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The ACR CT Accreditation program has existed since 2002. The CT Accreditation process includes the initial application, and the submission of clinical and phantom images and forms. The medial physicist plays a critical role in the accreditation process, along with the lead technologist and the supervising radiologist. A team approach is necessary to ensure that all information is accurate and appropriate for the examinations (both clinical and phantom) submitted for accreditation. The medical physicist should assist the facility in assessing the condition of the scanner as well as optimizing the clinical protocols. This lecture will provide a brief overview of the application steps, and some of the most common problems encountered during accreditation. Educational Objectives: 1. Understand the basics of the ACR CT Accreditation process. 2. Understand the relationship of the medical physicist in this process. 3. Understand some of the most common pitfalls in the accreditation process.

Purpose: To investigate the use of a simple contrast to noise metric and its ability to predict low contrast resolution in CT scans. Method and Materials: The ACR low contrast phantom was scanned with 120 kVp and various exposure levels ranging from 50 to 1600 effective mAs. Each scan was reconstructed with 5 mm thickness and 8 different reconstruction filters, ranging from very smooth (B10) through very sharp (B80). Each image was windowed and leveled to the same settings, anonymized to reduce reader bias and put in random order. The images were sent to 9 independent readers, experienced in evaluating the ACR phantom for low contrast resolution. Each reader scored the smallest size set of rods visible in each image. Separately, a simple contrast to noise ratio (CNR) was obtained for each image, calculated as (A‐B)/σ where A is the mean of an ROI placed over the 25mm rod, B is an ROI of samesize placed in the background next to the 25mm rod, and σ is the standard deviation of the background. Results: For many of the lower exposure and filter combinations, the largest 25mm rod was not visible and no measurement of CNR could be made. For those images in which it was visible, the CNR ranged from 0.15 for 300mAs and filter B70, to 6.4 for 1600mAs and filter B10. The measured CNR does correlate well with observer performance within a reconstruction filter setting, though there is wide variability in observer performance. However, CNR did not correlate well with observer performance across reconstruction filters. Conclusion: The correlation between CNR and observer performance suggests it may be possible to use this metric to predict low contrast performance for cases with a fixed reconstruction filter and might be useful if a limited range of filters are used.

In October, 2008, the ACR MRI Accreditation Program was updated to a more flexible, modular process. The ACR MR Accreditation process includes the initial application, and the submission of clinical and phantom images and forms. The medial physicist plays a critical role in the accreditation process, along with the lead technologist and the supervising radiologist. A team approach is necessary to ensure that all information is accurate and appropriate for the examinations (both clinical and phantom) submitted for accreditation. The medical physicist should assist the facility in assessing the condition of the scanner as well as optimizing the clinical protocols. This lecture will provide a brief overview of the application steps, and some of the most common problems encountered during clinical portion of the accreditation submission. Learning Objectives: 1. Understand the basics of the ACR MR Accreditation process. 2. Understand the relationship of the medical physicist in this process as it relates to clinical protocols. 3. Understand some of the most common pitfalls and misconceptions in the accreditation process.