Dual-phase Helical Computed Tomography Research Articles

Evaluation with low-dose dual-phase helical computed tomography of patients with thyroid lesions

Background The incidence of thyroid cancer has been increasing. Our aim was to evaluate the efficacy of low-dose dualphase helical computed tomography (CT) in the characterization of thyroid lesions, and to discuss the relationship between image characteristics and their pathology. Methods One hundred and six patients with thyroid lesions underwent low-dose dual-phase helical CT after the injection of contrast material. CT scans were obtained at arterial and venous phase with delays of 25 and 65 seconds, and tube current of 60 and 120 mA, respectively. The attenuation change in the lesion between the arterial and venous phase was analyzed and categorized as “increased,” “decreased,” “mixed” or “no change.” Results Histopathologic diagnosis was obtained by surgery in 106 patients (115 lesions). Of the 106 patients, 45 had nodular goiter, 5 thyroid adenoma, 6 thyroiditis, and 50 papillary thyroid carcinoma (PTC) (59 lesions). The attenuation value showed a significant difference (P <0.05) between the arterial and venous phase for the high attenuation area. There was statistical significant difference in terms of attenuation value in high attenuation areas at both phases and in low attenuation areas on arterial phase between nodular goiter and PTC (P <0.05). However, there was no significant difference in attenuation value between adenoma and PTC. Twenty-nine cases (76.3%) of goiter manifested mixed type, 3 cases (3/5) of adenoma showed decreased type, 6 cases (6/6) of thyroiditis showed increased type, and 55 cases (93.2%) of PTC showed decreased type attenuation. The sensitivity, specificity for thyroid carcinoma by dual-phase CT were 94.9% and 80.4% respectively. The overall diagnostic accuracy for thyroid lesions by dual-phase CT was 87.8%. Conclusions The performance of dual-phase helical CT is related to the pathological structure of the lesions. The analysis of enhancement patterns by using dual-phase helical CT will be helpful in the differential diagnosis of thyroid lesions.

Small hepatocellular carcinoma keeping hypodense during dual phase helical CT scan and correlative pathology

Rationale and Objectives: To evaluate the dual-phase helical computed tomography (CT) appearance of small hepato- cellular carcinoma (SHCC) with hypodense and to evaluate its correlation with pathology. Materials and Methods: The helical CT dual-phase appearance of 33 lesions with keeping hypodense was retrospectively analyzed, all lesions were confirmed as SHCC by histopathology. CT appearance included border, inner density. Results: In 33 lesions, which were confirmed as SHCC by pathology, keeping hypodense during hepatic arterial phase and portal venous phase, 19 lesions are ill-defined borders and 14 lesions are well-defined borders, 22 lesions show homogenous hypodense and 11 lesions show heterogeneous hypodense in non-enhancing CT scan; however, only 9 lesions are ill-defined borders and the other 24 lesions are well-defined borders with slightly irregular contours, only 9 lesions show homogenous hypodense and the other 24 lesions show heterogenous hypodense with flecks of more hypodense in enhancing CT scan. Conclusion: SHCC with hypodense prefers to have a well-defined border with slightly irregular contour, and flecks of more hypodense in the lesion in dual-phase enhancing helical CT scan.

The value of multidetector-row CT in the preoperative detection of pancreatic insulinomas

The authors sought to quantitatively analyse enhancement characteristics of pancreatic insulinomas in different phases and determine the value of multidetector-row computed tomography (CT) for detecting insulinomas. Forty-six patients with surgically proven insulinomas diagnosed between 2002 and 2007 were retrospectively reviewed. These patients underwent single-phase (group 1) or dual-phase (group 2) helical CT scanning. Sensitivity for detecting insulinomas in group 2 was superior to that in group 1 (p<0.05).The sensitivity for insulinoma detection in the arterial phase was superior to that in the portal-venous phase (p<0.05). The mean attenuation values of the insulinomas and normal pancreas during the unenhanced arterial and portal-venous phases were, respectively, 40.5+/-8.75 HU (Hounsfield units), 114.48+/-27.30 HU, 112.19+/-19.52 HU and 44.56+/-6.48 HU, 81.16+/-15.22 HU, 90.54+/-13.80 HU, and there was statistical difference between them (p=0.000). The contrast enhancement of insulinomas in the arterial and portal-venous phases was 74.03+/-29.51 HU and 70.90+/-21.93 HU, respectively, and there was no statistical difference between them (p=0.499). The tumour to normal-pancreas attenuation differences in the arterial and portal-venous phases were respectively 33.32+/-20.96 HU and 20.58+/-16.32 HU, respectively, and there was statistical difference between them (p=0.011). Dual-phase CT has a promising sensitivity in detecting pancreatic insulinomas. The acquisition of images in the arterial phase is more helpful for detecting insulinomas.

