1. Low Dose Head Computed Tomography Protocol for Evaluation of Non-traumatic Emergencies in Children Rishi Mhapsekar, MD Marilyn J. Siegel, MD Robert McKinstry MD, PhD Poster # EP-142

2. Disclosures Rishi Mhapsekar: Nothing to disclose Marilyn Siegel: Speaker for Siemens Healthcare Robert McKinstry: Nothing to disclose

3. Purpose The purpose of our study was to evaluate if an unenhanced low- dose head CT could consistently provide acceptable image quality and diagnostic information

4. Materials and Methods 584 pediatric head CT scans performed between January 2014 and December 2014 were retrospectively reviewed 365 CT scans were performed using a full dose protocol to assess for traumatic emergencies and 219 head CT scans were performed using low dose protocols to evaluate for non- traumatic emergencies

5. Materials and Methods CT examinations were performed on a 64-slice SOMATOM Definition AS scanner (Siemens Healthcare, Forchheim, Germany) equipped with automated tube-current modulation (CARE Dose4D) Full dose scans used quality references of 330 mAs and fixed 120 kV Low dose scans used references of 150 mAs and fixed 100 kV

6. Analysis All CT scans were reviewed for patient age, CT Dose Index Volume (CTDIvol) in mGy, Dose Length Product (DLP) in mGy.cm, milliamperage (mAs) and kilovoltage (kVp) Data was recorded from the patient dose record shown at the CT console Results of full and low dose scans were analyzed using Shapiro-Wilk W test and Wilcoxon rank sums test

7. Qualitative Analysis One reader graded image quality Diagnostic image quality was graded on a 3 point scale (1, poor and unacceptable; 2, good; 3, excellent) Diagnostic acceptability was based on visualization of the sharpness of ventricular outlines, tissue contrast, and shunts (when present) Diagnostic noise was graded on a 3 point scale (1, unacceptable; 2, present, but not affecting diagnosis; 3) absent)

8. Results Median patient ages for full and low dose head CT protocols were 8.0 and 6.0 years respectively (p > 0.05) Median CTDI vol for full and low dose CT protocols were 28.7 and 8.8 mGy respectively (p < 0.001) (69% difference)

9. Results Median DLP for full and low dose CT protocols were 496 and 146 mGy.cm respectively (p < 0.001) (71% difference) Median mAs for full and low dose CT protocols were 295 and 88 mAs respectively (p < 0.001) (70% difference)

10. Results ParameterLow Dose Protocol Full Dose Protocol % Change Median mAs8829570% Median CTDI28.78.869% Median DLP14649671%

11. Results Low dose pediatric head CTs were of diagnostic image quality - grade 2 or 3 (2, good; 3, excellent) Low dose CT noise was graded as 2 or 3 (2, present, but not affecting diagnosis; 3) absent)

12. Diagnostic Image Quality Low DoseFull Dose 15 year old girl with headache CTDI: 11.6; DLP: 164 Diagnostic quality, some noise 16 year old boy with trauma CTDI: 26.8 ; DLP: 582 Diagnostic quality, no noise

13. Conclusion Low dose head CT protocols in children using lower mAs and kV reduce CTDIvol, DLP, and mAs by approximately 70% Low-dose non-enhanced head CT provides diagnostically acceptable images in non- traumatic emergencies