Multiphasic Computed Tomography Imaging Research Articles

Computer-aided diagnosis of liver tumors on computed tomography images

Background and objectiveLiver cancer is the tenth most common cancer in the USA, and its incidence has been increasing for several decades. Early detection, diagnosis, and treatment of the disease are very important. Computed tomography (CT) is one of the most common and robust imaging techniques for the detection of liver cancer. CT scanners can provide multiple-phase sequential scans of the whole liver. In this study, we proposed a computer-aided diagnosis (CAD) system to diagnose liver cancer using the features of tumors obtained from multiphase CT images. MethodsA total of 71 histologically-proven liver tumors including 49 benign and 22 malignant lesions were evaluated with the proposed CAD system to evaluate its performance. Tumors were identified by the user and then segmented using a region growing algorithm. After tumor segmentation, three kinds of features were obtained for each tumor, including texture, shape, and kinetic curve. The texture was quantified using 3 dimensional (3-D) texture data of the tumor based on the grey level co-occurrence matrix (GLCM). Compactness, margin, and an elliptic model were used to describe the 3-D shape of the tumor. The kinetic curve was established from each phase of tumor and represented as variations in density between each phase. Backward elimination was used to select the best combination of features, and binary logistic regression analysis was used to classify the tumors with leave-one-out cross validation. ResultsThe accuracy and sensitivity for the texture were 71.82% and 68.18%, respectively, which were better than for the shape and kinetic curve under closed specificity. Combining all of the features achieved the highest accuracy (58/71, 81.69%), sensitivity (18/22, 81.82%), and specificity (40/49, 81.63%). The Az value of combining all features was 0.8713. ConclusionsCombining texture, shape, and kinetic curve features may be able to differentiate benign from malignant tumors in the liver using our proposed CAD system.

Structured Reporting of Multiphasic CT for Pancreatic Cancer: Potential Effect on Staging and Surgical Planning

To compare structured versus nonstructured reporting of multiphasic computed tomography (CT) for staging of pancreatic cancer and the effects of both types of reporting on subjective assessment of resectability. This institutional review board-approved, HIPAA-compliant retrospective study with waiver of informed consent included all patients who were referred for presurgical multiphasic CT of the pancreas between December 2006 and April 2011 at one institution before and after implementation (April 2008) of a structured reporting template. The template was created specifically for reporting multiphasic CT results to stage pancreatic cancer in patients and contained specific information relevant to surgical and oncologic planning. Multiphasic CT reports were assessed for the presence of 12 key features required for staging and surgical planning, including location, size, enhancement, node status, and vascular involvement. Three pancreatic surgeons evaluated the reports to assess resectability, surgical planning, and ease of extracting information before and after reviewing the multiphasic CT images blinded to the patient identifiers. The Student t test and χ(2) test were used for statistical analysis. Forty-eight (40%) structured and 72 (60%) nonstructured multiphasic CT reports were reviewed. Nonstructured reports contained a mean ± standard deviation of 7.3 key features ± 2.1 (range, 1-11) and structured reports contained 10.6 ± 0.9 (range, 9-12) features (P < .001). Information for surgical planning was deemed easily accessible in 94%, 60%, and 98% of structured and 47%, 54%, and 32% of nonstructured reports by the three surgeons, respectively (P < .001, .79, < .001). Surgeons had sufficient information for surgical planning in 96%, 69%, and 98% of structured and 31%, 43%, and 25% of nonstructured reports (P < .001, .009, and < .001). When surgeons reviewed reports in combination with multiphasic CT images, they were more likely to convert an answer of "unsure" regarding resectability to a definitive answer (ie, resectable or unresectable) when the reports were structured than when they were nonstructured. Structured reporting of pancreatic multiphasic CT provided superior evaluation of pancreatic cancer and facilitated surgical planning. Surgeons were more confident regarding decisions about tumor resectability when they reviewed structured reports before review of multiphasic CT images.

Content‐based image retrieval of multiphase CT images for focal liver lesion characterization

