Amy Brito Delgado BSC, Presenter: Nothing to Disclose

Rajeev Suri MD, Abstract Co-Author: Nothing to Disclose

Michael Aaron Charlton PhD, Abstract Co-Author: Nothing to Disclose

Gregory Ramsey MD, Abstract Co-Author: Nothing to Disclose

The purpose of this study is to measure the peak skin doses for four routinely high dose hepatic interventional procedures by using optically stimulated luminiscence dosimeters (OSL). This study compares actual measurements of the peak skin dose utilizing locally calibrated OSL dosimeters (NanoDot Landauer) with the traditional medical physics calculations of Peak Skin Dose. By doing so we aimed to assess the validity and accuracy of these calculations. Subsequently, the calculated and the actual doses were compared with the Reference Dose Levels (RDLs) set by the NCRP. 

Four OSLs per patient were affixed to the patient’s back overlying the expected location of the liver, ensuring that they were included in the fluoroscopic field of view. These OSLs were read with a Microstar II reader, and the highest dose was recorded as the OSL peak skin dose (OSL PSD), against which other calculated measurements were compared. PSDs were calculated using the displayed Cumulative air KERMA (per the Philips Allura XPer FD 20 DICOM display). Patient thickness (a critical component of the dose calculation) was assessed by three separate methods: (1) using calipers; (2) estimated by kV and SID (from DICOM); (3) estimated by height and weight.  

For 5 TIPS patients, mean OSL PSDs were 23.3% lower than RDLs. The OSL PSDs were higher than the calculated PSDs by 24.8% (1), 26.3% (2), and 21.7% (3). For 12 TACE patients mean OSL PSDs exceeded the reference dose levels by 75.4%. The OSL PSDs were higher than the calculated PSDs by 22.7% (1), 30.9% (2), and 27.7% (3). For 4 MAA patients mean OSL PSDs exceeded the reference dose levels by 36.7%. The OSL PSDs were higher than the calculated PSDs by 40.38% (1), 42.52% (2), and 38.91% (3).  

OSL PSDs were higher than the calculated PSD using all three methods. OSL PSDs most closely correlated with the calculations using height and weight for estimating patient thickness. Discordance between the two may be at least partially explained by patient positioning closer to the X-Ray tube than what was previously assumed. The fluoroscopic output variability has to be taken into account.

Knowledge of accurate Peak Skin Doses are relevant to deterministic effects, and can be verified using OSL dosimeters as they relate to the traditional medical physics method.

Brito Delgado, A, Suri, R, Charlton, M, Ramsey, G, Measurements, Analysis & Comparison with Calculations of Peak Skin Doses during Common Interventional Radiology Fluoroscopy Procedures.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012902.html