Imaging characteristics of papillary renal cell carcinoma by computed tomography scan and magnetic resonance imaging

To analyse the differences in the patterns between clear and papillary renal cell carcinomas using magnetic resonance imaging (MRI) and dual-phase helical computed tomography (CT). We examined seven patients with papillary renal cell carcinoma, and six with clear cell carcinoma. The highest attenuation value of tumors in the corticomedullary phase (CMP) and the excretory phase (EP) was measured using the observer-defined region of interest (ROI). MRI consisted of T1-weighted and T2-weighted spin-echo imaging. All five tumors except for one with papillary renal cell carcinoma showed homogenous hypointensity, but all six tumors with clear cell carcinoma showed heterogeneous hyperintensity on their T2-weighted images. In the CMP, the mean CT numbers of the papillary renal cell carcinomas were significantly lower than those of the clear cell carcinomas. The mean enhancement of the papillary renal cell carcinomas in the CMP and the EP was significantly lower than that of the clear renal cell carcinomas. The mean CT numbers of the clear cell carcinomas in the CMP were markedly increased from those on the unenhanced CT; those in the EP were decreased gradually. But the mean CT numbers of the papillary renal cell carcinomas in the EP were still slightly more increased than those in the CMP. The enhancement patterns of the papillary renal cell carcinomas in the CMP and the EP were homogenous, but those of the clear cell carcinomas were heterogeneous. We can speculate the differential diagnosis from clear to papillary renal cell carcinoma using MRI and dual-phase helical CT.

Three‐dimensional helical computed tomography cholangiography with minimum intensity projection in gallbladder carcinoma patients with obstructive jaundice: Comparison with magnetic resonance cholangiography and percutaneous transhepatic cholangiography

Computed tomography (CT) is traditionally used for evaluation and staging of gallbladder carcinoma (GC). However, in the subgroup of patients with obstructive jaundice, magnetic resonance cholangiography (MRC) is generally required to assess the level of biliary obstruction. The present study was undertaken to evaluate the diagnostic potential of three-dimensional helical CT cholangiography (3-D CTC) with minimum intensity projection (minIP), to determine the presence and level of biliary obstruction. Twenty-five consecutive patients with proven GC, presenting with clinical and biochemical features of obstructive jaundice, over a 1-year period were included in the study. Dual phase helical CT data was obtained in the arterial and venous phases, respectively, after intravenous contrast injection using a pressure injector. Axial CT data (both arterial and venous phase) was studied for staging and resectability of tumor. Three-dimensional helical CT cholangiography using minIP obtained from the venous phase data set, was used to assess the level of biliary obstruction and isolation of hepatic segmental ducts. Three-dimensional helical CT cholangiography findings were compared with MRC and percutaneous transhepatic cholangiography (PTC) (gold standard). None of the patients were operated on as they were all considered inoperable on axial CT images due to extensive local disease or distant metastasis. In all patients, 3-D CTC demonstrated dilated intrahepatic ducts up to tertiary branch level. The 3-D CTC correctly diagnosed the level of biliary obstruction and demonstrated isolated segmental ducts in all patients and correlated well in all cases with MRC and PTC findings in this regard. However, the 3-D CTC did not add any additional information over the axial source images. Three-dimensional helical CT cholangiography with minIP can correctly determine the level of biliary obstruction in patients with GC and may be a strong competitor with MRC, because it gives equivalent information with regard to the level of ductal obstruction even while being a part of an overall comprehensive CT staging study. Even though 3-D CTC did not provide additional information on top of the source images, the referring physicians found them very useful for conceptualization of the 3-D biliary anatomy.

Surgically staged focal liver lesions: accuracy and reproducibility of dual-phase helical CT for detection and characterization.

To assess the accuracy and reproducibility of dual-phase helical computed tomography (CT) in enabling preoperative detection and characterization of surgically staged focal liver lesions. Surgically and histopathologically proven liver lesions were evaluated by three experienced CT readers. These lesions were present in 77 patients who underwent dual-phase helical CT. Images were interpreted separately by the three blinded reviewers. Each lesion was graded on a nine-point scale of confidence, with 1 being definitely benign, 9 being definitely malignant, and 5 being indeterminate. The chi2 test was used to determine if the distribution of lesion classifications was different between readers. There was a total of 237 lesions: 73 were benign and 164 were malignant. Sensitivity for lesion detection was 69%, 70%, and 71% for the three reviewers, respectively. Specificity was 91%, 86%, and 90%, and the area under the curve for the alternative-free response receiver operating characteristic curve was 0.84, 0.83, and 0.85, respectively. The difference in the distributions of lesion classification between the three reviewers was not statistically significant (P =.67) as determined by chi2 analysis. Dual-phase CT has sensitivity of 69%-71% and high specificity (86%-91%) in enabling the detection and characterization of focal liver lesions. Interpretation is highly reproducible, as there is minimal variation between experienced reviewers.