Characterization of focal liver lesions with various imaging modalities can be very challenging in the clinical practice and is experience-dependent. The authors' aim is to develop an automatic method to facilitate the characterization of focal liver lesions (FLLs) using multiphase computed tomography (CT) images by radiologists. A multiphase-image retrieval system is proposed to retrieve a preconstructed database of FLLs with confirmed diagnoses, which can assist radiologists' decision-making in FLL characterization. It first localizes the FLL on multiphase CT scans using a hybrid generative-discriminative FLL detection method and a nonrigid B-spline registration method. Then, it extracts the multiphase density and texture features to numerically represent the FLL. Next, it compares the query FLL with the model FLLs in the database in terms of the feature and measures their similarities using the L1-norm based similarity scores. The model FLLs are ranked by similarities and the top results are finally provided to the users for their evidence studies. The system was tested on a database of 69 four-phase contrast-enhanced CT scans, consisting of six classes of liver lesions, and evaluated in terms of the precision-recall curve and the Bull's Eye Percentage Score (BEP). It obtained a BEP score of 78%. Compared with any single-phase based representation, the multiphase-based representation increased the BEP scores of the system, from 63%-65% to 78%. In a pilot study, two radiologists performed characterization of FLLs without and with the knowledge of the top five retrieved results. The results were evaluated in terms of the diagnostic accuracy, the receiver operating characteristic (ROC) curve and the mean diagnostic confidence. One radiologist's accuracy improved from 75% to 92%, the area under ROC curves (AUC) from 0.85 to 0.95 (p = 0.081), and the mean diagnostic confidence from 4.6 to 7.3 (p = 0.039). The second radiologist's accuracy did not change, at 75%, with AUC increasing from 0.72 to 0.75 (p = 0.709), and the mean confidence from 4.5 to 4.9 (p = 0.607). Multiphase CT images can be used in content-based image retrieval for FLL's categorization and result in good performance in comparison with single-phase CT images. The proposed method has the potential to improve the radiologists' diagnostic accuracy and confidence by providing visually similar lesions with confirmed diagnoses for their interpretation of clinical studies.

Contrast-enhanced US-guided Radiofrequency Ablation of Hepatocellular Carcinoma

PurposeContrast-enhanced ultrasound (US) has been shown to be an efficient imaging modality in guiding radiofrequency (RF) ablation of hepatocellular carcinomas (HCC). The purpose of the present study was to assess the usefulness of contrast-enhanced US in guiding RF ablation in patients with early-stage HCC that was not clearly visible on grayscale US or noncontrast computed tomography (CT). Materials and MethodsDuring a 17-month period, contrast-enhanced US–guided RF ablation was performed in 14 patients with 19 early-stage lesions that were poorly defined on grayscale US and noncontrast CT. Contrast-enhanced US was repeated after 30 minutes, and complete ablation was defined as absence of any arterial-phase enhancement within the ablated lesion. Patients were followed periodically with clinical evaluation, liver function tests, α-fetoprotein measurement, and multiphasic CT or magnetic resonance (MR) imaging for a minimum of 1 year after ablation to look for local recurrence or disease progression. Survival probability was estimated with the Kaplan–Meier method. ResultsComplete tumor ablation was achieved in all 19 lesions, with no evidence of residual or recurrent tumor in the ablated areas after a mean follow-up of 16 months. No major complications were observed in any patient. However, new lesions developed in other parts of the liver on follow-up scans in three patients, and were accordingly treated with RF ablation. Two patients died of disease progression or liver failure within the 1-year follow-up. ConclusionsFor early-stage HCCs not well visualized on unenhanced US or CT, contrast-enhanced US provides an additional tool to guide RF ablation.

Percutaneous Cryoablation of Renal Tumors: Patient Selection, Technique, and Postprocedural Imaging

Percutaneous cryoablation of renal tumors requires a number of important steps for success and relies heavily on imaging for treatment planning, intraprocedural guidance and monitoring, detection of untreated tumor, and surveillance for disease progression. Imaging-guided percutaneous cryoablation has several advantages over laparoscopic cryoablation. In particular, computed tomography (CT) and magnetic resonance (MR) imaging allow global evaluation of the ablation zone and an accurate depiction of the treatment margin. Ultrasonography allows real-time guidance of probe placement but cannot help depict ice ball formation as accurately as CT or MR imaging. Multiphasic CT or MR imaging should be performed at structured intervals following ablation. Treated tumors are expected to decrease in size over time, and lesion growth and internal or nodular enhancement are suspicious for tumor recurrence or progression. Complications include probe site pain, hematoma, incomplete ablation, and recurrent tumor. Current limitations of percutaneous cryoablation include the inability to control hemorrhage without intraarterial access and a lack of long-term follow-up data. Nevertheless, percutaneous cryoablation is an effective choice for minimally invasive nephron-sparing treatment of renal tumors.

