Use of BMI Guidelines and Individual Dose Tracking to Minimize Radiation Exposure from Low-dose Helical Chest CT Scanning in a Lung Cancer Screening Program

Rationale and Objectives

The increasing use of computed tomography (CT) has been accompanied by rising concerns over potential radiation-related health risks, especially cancer, and a need to minimize such risks.

Materials and Methods

We conducted 2186 low-dose helical chest CT scans among 1235 nuclear weapons workers at elevated risk of lung cancer, setting the CT scanner tube current at 30 mAs for all participants with BMI <35 kg/m 2 and permitting technologists to raise mAs levels for participants with BMI ≥35 kg/m 2 . Dose-length product (DLP) was recorded from the CT scanner, permitting calculation of effective dose. Phantom-based estimates of effective dose were also made. A chest radiologist recorded acceptability of image quality.

Results

The study population was significantly overweight: 79% exceeded a body mass index (BMI) >25 kg/m 2 and 37.1% exceeded a BMI ≥30 kg/m 2 . Nearly 90% of CT scans were performed using a tube current setting of 30 mAs and had a mean DLP-based effective dose of 1.3 mSv. The phantom-based estimate of effective dose was lower at 1.1 mSv. Among participants with a BMI ≥35 kg/m 2 , 92% were scanned at 40 or 50 mAs, which was associated with a DLP-based effective dose of 1.6 and 2.0 mSv, respectively. Image quality was satisfactory in 99.8% of scans.

Conclusion

Application of simple BMI-based guidelines and DLP tracking of low-dose helical chest CT scans in a lung cancer screening program minimizes radiation dose, even in a largely overweight population.

The use of computed tomography (CT) has increased sharply in the past two decades . Rapid technological advancements in CT scanner technology have led to shorter acquisition times, more user-friendly handling, and the ability to reconstruct high quality three-dimensional images of internal body structures.

Concomitantly, rising concern over potential radiation-related cancer risk has made the frequency and circumstances of CT scanner use the focus of a larger public health debate . Recent studies have described incidents of grossly excessive and variable radiation exposure associated with the use of diagnostic CT scans . Other studies have provided estimates of excess cancer deaths after CT scans .

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Methods

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Results

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Table 1

Age, Weight, Body Mass Index, Dose Length Product, and Effective Dose Associated with Low-dose CT Scans (May 15, 2009–March 31, 2010)

Female ( n = 423) Male ( n = 1763) All ( n = 2186) Mean age (y) 62.7 65.2 64.7 Mean weight (lb) 168.5 203.9 197.0 Mean and range of body mass index (kg/m 2 ) 28.7 (16.1–50.1) 28.9 (16.2–55.2) 28.9 (16.1–55.2) Mean and range of dose-length product (mGy-cm) 89.3 (60–173) 97.3 (56–247) 95.7 (56–247) Mean effective dose (mSv) 1.2 1.4 1.3

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Table 2

Computed Tomography Scanner Tube Current Levels Used According to Participant BMI

BMI (kg/m 2 ) Tube Current (mAs) Number of Scans per BMI Category 30 40 50 60 70 <30 1374 (99.9%) 1 (0.1%) 0 0 0 1375 30–34.9 533 (99.6%) 2 (0.4%) 0 0 0 535 ≥35 5 (1.8%) 170 (61.6%) 85 (30.8%) 13 (4.7%) 3 (1.1%) 276 Number (%) of scans at each mAs 1912 (87.5%) 173 (7.9%) 85 (3.9%) 13 (0.6%) 3 (0.1%) 2186 (100%)

BMI, body mass index.

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Discussion

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Conclusion

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Acknowledgments

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References

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Use of BMI Guidelines and Individual Dose Tracking to Minimize Radiation Exposure from Low-dose Helical Chest CT Scanning in a Lung Cancer Screening Program

Rationale and Objectives

Materials and Methods

Results

Conclusion

Methods

Results

Discussion

Conclusion

Acknowledgments

References

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