Dual-phase Helical CT Research Articles

Relationship between changes of serum concentrations of antiangiogenic factors and disease progression in patients of pancreatic carcinoma

To investigate the relationship between TSP-1, Angiostatin and Endostatin serum concentrations and progression of pancreatic adenocarcinoma. Fifty-six patients with suspected pancreatic cancer were enrolled in the study and divided into resectable group (n = 32) and unresectable group (n = 24) according to evaluation and staging with dual phase helical CT. Histopathologic examinations included postoperative final pathology and preoperative fine needle biopsies. Peripheral blood concentrations of antiangiogenic factors Angiostatin, Endostatin and TSP-1 were detected by using ELISA methods, selecting samples of health people as a control. Serum concentrations of antiangiogenic factors in pancreatic cancer group were significantly higher than those in health group (P < 0.01). Serum concentrations of Endostatin, Angiostatin and TSP-1 were significantly increased in unresectable group, and highly expressed in patients whom tumor sizes were greater than 2 cm and tumor invaded peripancreatic great vessels (P < 0.05). After operation, serum concentrations of Endostatin, Angiostatin and TSP-1 significantly decreased (P < 0.05). There were no significant difference between I, II stage group and III, IV group. Detection of serum concentrations of antiangiogenic factors may be used to evaluate the resectability of pancreatic cancer and may play important roles in growth, invasion and metastasis of pancreatic cancer.

Tumor Size Predicts Synchronous Metastatic Renal Cell Carcinoma: Implications for Surveillance of Small Renal Masses

Active surveillance of small incidental renal masses is associated with slow radiographic growth and a low risk of metastatic progression. Radiographic tumor size, in the absence of histological data, is the only prognostic indicator available when considering active surveillance. To better define the relationship between tumor size and the metastatic potential of small renal masses, we investigated whether radiographic tumor size predicts for the presence of synchronous metastases in renal cell carcinoma. We reviewed our institutional tumor registry to identify sporadic pathologically verified renal cell carcinoma treated during an 8-year period. We analyzed data regarding primary tumor size and the presence of biopsy proven synchronous metastatic disease at presentation. All N+M0 and nonpathologically confirmed M+ disease was excluded from analysis. We compared 110 cases of renal cell carcinoma with biopsy proven synchronous metastatic disease at presentation to 250 controls with clinically localized renal cell carcinoma. Tumors associated with synchronous metastasis were significantly larger than localized lesions (median 8.0 cm [range 2.2 to 20.0] vs 4.5 cm [range 0.3 to 17.5], p <0.0001). The probability of synchronous metastasis increased with increasing primary tumor size (p <0.0001). There were no patients with tumors 2 cm or smaller who presented with biopsy confirmed metastatic disease and less than 5% (5 of 110) of all synchronous metastasis occurred in tumors 3.0 cm or smaller. Logistic regression models determined that the odds of synchronous metastasis increased by 22% for each 1 cm increase in tumor size. Radiographic tumor size is a significant clinical predictor of the presence of biopsy proven synchronous metastatic renal cell carcinoma. In our series the odds of presenting with synchronous, biopsy proven metastatic disease increased by 22% with each 1 cm increase in tumor size. A 100% odds increase, or doubling of the risk of metastasis, occurs with a 3.5 cm increase in primary tumor size. These data have important implications for extent of disease evaluations in patients with large tumors and for the active surveillance of small enhancing renal masses.

Endocrine Pancreatic Tumours and Helical CT: Contrast Enhancement Is Correlated with Microvascular Density, Histoprognostic Factors and Survival

