Multiphase Liver CT Research Articles

Evaluation of liver metastasis in patients with breast cancer: Comparison of single-phase abdominopelvic CT and multi-phase liver CT.

To compare the usefulness of multi-phase liver CT and single-phase abdominopelvic CT (APCT) in evaluating liver metastasis in newly diagnosed breast cancer patients. In this retrospective study, a total of 7621 newly diagnosed breast cancer patients (mean age, 49.7years ± 10.1; 7598 women) who underwent single-phase APCT (n = 5536) or multi-phase liver CT (n = 2085) for staging workup between January 2016 and June 2019 were included. The staging CTs were categorized as having no metastasis, probable metastasis, or indeterminate lesions. MRI referral rate (proportion of patients underwent additional liver MRI), negative MRI rate (patients without true hepatic metastasis / patients underwent liver MRI), true positive CT rate (patients with true metastasis / patients categorized as probable metastasis), true metastasis rate among CT indeterminate (patients with true metastasis / patients categorized as indeterminate lesions), and overall liver metastasis rate were compared between the two groups. Further, the radiation dose was recorded for every patient. The proportions of having no metastasis and indeterminate lesions on the results of CT interpretation were significantly different between the two groups (P = 0.006). However, the MRI referral rate, negative MR rate, true positive CT rate, true metastasis rate among CT indeterminate, and overall liver metastasis rate were not significantly different between the two groups. Radiation dose of multi-phase CT was three times higher than that of single-phase CT. Multi-phase liver CT has little benefit over single-phase APCT in assessing liver metastasis in patients with breast cancer.

High-resolution MR imaging with gadoxetate disodium for the comprehensive evaluation of potential living liver donors.

Several major transplantation centers have used composite multimodality evaluation for the preoperative evaluation of potential living liver donors. This approach can be time-consuming and, although rare, can cause complications. We aimed to demonstrate the clinical feasibility of our comprehensive preoperative MR protocol for the preoperative assessment of living liver donor candidates instead of composite multimodality evaluation. Thirty-five consecutive living liver donor candidates underwent multiphasic liver CT and comprehensive donor protocol MR examinations for preoperative evaluation in a single large-volume liver transplantation (LT) center. Three blinded abdominal radiologists reviewed the CT and MR images for vascular and biliary variations. The strength of agreement between CT and MR angiography was assessed using the kappa index. The detection rate of biliary anatomical variations was calculated. The sensitivity and specificity for detecting significant steatosis (>5%) were calculated. The estimated total volume and right lobe volumes measured by MR volumetry were compared with the corresponding CT volumetry measurements using the intraclass correlation coefficient (ICC). Among the 35 patients, 26 underwent LT. The measurement of agreement showed a moderate to substantial agreement between CT and MR angiography interpretations (kappa values, 0.47-0.79; p < 0.001). Combining T2-weighted and T1-weighted MR cholangiography techniques detected all biliary anatomical variations in 9 of the 26 patients. MR-proton density fat fraction showed a sensitivity of 100% (3/3) and a specificity of 91.3% (21/23) for detecting pathologically determined steatosis (>5%). MR volumetry reached an excellent agreement with CT volumetry (reviewers 1 and 2: ICC, 0.92; 95% CI, 0.84-0.96). Our one-stop comprehensive liver donor MR imaging protocol can provide complete information regarding hepatic vascular and biliary anatomies, hepatic parenchymal quality, and liver volume for living liver donor candidates and can replace composite multimodality evaluation.

Prospective multicenter study on personalized and optimized MDCT contrast protocols: results on liver enhancement.

To determine a personalized and optimized contrast injection protocol for a uniform and optimal diagnostic level of liver parenchymal enhancement, in a large patient population enrolled in a multicenter study. Six hundred ninety-two patients who underwent a standardized multi-phase liver CT examination were prospectively assigned to one contrast media (CM) protocol group: G1 (100 mL fixed volume, 37 gI); G2 (600 mgI/kg of total body weight (TBW)); G3 (750 mgI/kg of fat-free mass (FFM)), and G4 (600 mgI/kg of FFM). Change in liver parenchyma CT number between unenhanced and contrast-enhanced images was measured by two radiologists, on 3-mm pre-contrast and portal phase axial reconstructions. The enhancement histograms were compared across CM protocols, specifically according to a target diagnostic value of 50 HU. The total amount of iodine dose was also compared among protocols by median and interquartile range (IQR). The Kruskal-Wallis and Mann-Whitney U tests were used to assess significant differences (p < 0.005), as appropriate. A significant difference (p < 0.001) was found across the groups with liver enhancement decreasing from median over-enhanced values of 77.0 (G1), 71.3 (G2), and 65.1 (G3) to a target enhancement of 53.2 HU for G4. Enhancement IQR was progressively reduced from 26.5 HU (G1), 26.0 HU (G2), and 17.8 HU (G3) to 14.5 HU (G4). G4 showed a median iodine dose of 26.0 gI, significantly lower (p < 0.001) than G3 (33.9 gI), G2 (38.8 gI), and G1 (37 gI). The 600 mgI/kg FFM-based protocol enabled a diagnostically optimized liver enhancement and improved patient-to-patient enhancement uniformity, while significantly reducing iodine load. • Consistent and clinically adequate liver enhancement is observed with personalized and optimized contrast injection protocol. • Fat-free mass is an appropriate body size parameter for correlation with liver parenchymal enhancement. • Diagnostic oncology follow-up liver CT examinations may be obtained using 600 mgI/kg of FFM.