Liver Lesions: Manganese-enhanced MR and Dual-Phase Helical CT for Preoperative Detection and Characterization—Comparison with Receiver Operating Characteristic Analysis

The purpose of this study was to compare, by means of receiver operating characteristic (ROC) analysis, dual-phase helical computed tomography (CT) and manganese-enhanced magnetic resonance (MR) imaging in the detection and characterization of hepatic lesions in patients prior to surgery. Twenty-five patients known to have or suspected of having hepatic lesions who were eligible for surgery underwent dual-phase (ie, arterial and portal phase) helical CT and phased-array MR imaging (ie, unenhanced fast spin-echo T2-weighted imaging and gradient-echo T1-weighted imaging performed before and after administration of mangafodipir trisodium). All images were reviewed independently by three off-site blinded reviewers who separately reviewed the CT scans and MR images. The standard of reference was findings at surgery, intraoperative ultrasonography (US), and histopathologic examination. ROC curves were established to analyze the results for each reader and modality. Ninety-four lesions (77 malignant and 17 benign) were revealed at surgery, intraoperative US, and/or histopathologic examination. The overall rate of lesion detection for the three readers at CT was 81.9% +/- 7.8, 90.4% +/- 5.9, and 76.6% +/- 8.6. At MR imaging, the detection rates were 72.3% +/- 9.0, 71.3% +/- 9.1, and 69.1% +/- 9.3 (P =.001 for the difference between MR and CT). The average rate of false-positive diagnoses in patients was 14.1% at CT and 6.4% at MR imaging (P =.06 for the difference between MR and CT). The mean areas under the alternative-free-response ROC curves were 0.74 for MR and 0.72 for CT (P =.751, not significant). In detection and characterization of liver lesions, manganese-enhanced MR imaging and dual-phase helical CT were not statistically different.

Congenital and acquired anomalies of the portal venous system.

Knowledge of the normal anatomy, most frequent variants, and congenital and acquired anomalies of the portal venous system is of great importance for liver surgery and interventional procedures such as creation of transjugular intrahepatic portosystemic shunts. Radiologic studies of the portal venous system include color Doppler ultrasonography (US), computed tomography (CT), magnetic resonance imaging, and arterial or direct portography. Among the most common branching variants of the portal vein are trifurcation, right anterior portal branch arising from the left portal vein, and right posterior portal branch arising from the main portal vein. Agenesis of the right or left portal vein is the most frequently reported congenital anomaly. Venous collateral vessels due to portal hypertension and cavernous transformation of the portal vein are best evaluated with cross-sectional imaging. Intrahepatic portosystemic, arterioportal, and arteriosystemic fistulas and associated perfusion anomalies have characteristic features at dual-phase helical CT. Color Doppler US is the single most useful tool for demonstration of aneurysms of the portal venous system and bland or neoplastic portal vein thrombosis. CT is also the best means of evaluating gas in the portal venous system, which is no longer an ominous sign and must be differentiated from aerobilia.

Late-phase enhancement of the upstream portion of pancreatic adenocarcinoma on dual-phase helical CT.

Late-phase enhancement of pancreatic parenchyma upstream (tail side) of pancreatic adenocarcinoma is found frequently on dual-phase helical computed tomography (CT). We measured the frequency of late-phase enhancement of the upstream portion of pancreatic adenocarcinoma and normal pancreatic parenchyma using dual-phase helical CT. Twenty-one patients with pancreatic adenocarcinoma and nontumorous pancreas upstream of tumors were compared with 100 control patients without pancreatic disease. Early and late scans started at 25 and 75 s, respectively, after intravenous injection of contrast material. The attenuation values of normal and nontumorous pancreas upstream of tumors were assessed in three phases: precontrast, early, and late enhanced. Enhancement ratio (ER) was calculated as ER = (late phase - precontrast)/(early phase - precontrast). Late-phase enhancements (ER > 1.0) were seen in 86% of upstream pancreas and 10% of normal pancreas. The mean ER of upstream pancreas was significantly higher than that of normal pancreas (p < 0.01). Late-phase enhancement of the pancreas upstream of the tumor is frequently observed in patients with pancreatic adenocarcinoma. Late-phase enhancement and histology showed a correlation for chronic obstructing pancreatitis in five patients.

