Model-Based Iterative Reconstruction Versus Adaptive Statistical Iterative Reconstruction and Filtered Back Projection in Liver 64-MDCT: Focal Lesion Detection, Lesion Conspicuity, and Image Noise

Abstract

OBJECTIVE The purpose of this study is to compare three CT image reconstruction algorithms for liver lesion detection and appearance, subjective lesion conspicuity, and measured noise. MATERIALS AND METHODS Thirty-six patients with known liver lesions were scanned with a routine clinical three-phase CT protocol using a weight-based noise index of 30 or 36. Image data from each phase were reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Randomized images were presented to two independent blinded reviewers to detect and categorize the appearance of lesions and to score lesion conspicuity. Lesion size, lesion density (in Hounsfield units), adjacent liver density (in Hounsfield units), and image noise were measured. Two different unblinded truth readers established the number, appearance, and location of lesions. RESULTS Fifty-one focal lesions were detected by truth readers. For blinded reviewers compared with truth readers, there was no difference for lesion detection among the reconstruction algorithms. Lesion appearance was statistically the same among the three reconstructions. Although one reviewer scored lesions as being more conspicuous with MBIR, the other scored them the same. There was significantly less background noise in air with MBIR (mean [± SD], 2.1 ± 1.4 HU) than with ASIR (8.9 ± 1.9 HU; p < 0.001) or FBP (10.6 ± 2.6 HU; p < 0.001). Mean lesion contrast-to-noise ratio was statistically significantly higher for MBIR (34.4 ± 29.1) than for ASIR (6.5 ± 4.9; p < 0.001) or FBP (6.3 ± 6.0; p < 0.001). CONCLUSION In routine-dose clinical CT of the liver, MBIR resulted in comparable lesion detection, lesion characterization, and subjective lesion conspicuity, but significantly lower background noise and higher contrast-to-noise ratio compared with ASIR or FBP. This finding suggests that further investigation of the use of MBIR to enable dose reduction in liver CT is warranted.

Impact of Model-Based Iterative Reconstruction on Image Quality of Contrast-Enhanced Neck CT

“…[1][2][3]5,6 In this study, overall image quality in neck CT examinations was improved with MBIR, potentially allowing the exchange of improved image quality for further radiation-dose reduction. A recent study applying MBIR to chest CT reported radiation-dose reductions approaching 70%-80%.…”

“…Both phantom and clinical studies have confirmed that the application of the MBIR algorithm results in an improved contrast-to-noise ratio (CNR), lower background noise (BN), [1][2][3][4] and reduction of helical conebeam artifacts. 2,4 Clinical studies in the delineation of arteries in the posterior fossa on 3D brain CT angiography, 1 improved liver lesion detection, 3,5 general evaluation of abdominopelvic CT, 2 and pediatric chest CT 6 all support the use of MBIR, with or without radiation-dose reduction.…”

“…2,4 Clinical studies in the delineation of arteries in the posterior fossa on 3D brain CT angiography, 1 improved liver lesion detection, 3,5 general evaluation of abdominopelvic CT, 2 and pediatric chest CT 6 all support the use of MBIR, with or without radiation-dose reduction. In this study, we compared objective and subjective image quality in neck CT images reconstructed with 2 different iterative reconstruction algorithms (MBIR versus 30% adaptive statistical iterative reconstruction [ASiR30]) by using the same raw dataset.…”

Radiation Dose Reduction in CT-Guided Spine Biopsies Does Not Reduce Diagnostic Yield

“…These include iterative reconstruction models such as adaptive statistical iterative reconstruction and model-based iterative reconstruction. [9][10][11][12][13][14][32][33][34][35][36][37][38][39][40] Although these imaging algorithms provide an additional method for dose reduction in CT-guided procedures, their availability is currently limited to newer CT scanners for routine diagnostic CT imaging. The greater availability of the iterative reconstruction software over time may allow for increased operator comfort when evaluating low-dose images during CT-guided procedures, potentially further reducing the radiation dose.…”

“…Pediatric patients and patients who receive multiple scans for acute disease follow-up, chronic conditions, and screening purposes often undergo CT with modified scanning protocols to reduce dose. [9][10][11][12][13][14] This type of protocol modification has also been used in CT-guided interventions to limit radiation dose when performing multiple scans during the procedure. 8,[15][16][17][18] Given the increased desire to reduce radiation dose to patients, we transitioned our protocols for CT-guided spine biopsies to use a lower dose.…”