Purpose: To assess the role of contrast-enhanced helical CT in the evaluation of tumour vascularity in endocrine pancreatic tumours (EPTs), and to determine the predictive factors of malignancy of EPTs at helical CT with CT-histopathological correlation. Materials and Methods: Thirty-seven consecutive patients with histopathologically proven EPTs underwent dual-phase helical CT. For each tumour detected, its density relative to the surrounding parenchyma was scored on the pancreatic phase using a 5-point scale. Radiological findings were correlated with histopathological (vessel density count) and clinical follow-up findings. Results: Thirty of 37 patients had non-functioning EPTs and overall 44 tumours were detected by helical CT (mean size 38, range 5–100 mm). CT showed calcifications in 10 tumours. Calcifications were associated with well-differentiated carcinomas (90%, p = 0.02). Vascular density assessed by light microscopy was significantly correlated with tumour enhancement at the pancreatic phase (p = 0.0001). Poorly differentiated carcinomas were less vascularised than well-differentiated tumours and carcinomas (34 vs. 264 vessels/mm², p = 0.0073). Tumour differentiation also correlated with tumour enhancement at the pancreatic phase (p = 0.0044, trend test): poorly differentiated carcinomas were hypoattenuating (71%) and isoattenuating or weakly hyperattenuating (29%), compared with well-differentiated carcinomas and tumours that were mainly moderately or strongly hyperattenuating (53%). In univariate analysis, poor tumoral differentiation, hepatic metastasis, high mitotic index, poor tumoral enhancement at the pancreatic phase and less vascularised tumours were correlated with decreased survival rate. Conclusion: Enhancement of EPT at CT is correlated with tumour vascularity assessed by light microscopy. Low-enhancing EPT at CT are correlated with poorly differentiated EPT and with a decrease in overall survival.

Laparoscopic radiofrequency ablation therapy in patients with hepatocellular carcinoma and liver cirrhosis

目的 探讨肝细胞癌合并肝硬化病人行腹腔镜射频消融(LRFA)治疗的可行性、安全性及疗效.方法 2001年8月至2003年12月,25例肝细胞癌合并肝硬化病人在全麻下进行了LRFA治疗.男19例,女6例,平均年龄(52.2±11.9)岁.术前经超声、螺旋CT或MRI等检查共发现瘤体38个,平均肿瘤直径(3.8±1.1)cm.肿瘤均位于肝脏表面、肝左外叶或邻近胆囊等空腔脏器.肝功能均为Child A或B级.合并慢性结石性胆囊炎3例,糖尿病2例,凝血功能障碍5例.术中行腹腔镜超声检查及病理活检.结果 25例病人腹腔镜及术中超声检查共发现瘤体41个.所有病例均顺利完成LRFA治疗,同时行胆囊切除术5例.平均手术时间(72.5±27.6)min.未出现出血、胆道、胃肠道及膈肌损伤等并发症.术后1个月螺旋CT扫描证实,肿瘤完全坏死率达100%.随访6～32个月(平均18个月),1例发现肝内新病灶,3例射频治疗部位复发,l例死于肿瘤复发及肝功能衰竭.结论肝细胞癌合并肝硬化病人行LRFA治疗是安全可行的,可提高肝细胞癌射频消融治疗效果,减少并发症。

Laparoscopy and Laparoscopic Ultrasound in the Evaluation of Pancreatic and Periampullary Tumours

Background and Aims: The pre-operative determination of resectability of pancreatic and peri-ampullary neoplasia assists the selection of patients for surgical or non-surgical treatment. This study investigated whether the addition of laparoscopy with laparoscopic ultrasound to dual-phase helical CT could improve the accuracy of assessment of resectability. Patients and Methods: Prospective study of 305 patients referred to a single unit for consideration of pancreatic resection who underwent dual-phase helical CT scanning ± laparoscopy with laparoscopic ultrasound. Data were collected on patient demographics, CT findings, assessment of operability, laparoscopic assessment (LA), surgical procedures and histology. Results: LA was undertaken in 239/305 patients, 190 of whom were considered CT resectable, and 49 CT unresectable. Of the 190 CT resectable patients, LA correctly identified unresectability in 28 (15%: metastases in 15; vascular encasement in 6; anaesthesia for laparoscopy found 7 unfit for major resection) and incorrectly in 2 (vascular encasement), but did not identify unresectability in 33; LA correctly confirmed resectability in the remainder (prediction improved, χ² = 9.73, p < 0.01). Of the 49 CT unresectable patients, LA correctly identified resectability in 4, and incorrectly in 12, and correctly identified unresectability in the remaining 33. Sixty-six of the 305 patients did not undergo LA, of whom 23 underwent resection. Conclusion: When added to dual-phase helical CT, laparoscopy with laparoscopic ultrasound provides valuable information that significantly improves the selection of patients for surgical or non-surgical treatment.