S2729 Not Your Typical Polyp: An Unusual Case of HCC Recurrence Following OLT

INTRODUCTION: OLT is a viable treatment option for select patients with ESLD and HCC. However, post-transplant recurrence of HCC occurs in approximately 20% of patients. Risk factors include explant tumor burden exceeding Milan criteria, lymphovascular invasion, and elevated pre-transplant AFP levels. The most common locations of metastatic HCC include the lungs, bones, and adrenal glands. We report an unusual case of HCC recurrence to the colon detected during colonoscopy. CASE DESCRIPTION/METHODS: A 69-year-old Caucasian male with a history of EtOH/NASH cirrhosis on the liver transplant list underwent routine abdominal imaging, which revealed a 2.0 × 1.7 cm liver mass compatible with HCC. AFP was within normal limits and there was no evidence of pulmonary metastasis. He underwent TACE and microwave ablation of 4 identified lesions. Follow-up multiphasic liver CT imaging at 1 and 3 months were negative. Patient subsequently underwent OLT 6 months after locoregional therapy. Explant pathology revealed 4 sites compatible with treated HCC in the left hepatic lobe with explant tumor burden within Milan criteria. Areas of incomplete necrosis showed well-differentiated HCC without any evidence of lymphovascular invasion.Patient’s post-OLT course was initially uncomplicated. Imaging at 1 year post-transplant demonstrated enlarging necrotic paraesophageal and gastroesophageal lymph nodes as well as focal circumferential ascending colonic wall thickening. Patient subsequently underwent endoscopy with EUS and FNA of the paraesophageal lymph node. Colonoscopy revealed a 20 mm hepatic flexure polyp, which was removed via piecemeal cold-snare EMR. Pathology of the paraesophageal lymph node and hepatic flexure polyp were consistent with metastatic HCC. Following tumor board discussion, patient was initiated on first-line systemic therapy. He continues to follow up in transplant clinic. DISCUSSION: To our knowledge, this is the first reported case of HCC metastasis to the colon presenting as a polypoid mucosal lesion. Despite having a low risk of recurrent HCC based on pre-transplant and explant tumor characteristics, our patient’s unusual presentation occurred at 1-year post-transplant. While the diagnosis of recurrent or metastatic HCC confers a guarded prognosis, there are an increasing number of options for systemic therapies. Clinicians should adopt a low threshold for further evaluation of abnormal imaging findings in this context to enable early detection of recurrent post-transplant HCC.Figure 1.: CT 6 months (left) and 12 months (right) post OLT demonstrating enlarging paraesophageal lymph node.Figure 2.: 20 mm hepatic flexure polyp removed via piece-meal cold snare EMR.Figure 3.: Pathology of paraesophageal lymph node (left) and hepatic flexure polyp (right) consistent with metastatic HCC.

Prognostic role of spleen volume measurement using computed tomography in patients with compensated chronic liver disease from hepatitis B viral infection

To determine the prognostic value of CT-based splenic volume measurement in patients with compensated chronic liver disease (cCLD) from chronic hepatitis B (CHB). A total of 584 patients having multiphasic liver CT scans between January and December 2011 were retrospectively reviewed. Spleen volume was measured using a semi-automated three-dimensional volumetric software program. Electronic medical records and national registry data were reviewed to determine the diagnosis of hepatocellular carcinoma (HCC), hepatic decompensation, or death. The cumulative incidence (CI) of the development of decompensation, HCC occurrence, and overall survival (OS) were estimated by the Kaplan-Meier method. The Cox proportional hazard regression model was used to evaluate prognostic factors. The optimal cutoff spleen volume to predict each outcome was obtained using a minimal p value approach method. After a median follow-up of 92months, 114 patients developed HCC with a 7-year CI of 17.2%. A larger spleen volume was a significant predictor of HCC occurrence (HR = 2.13, p= 0.009). Decompensation occurred in 30 patients with a 7-year CI of 5.0%, and a larger spleen volume was also significantly associated with the development of decompensation (HR = 4.66, p= 0.005). Twenty-three patients died, and their estimated 7-year OS was 96.4%. A larger spleen volume also significantly affected OS (HR = 6.15, p= 0.007). The optimal cutoff spleen volume was set at 532mL for HCC occurrence, 656.9mL for the development of decompensation, and 741.1mL for OS. A larger spleen volume was significantly associated with HCC occurrence, development of decompensation, and poor OS in patients with cCLD from CHB. • Spleen volume could be easily acquired from routine multiphasic liver CT scan using a semi-automated 3D volumetric software program with excellent inter-observer agreement. • A larger spleen volume was significantly associated with a higher rate of hepatocellular carcinoma occurrence, the development of decompensation, and poor overall survival in patients with compensated chronic liver disease from chronic hepatitis B.

