Establishment of Quality Assessment Standard for Mammographic Equipments: Evaluation of Phantom and Clinical Images

PURPOSE: The purpose of this study was to establish a quality standard for mammographic equipment in Korea and to eventually improve mammographic quality in clinics and hospitals throughout Korea by educating technicians and clinic personnel. MATERIALS AND METHODS: For the phantom test and on site assessment, we visited 37 sites and examined 43 sets of mammographic equipment. Items that were examined include phantom test, radiation dose measurement, developer assessment, etc. The phantom images were assessed visually and by optical density measurements. For the clinical image assessment, clinical images from 371 sites were examined following the new Korean standard for clinical image evaluation. The items examined include labeling, positioning, contrast, exposure, artifacts, collimation among others. RESULTS: Quality standard of mammographic equipment was satisfied in all equipment during on site visits. Average mean glandular dose was 114.9 mRad. All phantom image test scores were over 10 points (average, 10.8 points). However, optical density measurements were below 1.2 in 9 sets of equipment (20.9%). Clinical image evaluation revealed appropriate image quality in 83.5%, while images from non-radiologist clinics were adequate in 74.6% (91/122), which was the lowest score of any group. Images were satisfactory in 59.0% (219/371) based on evaluation by specialists following the new Korean standard for clinical image evaluation. Satisfactory images had a mean score of 81.7 (1 S.D.=8.9) and unsatisfactory images had a mean score of 61.9 (1 S.D=11). The correlation coefficient between the two observers was 0.93 (p<0.01) in 49 consecutive cases. CONCLUSION: The results of the phantom tests suggest that optical density measurements should be performed as part of a new quality standard for mammographic equipment. The new clinical evaluation criteria that was used in this study can be implemented with some modifications for future mammography quality control by the Korean government.

Quality Control of Medical Imaging

Medical imaging is the one of the most important diagnostic tools of modern medical science and quality control of the medical imaging is already systemized in the advanced countries. However, in Korea, quality control of medical imaging has not been properly performed until now and low quality examinations have been done without any regulation. The Korean Radiological Society, as society of supervision of medical imaging, has emphasized the importance of quality control and in 2003, the law for the quality control of medical imaging was made. In conformity of the law, the regulation of the quality control of medical imaging will commence, but this is just the beginning and there are still many tasks left for settling down and expanding the range of the quality control of the medical imaging. We reviewed the history of the quality control of medical imaging in Korea and explained the particulars of mammography, fluoroscopy, computed tomography and magnetic resonance imaging. We also looked into future prospect and tasks of the quality control of medical imaging.

Clinical Image Evaluation of Mammograms: A National Survey

PURPOSE: The goal of this study was to survey the overall quality of mammographic images in Korea. MATERIALS AND METHODS: A total of 598 mammographic images collected from 257 hospitals nationwide were reviewed in terms of eight image quality categories, namely positioning, compression, contrast, exposure, sharpness, noise, artifacts, and examination identification, and rated on a five-point scale: (1=severe deficiency, 2=major deficiency, 3=minor deficiency, 4=good, 5=best). Failure was defined as the occurrence of more than four major deficiencies or one severe deficiency (score of 1 or 2). The results were compared among hospitals of varying kinds, and common problems in clinical image quality were identified. RESULTS: Two hundred and seventeen mammographic images (36.3%) failed the evaluation. Poor images were found in descending order of frequency, at The Society for Medical Examination (33/69, 47.8%), non-radiology clinics (42/88, 47.7%), general hospitals (92/216, 42.6%), radiology clinics (39/102, 38.2%), and university hospitals (11/123, 8.9%) (p<0.01, Chi-square test). Among the 598 images, serious problems which occurred were related to positioning in 23.7% of instances (n=142) (p<0.01, Chi-square test), examination identification in 5.7% (n=34), exposure in 5.4% (n=32), contrast in 4.2% (n=25), sharpness in 2.7% (n=16), compression in 2.5% (n=15), artifacts in 2.5% (n=15), and noise in 0.3% (n=2). CONCLUSION: This study showed that in Korea, 36.3% of the mammograms examined in this sampling had important image-related defects that might have led to serious errors in patient management. The failure rate was significantly higher in non-radiology clinics and at The Society for Medical Examination than at university hospitals.

Screening Mammography in a Health Promotion Center for 5 Years: Results of Medical Audits

PURPOSE: The purpose of this study was to perform a medical audit of the screening of mammographic results according to ACR BI-RADS Follow-Up and Outcome Monitoring and to evaluate the efficacy of screening mammography in the early detection of breast cancer. MATERIALS AND METHODS: We reviewed the results of 15,300 mammographic examinations of 13, 889 women aged 30 -75 years who underwent mammography at least once at the Severance Health Promotion Center between 1994 and 1998. Women with abnormal mammographic findings were recalled for additional study and those with dense breast composition (3, 4) underwent additional ultrasound. All results were categorized on the basis of the ACR BI-RADS final assessment scale, 1 -5. We reviewed the pathologic or follow-up results of all women in categories 4 and 5, and/or those in any category who took the films out of the health center. RESULTS: The recall rate was 13%. Biopsy or surgical Consultation was recommended for 92 women and biopsy was performed in 52. Pathology revealed 17 cancers and 35 benign lesions. Positive predictive value 2 was found in 18.5% of cases, and positive predictive value 3 in 33%. The cancer detection rate was 1.2/1,000, and sensitivity was 89.5%. Invasive cancers smaller than 1cm or in situ ductal cancers were found in eight of 17 cases (47%), while node-positive invasive cancers were found in nine of 14 cases (64%). Four of 17 mammo-graphically detected cancers were palpated by a surgeon. CONCLUSION: In asymptomatic women, screening mammography is an effective method for the detection of early breast cancer.

Mammographic Radiation Dose Measurement

PURPOSE: To measure the mammographic radiation dose of different mammographic units and views as compared to the American College of Radiology Recommendations. MATERIALS AND METHODS: We measured the kVp, entrance dose and average glandular dose for three mammo-graphic units(two Giotto Hi-Tech Mammography, IMS, Bologna, Italy, one Senographe 500T, GE Medical Systems, Milwaukee, Wis., U.S.A.) in the 26 -33 kV range. Dose measurement for magnification compression view was obtained for two machines and dose measurement for stereotactic views was obtained for one machine. RESULTS: For each machine, the entrance dose was within the range of 3.400 -6.077, 4.383 -11.403, 3.790 -6 . 497 mSv, respectively, and the average glandular dose was within the range of 0.74 -1.96 mGy. The entrance and average glandular dose were 17.14, 18.00 mSv, and 3.73, 3.92 mGy for the magnification compression view and 2.41 -2.92 mSv, 0.50 -0.61 mGy for stereotactic views. The error range of kVp was ~1 1 . 3 ~+1.9 %. CONCLUSION: The entrance dose and average glandular dose were above the limit of the American College of Radiology Recommendations. It is necessary to develop a Korean standard on the basis of the above data.