Iterative reconstruction improves image quality and reduces radiation dose in trauma protocols; A human cadaver study.

BACKGROUND: Radiation-related cancer risk is an object of concern in CT of trauma patients, as these represent a young population. Different radiation reducing methods, including iterative reconstruction (IR), and spilt bolus techniques have been introduced in the recent years in different large scale trauma centers. PURPOSE: To compare image quality in human cadaver exposed to thoracoabdominal computed tomography using IR and standard filtered back-projection (FBP) at different dose levels. MATERIAL AND METHODS: Ten cadavers were scanned at full dose and a dose reduction in CTDIvol of 5 mGy (low dose 1) and 7.5 mGy (low dose 2) on a Siemens Definition Flash 128-slice computed tomography scanner. Low dose images were reconstructed with FBP and Sinogram affirmed iterative reconstruction (SAFIRE) level 2 and 4. Quantitative image quality was analyzed by comparison of contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). Qualitative image quality was evaluated by use of visual grading regression (VGR) by four radiologists. RESULTS: Readers preferred SAFIRE reconstructed images over FBP at a dose reduction of 40% (low dose 1) and 56% (low dose 2), with significant difference in overall impression of image quality. CNR and SNR showed significant improvement for images reconstructed with SAFIRE 2 and 4 compared to FBP at both low dose levels. CONCLUSIONS: Iterative image reconstruction, SAFIRE 2 and 4, resulted in equal or improved image quality at a dose reduction of up to 56% compared to full dose FBP and may be used a strong radiation reduction tool in the young trauma population.

Improved image quality in abdominal computed tomography reconstructed with a novel Deep Learning Image Reconstruction technique - initial clinical experience.

BACKGROUND: A novel Deep Learning Image Reconstruction (DLIR) technique for computed tomography has recently received clinical approval. PURPOSE: To assess image quality in abdominal computed tomography reconstructed with DLIR, and compare with standardly applied iterative reconstruction. MATERIAL AND METHODS: Ten abdominal computed tomography scans were reconstructed with iterative reconstruction and DLIR of medium and high strength, with 0.625 mm and 2.5 mm slice thickness. Image quality was assessed using eight visual grading criteria in a side-by-side comparative setting. All series were presented twice to evaluate intraobserver agreement. Reader scores were compared using univariate logistic regression. Image noise and contrast-to-noise ratio were calculated for quantitative analyses. RESULTS: For 2.5 mm slice thickness, DLIR images were more frequently perceived as equal or better than iterative reconstruction across all visual grading criteria (for both DLIR of medium and high strength, p < 0.001). Correspondingly, DLIR images were more frequently perceived as better (as opposed to equal or in favor of iterative reconstruction) for visual reproduction of liver parenchyma, intrahepatic vascular structures as well as overall impression of image noise and texture (p < 0.001). This improved image quality was also observed for 0.625 mm slice images reconstructed with DLIR of high strength when directly comparing to traditional iterative reconstruction in 2.5 mm slices. Image noise was significantly lower and contrast-to-noise ratio measurements significantly higher for images reconstructed with DLIR compared to iterative reconstruction (p < 0.01). CONCLUSIONS: Abdominal computed tomography images reconstructed using a DLIR technique shows improved image quality when compared to standardly applied iterative reconstruction across a variety of clinical image quality criteria.

Triple-split-bolus versus single-bolus CT in abdominal trauma patients: a comparative study.

Background Split-bolus computed tomography (CT) is a recent development in trauma imaging. Instead of multiple scans in different contrast phases after a single contrast bolus, split-bolus protocols consist of one single scan of the thorax and abdomen after two or three contrast injections at different points of time. Purpose To evaluate and compare image quality and injury findings of a new triple-split-bolus CT (TS-CT) protocol of thorax and abdomen with those of a portal venous phase CT (PV-CT) in the same patient group. Material and Methods Trauma patients in 2009-2012 who underwent both the TS-CT initially and a PV-CT during the next six weeks were included. The TS-CT examination was performed as one CT run after application of three contrast boluses (total 175 mL) to enhance renal pelvis and urinary tract, the abdominal organs, and the large arterial vessels. The PV-CT had a fixed delay of 85 s. We measured attenuation in Hounsfield units (HU), evaluated possible organ injury and assessed image quality on a 5-point scale. Results Thirty-five patients were included. Attenuation measurements of major abdominal vessels, organs, and renal pelvis were significantly higher with the TS-CT protocol. Performance in organ injury diagnosis and image quality was equal in both protocols. Conclusion The overall performance of the TS-CT protocol is similar to the standard PV-CT. Excellent visualization of the arterial tree and the collecting system may eliminate the need for separate scans.

Diagnostic performance of CT, MRI and PET/CT in patients with suspected colorectal liver metastases: the superiority of MRI.

BACKGROUND: Meticulous imaging of colorectal liver metastases (CRLM) is mandatory to optimize outcome after liver resection. However, the detection of CRLM is still challenging. PURPOSE: To evaluate prospectively if magnetic resonance imaging (MRI) with diffusion-weighted and Gd-EOB-DTPA-enhanced sequences had a better diagnostic performance for CRLM compared to computed tomography (CT) and fluorine-18 fluorodeoxyglucose positron emission tomography (PET/CT). MATERIAL AND METHODS: Forty-six patients scheduled for resection of suspected CRLM were evaluated prospectively from September 2011 to January 2013. None of the patients had undergone previous treatment for their CRLM. Multiphase CT, liver MRI with diffusion-weighted and dynamic Gd-EOB-DTPA-enhanced sequences and low-dose PET/CT were performed. Two independent, blinded readers evaluated the examinations. The reference standard was histopathological confirmation (81/140 CRLM) or follow-up. RESULTS: A total of 140 CRLM and 196 benign lesions were identified. On a per-lesion basis, MRI had the significantly highest sensitivity overall and for CRLM < 10 mm (P < 0.001). Overall sensitivity/specificity and PPV/NPV were 68%/94% and 89%/81% for CT, 90%/87% and 82%/93% for MRI, and 61%/99% and 97%/78% for PET/CT. For CRLM < 10 mm it was 16%/96% and 54%/80% for CT, 74%/88% and 64%/93% for MRI, and 9%/98% and 57%/79% for PET/CT. CONCLUSION: MRI had the significantly highest sensitivity compared with CT and PET/CT, particularly for CRLM < 10 mm. Therefore, detection of CRLM should be based on MRI.