Pancreatic Adenocarcinoma: Dual-Phase Helical CT with Surgical and Histopathologic Correlation

Purpose: To determine the accuracy of dual-phase helical CT in assessing the resectability of pancreatic ductal adenocarcinoma, and to correlate the CT findings with the surgical and histopathologic findings. Materials and Methods: Thirty patients with pathologically proven cancer of the pancreas underwent arterialand portal- phase helical CT scanning, and in two of these, single-level dynamic CT was performed during celiac and superior mesenteric arteriography. In 17 patients who underwent surgery for potentially resectable cancer of the pancreatic head, tumor resectability was assessed. The CT findings were analyzed and correlated with these of surgery and histopathology. Results: In 13 (76%) of the 17 patients who underwent surgery, tumors were resectable. Their average size was 2.76 cm (arterial phase), 2.30 cm (portal phase), and 2.48 cm (pathologically determined) and the overall accuracy of helical CT for assessing resectability was 87%. In all patients, the central portion of the tumors exhibited hypoattenuation at both phases; the peripheral portion showed hypoattenuation at the arterial phase and iso- (n=10) or hyperattenuation (n=3) at the portal phase. Single-level dynamic CT depicted a persistently ypoattenuating central portion and progressive and prolonged enhancement of the periphery. CT-histopathologic correlation showed that central hypoattenuation indicated the presence of tumor cells, necrosis (n=3) and mucin (n=4), while the peripheral iso- or hyperattenuated areas seen at the portal phase represented fibrosis and inflammatory infiltration. Histopathologic examination revealed tumoral infiltration of peripancreatic fat tissue (n=11) and microvascular invasion of major peripancreatic vessels (n=7). Conclusion: The dual-phase helical CT is useful in the determination of resectability in pancreas cancer and CT findings represent well the histopathologic features of pancreas cancer.

Vascular sequelae of cirrhosis: evaluation with dual-phase helical CT.

Vascular sequelae of cirrhosis: evaluation with dual-phase helical CT.

Hepatofugal portal flow in advanced liver cirrhosis with spontaneous portosystemic shunts: effects on parenchymal hepatic enhancement at dual-phase helical CT.

We investigated whether spontaneous hepatofugal portal flow in advanced cirrhosis affects hepatic enhancement on dual-phase helical computed tomography. Fifteen patients with hepatofugal portal flow on Doppler sonography and angiography (group 1) and 15 age- and sex-matched patients with hepatopetal portal flow (control; group 2) underwent dual-phase helical computed tomography. Vascular and liver attenuation values were measured on unenhanced scans and scans obtained during hepatic arterial (HAP; 25 s) and portal venous (PVP; 70 s) phases. Portal vein enhancement was lower during PVP in group 1 than in group 2 ( p < 0.0001). Liver enhancement was higher during HAP and lower and delayed during PVP in group 1 versus group 2 ( p < 0.0001). In hepatofugal portal flow, liver enhancement is increased during HAP and compensating for decreased and delayed liver enhancement during PVP, resulting in potential decreased hypervascular tumor conspicuity.