Lymphoplasmacytic sclerosing cholangitis: assessment of clinical, CT, and pathological findings

To assess the clinical, computed tomography (CT), and pathological findings in patients with lymphoplasmacytic sclerosing cholangitis. Fifteen consecutive patients (four women and 11 men, mean age 71 years) with lymphoplasmacytic sclerosing cholangitis and without the characteristic features of underlying disorders causing benign biliary strictures were retrospectively recruited. Two radiologists evaluated multiphase contrast-enhanced CT images acquired with 0.5 or 1-mm collimation. One pathologist performed all histological examinations, including IgG4 immunostaining. The intrahepatic biliary ducts showed dilatation in all 15 patients, but only seven presented with jaundice. Although laboratory data were not available in all patients, serum gammaglobulin and IgG levels were elevated in five of six patients and six of eight patients, respectively. Anti-nuclear antibody was detected in three of six patients. The involved biliary ducts showed the following CT findings: involvement of the hilar biliary duct (14/15), a mean wall thickness of 4.9 mm, a smooth margin (10/15), a narrow but visible lumen (6/15), hyper-attenuation during the late arterial phase (9/15), homogeneous hyper-attenuation during the delayed phase (11/11), and no vascular invasion (14/15). Abnormal findings in the pancreas and urinary tract were detected in eight of 15 patients. In 13 patients with adequate specimens, moderate to severe lymphoplasmacytic infiltration associated with dense fibrosis was observed. Infiltration of IgG4-positive plasma cells was moderate or severe in nine patients and minimal or absent in four patients. Lymphoplasmacytic sclerosing cholangitis exhibits relatively characteristic clinical and CT findings, although they are not sufficiently specific for differentiation from other biliary diseases.

Small hepatocellular carcinomas in cirrhosis: differences in contrast enhancement effects between helical CT and MR imaging during multiphasic dynamic imaging

The purpose of this study was to evaluate differences in the degrees of contrast enhancement effects of small hepatocellular carcinomas (HCCs) in patients with cirrhosis between helical computed tomography (CT) and magnetic resonance (MR) imaging during multiphasic contrast-enhanced dynamic imaging and to determine the diagnostic value of MR imaging especially in assessing hypovascular HCCs detected as hypoattenuating nodules on late-phase CT. This study included 64 small HCCs (<3 cm in diameter) in 40 patients with chronic hepatitis or cirrhosis who underwent multiphasic (arterial, portal and late phases) contrast-enhanced dynamic helical CT and MR imaging. The contrast enhancement patterns of each lesion in the arterial and late phases were evaluated by two radiologists experienced in liver MR imaging and categorized as one of five grades (1=hypoattenuated/hypointense; 2=slightly hypoattenuated/hypointense; 3=isoattenuated/isointense; 4=slightly hyperattenuated/hyperintense; 5=hyperattenuated/hyperintense), compared with the surrounding liver parenchyma. Forty-three (67%) of 64 lesions showed Grade 4 (n=24) or Grade 5 (n=19) enhancement on arterial-phase CT, while 51 (80%) of 64 lesions showed Grade 4 (n=20) or Grade 5 (n=31) enhancement on arterial-phase MR imaging, indicating hypervascular HCCs. The grading score of hypervascular HCCs on arterial-phase MR imaging (mean: 4.61) was significantly (P<.01) higher than that for hypervascular HCCs on arterial-phase CT (mean: 4.20), showing better detection of the hypervascularity (arterial enhancement) of the lesion on arterial-phase MR imaging. Regarding hypovascular HCCs, all (100%) of 21 hypovascular HCCs on CT showed Grade 1 (n=10) or Grade 2 (n=11) enhancement on late-phase CT, seen as hypoattenuation. In contrast, 8 (62%) of 13 hypovascular HCCs on MR imaging showed Grade 1 (n=1) or Grade 2 (n=7) enhancement on late-phase MR imaging, seen as hypointensity. Grading scores of hypovascular HCCs on late-phase images were significantly (P<.001) lower on CT than on MR imaging (mean score: 1.52 vs. 2.31), indicating better washout effects for hypovascular HCCs on late-phase CT. The washout effects for small HCCs on late-phase MR imaging were inferior to those for small HCCs on late-phase CT. Especially, hypovascular HCCs demonstrated as hypoattenuating nodules on late-phase CT were often not seen on late-phase MR imaging, requiring careful evaluation of other sequences, including unenhanced T(1)-weighted and T(2)-weighted MR images.

