Experimentally determined spectral optimization for dedicated breast computed tomography

Journal Article · Tue Feb 15 00:00:00 EST 2011 · Medical Physics

DOI:https://doi.org/10.1118/1.3537077· OSTI ID:22096904

Prionas, Nicolas D.; Huang, Shih-Ying; Boone, John M. ^[1]

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1. Department of Radiology, University of California Davis Medical Center, 4860 Y Street, Suite 3100 Sacramento, California 95817 (United States)

Purpose: The current study aimed to experimentally identify the optimal technique factors (x-ray tube potential and added filtration material/thickness) to maximize soft-tissue contrast, microcalcification contrast, and iodine contrast enhancement using cadaveric breast specimens imaged with dedicated breast computed tomography (bCT). Secondarily, the study aimed to evaluate the accuracy of phantom materials as tissue surrogates and to characterize the change in accuracy with varying bCT technique factors. Methods: A cadaveric breast specimen was acquired under appropriate approval and scanned using a prototype bCT scanner. Inserted into the specimen were cylindrical inserts of polyethylene, water, iodine contrast medium (iodixanol, 2.5 mg/ml), and calcium hydroxyapatite (100 mg/ml). Six x-ray tube potentials (50, 60, 70, 80, 90, and 100 kVp) and three different filters (0.2 mm Cu, 1.5 mm Al, and 0.2 mm Sn) were tested. For each set of technique factors, the intensity (linear attenuation coefficient) and noise were measured within six regions of interest (ROIs): Glandular tissue, adipose tissue, polyethylene, water, iodine contrast medium, and calcium hydroxyapatite. Dose-normalized contrast to noise ratio (CNRD) was measured for pairwise comparisons among the six ROIs. Regression models were used to estimate the effect of tube potential and added filtration on intensity, noise, and CNRD. Results: Iodine contrast enhancement was maximized using 60 kVp and 0.2 mm Cu. Microcalcification contrast and soft-tissue contrast were maximized at 60 kVp. The 0.2 mm Cu filter achieved significantly higher CNRD for iodine contrast enhancement than the other two filters (p=0.01), but microcalcification contrast and soft-tissue contrast were similar using the copper and aluminum filters. The average percent difference in linear attenuation coefficient, across all tube potentials, for polyethylene versus adipose tissue was 1.8%, 1.7%, and 1.3% for 0.2 mm Cu, 1.5 mm Al, and 0.2 mm Sn, respectively. For water versus glandular tissue, the average percent difference was 2.7%, 3.9%, and 4.2% for the three filter types. Conclusions: Contrast-enhanced bCT, using injected iodine contrast medium, may be optimized for maximum contrast of enhancing lesions at 60 kVp with 0.2 mm Cu filtration. Soft-tissue contrast and microcalcification contrast may also benefit from lower tube potentials (60 kVp). The linear attenuation coefficients of water and polyethylene slightly overestimate the values of their corresponding tissues, but the reported differences may serve as guidance for dosimetry and quality assurance using tissue equivalent phantoms.

• OSTI ID: 22096904
• Journal Information: Medical Physics, Vol. 38, Issue 2; Other Information: (c) 2011 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
ACCURACY
ADIPOSE TISSUE
ALUMINIUM
APATITES
BIOPHYSICS
CALCIUM PHOSPHATES
COMPUTERIZED TOMOGRAPHY
CONTRAST MEDIA
COPPER
DIAGNOSIS
DOSIMETRY
GYNECOLOGY
IODINE
MAMMARY GLANDS
NEOPLASMS
OPTIMIZATION
PATIENTS
PHANTOMS
POLYETHYLENES
QUALITY ASSURANCE
RADIATION DOSES
WATER
X-RAY TUBES