David A. Zamora MS, Abstract Co-Author: Nothing to Disclose

Kalpana M. Kanal PhD, Presenter: Nothing to Disclose

Renee L. Dickinson MS, Abstract Co-Author: Nothing to Disclose

William Phelps Shuman MD, Abstract Co-Author: Research Grant, General Electric Company

Brent K. Stewart PhD, Abstract Co-Author: Nothing to Disclose

The aim of this work is to implement vendor mandated alert value (AV) and notification value (NV) Dose-Check metrics into neuro radiology CT exams without negatively impacting clinical workflow and to evaluate these tools as a means of active dose notification.

Preliminary clinical introduction of NV included usage of the CTDIvol (rather than DLP to minimize variation of scan extent) on neurological exams, which normally utilize manual (rather than modulated) tube current. Appropriate NV levels were established using AAPM recommendations, ACR Dose Index Registry results, and scanner-projected CTDIvol values. The NV represents an expected ‘reasonable’ CTDIvol (or DLP) value, and is assigned at the group level of the protocol prescription; projected surpassing of the NV displays a simple warning message. When an NV alert is issued, the technologist attains and documents radiologist approval and then continues the exam. Similarly, the AV is a threshold compared to the max cumulative CTDIvol at any scan location. If the forthcoming scan is projected to surpass the AV, login credentials and reason for continuing with exam are required to proceed with the scan. Our institution collectively established an AV of 1000 mGy to allow for expected high doses commonly observed for cerebral perfusion exams. Clinical NV and AV alerts were documented with an available audit tool.

Effective implementation requires a balance of appropriate alerting and reasonable clinical interruption. After four months (2 scanners), the audit tool documented 6 NV alerts (2 T-spine, 2 C-spine, 2 Neck). Alerts came about from manual modification of the standard protocol by the technologist (e.g. rods/screws present in the L-spine region). On average, the projected CTDIvol exceeded the NV by 8.4% for spine and 18.5% for neck. Adverse effects on clinical workflow have not been experienced.

Active monitoring using AV and NV is a useful, non-invasive tool in minimizing the likelihood of abnormal incremental overdose (NV) and of gross overdose (AV). Future work will involve the more complex process of introducing NV values for abdominal exams that rely on automatic tube current modulation.

The XR-25 standard represents an early attempt to actively monitor CT radiation dose prior to patient exposure in hopes of mitigating gross/incremental overdose and to minimize deterministic effects.

Zamora, D, Kanal, K, Dickinson, R, Shuman, W, Stewart, B, Clinical Implementation of the NEMA (MITA) XR-25 CT Dose-Check Standard.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043862.html