AJR: Low-dose CT protocol feasible for lung nodule surveillance
CT radiation dose as low as 3 percent of the current standard may be sufficient for follow-up monitoring of lung nodules, according to study findings published in the September issue of the American Journal of Roentgenology.
Reviewing data from thoracic CT scans of 50 patients, Andreas Christe, MD, of University of Bern, in Switzerland, and colleagues found a low-dose CT protocol was feasible for identifying lung nodules, compared to identification using high-dose scans. Importantly, he noted, lowering current-time settings significantly reduced radiation risk.
“The risk of radiation induced cancer death for one standard chest CT is estimated at roughly one in 4,000 and could be reduced hypothetically to one in 120,000 with this low-dose protocol,” Christe said in a statement.
In the study, three radiologists reviewed images of 50 patients taken at 300 milliampere-seconds (mAs), as well as images reconstructed with raw data at 12 different lower doses. They analyzed a total of 125 cuboids found in 41 patients and another 27 cuboids from nine patients found to be without disease. With the exception of two dose levels, researchers found the lesser levels did not impact reader sensitivity. “The tube current-times level of 10 mAs did not exhibit a significant difference in individual reader sensitivity compared with the standard 300 mAs,” said Christe.
Radiologists were able to identify an average of 88 percent of the lung nodules at 10 mAs, compared to an average of 91 percent at 300 mAs, or thirty times the dose level.
“The readers had one thing in common: sensitivity for all 125 nodules was not significantly influenced by dose level,” the authors wrote.
Christe currently uses a CT dose of 40 mAs to monitor lung nodules at his clinical practice. “We are using a slightly higher dose because the 10 mAs resulted from a study design with dose simulations and smaller field of views than is routine in clinical practice,” he said. Christe may revise the protocol pending results from a follow-up clinical study.
In another aspect of the study, investigators also found that computer-aided volume measurement in follow-up of lung nodules decreased the variability found when radiologists did measurements manually. “It is essential that we can get exact measurements of nodules so we can determine if the nodule has grown between CT exams,” he said.
Reviewing data from thoracic CT scans of 50 patients, Andreas Christe, MD, of University of Bern, in Switzerland, and colleagues found a low-dose CT protocol was feasible for identifying lung nodules, compared to identification using high-dose scans. Importantly, he noted, lowering current-time settings significantly reduced radiation risk.
“The risk of radiation induced cancer death for one standard chest CT is estimated at roughly one in 4,000 and could be reduced hypothetically to one in 120,000 with this low-dose protocol,” Christe said in a statement.
In the study, three radiologists reviewed images of 50 patients taken at 300 milliampere-seconds (mAs), as well as images reconstructed with raw data at 12 different lower doses. They analyzed a total of 125 cuboids found in 41 patients and another 27 cuboids from nine patients found to be without disease. With the exception of two dose levels, researchers found the lesser levels did not impact reader sensitivity. “The tube current-times level of 10 mAs did not exhibit a significant difference in individual reader sensitivity compared with the standard 300 mAs,” said Christe.
Radiologists were able to identify an average of 88 percent of the lung nodules at 10 mAs, compared to an average of 91 percent at 300 mAs, or thirty times the dose level.
“The readers had one thing in common: sensitivity for all 125 nodules was not significantly influenced by dose level,” the authors wrote.
Christe currently uses a CT dose of 40 mAs to monitor lung nodules at his clinical practice. “We are using a slightly higher dose because the 10 mAs resulted from a study design with dose simulations and smaller field of views than is routine in clinical practice,” he said. Christe may revise the protocol pending results from a follow-up clinical study.
In another aspect of the study, investigators also found that computer-aided volume measurement in follow-up of lung nodules decreased the variability found when radiologists did measurements manually. “It is essential that we can get exact measurements of nodules so we can determine if the nodule has grown between CT exams,” he said.