CT metal artifact reduction - single energy metal artifact reduction (SEMAR) algorithm

Case contributed by Dinesh Brand
Diagnosis not applicable


Recent abdominal surgery. Elevated white cell count.

Patient Data

Age: 70 years
Gender: Male

There is a right and left hip prosthesis causing artifact degrading pelvic image quality.

Single Energy Metal Artifact Reduction SEMAR

There is no evidence of free intra-peritoneal gas. There is focal soft tissue thickening noted in and around the anterior abdominal wall, with stranding extending into the adjacent fat; the appearances suggestive of acute inflammation, granulomatous inflammation or scar formation. There is evidence of dehiscence of the surgical scar in the lower abdominal wall. There is no evidence of an associated post-operative fluid collection. There is no evidence of a dominant distended loop of gas filled bowel; to suggest the differential diagnosis of closed loop obstruction. There are no signs to suggest bowel wall ischemia. There is no convincing evidence of an abdominal loculated fluid collection.

Case Discussion

Metallic implants cause beam hardening effects and photon starvation resulting in streak artifacts. This can interfere with the evaluation of adjacent soft tissues as well the prostheses and supporting bone structures as in this case. Single energy metal artifact reduction (SEMAR) reconstruction technique (Canon/Toshiba) was used on the volumetric scan eliminating streak artifacts that were seen on the raw data allowing for more accurate diagnosis of the clinical presentation. 

Metal artifact reduction (MAR) algorithms can be set in the scan protocol allowing for fully automatic reconstruction, requiring no additional operator input. A study in 2015 showed that a comparison between three MAR algorithms implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to prostheses and between the two prostheses 1.

Disclosure: I, Dinesh Brand, have no actual or potential ethical or financial conflict of interest in relation to this device. This case is not intended to be a personal endorsement or recommendation of this product.

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