The Detectability of Hepatic Metastases in Candidates of Radiofrequency Ablation: Comparison for Helical CT Scanning and Late-Phase Pulse-Inversion Harmonic Imaging

Purpose: To compare dual-phase helical CT and pulse inversion harmonic US using microbubble contrast agents in the detection of hepatic metastases prior to radiofrequency (RF) ablation. Materials and Methods: Twenty-one patients in whom hepatic metastases from colorectal cancer had been diagnosed by dual-phase CT scanning and who were considered to be candidates for RF ablation underwent pulse-inversion barmonic US examination. Images were obtained 5 minutes after the bolus injection of microbubble contrast agent SH U 508 A (4.0 g, 300 mg/mL). The number of metastatic tumors revealed by CT and US was determined, and the findings were statistically analysed. The influence of the results of US examination on treatment planning was also evaluated. Results: In 21 patients, 48 metastatic lesions were detected by helical CT, and 56 lesions by US. These eight additional lesions revealed by US occurred in six patients (29%), and their diameter was 3-13 (mean, 7.2) mm. In three of these patients, RF ablation could not be performed, while in the other three, the additional lesions were ablated. Conclusion: Pulse-inversion harmonic US imaging using microbubble contrast agents may depict small hepatic metastatic tumors that were not apparent at CT. US-therefore appears to be useful in the planning of treatment prior to the RF ablation of hepatic metastases.

Radiofrequency Thermal Ablation of Hepatocellular Carcinoma

We evaluated the accuracy of contrast-enhanced harmonic power Doppler sonography in assessing the outcome of radiofrequency thermal ablation of hepatocellular carcinoma. Fifty patients with 65 hepatocellular carcinoma nodules (1-5 cm in diameter; mean diameter, 2.5 cm) were studied using unenhanced and contrast-enhanced harmonic power Doppler sonography before and after IV administration of a microbubble contrast agent. The examinations were repeated after treatment of the tumors with radiofrequency ablation. Findings of the Doppler studies were compared with those of dual-phase helical CT, which were used as points of reference for assessing treatment outcome. Before radiofrequency treatment, intratumoral blood flow was revealed by unenhanced power Doppler sonography in 48 (74%) of 65 hepatocellular carcinoma nodules. After injection of the contrast agent, intratumoral enhancement was observed in 61 (94%) of 65 hepatocellular carcinomas (p < 0.01). After radiofrequency treatment, all 51 (84%) of the 61 hepatocellular carcinomas found to be necrotic on helical CT scans failed to show enhancement on power Doppler sonograms. In nine of the 10 lesions that showed a residual viable tumor on helical CT scans, persistent intratumoral enhancement-matching the enhancing areas on helical CT images-was revealed by power Doppler sonography. These nine hepatocellular carcinomas were subjected to repeated radiofrequency thermal ablation with the guidance of contrast-enhanced power Doppler sonography. Complete necrosis was seen after the second treatment session in six of the nine lesions. Contrast-enhanced harmonic power Doppler sonography is an accurate technique for assessing the outcome of radiofrequency thermal ablation of hepatocellular carcinoma and may be useful in guiding additional treatment in patients with incomplete response to initial efforts.

Contrast-enhanced helical CT of the head and neck: improved conspicuity of squamous cell carcinoma on delayed scans.

We evaluated the impact of delayed scans on the conspicuity of squamous cell carcinoma in helical CT of the head and neck. Twenty-seven patients with biopsy-proven squamous cell carcinoma of the head and neck underwent dual-phase helical CT examinations using 100 mL of nonionic contrast material. In all patients, the early phase started 30 sec after the commencement of injection. The patients were assigned to one of two groups in which the delayed phase started either 180 sec (group A, n = 13) or 300 sec (group B, n = 14) after the start of injection. The overall image quality, including vascular opacification and the quality of lesion conspicuity, was determined according to a three-point scoring system. Overall image quality scored better on the early scans (score, 1.4 +/- 0.5) than on the late scans with a 180-sec (score, 1.6 +/- 0.6; p = 0.03) or a 300-sec delay (score, 2.4 +/- 0.5; p = 0.002). Tumor conspicuity scored better on scans with a 180-sec delay (score, 1.4 +/- 0.5) than on the scans with a 30-sec delay (score, 2.3 +/- 0.7; p = 0.02) or the scans with a 300-sec delay (score, 2.3 +/- 0.7; p = 0.03). In eight (62%) of 13 patients in group A and in six (43%) of 14 patients in group B, the tumor was better delineated on the late scans than on the early scans. Although early scans provide optimal vascular enhancement and are therefore necessary for helical CT studies of the head and neck, additional delayed scans may improve lesion detection in patients with squamous cell carcinoma of the head and neck.

