Charlie Sayer MBBS,FRCR, Abstract Co-Author: Nothing to Disclose

Sananda Haldar MBBS, Abstract Co-Author: Nothing to Disclose

Tharsi Sarvananthan MBBS, MRCS, Abstract Co-Author: Nothing to Disclose

Ahmed Daghir MRCP, FRCR, Presenter: Nothing to Disclose

To investigate the effect of patient arm position on dose, subjective and objective image quality in split bolus whole body CT in polytrauma.

As part of a large retrospective cohort study at a UK major trauma centre we performed a comparison study of the effect of position the patient with the arms down and the arms up. From a data set of 177 patients scanned over a 9 month period 31 patients were scanned with the arms elevated above the shoulder girdle. Patients were matched for body size and presence of a scoop with 31 patients scanned with both arms down to the sides. Measurement of: Dose (DLP mGy/cm); Subjective image quality in five regions (liver, spleen, aorta, lung bases and T6-L3 vertebrae) using a 3 point scale (1 = no artefact, 2 = minor artefact and 3 = major artefact non-diagnostic); and objective noise (standard deviation (SD) of the average CT number (HU) for a 4cm ROI in liver segment 6/7) was performed for both groups.

There was a significant improvement in the subjective assessment of image quality in all the regions of interest (p <0.05). In the arms up group there was a single score of 3 (major artefact, non-diagnostic) out of 155 assessed regions (0.65%) compared to 20 out of 155 assessed regions (12.9%) in the arms down group (p=0.01 x 10-30). In the arms down group in 96.8% (n=30) of artefact scored 2 or 3 was judged to be predominantly caused by the arms (rather than scoop or external lines). In the arms up group where there was measurable artefact this was most often due to the presence of the scoop (32.3%, n = 10) followed by external lines (12.9%, n = 4). Preliminary data show a reduction in mean dose in the arms up group (1110 mGy/cm vs 1216 mGy/cm), although this difference was not statistically significant (p = 0.11). No significant effect on objective image noise in either the arms up or arms down groups was observed (p = 0.06).

When practical and safe to do so positioning the patient with the arms raised results in a significant improvement in subjective image quality and the rate of non-diagnostic scans. Although the effect on dose and objective noise were not statistically significant, trends towards lower dose and improved objective image quality were found.

In whole body trauma CT positioning the patient with the arms raised results in a significant improvement in subjective image quality and the rate of non-diagnostic scans

Sayer, C, Haldar, S, Sarvananthan, T, Daghir, A, Hands up! The Effect of Arm Position on Dose and Image Quality in Whole Body CT for Multitrauma.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13021697.html