TH-EF-BRA-04: Direct Organ Dose Measurements in a Human Cadaver Scanned with Pediatric CT Protocols

Authors


Abstract

Purpose:

To measure pediatric organ doses and assess clinical image quality in a cadaver scanned with pediatric protocols on a clinical CT scanner.

Methods:

Organ doses were measured in the thoracic and abdominal regions of a small sized cadaver by inserting optically stimulated luminescent dosimeters (OSLDs) into various organs. The subject's effective diameter was measured as 22.9 cm in the chest, and 22.3 cm in the abdomen, corresponding to the size of an 11-year old pediatric patient, based on AAPM Report No. 204. The subject was scanned with a pediatric chest and pediatric abdomen protocol on a Toshiba Aquilion ONE CT scanner. Scans were acquired with filtered back projection (FBP) and iterative reconstruction (IR) to quantify organ dose reduction capabilities of IR in pediatric patients. The subject was scanned with reduced dose protocols by increasing the noise tolerance level (SD) from 12.5 to 17.5 and 25.0. Image quality was assessed by a blinded observer study utilizing pediatric radiologists. Readers graded the images with a three point scale on the basis of diagnostic ability.

Results:

In comparing IR versus FBP reconstructed images, we measured average organ dose reductions of 25% and 32% for the chest and abdomen scans, respectively. Increasing the SD from 12.5 to 17.5 offered organ dose savings of 51% and 58% for the chest and abdomen scans. Further dose reduction was achieved by increasing the SD to 25, allowing substantial dose savings of 75% and 80% for the chest and abdomen scans. The majority of the images were found to be of acceptable image quality.

Conclusion:

Organ dose quantification and reduction were investigated in this clinical CT study. Iterative reconstruction algorithms provide significant dose reduction to pediatric patients undergoing CT scans. Further dose reductions can be achieved by increasing noise tolerance levels while still maintaining acceptable image quality.

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