CT Radiation Dose Reduction

Source:  CT Radiation Dose Reduction    Tag:  anteroposterior

Dose Reduction for Abdominal and Pelvic MDCT After Change to Graduated Weight-Based Protocol for Selecting Quality Reference Tube Current, Peak Kilovoltage, and Slice Collimation
Brian R. Herts1, 2, Mark E. Baker1, 3, Nancy Obuchowski1, 4, Andrew Primak5, Erika Schneider1, Harpreet Rhana6 and Frank Dong1, 7
Affiliations: 1 Imaging Institute, Cleveland Clinic, Desk Hb6, 9500 Euclid Ave, Cleveland, OH 44195.

2 Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, OH.

3 Digestive Disease Institute, Cleveland Clinic, Cleveland, OH.

4 Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, OH.

5 Siemens Healthcare, Malvern, PA.

6 Primordial Design, San Mateo, CA.

7 Section of Medical Physics, Cleveland Clinic, Cleveland, OH.

Citation: American Journal of Roentgenology. 2013;200:1298-1303
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OBJECTIVE. The purpose of this article is to determine the decrease in volume CT dose index (CTDIvol) and dose-length product (DLP) achieved by switching from fixed quality reference tube current protocols with automatic tube current modulation to protocols adjusting the quality reference tube current, slice collimation, and peak kilovoltage according to patient weight.

MATERIALS AND METHODS. All adult patients who underwent CT examinations of the abdomen or abdomen and pelvis during 2010 using weight-based protocols who also underwent a CT examination in 2008 or 2009 using fixed quality reference tube current protocols were identified from the radiology information system. Protocol pages were electronically retrieved, and the CT model, examination date, scan protocol, CTDIvol, and DLP were extracted from the DICOM header or by optical character recognition. There were 15,779 scans with dose records for 2700 patients. Changes in CTDIvol and DLP were compared only between examinations of the same patient and same CT system model for examinations performed in 2008 or 2009 and those performed in 2010. The final analysis consisted of 1117 comparisons in 1057 patients, and 1209 comparisons in 988 patients for CTDIvol and DLP, respectively.

RESULTS. The change to a weight-based protocol resulted in a statistically significant reduction in CTDIvol and DLP on three MDCT system models (p < 0.001). The largest average CTDIvol decrease was 13.9%, and the largest average DLP decrease was 16.1% on a 64-MDCT system. Both the CTDIvol and DLP decreased the most for patients who weighed less than 250 lb (112.5 kg).

CONCLUSION. Adjusting the CT protocol by selecting parameters according to patient weight is a viable method for reducing CT radiation dose. The largest reductions occurred in the patients weighing less than 250 lb.

Lateral Topography for Reducing Effective Dose in Low-Dose Chest CT
Dong-Ho Bang1, Daekeon Lim1, Wi-Sub Hwang1, Seong-Hoon Park2, Ok-man Jeong1, Kyung Wook Kang1 and Hohyung Kang1
Affiliations: 1 Department of Radiology, Aerospace Medical Center, PO Box 335-21, Ssangsu-ri, Namil-myeon, Cheongwongun, Chungbuk, Korea.

2 Department of Radiology and the Institute for Radiological Imaging Science, Wonkwang University School of Medicine, Iksan, Korea.

Citation: American Journal of Roentgenology. 2013;200:1294-1297
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OBJECTIVE. The purposes of this study were to assess radiation exposure during low-dose chest CT by using lateral topography and to compare the lateral topographic findings with findings obtained with anteroposterior topography alone and anteroposterior and lateral topography combined.

SUBJECTS AND METHODS. From November 2011 to February 2012, 210 male subjects were enrolled in the study. Age, weight, and height of the men were recorded. All subjects were placed into one of three subgroups based on the type of topographic image obtained: anteroposterior topography, lateral topography, and both anteroposterior and lateral topography. Imaging was performed with a 128-MDCT scanner. CT, except for topography, was the same for all subjects. A radiologist analyzed each image, recorded scan length, checked for any insufficiencies in the FOV, and calculated the effective radiation dose. One-way analysis of variance and multiple comparisons were used to compare the effective radiation exposure and scan length between groups.

RESULTS. The mean scan length in the anteroposterior topography group was significantly greater than that of the lateral topography group and the combined anteroposterior and lateral topography group (p < 0.001). The mean effective radiation dose for the lateral topography group (0.735 ± 0.033 mSv) was significantly lower than that for the anteroposterior topography group (0.763 ± 0.038 mSv) and the combined anteroposterior and lateral topography group (0.773 ± 0.038) (p < 0.001).

CONCLUSION. Lateral topographic low-dose CT was associated with a lower effective radiation dose and scan length than either anteroposterior topographic low-dose chest CT or low-dose chest CT with both anteroposterior and lateral topograms.

Can Contrast Media Increase Organ Doses in CT Examinations? A Clinical Study
Ernesto Amato1, Ignazio Salamone1, Serena Naso1, Antonio Bottari1, Michele Gaeta1 and Alfredo Blandino1
Affiliation: 1 All authors: Section of Radiological Sciences, Department of Biomedical Sciences and Morphologic and Functional Imaging, University of Messina, Via Consolare Valeria 1, Messina I-98125, Italy.

Citation: American Journal of Roentgenology. 2013;200:1288-1293
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OBJECTIVE. The purpose of this article is to quantify the CT radiation dose increment in five organs resulting from the administration of iodinated contrast medium.

MATERIALS AND METHODS. Forty consecutive patients who underwent both un-enhanced and contrast-enhanced thoracoabdominal CT were included in our retrospective study. The dose increase between CT before and after contrast agent administration was evaluated in the portal phase for the thyroid, liver, spleen, pancreas, and kidneys by applying a previously validated method.

RESULTS. An increase in radiation dose was noted in all organs studied. Average dose increments were 19% for liver, 71% for kidneys, 33% for spleen and pancreas, and 41% for thyroid. Kidneys exhibited the maximum dose increment, whereas the pancreas showed the widest variance because of the differences in fibro-fatty involution. Finally, thyroids with high attenuation values on unenhanced CT showed a lower Hounsfield unit increase and, thus, a smaller increment in the dose.

CONCLUSION. Our study showed an increase in radiation dose in several parenchymatous tissues on contrast-enhanced CT. Our method allowed us to evaluate the dose increase from the change in attenuation measured in Hounsfield units. Because diagnostic protocols require multiple acquisitions after the contrast agent administration, such a dose increase should be considered when optimizing these protocols.