Pancreatic carcinoma: MR, MR angiography and dynamic helical CT in the evaluation of vascular invasion

Objective: To assess the value of MR angiography in combination with contrast-enhanced MR imaging, and to compare MR imaging including MR angiography with dynamic contrast-enhanced dual phase helical CT in the preoperative assessment of vascular invasion in patients with suspected pancreatic carcinoma. Methods and material: MR imaging only, MR imaging including MR angiography and dynamic contrast-enhanced dual phase helical CT images of 48 patients who were operated due to suspicion of pancreas cancer were correlated with the surgery results in terms of vascular invasion. Pathologic diagnosis were pancreatic adenocarcinoma in 31 patients of which nine had surgically confirmed vascular invasion. Sensitivity, specificity, predictive values (including 95% confidence intervals) and accuracy of MR imaging only, MR imaging including MR angiography and helical CT were calculated. Results: Sensitivity, specificity, positive and negative predictive values and accuracy were 56, 100, 100, 85, 87%; 67, 100, 100, 88, 90% and 67, 100, 100, 88, 90%, respectively, for MR imaging only, MR imaging including MR angiography and helical CT in the adenocarcinoma group. The corresponding figures in the overall study group were 56, 97, 83, 90, 90%; 67, 97, 86, 93, 92% and 67, 97, 86, 93, 92%. Confidence intervals (95%) showed that the differences in the diagnostic efficacy of the techniques were not statistically significant in the overall study group, but the confidence intervals were undefined in the adenocarcinoma group due to the small sample size. Conclusion: Diagnostic efficacy of MR imaging when combined with MR angiography is equal to that of dynamic contrast-enhanced dual phase helical CT in the assessment of vascular invasion of pancreatic tumors.

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.

Alterations in hepatic perfusion resulting from splanchnic venous luminal compromise caused by pancreatic carcinoma.

We determined whether alterations in hepatic enhancement exist on dual phase helical CT of the liver in patients with splanchnic venous luminal compromise resulting from pancreatic adenocarcinoma. We examined the extent of hepatic enhancement on dual phase helical CT in 22 patients with pancreatic adenocarcinoma. Eleven patients had splanchnic venous luminal narrowing (flattening along at least 120 degrees of the circumference) of the superior mesenteric vein with (n = 3) or without (n = 8) portal vein involvement caused by tumor. In the remaining patients, splanchnic vasculature appeared normal. An additional 16 patients without pancreatic or hepatic abnormality who underwent dual phase helical CT served as control subjects. We compared the extent of arterial phase and portal venous phase enhancement among the three groups. The group of patients with splanchnic venous luminal compromise had significantly higher hepatic enhancement during the arterial phase (p < 0.01) and lower enhancement during the portal venous phase (p < 0.05) compared with the other two groups of patients. No significant difference in hepatic enhancement during either phase was noted between the control subjects and the patients with normal vasculature. Because hepatic enhancement correlates with perfusion, splanchnic venous luminal compromise resulting from pancreatic adenocarcinoma likely causes decreased portal venous flow and compensatory increased hepatic arterial flow. This finding supports other evidence of a homeostatic mechanism that maintains hepatic perfusion.

Dual phase hepatic CT: influence of scanning direction on liver attenuation.

We measured changes in hepatic attenuation during arterial and portal phase acquisition of hepatic CT in the craniocaudal and caudocranial directions. In 10 of 20 patients undergoing dual phase helical CT during staging for colorectal cancer, images in both phases were obtained in the craniocaudal direction. Ten patients underwent imaging in the caudocranial direction. Attenuation values in the aorta and in the peripheral and central liver regions of interest were measured on each slice. Central and peripheral liver attenuation was also measured in 10 additional patients undergoing unenhanced CT. Both peripheral and central regions of interest revealed progressively increasing attenuation during the arterial phase, irrespective of scanning direction. During the portal phase, hepatic attenuation was stable in the craniocaudal direction but decreased in the caudocranial direction (p < 0.05, Wilcoxon's signed rank sum test). Central hepatic attenuation was lower than peripheral attenuation in unenhanced livers and in enhanced livers during both phases of caudocranial acquisition. We determined no significant difference during the arterial phase of enhancement in the craniocaudal direction. The direction of acquisition does not influence sequential liver enhancement during the arterial phase. Craniocaudal acquisition produces more stable enhancement during the portal phase. Differences in attenuation between the central and peripheral areas of the liver are probably unrelated to contrast administration.