Prior iterative reconstruction (PIR) to lower radiation dose and preserve radiologist performance for multiphase liver CT: a multi-reader pilot study.

Prior iterative reconstruction (PIR) spatially registers CT image data from multiple phases of enhancement to reduce image noise. We evaluated PIR in contrast-enhanced multiphase liver CT. Patients with archived projection CT data with proven malignant or benign liver lesions, or without lesions, by reference criteria were included. Lower-dose PIR images were reconstructed using validated noise insertion from multiphase CT exams (50% dose in 2 phases, 25% dose in 1 phase). The phase of enhancement most relevant to the diagnostic task was selected for evaluation. Four radiologists reviewed routine-dose and lower-dose PIR images, circumscribing liver lesions and rating confidence for malignancy (0 to 100) and image quality. JAFROC Figures of Merit (FOM) were calculated. 31 patients had 60 liver lesions (28 primary hepaticmalignancies, 6 hepatic metastases, 26 benign lesions). Pooled JAFROC FOM for malignancy for routine-dose CT was 0.615 (95% CI 0.464, 0.767) compared to 0.662 for PIR (95% CI 0.527, 0.797). The estimated FOM difference between the routine-dose and lower-dose PIR images was + 0.047 (95% CI - 0.023, + 0.116). Pooled sensitivity/specificity for routine-dose images was 70%/68% compared to 73%/66% for lower-dose PIR. Lower-dose PIR had lower diagnostic image quality (mean 3.8 vs. 4.2, p = 0.0009) and sharpness (mean 2.3 vs. 2.0, p = 0.0071). PIR is a promising method to reduce radiation dose for multiphase abdominal CT, preserving observer performance despite small reductions in image quality. Further work is warranted.

Advanced Virtual Monochromatic Images from Dual Source Dual-Energy CT for a Reduction in the Contrast Medium Dose (389 mgI/kg) in Multiphase Liver CT: Evaluation of Image Quality and Focal Lesion Conspicuity

Background: Low-energy advanced virtual monochromatic images (VMIs) from dual source dual-energy CT (DSCT) could be applied to reduce contrast medium dose due to superior iodine contrast-to-noise ratios (CNRs). Objectives: To investigate feasibility of advanced VMIs from DSCT to reduce contrast medium dose in multiphase liver CT without impairing image quality and conspicuity of focal hepatic lesions (FHLs). Patients and Methods: Ninety-four patients with 110 FHLs underwent follow-up CT twice prospectively with different protocols: protocol A, conventional 100 kVp and 555 mgI/kg; protocol B, dual-energy mode and 389 mgI/kg. The signal-to-noise ratio (SNR) and lesion-to-liver CNR were compared between the VMIs (40 - 120 keV, 10-keV interval) reconstructed using advanced image-based algorithm and conventional images. Two radiologists qualitatively evaluated VMIs, compared with the 100 kVp images, using a six-point scale. Results: The SNRs of pancreas, aorta, portal and hepatic vein were similar to those at 100 kVp images (P > 0.05) at 40-50 keV images during late arterial phase (LAP) and at 40-60 keV images during portal venous phase (PVP) except for the SNRs of aorta and veins at 40 keV images which were significantly higher (P 0.05) during LAP. The CNR of 58 hypovascular FHLs was similar at 40 - 120 keV images (P > 0.05) during PVP. Among the VMIs, 50 keV and 50 - 60 keV images received the highest scores (P < 0.0315 and P < 0.0041) by both reviewers during LAP and PVP, respectively. Conclusion: Advanced 50 - 60 keV images from DSCT allowed contrast dose reduction by 30% in multiphase liver CT without impairing image quality and conspicuity of FHLs, compared with the conventional 100 kVp images with 555 mgI/kg.

