Recent technologic advances have markedly enhanced the clinical applications of computed tomography (CT). While the benefits of CT exceed the harmful effects of radiation exposure in patients, increasing radiation doses to the population have raised a compelling case for reduction of radiation exposure from CT. Strategies for radiation dose reduction are difficult to devise, however, because of a lack of guidelines regarding CT examination and scanning techniques. Various methods and strategies based on individual patient attributes and CT technology have been explored for dose optimization. It is the purpose of this review article to outline basic principles of CT radiation exposure and emphasize the need for CT radiation dose optimization based on modification of scanning parameters and application of recent technologic innovations.

Strategies for CT radiation dose optimization.

In the past decade, the tremendous advances in computed tomography (CT) technology and applications have increased the clinical utilization of CT, creating concerns about individual and population doses of ionizing radiation. Scanner manufacturers have subsequently implemented several options to appropriately manage or reduce the radiation dose from CT. Modulation of the x-ray tube current during scanning is one effective method of managing the dose. However, the distinctions between the various tube current modulation products are not clear from the product names or descriptions. Depending on the scanner model, the tube current may be modulated according to patient attenuation or a sinusoidal-type function. The modulation may be fully preprogrammed, implemented in near-real time by using a feedback mechanism, or achieved with both preprogramming and a feedback loop. The dose modulation may occur angularly around the patient, along the long axis of the patient, or both. Finally, the system may allow use o...

https://pubs.rsna.org/doi/pdf/10.1148/rg.262055138

CT dose reduction and dose management tools: overview of available options.

Strategies for reducing radiation dose in CT.

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The Measurement, Reporting, and Management of Radiation Dose in CT

PURPOSE: To investigate how changes in kilovolt peak and milliampere second settings, and patient weight affect transmitted x-ray energy fluence and the image contrast-to-noise ratio (CNR) at abdominal computed tomography (CT). MATERIALS AND METHODS: Cylinders of water were used as patient models, and x-ray spectra, including x-ray tube potentials of 80–140 kVp, were investigated. The mean photon energy and energy fluence transmitted through water cylinders with varying diameters and the image contrast for fat, muscle, bone, and iodine relative to water were determined. The effect of changing the x-ray tube potential on CNR also was investigated. RESULTS: At a constant kVp, increasing patient weight from 10 kg to 120 kg reduced the transmitted energy fluence by two orders of magnitude. Changing the x-ray tube potential from 80 kVp to 140 kVp increased the mean photon energy from approximately 52 keV to approximately 72 keV and thus reduced the image contrast relative to water by 12% for muscle, 21% for fa...

Technique Factors and Image Quality as Functions of Patient Weight at Abdominal CT

The effect of different mAs settings on computed tomobraphy (CT) image quality was evaluated by a clinical study and phantom studies. In the clinical portion of this study, a number of CT images, obtained at various mAs settings, were reviewed by experienced CT interpreters. From these same images, graphs were charted of the root-mean-standard deviation (RMSD) vs. body size; there appeared to be a linear relationship between noise, as measured by RMSD, and body size. A performance phantom was used to evaluate the effect of the different mAs settings on resolution. There was some loss in low contrast resolution at 6 and 20 mAs; however, the resolution was identical at 40 and 100 mAs.

The effect of mAs variation upon computed tomography image quality as evaluated by in vivo and in vitro studies

Four patients with primary sclerosing cholangitis (PSC) were examined with the hepatobiliary agent Tc-99m-labeled DISIDA (diisopropylphenylcarbamoyl iminodiacetic acid), and the results correlated with those of invasive cholangiography. Three of the four patients exhibited a typical pattern of multiple, persistent focal "hot spots" in the duct system, representing stasis within the segmental ductal dilatations (beading), also seen on cholangiography. Cholescintigraphy is superior to cholangiography in cases of suspected PSC where there is nonfilling of biliary radicals due to high-grade stenosis. The finding of delayed hepatic parenchymal clearance can allow estimation of the degree of obstruction of the various branches of the major bile ducts. Cholescintigraphy offers a noninvasive method of investigating patients with suspected sclerosing cholangitis, leading to earlier diagnosis. Confirmation with invasive cholangiographic procedures is recommended.

F. D. Miraldi

Papers

The effect of mAs variation upon computed tomography image quality as evaluated by in vivo and in vitro studies

Sclerosing cholangitis: Cholescintigraphy with Tc-99m-labeled DISIDA