Abdominal multislice CT for obese patients: effect on image quality and radiation dose in a phantom study.

RATIONALE AND OBJECTIVES To evaluate the effect of a modified abdominal multislice computed tomography (CT) protocol for obese patients on image quality and radiation dose. MATERIALS AND METHODS An adult female anthropomorphic phantom was used to simulate obese patients by adding one or two 4-cm circumferential layers of fat-equivalent material to the abdominal portion. The phantom was scanned with a subcutaneous fat thickness of 0, 4, and 8 cm using the following parameters (detector configuration/beam pitch/table feed per rotation/gantry rotation time/kV/mA): standard protocol A: 16 x 0.625 mm/1.75/17.5 mm/0.5 seconds/140/380, and modified protocol B: 16 x 1.25 mm/1.375/27.5 mm/1.0 seconds/140/380. Radiation doses to six abdominal organs and the skin, image noise values, and contrast-to-noise ratios (CNRs) were analyzed. Statistical analysis included analysis of variance, Wilcoxon rank sum, and Student's t-test (P < .05). RESULTS Applying the modified protocol B with one or two fat rings, the image noise decreased significantly (P < .05), and simultaneously, the CNR increased significantly compared with protocol A (P < .05). Organ doses significantly increased, up to 54.7%, comparing modified protocol B with one fat ring to the routine protocol A with no fat rings (P < .05). However, no significant change in organ dose was seen for protocol B with two fat rings compared with protocol A without fat rings (range -2.1% to 8.1%) (P > .05). CONCLUSIONS Using a modified abdominal multislice CT protocol for obese patients with 8 cm or more of subcutaneous fat, image quality can be substantially improved without a significant increase in radiation dose to the abdominal organs.

[1]  E. Mun,et al.  Current status of medical and surgical therapy for obesity. , 2001, Gastroenterology.

[2]  B. Popkin,et al.  Trends of obesity and underweight in older children and adolescents in the United States, Brazil, China, and Russia. , 2002, The American journal of clinical nutrition.

[3]  Thomas L Toth,et al.  Low-dose CT of the abdomen: evaluation of image improvement with use of noise reduction filters pilot study. , 2003, Radiology.

[4]  James H Thrall,et al.  Clinical comparison of standard-dose and 50% reduced-dose abdominal CT: effect on image quality. , 2002, AJR. American journal of roentgenology.

[5]  Thomas L Toth,et al.  Comparison of Z-axis automatic tube current modulation technique with fixed tube current CT scanning of abdomen and pelvis. , 2004, Radiology.

[6]  W. Huda.  Dose and image quality in CT , 2002, Pediatric Radiology.

[7]  Individual modulation of the tube current-seconds to achieve similar levels of image noise in contrast-enhanced abdominal CT. , 2005, AJR. American journal of roentgenology.

[8]  J. Haaga,et al.  Radiation dose management: weighing risk versus benefit. , 2001, AJR. American journal of roentgenology.

[9]  D. Frush,et al.  Validation of metal oxide semiconductor field effect transistor technology for organ dose assessment during CT: comparison with thermoluminescent dosimetry. , 2007, AJR. American journal of roentgenology.

[10]  W Huda,et al.  Image mottle in abdominal CT. , 1999, Investigative radiology.

[11]  K. Flegal,et al.  Prevalence of overweight and obesity in the United States, 1999-2004. , 2006, JAMA.

[12]  J. Haaga,et al.  The effect of mAs variation upon computed tomography image quality as evaluated by in vivo and in vitro studies. , 1981, Radiology.

[13]  W. Hendee.  Medical Radiation Physics , 2020, Definitions.

[14]  M. Kalra,et al.  Techniques and applications of automatic tube current modulation for CT. , 2004, Radiology.

[15]  Ambady Ramachandran,et al.  Computed axial tomographic scan measurement of abdominal fat distribution and its correlation with anthropometry and insulin secretion in healthy Asian Indians. , 1997, Metabolism: clinical and experimental.

[16]  T. Fukunaga,et al.  Influences of age and sex on abdominal muscle and subcutaneous fat thickness , 2004, European Journal of Applied Physiology.

[17]  M. V. van Leeuwen,et al.  A rational approach to dose reduction in CT: individualized scan protocols , 2001, European Radiology.

[18]  J. Tuomilehto,et al.  Trends in obesity and energy supply in the WHO MONICA Project , 2004, International Journal of Obesity.

[19]  S. Silverman,et al.  Patient and personnel exposure during CT fluoroscopy-guided interventional procedures. , 2000, Radiology.

[20]  A S Brody,et al.  Minimizing radiation dose for pediatric body applications of single-detector helical CT: strategies at a large Children's Hospital. , 2001, AJR. American journal of roentgenology.

[21]  C. McCollough,et al.  CT dose reduction and dose management tools: overview of available options. , 2006, Radiographics : a review publication of the Radiological Society of North America, Inc.