Radiographic trends of dental offices and dental schools

Trends in the utilization of medical procedures that use ionizing radiation

Medical procedures that use ionizing radiation have grown rapidly in volume over the last two decades and constitute a substantial portion of the collective radiation doses to the U.S. population. The purpose of this study is to describe the components of this growth. Summarized claims data from Medicare are used to describe trends for the period 1986-2005; supplemental data from other payers and surveys are used for verification and to describe age distributions of those who have these procedures. A notable trend is the rapid growth of CT and nuclear medicine, with CT volume per fee-for-service Medicare enrollee growing, on average, at 8% per y and nuclear medicine at 7% per y during the period 1986-2005. Cardiac procedures-nuclear medicine and interventional radiology-grew at over 15% per y per fee-for-service enrollee during the same period. The share of nuclear medicine procedures performed in physician offices increased from 10% in 1986 to 55% in 2005; the share of CT in the emergency room increased from 3% in 1992 to 17% in 2005. With this expansion in imaging volumes across practice settings, there is an increased need for radiation safety education of ordering physicians, imaging physicians, and patients, so that adequate consideration is given to radiation risk when determining the appropriateness of a prescribed procedure.

Nationwide Evaluation of X-ray Trends Survey of Abdomen and Lumbosacral Spine Radiography

Results of the 1995 Nationwide Evaluation of X-ray Trends (NEXT) survey of facilities that perform diagnostic radiographic examinations of the abdomen and lumbosacral spine were compared with those of previous NEXT surveys conducted in 1987 and 1989. A clinically validated radiographic phantom was used in the 1995 survey to capture data about radiation exposure and image quality. Additional data were obtained regarding clinical techniques, facility workloads, x-ray beam quality, film processing quality, and darkroom fog. Mean skin-entrance air kerma for the abdomen examination dropped from 3.2 mGy (in 1987) to 2.8 mGy at hospitals and from 3.4 mGy (in 1989) to 3.0 mGy at nonhospital facilities. Mean skin-entrance air kerma also decreased for the lumbosacral spine examination from 3.7 mGy (in 1987) to 3.3 mGy at hospitals and from 3.8 mGy (in 1989) to 3.2 mGy at nonhospital facilities. The quality of film processing improved, although 58 (18.3%) of 317 surveyed facilities did not meet the Mammography Quality Standards Act standard for film processing quality, compared with 185 (5.9%) of 3,120 mammography facilities inspected in 1995. Finally, 181 (58.0%) of 312 surveyed facilities had darkroom fog levels greater than the Mammography Quality Standards Act standard, compared with 1,426 (16.6%) of 8,605 mammography facilities inspected in 1995.

Effect of iterative restoration on the detection of artificially induced vertical radicular fractures by Tuned Aperture Computed Tomography

OBJECTIVE

The purpose of this study was to evaluate the effect of the number of iterative restorations (IR) on the diagnostic accuracy of Tuned Aperture Computed Tomography images (TACT) for detection of induced vertical/oblique root fractures in mandibular teeth.

STUDY DESIGN

Fractures were induced in 28 single-rooted, endodontically treated cadaver mandibular teeth while another 26 such teeth served as controls. TACT slices reconstructed by using 9 arbitrary projections (angular disparity of 9 degrees -20 degrees) were iteratively restored 1, 2, and 3 times. Eight observers scored their diagnoses by using a confidence rating scale. Ground truth was available from direct examination with transillumination, following extraction.

RESULTS

Mean areas under the representative ROC curves for the 3 operations were 0.96 (3 IRs), 0.87 (2 IRs), and 0.86 (1 IRs). Analysis of variance demonstrated significant differences between 3 and 1 to 2 IRs (P <.01), as well as between observers (P <.01).

CONCLUSION

Diagnostic accuracy of TACT for vertical/oblique root fracture detection improved after 3 IRs.

Radiation dose-reduction techniques in North American dental schools

OBJECTIVE

The purpose of this investigation was to describe the extent to which dental schools use materials, equipment, and quality-assurance protocols that reduce radiation exposure to patients.

STUDY DESIGN

Questionnaires soliciting information regarding intraoral and extraoral radiographic practices and quality-assurance procedures were sent to the directors of oral and maxillofacial radiology (OMR) at the 65 schools of dentistry in the United States and Canada.

RESULTS

The response rate was 100%. E-speed film is used at 86% of institutions. Direct digital radiography is used at 58% of institutions for intraoral imaging and 11% for extraoral radiography. Other dose-reducing techniques include long source-film distances (88%), rectangular beam limitation (47%), leaded aprons (95% for extraoral films; 85% with thyroid collars for intraoral films), and rare earth intensifying screens (100%). The most commonly used tube potential is 70 kVp (88%). The director of OMR is solely responsible for radiographic policies at approximately 75% of institutions. Regular tests for film fog, speed, and contrast are done at roughly 75% of schools, while over 90% test darkroom lighting and x-ray equipment.

CONCLUSIONS

Some dose-reducing strategies are commonly used in dental schools, while others have not gained wide acceptance.

Detection of artificially induced vertical radicular fractures using tuned aperture computed tomography

This study compared the accuracy of three imaging modalities for the detection of artificially induced vertical root fractures (VRF) on teeth in cadaver mandibles. Fifty-four single-rooted, endodontically treated mandibular teeth being prepared to carry posts were evaluated using direct digital radiography (DDI) with a Schick sensor, unprocessed Tuned Aperture Computed Tomography (TACT-U) images and iteratively restored TACT (TACT-IR) images. Twenty-eight of these teeth had been subjected to fracture induction using an apically driven force. Nine basis images were used for each TACT image generation. Eight observers used a five-point confidence rating scale to record the confidence with which they considered a fracture to be present or not. Sensitivity and specificity values were computed and receiver operating characteristic (ROC) curves were generated. The areas under the curves (Az) used as an indication of the diagnostic accuracy of the imaging system were as follows: DDI: 0.37; TACT-U: 0.77 and TACT-IR: 0.81. DDI was significantly inferior to the TACT modalities. Differences in detection efficacy based on observers and observation sessions were noted on ANOVA and post-hoc Tukey's tests. This study indicates that TACT is the imaging modality of choice for VRF in endodontically treated teeth.