Impact of iterative reconstructions on image quality and detectability of focal liver lesions in low-energy monochromatic images |
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| Affiliation: | 1. Department of Medical Imaging, CHU Nimes, Univ Montpellier, Medical Imaging Group Nimes, EA 2415, Nîmes, France;2. Service d’imagerie médicale, GIE Imagerie, Institut de Cancérologie du Gard, Nîmes, France;3. GE Healthcare, Buc, France;1. Nagoya University Graduate School of Medicine, 1-1-20, Daikominami, Higashi-ku, Nagoya, Japan;2. National Cancer Center Hospital East, Department of Radiological Technology, 6-5-1 Kashiwanoha, Kashiwa, Japan;3. National Institutes for Quantum and Radiological Science and Technology, Center for Advanced Radiation Emergency Medicine, Department of Radiation Measurement and Dose Assessment, 4-9-1 Anagawa, Inage-ku, Chiba, Japan;4. National Cancer Center Hospital East, Department of Medical Informatics, 6-5-1 Kashiwanoha, Kashiwa, Japan;5. Canon Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi, Japan;1. Cockcroft Institute, Warrington WA4 4AD, United Kingdom;2. University of Liverpool, Merseyside L69 3BX, United Kingdom;3. The Clatterbridge Cancer Centre NHS Foundation Trust, Wirral CH63 4JY, United Kingdom;4. University College London, University of London, London WC1E 6BT, United Kingdom;5. John Adams Institute at Royal Holloway, University of London, Egham TW20 0EX, United Kingdom;1. Medical Physics, San Raffaele Hospital Scientific Institute, Milan, Italy;2. Radiotherapy, San Raffaele Hospital Scientific Institute, Milan, Italy;1. Proton Therapy Center, National Cancer Center, Goyang, Republic of Korea;2. Department of Bio-Convergence Engineering, Korea University, Seoul, Republic of Korea;3. Department of Radiation Oncology, Samsung Medical Center, Seoul, Republic of Korea;1. Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany;2. Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Hospital, Baltimore, MD;3. Department of Radiology, General Hospital Celle, Celle, Germany;4. Department of Surgery, Division of Surgical Oncology and Thoracic Surgery, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany;5. Division of Computed Tomography, Siemens Healthcare Sector, Forchheim, Germany |
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| Abstract: | PurposeTo assess the impact of iterative reconstructions on image quality and detectability of focal liver lesions in low-energy monochromatic images from a Fast kV-Switching Dual Energy CT (KVSCT) platform.MethodsAcquisitions on an image-quality phantom were performed using a KVSCT for three dose levels (CTDIvol:12.72/10.76/8.79 mGy). Raw data were reconstructed for five energy levels (40/50/60/70/80 keV) using Filtered Back Projection (FBP) and four levels of ASIR (ASIR30/ASIR50/ASIR70/ASIR100). Noise power spectrum (NPS) and task-based transfer function (TTF) were measured before computing a Detectability index (d′) to model the detection task of liver metastasis (LM) and hepatocellular carcinoma (HCC) as function of keV.ResultsFrom 40 to 70 keV, noise-magnitude was reduced on average by −68% ± 1% with FBP; −61% ± 3% with ASIR50 and −52% ± 6% with ASIR100. The mean spatial frequency of the NPS decreased when the energy level decreased and the iterative level increased. TTF values at 50% decreased as the energy level increased and as the percentage of ASIR increased. The detectability of both lesions increased with increasing dose level and percentage of ASIR. For the LM, d′ peaked at 70 keV for all reconstruction types, except for ASIR70 at 12.72 mGy and ASIR100, where d' peaked at 50 keV. For HCC, d’ peaked at 60 keV for FBP and ASIR30 but peaked at 50 keV for ASIR50, ASIR70 and ASIR100.ConclusionsUsing percentage of ASIR above 50% at low-energy monochromatic images could limit the increase of noise-magnitude, benefit from spatial resolution improvement and hence enhance detectability of subtle low contrast focal liver lesions such as HCC. |
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| Keywords: | Multidetector Computed tomography Dual-energy Iterative reconstruction Task-based image quality assessment ASIR" },{" #name" :" keyword" ," $" :{" id" :" k0030" }," $$" :[{" #name" :" text" ," _" :" Adaptive Statistical Iterative Reconstruction CT" },{" #name" :" keyword" ," $" :{" id" :" k0040" }," $$" :[{" #name" :" text" ," _" :" Computed Tomography Volume CT dose index Detectability index DECT" },{" #name" :" keyword" ," $" :{" id" :" k0070" }," $$" :[{" #name" :" text" ," _" :" Dual-energy CT ESF" },{" #name" :" keyword" ," $" :{" id" :" k0080" }," $$" :[{" #name" :" text" ," _" :" Edge spread function FBP" },{" #name" :" keyword" ," $" :{" id" :" k0090" }," $$" :[{" #name" :" text" ," _" :" Filtered Back Projection HCC" },{" #name" :" keyword" ," $" :{" id" :" k0100" }," $$" :[{" #name" :" text" ," _" :" Hepatocellular carcinoma IR" },{" #name" :" keyword" ," $" :{" id" :" k0110" }," $$" :[{" #name" :" text" ," _" :" Iterative reconstruction KVSCT" },{" #name" :" keyword" ," $" :{" id" :" k0120" }," $$" :[{" #name" :" text" ," _" :" Fast kV switching CT LM" },{" #name" :" keyword" ," $" :{" id" :" k0130" }," $$" :[{" #name" :" text" ," _" :" Liver metastasis LSF" },{" #name" :" keyword" ," $" :{" id" :" k0140" }," $$" :[{" #name" :" text" ," _" :" Line spread function NPS" },{" #name" :" keyword" ," $" :{" id" :" k0150" }," $$" :[{" #name" :" text" ," _" :" Noise power spectrum SECT" },{" #name" :" keyword" ," $" :{" id" :" k0160" }," $$" :[{" #name" :" text" ," _" :" Single-energy CT TTF" },{" #name" :" keyword" ," $" :{" id" :" k0170" }," $$" :[{" #name" :" text" ," _" :" Task-based transfer function |
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