Comparison of patient dose from routine multi-phase and dynamic liver perfusion CT studies taking into account the effect of iodinated contrast administration

Objectives: To accurately determine and compare patient radiation burden from routine multi-phase CT (MPCT) and dynamic CT liver perfusion (CTLP) studies taking into account the effect of iodine uptake of exposed tissues/organs.Materials and Methods: 40 consecutive MPCT of upper abdomen and 40 consecutive CTLP studies performed on a modern CT scanner were retrospectively studied. Iodine uptake of radiosensitive tissues at the time of acquisition was calculated through the difference of tissues’ CT numbers between NECT and CECT images. Monte Carlo simulation and mathematical anthropomorphic phantoms were employed to derive patient-size-specific organ dose data from each scan involved taking into account the effect of iodinated contrast uptake on absorbed dose. Effective dose estimates were derived for routine multiphase CT and CTLP by summing up the contribution of NECT and CECT scans involved.Results: The mean underestimation error in organ doses from CECT exposures if iodine uptake is not encountered was found to be 2.2%–38.9%. The effective dose to an average-size patient from routine 3-phase CT, 4-phase CT and CTLP studies was found to be 20.6, 27.7 and 25.8 mSv, respectively. Effective dose from CTLP was found lower than 4-phase CT of upper abdomen irrespective of patient body size. Compared to 3-phase CT, the radiation burden from CTLP was found to be higher for average size-patients but again lower for overweight patients.Conclusions: Modern CT technology allows CTLP studies at comparable or even lower patient radiation burden compared to routine multi-phase liver CT imaging.

Evaluation of Post-Stereotactic Body Radiation Therapy Response Assessment for Hepatocellular Carcinoma: An Appraisal of RECIST, m-RECIST and WHO Criteria

Response Evaluation Criteria in Solid Tumors (RECIST) is a validated criterion to evaluate response to liver directed therapy in hepatocellular carcinoma (HCC); however, RECIST criteria are inadequate for assessing early response to Stereotactic Body Radiotherapy (SBRT). In this analysis, we evaluated post-treatment response assessment using RECIST, modified-RECIST and World Health Organization (WHO) criteria in patients receiving SBRT for HCC. This retrospective analysis included HCC patients treated with SBRT at two institutions between 2009 and 2016. Included patients had pathologically proven or met radiologic criteria for the diagnosis of HCC and received SBRT. Additionally, only patients with a multiphase contrast liver MR or CT imaging scan in the 6 weeks prior to SBRT and at least one follow-up MR/CT 1-6 months post-SBRT were included in this analysis. For each lesion treated with SBRT, the maximum two diameters, the maximum bidimensional enhancement diameter, the product of the bidimensional diameters and the product of bidimensional enhancement diameters were measured. From these parameters, post-SBRT response was assessed according to RECIST 1.1, mRECIST, and WHO criteria. Fifty-six lesions in 45 patients (32 M, 13 F; mean age: 66.7 ± 7.6 years) were included in this analysis. Twenty-five of these lesions were previously treated with liver-directed therapies. Sixteen lesions were followed with CT and 40 with MR. 14 of the 56 (25%) treated lesions were isointense to the surrounding liver parenchyma in the arterial phase on at least one follow-up examination. Hyperenhancement of the adjacent liver parenchyma was observed for several months post-SBRT. For two lesions previously treated non-SBRT, the SBRT target was a residual tumor at the periphery of the original lesion; in post-SBRT images of these lesions, it was similarly impossible to distinguish between residual tumor and hyperenhancing normal liver parenchyma. The post-SBRT liver parenchymal enhancement limited standard therapeutic response assessment. For RECIST 1.1 and WHO criteria, the lesion diameter evaluation was limited in 1 lesion and pseudoprogression was seen in 2 lesions; with mRECIST criteria, the lesion viability evaluation was limited by isointensity in the arterial phase to the surrounding liver parenchyma in 23 examinations (0-6 months follow-up: 12 exams; 7-12 months follow-up: 7 exams; 13-24 months: 4 exams) and pseudoprogression was seen in 4 lesions. Liver parenchymal changes induced by SBRT may limit post-treatment assessment using current response assessment criteria, especially during early follow-up examinations. New criteria should be evaluated to assess post-SBRT treatment response.

Iterative reconstructions in multiphasic CT imaging of the liver: qualitative and task-based analyses of image quality

To evaluate the clinical benefits on image quality (IQ) of adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) in multiphasic liver CT compared to filtered back-projection (FBP), in patients and on phantoms using a novel task-based metric. Image data of 65 patients who underwent a routine multiphasic liver CT during a 1-month period were reconstructed with FBP, ASIR50, ASIR80, and MBIR. IQ was assessed qualitatively by ranking the most distal hepatic artery (HA) and portal vein (PV) visible; and quantitatively by measuring contrast-to-noise ratio (CNR) of the liver parenchyma, HA and PV. IQ was compared between each reconstruction and correlated to CNR and detectability index (d') measurements computed on phantoms scanned with the same CT protocol as for patients. HA and PV were seen more distally on MBIR and ASIR80 compared to FBP (p≤0.001). The CNR correlated weakly between patient and phantom (r=0.76 and 0.80 for HA and PV, respectively), whereas d' correlated strongly with the division order of HA and PV (r=0.96 and 0.95, respectively). MBIR and ASIR significantly improve the IQ of multiphasic liver CT, especially through better distal detection of HA and PV, in agreement with the adapted task-based metric d' estimated on phantoms.

