeding the RVs is using higher radiation doses than is 80% of the equipment in the surveys. Radiation doses for specific projections, with standard phantoms, should be measured annually, as recommended by the American College of Radiology. When the RVs are exceeded, the medical physicist should investigate the cause and determine, in cooperation with the responsible radiologist, whether these doses are justified or the imaging system should be optimized to reduce patient radiation doses. RVs are a useful tool for comparing patient radiation doses at institutions throughout the United States and for providing information about radiographic equipment performance.

The recently published Report No. 147 of The National Council on Radiation Protection and Measurements entitled “Structural shielding design for medical x‐ray imaging facilities” provides an update of shielding recommendations for x rays used for medical imaging. The goal of this report is to ensure that the shielding in these facilities limits radiation exposures to employees and members of the public to acceptable levels. Board certified medical and health physicists, as defined in this report, are the “qualified experts” who are competent to design radiation shielding for these facilities. As such, physicists must be aware of the new technical information and the changes from previous reports that Report No. 147 supersedes. In this article we summarize the new data, models and recommendations for the design of radiation barriers in medical imaging facilities that are presented in Report No. 147.

HomeRadiologyVol. 231, No. 3 PreviousNext In MemoriamRobert S. Landauer, JrJoel E. GrayJoel E. GrayJoel E. GrayPublished Online:Jun 1 2004https://doi.org/10.1148/radiol.2313042517MoreSectionsFull textPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In Article HistoryPublished in print: June 2004 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 231, No. 3 Metrics Altmetric Score PDF download

The purpose of this clinical study was to establish the non-inferiority of amorphous selenium (aSe) digital mammographic images to charge-coupled device (CCD) images. A features analysis was carried out to compare the quality of the images produced with a scintillator-CCD-fiber optic system to an aSe system. Six radiologists compared six features from the mammographic images, all of which contained suspected pathology, for 60 patients. The results indicate that the aSe images are similar to or better than the CCD images 94.0% of the time.

If the standard fIltered backprojection algorithm with a filter of the form g i f) = jf]h(f) is applied to noisy projections, all of which have a noise power spectra density o-S% spro -(f), then the resultin mensional Nf D of the form, S(f) s must approach a nun-zeru constant jection noise, the CT noise at low frequency suppression results in a long range negative spatial correlation of the CT noise, If white noise is spatially averaged ,;er a circle of diameter d, then the variance In 4~ averaged values w%ll behave as G' rt d For CT noise the variance drups faster than d Simple sLgnal-to-noise ratio cunsiderathxz suggest that the dependence of minimum detect: able contrast qon the diameter of the circle to be detected could be significantly different in the presence of CT noise than in that of white noise, Simulated reconstructions of a suitable detectability pattern demonstrate these differences may not exrist unless the image is spatially smoothed befure observatian. It is pointed out that the pixel width used in the image displ_ay should be from 113 to l/2 the width of the point spread functhn in order to avoid discrete binning problems.

Medical PhysicsVolume 26, Issue 1 p. 1-4 Free Access In the next decade automated computer analysis will be an accepted sole method to separate “normal” from “abnormal” radiological images Kenneth R. Hoffman, Kenneth R. Hoffman Department of Radiology, University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637Search for more papers by this authorJoel E. Gray, Joel E. Gray 2804 Second Street SW, Suite 334, Rochester, Minnesota 55902Search for more papers by this author Kenneth R. Hoffman, Kenneth R. Hoffman Department of Radiology, University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637Search for more papers by this authorJoel E. Gray, Joel E. Gray 2804 Second Street SW, Suite 334, Rochester, Minnesota 55902Search for more papers by this author First published: 05 January 1999 https://doi.org/10.1118/1.598473Citations: 10AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume26, Issue1January 1999Pages 1-4 RelatedInformation

This article investigates whether CT scanners used primarily for either head or body work have scattered radiation levels that may impact shielding considerations. Several 35 x 43 cm film cassettes were used to cover the floor area around a General Electric Hi-Speed Advantage CT unit. Regions of maximum exposure were identified (visually with sensitometric confirmation). An ion chamber was used to obtain radiation exposure levels for typical head and body protocols. Greater scattered radiation was found behind the gantry for head scanning (20 vs. 16 microGy for a body scan) while greater scatter was observed in front of the scanner for body scans (46 vs. 31 microGy for the head scan). The resulting annual doses to the floor from typical workloads (assuming 32 cases a day) can be as great as 0.63 Gy for head protocols or 1 Gy from body work. Care may be needed to assure adequate shielding for floor areas near CT scanners specializing in either head or body work. Also, while increased throughput with helical scanners is currently x-ray tube heat limited, shielding plans should allow for enhanced heat capacity (and greater throughput) in future generation scanners.

OBJECTIVE:Viewing conditions can affect an observer's performance in object detection. Our objective was to determine the effect of viewbox masking and luminance on the detection of small low-contrast objects revealed by mammography.MATERIALS AND METHODS:Mammographic contrast-detail images having various film densities were viewed on masked and unmasked viewboxes. Similar images with fixed film contrast and density were viewed when luminance ranged from 250 to 8000 nits (1 nit = 1 cd/m2).RESULTS:Detection of small low-contrast objects was significantly easier using a masked viewbox with high luminance that using a regular unmasked viewbox. When a regular viewbox (approximately 3000 nits) was used masking had a more significant effect on films with high optical densities than on films with low optical densities. Brighter, masked viewboxes improved detection on films with higher optical densities.CONCLUSION:Better detection of small low-contrast objects results when mammographic images are masked and viewed on high-luminance viewboxes than when a regular unmasked viewbox is used.

We recently installed picture archive and communication systems (PACS) from three different vendors on our campus for evaluation. A major part of this evaluation involved assessing the capabilities of these systems for displaying computed radiography (CR) images for primary interpretation. The three PACS provided different functionality for CR image display in terms of availability of the proprietary Fuji CR image processing algorithms, availability of user-specified contrast look-up tables, and application of the processing at the time of CR image capture or image display. We found that the Fuji processing algorithms were important for printing film, but were not necessary for acceptable soft-copy display. Non-linear contrast processing produced superior results compared to simple linear processing (via standard window width and level controls). Display processing was best applied immediately prior to the display operation, as opposed to at the image capture time. This allows the display to be adjusted to demonstrate the full 10-bit range of the CR image, and also allows raw CR data (i.e. not optimized for any particular display device) to be stored in the long-term archive.

Previous darkroom shielding requirements for medical x-ray film-assumed that the film should not be exposed to diagnostic x-ray radiation levels greater than 2 microGy (0.2 mR) for the life of the film. Modern medical x-ray films are much less sensitive to ionizing radiation, with most films showing at least an order of magnitude less sensitivity than previously assumed. Conversely, these same films when loaded in cassettes using modern intensifying screens exhibit an order of magnitude greater sensitivity when these cassettes are exposed to ionizing radiation. These data suggest that protection of modern medical x-ray film, stored in a darkroom, may require less shielding than previously assumed. Conversely, film loaded in a cassette will require greater shielding.