Radiologic Technology最新文献

Purpose: To explore the data and supporting evidence for the 2019 statement by the American Association of Physicists in Medicine (AAPM) that recommends limits to the routine use of fetal and gonadal shielding in medical imaging.

Methods: Three researchers searched 5 online databases, selecting articles from scholarly journals and radiology trade publications. Search results were filtered to include literature published from January 1, 2016, to August 9, 2022, to ensure relevance and provide historical background for the 2019 AAPM statement.

Results: The use of patient shielding during medical imaging did not reduce dose, and in certain instances, increased dose received by patients during computed tomography, fluoroscopy, or dental imaging. The use of shielding interfered with technology designed to reduce patient dose, including automatic exposure control and dose modulation. Research showed that errors in shield placement were common and that shields can act as sources of infection or carriers of harmful lead dust.

Discussion: In each article reviewed, a compelling case was made for discontinuing routine patient shielding during radiographic procedures. Serious opposition to the discontinuation of the shielding practice was not found. Opportunities exist for further study into technologists' and the public's understanding of the effects of radiation and technologists' compliance with new shielding policies.

Conclusion: The challenges with properly using shielding, paired with recent technological advancements and a new understanding of radiation protection, have negated the need for contact shielding. This legacy practice can be discontinued in clinical settings, and educational materials for technologists and students should be updated to reflect these changes.

Purpose: To measure the effect of increasing kilovoltage peak (kVp) and copper filtration thickness on entrance skin exposure and contrast resolution for chest radiography performed using digital flat-panel detectors.

Methods: A phantom-based experiment was conducted in which 24 radiographs of a quality control chest phantom were obtained at varying kVp levels and copper filtration thicknesses. The entrance skin exposure was measured and analyzed for each exposure. All radiographs were analyzed based on measured pixel values and contrast:noise ratio (CNR) and using subjective analysis, which focused on contrast resolution assessment performed by 4 radiologists.

Results: The results from the subjective image analysis showed that increasing copper filtration in increments of 0.1 mm resulted in less of a decrease in contrast resolution compared with increasing the kVp by 10 kVp, and that contrast resolution is more dependent on energy level than on filtration. The results from objective image analysis indicated that CNR decreased when kVp increased at all filtration thicknesses, but consistent dependency between CNR and filtration was not evident. Exposure data analysis showed an average 46% decrease in entrance skin exposure for each increase of 0.1 mm in copper filtration thickness.

Discussion: Although subjective and objective data analysis results indicated that increases of copper filtration are more beneficial to maintaining contrast resolution and reducing entrance skin exposure compared with increases of kVp, objective image data analysis showed a greater reduction in contrast resolution when kVp is increased. These results validate previous research that concluded that copper filtration should be considered as a dose-reduction and image-optimization strategy in digital radiography departments.

Conclusion: Although entrance skin exposure reduction can be accomplished using higher kVp and copper filtration, increasing copper filtration thickness could be considered to minimize the loss of contrast resolution for routine chest imaging when digital flat-panel detectors are used.

Purpose: To evaluate the effect of contrast timing, contrast volume, and contrast flow rate on the image quality of pulmonary arteries in computed tomography angiography (CTA) and to assess if bolus-tracking region of interest (ROI) positioning in the left atrium, which is used for triple-rule-out CTA, allows for sufficient depiction of the pulmonary arteries.

Methods: In this retrospective single-center study, data were collected for patients who underwent thoracic CTA during a specific period. Two groups of 121 patients each were created based on bolus-tracking ROI positioning in the main pulmonary artery or left atrium using propensity score matching. Image quality of the pulmonary arteries was evaluated using quantitative and qualitative scores. Subgroups were formed to examine the influence of contrast volume and flow rate. Two radiologists determined if pulmonary embolism was present, if pulmonary embolism could be excluded with certainty, and from which level pulmonary embolism could be excluded with certainty. Interrater reliability also was evaluated.

Results: ROI positioning in the main pulmonary artery scored significantly higher compared with the left atrium. There was no significant difference in subgroups of patients who were examined with 60 mL or more contrast volume and less than 4 mL/s flow rate; scores were similar or better than in the overall study population. Pulmonary embolism was not able to be excluded with certainty for each 1 patient in these subgroups compared with a high percentage in the overall study population.

Discussion: ROI positioning in the left atrium in combination with the 60 mL or more contrast volume and less than 4 mL/s flow rate does not adversely affect depiction of the pulmonary arteries compared with conventional ROI positioning in the main pulmonary artery.

Conclusion: When using 60 mL or more contrast volume and less than 4 mL/s flow rate, ROI positioning in the left atrium, which is used in triple-rule-out CTA, is sufficient for the assessment of pulmonary arteries.