Triple Arterial Phase CT of the Liver with Radiation Dose Equivalent to That of Single Arterial Phase CT: Initial Experience.

Purpose To develop and evaluate a triple arterial phase CT liver protocol with a similar radiation dose to that of standard single arterial phase CT in study subjects suspected of having hepatocellular carcinoma (HCC). Materials and Methods The study consisted of a retrospective part A for protocol development (n = 15) and a prospective part B to evaluate diagnostic accuracy (n = 38). All 53 participants underwent perfusion CT with 50 mL contrast material between August 2013 and September 2014. Group B underwent an additional standard multiphasic liver CT examination with 120 mL of contrast material (range, 70-143 mL). Image sets from triple arterial phase imaging were reconstructed from perfusion CT by fusing images from three dedicated arterial time points. Triple arterial phase CT and standard single arterial phase CT were compared by two readers, who assessed subjective image quality and HCC detection rate. A third reader served as reference reader and assessed objective image quality. The paired Student t test, Wilcoxon signed rank test, jackknife alternative free-response receiver operating characteristic (JAFROC), and JAFROC curve were applied. Results The mean volume CT dose index was 11.6 mGy for triple arterial phase CT and 11.9 mGy for standard single arterial phase CT (P = .73). Triple arterial phase CT showed lower image noise and better contrast-to-noise ratio compared with standard single arterial phase CT (P < .001 and P = .032, respectively); however, there was no significant difference in lesion-to-liver-contrast ratio (P = .31). Subjective image quality was good for both protocols. The detection rate of the 65 HCC lesions was 82% for reader 1 and 83% for reader 2 at triple arterial phase CT and 80% for reader 1 and 77% for reader 2 at standard single arterial phase CT (P = .4). Conclusion Triple arterial phase imaging is feasible at the same radiation dose as that used for standard single arterial phase CT. Triple arterial phase imaging provides equivalent to superior image quality and equal HCC detection rate despite the use of less than half the contrast material dose used at standard single arterial phase CT. © RSNA, 2018.

Rapid switching kVp dual energy CT: Value of reconstructed dual energy CT images and organ dose assessment in multiphasic liver CT exams

PurposeClinical applications of dual energy computed tomography (DECT) have been widely reported; however, the importance of the different image reconstructions and radiation organ dose remains a relevant area of investigation, particularly considering the different commercially available DECT equipment. Therefore, the purpose of this study was to assess the image reliability and compare the information content between several image reconstructions in a rapid-switching DECT (rsDECT), and assess radiation organ dose between rsDECT and conventional single-energy computed tomography (SECT) exams. Materials and methodsThis Institutional Review Board-approved retrospective study included 98 consecutive patients who had a history of liver cancer and underwent multiphasic liver CT exams with rsDECT applied during the late arterial phase between June 2015 and December 2015. Virtual monochromatic 70 keV, material density images (MDI) iodine (-water) and virtual unenhanced (VUE) images were generated. Radiation dose analysis was performed in a subset of 44 patients who had also undergone a multiphasic SECT examination within 6 months of the rsDECT. Four board-certified abdominal radiologists reviewed 24–25 patients each, and a fifth radiologist re-evaluated all the scans to reach a consensus. The following imaging aspects were assessed by the radiologists: (a) attenuation measurements were made in the liver and spleen in VUE and true unenhanced (TUE) images; (b) subjective evaluation for lesion detection and conspicuity on MDI iodine (-water)/VUE images compared with the virtual monochromatic images/TUE images; and (c) overall image quality using a five-point Likert scale. The radiation dose analyses were evaluated in the subset of 44 patients regarding the following parameters: CTDIvol, dose length product, patient’s effective diameter and organ dose using a Monte Carlo-based software, VirtualDose™ (Virtual Phantoms, Inc.) to 21 organs. ResultsOn average, image noise on the TUE images was 49% higher within the liver (p < 0.0001) and 48% higher within the spleen (p < 0.0001). CT numbers for the spleen were significantly higher on VUE images (p < 0.0001). Twenty-eight lesions in 24/98 (24.5%) patients were not observed on the VUE images. The conspicuity of vascular anatomy was considered better on MDI iodine (-water) Images 26.5% of patients. Using the Likert scale, the rsDECT image quality was considered to be satisfactory. Considering the subset of 44 patients with recent SECT, the organ dose was, on average, 37.4% less with rsDECT. As the patient’s effective diameter decreased, the differences in dose between the rsDECT and SECT increased, with the total average organ dose being less by 65.1% when rsDECT was used. ConclusionVUE images in the population had lower image noise than TUE images; however, a few small and hyperdense findings were not characterized on VUE images. Delineation of vascular anatomy was considered better in around a quarter of patients on MDI iodine (-water) images. Finally, radiation dose, particularly organ dose, was found to be lower with rsDECT, especially in smaller patients.