Computed Tomography Features of an Intraductal Polypoid Mass

To determine the computed tomography (CT) features capable of differentiating hepatocellular carcinoma (HCC) with bile duct tumor invasion (BDTI) from intraductal cholangiocarcinoma (IDCC). Multiphasic CT images of 14 patients with HCC with BDTI and 18 patients with IDCC were retrospectively reviewed. Analysis of the CT findings included the size, location, and margin of the intraductal mass; enhancement pattern of intraductal lesions; degree of ductal dilatation; presence of downstream ductal dilatation and ductal wall thickening; presence of a parenchymal mass and its size; continuity of the parenchymal mass with the intraductal mass; and liver cirrhosis. Objective evaluation of the enhancement patterns of intraductal tumors was done by measuring the CT attenuation coefficients of the tumors and the uninvolved hepatic parenchyma in each phase. Among these findings, statistically significant variables were then determined using the Fisher's exact test or Mann-Whitney U test. Significant variables that helped to differentiate HCC with BDTI from IDCC included the presence of a parenchymal mass, liver cirrhosis, and a hyperattenuating intraductal tumor on the hepatic arterial phase (HAP). On unenhanced images, the tumor-to-liver contrast of IDCC (16.7+/-8.1) was greater than that of HCC with BDTI (6.4+/-10.4), but on the HAP, that of HCC with BDTI (26.5+/-28.2) was greater than that of IDCC (5.9+/-18.7) (P<0.05). In addition, there was a significant difference in the enhancement ratio of the intraductal tumors on the portal venous phase between the 2 conditions (P=0.003). Several objective and subjective multiphasic CT findings may help to differentiate HCC with BDTI from IDCC.

Hepatocellular Carcinoma in Patients with Chronic Liver Disease: Comparison of SPIO-enhanced MR Imaging and 16–Detector Row CT

To compare the sensitivity, positive predictive value, and diagnostic accuracy of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging with those of 16-detector row computed tomography (CT) for the detection of hepatocellular carcinoma (HCC) in patients with hepatitis B-induced cirrhosis. Institutional Review Board approval was obtained for this study, and informed consent was obtained from all patients. A total of 44 patients (36 men, eight women; age range, 35-67 years) with 59 HCCs and mild liver cirrhosis (Child-Pugh score A or B) underwent multiphasic CT and SPIO-enhanced MR imaging. The diagnosis of HCC was established at surgical resection (n = 31) and percutaneous biopsy (n = 28). SPIO-enhanced MR imaging was composed of T2-weighted turbo spin-echo and T2*-weighted gradient-echo sequences. Multiphasic CT consisted of four phases (ie, early arterial, late arterial, portal venous, and equilibrium). Three observers independently analyzed each image in random order. Sensitivity, positive predictive value, and diagnostic accuracy were calculated by using the alternative free-response receiver operating characteristic analysis for multi-detector row CT and SPIO-enhanced MR imaging. Although not significant (P > .05), the area under the receiver operating characteristic curve for SPIO-enhanced MR imaging (mean, 0.90) was higher than that for multi-detector row CT (mean, 0.82) for all observers. Also, although no significant difference was demonstrated by any of the three observers (P > .05), there was a trend toward increased sensitivity on both a per-lesion and a per-patient basis for SPIO-enhanced MR imaging (mean, 84.7% and 94.7%, respectively) compared with multi-detector row CT (mean, 76.9% and 88.6%, respectively). No significant difference in positive predictive value was observed between modalities. SPIO-enhanced MR imaging and multiphasic CT show similar diagnostic accuracy, sensitivity, and positive predictive value for the detection of HCC in patients with relatively mild hepatitis B-induced cirrhosis.

Bladder cancer: analysis of multi-detector row helical CT enhancement pattern and accuracy in tumor detection and perivesical staging.

To evaluate the enhancement pattern of bladder cancer and the accuracy of multi-detector row helical computed tomography (CT) in the detection and staging of bladder cancer. In 20 patients, the attenuation value of bladder cancer was measured on dynamic contrast material-enhanced multiphasic CT images obtained with scanning delays of 40, 60, 80, and 100 seconds. In 67 patients, CT data were obtained with a 60-second scanning delay that covered the bladder (section thickness, 2.5 mm; beam pitch, 1.5) and a 180-second scanning delay that covered the abdomen (section thickness, 5 mm; beam pitch, 1.5). We prospectively evaluated CT images and compared findings at CT with findings at histologic examination. We evaluated cancer detection rate, positive predictive value of cancer detection, and sensitivity and specificity in the diagnosis of perivesical invasion. The attenuation value of bladder cancers was significantly higher on 60- (105 HU +/- 16) and 80-second (97 HU +/- 15) delayed CT images than on the other images (P <.05). The cancer detection rate and positive predictive value for cancer detection were 97% and 95%, respectively, in 67 patients and increased to 100% and 100%, respectively, in 44 patients with a time interval of 7 or more days between transurethral resection of the bladder (TURB) and CT examination. Sensitivity and specificity in the diagnosis of perivesical invasion were 89% and 95%, respectively, in 67 patients and increased to 92% and 98%, respectively, in 44 patients with a time interval of 7 or more days between TURB and CT examination. Bladder cancer tends to show peak enhancement with the 60-second scanning delay. Multi-detector row helical CT is useful in the detection and staging of bladder cancer.