Hepatic hemangiosarcoma: imaging findings and differential diagnosis.

Primary hepatic angiosarcoma is a rare mesenchymal tumor of the liver that usually presents with nonspecific symptoms in elderly men. We present four cases of hepatic hemangiosarcoma and discuss the imaging characteristics of this entity. Our series shows that this tumor is not uncommon in younger patients with no associated risk factors such as previous exposure to thorotrast or vinyl chloride. Our experiences on a limited number of patients suggests that the combined use of angiography and dual-phase helical CT provides a better identification of the tumor and its complications. Analysis of imaging studies in patients with hepatic hemangiosarcoma reveals hypervascular lesions. Common complications were portal vein thrombosis, Budd-Chiari syndrome, as well as arterio-venous or arterio-portal shunts. Due to the vascularity of the tumor, percutaneous liver biopsy is hazardous.

Pancreatic Cancer: Comparison of Two Series of Dual-phase Helical CT in Detection of Tumor and in Assessing Vascular Invasion

Purpose: To compare the clinical utility of two series of dual-phase helical CT scans of the pancreas for tumor detectability and for the evaluation of vascular invasion. Materials and Methods: Two series of dual-phase helical CT scans of the pancreas were performed in 49 patients with pancreatic adenocarcinoma proven by pathology (n=21) and by clinical findings (n=28). The first series, in 24 patients, was obtained with a 45-sec (pancreatic phase) and an 80-sec delay (hepatic phase), and for the second series, in 25 patients, the corresponding delay times were 35 and 75 secs. A total of 120 ml non-ionic contrast media was injected of a speed of 3 ml/sec. Tumor conspicuity for each phase was assessed by measuring the attenuation number of the pancreatic mass and of normal pancreas. Enhancement of the celiac axis (CA), superior mesenteric artery (SMA), and superior mesenteric and portal veins was assessed by measuring the attenuation number of each phase. Results: A comparison of the first and second series revealed no statistically significant tumor conspicuity. Enhancement of the celiac axis and superior mesenteric artery was better on scans obtained at 35-sec/75-sec delay (CA 254 ; p

Cirrhotic liver enhancement on dual-phase helical CT: comparison with noncirrhotic livers in 146 patients.

The purpose of this study was to prospectively determine any differences in vascular and liver enhancement between patients with cirrhosis and patients without cirrhosis during both the arterial and portal venous phases on dual-phase helical CT. Fifty-eight patients with histologically proven cirrhosis (group 1) and 88 without cirrhosis (group 2 = normal findings on CT, group 3 = metastases, group 4 = other liver diseases) underwent dual-phase helical CT of the liver. Attenuation values of liver and vessels were measured on unenhanced scans and on scans obtained during the arterial and portal venous phases. The mean enhancement values per time interval (5 sec) were determined. Results were analyzed taking into account various intrinsic patient parameters. We found no statistically significant difference in terms of mean vascular enhancement and mean liver enhancement during the arterial imaging phase for each time interval among all the groups. The mean peak enhancement and mean liver enhancement during the portal venous phase were significantly lower in group 1 than in other groups. Time to peak enhancement was significantly delayed in group 1. In spite of the hepatic arterial buffer response, mean liver enhancement during the arterial phase was not significantly different in patients with cirrhosis compared with patients without cirrhosis. Although portal vein enhancement did not differ significantly, enhancement of cirrhotic liver was significantly lower during the portal venous phase and delayed, presumably because of decreased peripheral portal perfusion. The contrast injection protocol may be tailored to optimize conspicuity of hypovascular tumor.