Intravoxel incoherent motion (IVIM) analysis of vertebral bone marrow changes after radiation exposure from diagnostic imaging and interventional procedures.

Background High cumulative radiation dose in cancer patients warrants systemic examination of possible changes in bone marrow. Purpose To assess retrospectively changes in vertebral bone marrow diffusion and perfusion using intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in hepatocellular carcinoma (HCC) patients after exposure to radiation from diagnostic imaging and interventional procedures. Material and Methods A total of 21 IVIM-DWI sets in 20 HCC patients, consisting of baseline and follow-up liver magnetic resonance imaging (MRI) with an interval less than 100 days, were reviewed after varying levels of radiation exposure from transarterial chemoembolization (TACE), multiphase liver CT, and abdominal radiography. IVIM parameters (apparent diffusion coefficient [ADC], true diffusion coefficient [D], pseudodiffusion coefficient [D*], and perfusion fraction [PF]) of vertebral bone marrow were analyzed for significant differences between baseline and follow-up MRI using Wilcoxon signed-rank test, and for correlations with cumulative effective dose, as well as time interval between last radiation exposure and follow-up MRI using Spearman's correlation. Results Compared to baseline MRI, ADC, D*, and PF significantly decreased on follow-up MRI (ADC: median [interquartile range], 0.405 × 103 mm2/s [0.364-0.477] versus 0.390 [0.348-0.461]; D*: 24.011 [18.141-29.584] versus 20.815 [15.022-28.347]; PF: 10.960% [8.828-12.985] versus 9.125 [8.606-12.803]) ( P < 0.05). There was no significant difference in D ( P = 0.807). Cumulative effective dose was moderately correlated with decrease in D* (r = 0.434). In addition, longer intervals between last exposure and follow-up MRI showed negative correlations with changes in D and ADC (r = -0.352 and -0.333, respectively). Conclusion Vertebral bone marrow diffusion and perfusion parameters were significantly changed after exposure to medical radiation.

Core samples for radiomics features that are insensitive to tumor segmentation: method and pilot study using CT images of hepatocellular carcinoma.

The purpose of this study is to investigate the utility of obtaining "core samples" of regions in CT volume scans for extraction of radiomic features. We asked four readers to outline tumors in three representative slices from each phase of multiphasic liver CT images taken from 29 patients (1128 segmentations) with hepatocellular carcinoma. Core samples were obtained by automatically tracing the maximal circle inscribed in the outlines. Image features describing the intensity, texture, shape, and margin were used to describe the segmented lesion. We calculated the intraclass correlation between the features extracted from the readers' segmentations and their core samples to characterize robustness to segmentation between readers, and between human-based segmentation and core sampling. We conclude that despite the high interreader variability in manually delineating the tumor (average overlap of 43% across all readers), certain features such as intensity and texture features are robust to segmentation. More importantly, this same subset of features can be obtained from the core samples, providing as much information as detailed segmentation while being simpler and faster to obtain.

Automatic detection method of hepatocellular carcinomas using the non-rigid registration method of multi-phase liver CT images.

Multi-phase CT images are obtained sequentially after the injection of contrast agents so that there is a large amount of local deformation between images due to the respiratory and heart motion. Therefore, a non-rigid registration technique is required in order to establish the anatomical correspondence between the multi-phase CT images for liver CAD (computer-aided diagnosis). In this paper, we propose the automatic detection method of hepatocellular carcinomas using the non-rigid registration method of multi-phase CT images. Global movements between multi-phase CT images are aligned by rigid registration based on normalized mutual information. Local deformations between multi-phase CT images are modeled by non-rigid registration based on B-spline deformable model. After the registration of multi-phase CT images, hepatocellular carcinomas are automatically detected by analyzing the original and subtraction information of the registered multi-phase CT images. We applied our method to twenty five multi-phase CT datasets. Experimental results showed that the multi-phase CT images were accurately aligned. All of the hepatocellular carcinomas including small size ones in our 25 subjects were accurately detected using our method. We conclude that our method is useful for detecting hepatocellular carcinomas.

