Lumbar Spine CT Radiation Dose Reduced by Decreasing Tube Voltage

An algorithm that takes the patient’s size into consideration can slash the radiation dose by 41% in lumbar spine computed tomography (CT) without losing the diagnostic quality of the images.

Researchers from Yeouido St. Mary’s Hospital (Seoul, Korea) examined 107 patients using semiautomated attenuation-based tube potential selection, which optimized tube potential at 100 kV rather than the standard 120 kV. Decreasing the voltage decreased the radiation dose from a mean of 21.78 mGy to a mean of 12.77 mGy, but it can increase the image noise (graininess), according to Dr. Junghyun Lim, lead author of the study.

The images were reconstructed using either the conventional filtered back projection or iterative reconstruction—a technique designed to decrease image noise. Two musculoskeletal radiologists reviewed the images and then scored them based on level of noise, visibility of structure and confidence of diagnosis. They concluded that irrespective of the reconstruction technique, the lower kilovoltage images were of diagnostic quality, according to Dr. Lim. “We conducted objective measurements of image noise as well,” noted Dr. Lim. “The objective measurements favored the images that had undergone iterative reconstruction.”

Dr. Lim noted that his facility performs between 140-150 lumbar CT scans each month. Based on the results of this study, “the routine lumbar spine CT exam is now conducted at 100 kV using filtered back projection,” he said.

The study’s findings were presented at the American Roentgen Ray Society (ARRS) annual meeting, held April 2013 in Washington DC (USA).

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Yeouido St. Mary’s Hospital