[Challenges for computed tomography of overweight patients]

Area of Science:

• Medical Imaging
• Radiology
• Diagnostic Imaging

Background:

• Morbidly obese patients often require computed tomography (CT) for non-invasive diagnostics.
• Standard CT scanners have limitations in weight capacity, dose, and image quality for this population.

Purpose of the Study:

• To analyze weight limits, radiation dose, and image quality of standard CT scanners.
• To determine the diagnostic value and radiation dose of a dual source XXL mode CT scanner for morbidly obese patients.

Main Methods:

• Retrospective analysis of 15 morbidly obese patients (average weight 189.6 ± 42 kg) examined with the XXL mode.
• Intraindividual comparison of XXL and standard protocols in 7 patients.
• Inclusion of 14 patients (90-150 kg) examined with standard protocols as references.
• Examination of a large abdomen phantom to compare dose efficiency.

Main Results:

• The dual source XXL mode resulted in significantly higher radiation doses (CTDIvol XXL 72.9 ± 23 mGy vs. standard 16.7 ± 11 mGy).
• Image noise was higher in the XXL group but significantly lower in intraindividual comparisons (e.g., liver: 24.2 ± 14 HU vs. 36.3 ± 20 HU).
• The XXL protocol achieved diagnostic image quality in all cases, whereas 43% of standard protocol examinations were non-diagnostic.

Conclusions:

• Standard CT techniques are suitable for patients up to 150 kg.
• The dual source XXL mode is necessary for reliable diagnostic image quality in patients exceeding 150 kg, despite increased radiation dose.
• Standard dose conversion factors may overestimate the biologically relevant equivalent dose in XXL mode scans.