ACR ACCREDITATION:FAQS FOR MEDICAL PHYSICISTS Priscilla F. Butler, MS, Senior Director and Medical Physicist, ACR Quality and Safety

Does your facility need help on applying for accreditation? In each issue of this newsletter, I'll present frequently asked questions (FAQs) of particular importance for medical physicists. You may also check out the ACR's accreditation web site portal for more FAQs, accreditation application information, and QC forms.

The following questions are for the ACR Computed Tomography Accreditation Program. Please feel free to contact us if you have questions about CT accreditation.

Q.The ACR now requests that facilities provide their Dose Notification values (mGy), as described by MITA Standard XR-25 (and included in XR-29), on the CT Phantom Site Scanning Data Form. Is this required for CT accreditation?
A.No, completion of Dose Notification values is not required for ACR CT Accreditation. The new Dose Notification values described by MITA XR-25 (and included in XR-29) are now requested in the phantom site scanning data form for informational purposes only and is intended to raise your facility's awareness and understanding of this feature as it may apply to your scanner and protocol. XR-29 compliance is not a requirement of CT Accreditation. Therefore, this field is optional. Please visit the ACR NEMA XR-29 (MITA Smart Dose) Standard Frequently Asked Questions for further information on XR-29 and the CMS rule.

Q.The adult head, adult abdomen, pediatric head and pediatric abdomen dose calculation forms now include a field to enter the CTDIvol reported by the scanner (mGy) for the protocol entered into the phantom site scanning data form. Is this required? How do I obtain this value?
A.This is an optional field. When prescribing the phantom scans using the adult head, adult abdomen, pediatric head and pediatric abdomen protocols for ACR CT accreditation phantom testing, the scanner will report the expected CTDIvol for the respective protocol. This data may be entered into the dose calculation form and the database will calculate the percent difference between the calculated CTDIvol and the CTDIvol reported by the scanner. While this value is not scored as a part of accreditation, the percent difference should be less than 20%. Measured values not within 20% of the values reported by the scanner should be investigated. We recommend contacting your Qualified Medical Physicist (QMP) for assistance if needed. The CTDIvol reported by the scanner (mGy) and the percent difference between the calculated CTDIvol and the CTDIvol reported by the scanner are for informational purposes only, will not be evaluated by the reviewers and will not contribute to deficiencies at this time.

Q.The adult abdomen and pediatric abdomen dose calculation forms now include an SSDE for 35 and 18.5 cm water equivalent diameter (mGy). What is the purpose of this new calculation and how is it scored for accreditation?
A.Size specific dose estimate (SSDE) is a calculation that allows an estimation of patient dose based on CTDIvol and patient size. This value is for informational purposes only and will not be scored as a part of accreditation at this time. For more information on CT dose and SSDE, please visit the Alliance for Quality Computed Tomography Education Slides. Your Qualified Medical Physicist (QMP) may also refer to AAPM Reports 204 and 220.

Q.The pediatric abdomen (40-50 lb) dose calculation for accreditation submission now provides a choice of a 16 or 32 cm phantom. How do I know which one is required for my scanner and how does this affect the CTDIvol reference values and pass/fail criteria for the pediatric abdomen protocol?
A.For pediatric abdomen (40-50 lb.) protocols, some CT scanners report CTDIvol using the 16 cm phantom, while others use the 32 cm phantom. The medical physicist should select the phantom (16 or 32 cm) that is used by the scanner to report CTDIvol. For accreditation, the adjusted reference values and pass/fail criteria are as follows:

	Reference Levels CTDIvol (mGy)	Pass/Fail Criteria CTDIvol (mGy)
Pediatric Abdomen (40-50 lb) – 16 cm phantom (existing)	15	20
Pediatric Abdomen (40-50 lb) – 32 cm phantom	7.5	10

Q.My scanner reports the pediatric abdomen protocol with a 32 cm phantom but my Qualified Medical Physicist (QMP) has already tested with a 16 cm phantom. Does my QMP need to rescan the pediatric abdomen dose phantom using a 32 cm phantom?
A.No. If the QMP scanned the 16 cm phantom, then ensure that the 16 cm phantom is selected in the pediatric abdomen dose calculation form. The phantom selected in the pediatric abdomen dose calculation form must match the scanned phantom pediatric abdomen dose images and resultant dose measurements.

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