Automatic Tube Voltage Selection Reduced Radiation Dose

August 4, 2014

Automatic tube voltage selection automatically adjusts the tube current depending on patient size and attenuation.

Researchers were able to significantly reduce radiation dose in patients undergoing chest or abdominal CT by simultaneously using automatic tube current modulation (ATCM) and automatic tube voltage selection (ATVS), according to the results of a study published in the American Journal of Roentgenology.

“The ATVS tool reduced effective tube voltage in many patients, resulting in a dose reduction of 18%, showing the potential of this new dose modulation tool,” wrote Caroline Mayer, MD, of the University Medical Center Mannheim, Germany, and colleagues.

In recent years, ATCM has been introduced as a method to reduce radiation dose. More recently though, dose reductions using ATVS have been increasingly hot topic. According to the study, ATVS, “automatically adjusts the tube current on the basis of patient size and attenuation.”

In this study, the researchers examined whether combined use of ATCM and ATVS could reduce radiation dose further than ATCM alone. The researchers enrolled 617 patients who underwent contrast-enhanced chest or abdominal CT with ATCM and a fixed body mass index adjusted tube voltage (Group A), or both ATCM and ATVS (Group B). There were no statistically significant differences for body constitution parameters between patients in the two groups.

Patients assigned to Group B had a higher mean contrast-to-noise ratio and signal-to-noise ratio of abdomen and chest CT (P<.0001). A comparison of radiation dose showed that patients assigned to the combination of ATCM and ATVS had an 18 percent reduction in radiation dose compared to patients who had ATCM alone (P<.0001).

When looking at results for chest CT alone, there was a tube voltage reduction from 120 to 100 kV in the majority of patients. The results showed an overall dose reduction of 16.8 percent for patients assigned to group B compared with Group A (P=.0034). The researchers further isolated the results to only those patients who benefitted from the ATVS tool and found a dose reduction of 35 percent for chest CT.

Among patients who underwent abdominal CT, there was a tube voltage reduction to 100 kV in 48 patients, and increase to 130 kV in four patients, and an unchanged voltage in 83 patients. Results showed a dose reduction of 18.4 percent for patients in Group B compared with Group A. When looking at only those patients who benefited from the ATVS tool there was a 42 percent radiation dose reduction.

“Surprisingly, tube current modulation did not increase simultaneously with a decrease in tube voltage on the ATVS study as we expected,” the researchers wrote. “The use of ATVS for chest and abdominal CT results in a significant dose reduction while maintaining adequate image quality and diagnostic confidence without user interaction.”