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1.  Metal Artifact Reduction From Reformatted Projections for Hip Prostheses in Multislice Helical Computed Tomography 
Investigative radiology  2009;44(11):691-696.
Purpose
Hip prosthesis is one of the most common types of metal implants and can cause significant artifacts in computed tomography (CT) examinations. The purpose of this work was to develop a projection-based method for reducing metal artifacts caused by hip prostheses in multislice helical CT.
Method and Materials
The proposed method is based on a novel concept, reformatted projection, which is formed by combining the projection data at the same view angle over the full longitudinal scan range. Detection and segmentation of the metal were performed on each reformatted projection image. Two dimensional interpolation based on Delaunay triangulation was used to fill voids left after removal of the metal in the reformatted projection. The corrected data were then reconstructed using a commercially available algorithm. The main advantage of this method is that both the detection of the metal objects and the interpolations are performed on complete reformatted projections with the entire metal region present, which is particularly useful for long hip prostheses. Twenty clinical abdominal/pelvis exams with hip prostheses were corrected and clinically evaluated.
Results
The overall image quality and the conspicuity in some critical organs were significantly improved compared with the uncorrected images: overall quality (P = 0.0024); bladder base (P = 0.0027), and rectum (P = 0.0078). The average noise level in the bladder base was reduced from 86.7 HU to 36.2 HU. In 17 of 20 cases, the radiologists preferred either coronal (13) or axial (4) views of the corrected images.
Conclusions
A novel method for reducing metal artifact in multislice helical CT was developed. Initial clinical results showed that the proposed method can effectively reduce the artifacts caused by metal implants for the cases of unilateral and bilateral hip prothesis.
doi:10.1097/RLI.0b013e3181b0a2f9
PMCID: PMC3966535  PMID: 19809345
computed tomography (CT); multi-slice helical CT; metal artifact reduction
2.  Radiation dose reduction in computed tomography: techniques and future perspective 
Imaging in medicine  2009;1(1):65-84.
Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine. Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk. This article summarizes the general technical strategies that are commonly used for radiation dose management in CT. Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented.
doi:10.2217/iim.09.5
PMCID: PMC3271708  PMID: 22308169
computed tomography; CT; CT technology; radiation dose reduction; radiation risk
3.  Diagnostic Ionizing Radiation Exposure in a Population-Based Cohort of Patients with Inflammatory Bowel Disease 
Objective
For diagnosis, assessing disease activity, complications and extraintestinal manifestations, and monitoring response to therapy, patients with inflammatory bowel disease undergo many radiological studies employing ionizing radiation. However, the extent of radiation exposure in these patients is unknown.
Methods
A population-based inception cohort of 215 patients with inflammatory bowel disease from Olmsted County, Minnesota, diagnosed between 1990 and 2001, was identified. The total effective dose of diagnostic ionizing radiation was estimated for each patient. Linear regression was used to assess the median total effective dose since symptom onset.
Results
The number of patients with Crohn's disease and ulcerative colitis was 103 and 112, with a mean age at diagnosis of 38.6 and 39.4 yr, respectively. Mean follow-up was 8.9 yr for Crohn's disease and 9.0 yr for ulcerative colitis. Median total effective dose for Crohn's disease was 26.6 millisieverts (mSv) (range, 0–279) versus 10.5 mSv (range, 0–251) for ulcerative colitis (P < 0.001). Computed tomography accounted for 51% and 40% of total effective dose, respectively. Patients with Crohn's disease had 2.46 times higher total effective dose than ulcerative colitis patients (P = 0.001), adjusting for duration of disease.
Conclusions
Annualizing our data, the radiation exposure in the inflammatory bowel disease population was equivalent to the average annual background radiation dose from naturally occurring sources in the U.S. (3.0 mSv). However, a subset of patients had substantially higher doses. The development of imaging management guidelines to minimize radiation dose, dose-reduction techniques in computed tomography, and faster, more robust magnetic resonance techniques are warranted.
doi:10.1111/j.1572-0241.2008.01920.x
PMCID: PMC2831296  PMID: 18564113
4.  Strategies for Reducing Radiation Dose in CT 
doi:10.1016/j.rcl.2008.10.006
PMCID: PMC2743386  PMID: 19195532
CT; Radiation Dose; Cardiac CT; Dose Reduction; Automatic Exposure Control; Effective Dose

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