Hepatic abnormalities related to blood flow: evaluation with dual-phase helical CT.

B. I. Choi, J. W. Chung, Y. Itai, O. Matsui, J. K. Han, M. C. Han 1 Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine 28, Yongon-Dong, Chongno-Gu, Seoul, 110-744, Korea 2 Institute of Clinical Medicine University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305, Japan 3 Department of Radiology, Kanazawa University School of Medicine, 13-1 Takaramachi, Kanazawa 920, Japan

La Tomografia Computerizzata Del Carcinoma Pancreatico

Few pancreatic carcinomas (5-22%) are resectable at the time of diagnosis because this lesion is seldom diagnosed in an early stage. A considerable improvement in the rate of survival is described only for resectable tumors: it is extremely necessary to find an imaging technique for early diagnosis and for accurate staging of pancreatic carcinoma to discern operable from inoperable cancer. The sensitivity of CT in predicting that pancreatic carcinoma is unresectable has been described as approaching 100%. However the reverse is not true. More than one third of the tumors revealed with CT and interpreted as resectable cannot be excised. The major reason for errors with CT are failure to detected liver metastases, peritoneal implants, lymphnode involvement and encasement of the great vessels by tumor. Significant progress has recently been made to improve the detection of these details with the recent introduction of helical CT with infusion of a bolus of contrast material and thin section collimation. Traditionally, when a single sequence of images was acquired during abdominal CT, the time of the acquisition was dominated by the requirement to scan during maximal hepatic enhancement, which unfortunately may not be optimal for evaluation of the pancreas. With the advent of helical CT, the acquisition of two sets of images after infusion of contrast material is now possible; the first one takes place during the arterial enhancement; it is useful to detect tumor vascular encasement and the maximum difference of tissue attenuation between normal greater pancreatic enhancement and hypo-dense pancreatic mass, less vascularizated. It appears that the peak parenchymal enhancement achieved with helical CT may improve the sensitivity of CT scanning in detecting pancreatic carcinoma, especially small tumors confined within the organ. The second phase takes place during the venous or portal enhancement and provides useful information about venous encasement and hepatic metastasis. Extraglandular extension with invasion of adjacent major arterial (celiac axis or its branches, superior mesenteric artery) and venous (portal, splenic, superior mesenteric) appear as soft-tissue attenuation thickening obscuring the perivascular fat, with deformity, thrombosis or occlusion of the vessels. In cases of venous occlusion, collateral vein can be identified. Dilatation of the small veins that surround the head of the pancreas might be used as an additional criterion of extrapancreatic extension of neoplasia. With the features of spiral CT (contrast material optimization and continuous scanning), the detection of small lesions in the liver and peritoneal implants has been increased. Helical CT seems not to detect anything else about lymph-node involvement than conventional CT, limited by the same morphologic criteria. The only CT means of detection of node involvement by pancreatic carcinoma is the pathologic enlargement of lymph nodes without specificity for neoplastic or not neoplastic ones. In many cases 2D, 3D and MIP imaging are helpful to evaluate vasculature encasement, especially for visualization of vessels which lie in oblique, coronal or sagittal plane. Consequently helical CT has the potential to become an alternative angiographic technique. Many studies have been done to evaluate spiral CT potential impact and to compare the value of this technique with other ones in the initial diagnosis and staging of pancreatic carcinoma. One of these studies compares dual-phase helical CT and endoscopic endo-sonography. The Authors observe that the two techniques do not differ significant statistically in detecting pancreatic carcinoma, except endoscopic sonography is more sensitive than helical CT for tumors smaller than 15-20 mm. They found the accuracy to predict unresectable carcinoma is 100% for dual-phase helical CT and less for endoscopic endo-sonography (86%). They also affirm that the accuracy for predicting resectability is 90%, similar for endoscopic sonography, but greater than conventional CT whose major limitation is to underestimate the extent of disease.