SU‐E‐J‐260: Quantitative Image Feature Analysis of Multiphase Liver CT for Hepatocellular Carcinoma (HCC) in Radiation Therapy

Purpose:To identify the effective quantitative image features (radiomics features) for prediction of response, survival, recurrence and metastasis of hepatocellular carcinoma (HCC) in radiotherapy.Methods:Multiphase contrast enhanced liver CT images were acquired in 16 patients with HCC on pre and post radiation therapy (RT). In this study, arterial phase CT images were selected to analyze the effectiveness of image features for the prediction of treatment outcome of HCC to RT. Response evaluated by RECIST criteria, survival, local recurrence (LR), distant metastasis (DM) and liver metastasis (LM) were examined. A radiation oncologist manually delineated the tumor and normal liver on pre and post CT scans, respectively. Quantitative image features were extracted to characterize the intensity distribution (n=8), spatial patterns (texture, n=36), and shape (n=16) of the tumor and liver, respectively. Moreover, differences between pre and post image features were calculated (n=120). A total of 360 features were extracted and then analyzed by unpaired student's t‐test to rank the effectiveness of features for the prediction of response.Results:The five most effective features were selected for prediction of each outcome. Significant predictors for tumor response and survival are changes in tumor shape (Second Major Axes Length, p= 0.002; Eccentricity, p=0.0002), for LR, liver texture (Standard Deviation (SD) of High Grey Level Run Emphasis and SD of Entropy, both p=0.005) on pre and post CT images, for DM, tumor texture (SD of Entropy, p=0.01) on pre CT image and for LM, liver (Mean of Cluster Shade, p=0.004) and tumor texture (SD of Entropy, p=0.006) on pre CT image. Intensity distribution features were not significant (p&gt;0.09).Conclusion:Quantitative CT image features were found to be potential predictors of the five endpoints of HCC in RT.This work was supported in part by the National Cancer Institute Grant R01CA172638.

Added value of arterial enhancement fraction color maps for the characterization of small hepatic low-attenuating lesions in patients with colorectal cancer.

ObjectiveTo assess the added value of arterial enhancement fraction (AEF) color maps for the differentiation of small metastases from hepatic benign lesions.Subjects and MethodsWe retrospectively analyzed 46 patients with colorectal cancer who underwent multiphasic liver CT imaging and had low-attenuating liver lesions smaller than 3 cm (123 total lesions; metastasis: benign = 32:91). AEF color maps of the liver were created from multiphasic liver CT images using dedicated software. Two radiologists independently reviewed multiphasic CT image sets alone and in combination with image sets with AEF color maps using a five-point scale. The additional diagnostic value of the color maps was assessed by means of receiver-operating characteristic (ROC) analysis.ResultsThe area under the ROC curve (Az) increased when multiphasic CT images were combined with AEF color map analysis as compared with evaluation based only on multiphasic CT images (from 0.698 to 0.897 for reader 1, and from 0.825 to 0.945 for reader 2; P < 0.001 and 0.002, respectively). The increase Az was especially significant for lesions less than 1 cm (from 0.702 to 0.888 for reader 1, and from 0.768 to 0.958 for reader 2; P = 0.001 and P = 0.001, respectively). The mean AEF of tumor-adjacent parenchyma (35.07 ± 27.2) was significantly higher than that of tumor-free liver parenchyma (27.3 ± 20.6) (P = 0.04).ConclusionsAEF color mapping can improve the diagnostic performance for small hepatic metastases from colorectal cancer and may allow for the elimination of additional examinations.

Patient-Tailored Scan Delay for Multiphase Liver CT: Improved Scan Quality and Lesion Conspicuity With a Novel Timing Bolus Method

The purpose of this study was to compare scan quality and lesion conspicuity for late arterial and portal venous phase liver CT scans using fixed versus patient-tailored scan delay derived with an evidence-based timing bolus method. We retrospectively identified the cases of 73 patients who underwent both multiphase liver CT with fixed late arterial and portal venous phase scan delay times of 45 and 80 seconds and subsequent multiphase liver CT with patient-tailored scan delay determined with a timing bolus and a previously reported relation between the time to peak aortic and liver enhancement. Both late arterial and portal venous phase scans were graded in terms of scan quality. Hepatic lesion conspicuity (difference in attenuation between lesion and liver parenchyma) for hypervascular lesions (late arterial phase) and hypovascular lesions (portal venous phase) was recorded. Patient-tailored scan delay reflected a wide range of times to peak aortic enhancement (mean, 24 seconds; range, 18-32 seconds) and yielded a greater proportion of optimal scans compared with fixed scan delay for both late arterial phase (92% versus 74%, p < 0.01) and portal venous phase (86% versus 70%, p < 0.05) scans. Mean hypervascular lesion conspicuity was greater for lesions imaged with patient-tailored scan delay rather than fixed scan delay (84.0 versus 57.0 HU, p < 0.01). Compared with examinations with fixed scan delay, multiphase liver CT that incorporates patient-tailored scan delay produces more optimally timed late arterial and portal venous phase CT scans with greater lesion conspicuity.