Dual Phase Helical CT Versus Portal Venous Phase CT For the Detection of Colorectal Liver Metastases: Correlation with Intra-operative Sonography, Surgical and Pathological Findings

AIM: To assess whether dual phase helical computed tomography (DPCT) of the liver improves the detection of colorectal liver metastases compared with portal venous phase (PVP) imaging alone.MATERIALS AND METHODS: DPCT was performed in 33 consecutive patients before laparotomy for resection of colorectal liver metastases. CT comprised 8-mm slice collimation with a pitch of 1 to 1.25; imaging was commenced 20–25 and 65–70 s after the start of injection of 150ml of contrast medium at 5ml/s to coincide with hepatic arterial phase (HAP) and PVP contrast enhancement, respectively. Four blinded observers independently reviewed the HAP, PVP and DPCT images recording the site and size of all lesions. Alternative-free response receiver operating characteristic (AFROC) methodology was used to analyse the results, which were correlated with surgery, intra-operative ultrasound and histology.RESULTS: The mean observer sensitivities for malignant lesion detection were 75.3% for DPCT, 69.7% for PVP imaging and 66.7% for HAP imaging alone. There was a statistically significant improvement in malignant lesion detection using DPCT when compared with PVP imaging alone (P<0.05). The mean areas under the AFROC curves were 0.84 for DPCT and 0.82 for PVP (P<0.03) imaging alone.CONCLUSION: The detection of colorectal liver metastases was marginally better with DPCT than with PVP imaging alone, but the discovery of additional lesions did not affect the management of any of the patients in this study. Scott, D.J.et al.(2001). Clinical Radiology56, 235–242.

Pancreatic arterial anatomy: depiction with dual-phase helical CT.

To determine the efficacy of arterial phase helical computed tomography (CT) for the depiction of small pancreatic arteries. Arterial phase helical CT (3-mm collimation, 1-mm reconstruction interval) was performed during power injection of 180 mL of ioversol at 5 mL/sec. Two radiologists reviewed 100 consecutive arterial phase helical CT scans of the pancreas in patients with normal glands and recorded the frequency of visualization of the major visceral (celiac, hepatic, splenic, gastroduodenal, superior mesenteric) and small pancreatic (dorsal pancreatic, right branch of the dorsal pancreatic, pancreaticomagna, caudal pancreatic, transverse pancreatic, anterior and posterior arcade, and inferior pancreaticoduodenal) arteries. Scans in 87 patients were technically satisfactory and were included in the analysis. The major visceral arteries were seen in all patients. The following secondary pancreatic arteries were seen: dorsal pancreatic, 82 (94%) patients; pancreaticomagna, 45 (52%); caudal pancreatic, 34 (39%); transverse pancreatic, 36 (41%); right branch of the dorsal pancreatic, eight (9%); anterior arcade, 47 (54%); posterior arcade, 63 (72%); and inferior pancreaticoduodenal, 73 (84%). Small pancreatic arteries can be delineated on arterial phase helical CT scans by using optimized techniques.

Pancreatic cancer: value of dual-phase helical CT in assessing resectability.

To evaluate the use of dual-phase helical computed tomography (CT) (with or without CT angiography) to assess resectability in patients suspected to have pancreatic cancer. Tumor resectability was prospectively evaluated in 89 patients who later underwent surgery for suspected pancreatic cancer. Helical CT scans were obtained in the vascular phase and a phase of maximal hepatic enhancement. CT angiograms were produced with multiprojection volume reconstruction and maximum-intensity projection. CT results were correlated with surgical and histopathologic results. Helical CT allowed detection of pancreatic cancer in 74 of 76 cases (97%). There were six false-positive results (positive predictive value, 92%). For prediction of irresectability, helical CT had an accuracy of 91%, negative predictive value of 79%, and sensitivity of 91%. Helical CT allowed detection of liver metastases in 21 of 28 cases (75%), nodal involvement in 13 of 24 cases (54%), and vascular invasion in 35 of 40 cases (88%). CT angiography demonstrated 30 of the 35 cases of vascular invasion detected with helical CT (86%). Use of dual-phase helical CT improves prediction of resectability in patients with pancreatic cancer. CT angiography cannot show all of the findings seen on helical scans.

Quantitative evaluation of pancreatic enhancement during dual-phase helical CT.

To determine the improvement in pancreatic enhancement at helical computed tomography (CT) performed with an early delay after administration of contrast material compared with that performed with a standard delay. Dual-phase helical CT of the abdomen was performed in 120 patients with a 150-mL bolus of contrast material infused at 5 mL/sec. Early and standard delayed scanning was performed beginning at 20 seconds and 49-71 seconds, respectively. Regions of interest were measured in the head, body, and tail of the pancreas in 92 patients. The difference in enhancement between early and standard delayed scanning was calculated. Mean pancreatic enhancement was 82 HU +/- 3 (standard error) with an early delay, whereas enhancement on standard delay scans was 62 HU +/- 2 (P < .001). An improvement in enhancement greater than 10 HU was attained in 66 of 92 cases (72%). Pancreatic enhancement at helical CT with an early delay after contrast material administration is often significantly greater than the enhancement seen with a standard delay when a monophasic, rapidly infused bolus of contrast material is used.