Low-dose Whole Body Computed Tomography Scanning

Computed Tomography, Image Quality

Computed tomography represents the mainstay for diagnosing various diseases in the whole body. Over the past decade, enormous efforts were undertaken by both CT manufacturers and radiologist to reduce the radiation dose to patients. Today, the dose is significantly lower that it was before the era of multislice CT and iterative reconstruction methods. The X-ray beam originating from the tube in a CT system contains a spectrum of different energies, whereby the harder beams with higher energy penetrate the patient better, and the softer beams will be absorbed through the patient's tissues. Recent research has been shown that the radiation dose can be further reduced by improved primary beam filtering in CT. This study is intended to compare the radiation dose in clinically indicated, routine CT examination while maintaining a diagnostic image quality, on a new CT system with modified primary beam filtering.

At the Joint Department of Medical Imaging (JDMI), the investigators periodically adjust the radiation dose and modify the clinical imaging protocols in order to continuously optimize image quality in CT. The investigators have formalized the process of radiation dose adjustments by implementing a CT dose committee that meets on a monthly basis and reviews imaging protocols (SOP). The committee includes radiologists, technologists, vendor representative (if needed), managers and the radiation protection officer. Part of the review is the investigator's in-house developed Coral image quality review program as well as the clinically used radiation dose monitoring software (Radiometric). Part of the evaluation study of the new CT system is to monitor 520 patients who will undergo a clinically indicated CT scan on the new system. Identical to standard-of-care (SOC) quality insurance, the investigators will use the existing monitoring software (Radiometric, JDMI) in order to capture the data in the existing database. The investigators will also capture quality data through the existing CT image quality feedback tool. After installation of the new CT system, the investigators will maintain the radiation dose as currently applied in the standard JDMI wide imaging protocols and examine 20 patients on the new system; radiation dose and image quality feedback will be recorded in the identical fashion to standard operating procedures (CT image quality and radiation dose committee). Subsequently, the investigators will drop the dose by approx. 10% for each scanning protocol and scan the subsequent 250 patients while concurrently analyzing the impact on the collective dose to the patient population. Based on the expected increase in image noise, the investigators will calculate the possible additional dose reduction in percent and modify all protocols accordingly for the subsequent 250 patients. This step-down approach ensures that no CT scan will be performed with too little dose, and that all CT scans remain diagnostic.

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