Time-resolved computed tomography of the liver: retrospective, multi-phase image reconstruction derived from volumetric perfusion imaging

To assess feasibility and image quality (IQ) of a new post-processing algorithm for retrospective extraction of an optimised multi-phase CT (time-resolved CT) of the liver from volumetric perfusion imaging. Sixteen patients underwent clinically indicated perfusion CT using 4D spiral mode of dual-source 128-slice CT. Three image sets were reconstructed: motion-corrected and noise-reduced (MCNR) images derived from 4D raw data; maximum and average intensity projections (time MIP/AVG) of the arterial/portal/portal-venous phases and all phases (total MIP/ AVG) derived from retrospective fusion of dedicated MCNR split series. Two readers assessed the IQ, detection rate and evaluation time; one reader assessed image noise and lesion-to-liver contrast. Time-resolved CT was feasible in all patients. Each post-processing step yielded a significant reduction of image noise and evaluation time, maintaining lesion-to-liver contrast. Time MIPs/AVGs showed the highest overall IQ without relevant motion artefacts and best depiction of arterial and portal/portal-venous phases respectively. Time MIPs demonstrated a significantly higher detection rate for arterialised liver lesions than total MIPs/AVGs and the raw data series. Time-resolved CT allows data from volumetric perfusion imaging to be condensed into an optimised multi-phase liver CT, yielding a superior IQ and higher detection rate for arterialised liver lesions than the raw data series. • Four-dimensional computed tomography is limited by motion artefacts and poor image quality. • Time-resolved-CT facilitates 4D-CT data visualisation, segmentation and analysis by condensing raw data. • Time-resolved CT demonstrates better image quality than raw data images. • Time-resolved CT improves detection of arterialised liver lesions in cirrhotic patients.

Liver CT Multiphase Image Registration and a Fast Algorithm for Its Numerical Approximation

Contrast-enhanced multiphase liver CT is currently a standard of practice in hepatic imaging for medical diagnosis of liver diseases. We presented a novel image registration method for liver CT multiphase images. Firstly, a biomechanical model is proposed to describe the procedure of image registration, and expressed by an energy function. Then the numerical approximation of the energy function based on three dimensional Level-Set method is implemented which is accelerated by Compute Unified Device Architecture (CUDA) to make sure that our method can meet the clinical real-time requirement. Experiments show that our method can accurately register liver CT multiphase images. And compared with other algorithm, our method is much faster, and higher the image resolution is, bigger the speed-up ration is. Multiphase liver CT is widely used to detect and characterize liver lesions as different types of tumors enhance differently during each phase. The four phases are precontrast phase, arterial phase, portal venous phase, and delayed phase. Precontrast liver scans are used to detect calcifications, visualize hemorrhage from trauma, and demonstrate hyper vascular lesions which appear hypodense compared to the surrounding liver parenchyma. The arterial phase of scanning is performed approximately 30 seconds after the contrast injection is initiated and is most accurately determined by using bolus tracking software to monitor the level of contrast enhancement in the aorta and automatically triggering the scan when it reaches a pre determined level of enhancement (eg 120HU). Hyper vascular lesions enhance during the arterial phase and appear hyperdense. Arterial phase images are also used for pre operative evaluation of the arterial vasculature through the use of maximum intensity projection (MIP) and 3D reconstructions. The portal venous phase is performed 70-90 seconds post contrast and hypo vascular lesions appear hypodense and hyper vascular lesions appear isodense (same density as surrounding liver).The delayed phase is performed 5-10 minutes post contrast and is used to further characterize lesions. Clinicians need to make diagnosis based on the medical information from liver CT multiphase images, especially from arterial phase and portal venous phase. However, during the image data acquisition, tissues and organs in liver CT images from different phase may have subtle differences due to breath, heartbeat, subconscious physical movement, and so on, which may mislead clinicians and increase difficulties of making diagnosis. In order to solve this problem, image registration algorithms between multiphase images are necessary, which can enable the radiologist to fuse the needed information for diagnosis or operation planning. Zhai K and colleagues presented an image registration method which finds an accurate alignment of arterial phase and portal venous phase liver CT images(1), they combined global rigid registration (affine) and local nonrigid deformable registration (B-spline) in a manner of alternative iterations, and extended traditional two-step registration to iterative multi-step registration. Cao Y and colleagues proposed a feature-based non-rigid registration approach for multiphase liver CT images(2), this algorithm is comprised of four steps: firstly, extracting corners and edges from referenced and floating images using Harris corner detector; secondly, using joint descriptor of SIFT and shape context to describe features; thirdly, segmenting the entire abdominal region into two sub-regions and matching the sub-regions respectively; finally, using thin-plate splines to model deformation field between correspondences. Erdt M and colleagues firstly make a pre-segmentation of the liver in the different phase, then use the resulting shape information of the volumes to coarsely register by