Dynamic computed tomography of hepatocellular carcinoma

Nineteen patients with clinically proven hepatocellular carcinoma were studied by dynamic computed tomographic (CT) scanning. Ten consecutive 3 sec scans were performed within 30 sec, providing uninterrupted data collection. Dynamic CT scanning was useful in recognizing tumor vascularity, multiple small tumors, isodense tumors on conventional CT scans, the capsule of an encapsulated hepatocellular carcinoma, arteriovenous shunts, and vascular pools. Time-density curves were useful in evaluating the hemodynamics of the tumors; these could be classified into three types according to differences in their enhancement patterns.     

Quantitative single-photon emission tomography for tumour blood flow measurement in bronchial carcinoma

A single-photon emission tomography (SPET) technique for the absolute measurement of tumour perfusion is described. Phantom studies have shown that source-background ratios are dependent upon source size and radial position within the phantom. A means of correcting source-background count ratios for these variables has been developed and used to correct tumour-lung ratios obtained in 28 patients with bronchial carcinomas who underwent technetium-99m hexamethyl-propylene amine oxime (^99mTc-HMPAO) SPET. On SPET images, the normal lung appears as a relatively homogeneous background. The relationship between ^99mTc background concentration (kBq/ml) and counts/pixel was determined from phantom studies and the tumour ^99mTc concentration from the background ^99mTc concentration and corrected tumour-lung ratio. The total activity of the lipophilic ^99mTc-HMPAO species injected was measured. The activity reaching the systemic circulation (A _sys) was obtained by subtracting the activity trapped in the pulmonary circulation (obtained from background ^99mTc concentration and lung volume). Tumour blood flow may then be calculated from fraction of A _sys contained in the tumour provided cardiac output and extraction fraction are known. Blood flow through the central region of tumours ranged from zero to 59.0 (mean 14.1) ml min^–1 100 g^–1 and through the whole tumour from 0.6 to 68.0 (mean 20.6) ml min^–1 100 g^–1.     

Evaluation of arterial embolization therapy for hepatocellular carcinoma by computed tomography

Changes in tumor area and the attenuation value determined from computed tomography (CT) slice section of the tumor at its maximum size were investigated in 18 patients with hepatocellular carcinoma who were studied by CT after arterial embolization therapy. The tumor area was reduced in all cases after embolization therapy. Greater than 50% reduction of the tumor area occurred during the follow-up period in 13 cases (87%). In cases evaluated by follow-up CT, the relative attenuation value of tumor to nontumor regions decreased during the initial stage after embolization therapy, but showed a tendency towards greater elevation than in the initial stage, despite tumor reduction. This change in the attenuation value was considered to reflect necrosis and shrinkage of the tumor after embolization therapy. The absence of such changes in nontumor regions supports the use of arterial embolization therapy as an effective, conservative treatment for hepatocellular carcinoma. Follow-up examination by CT of hepatocellular carcinoma after embolization therapy contributes to the posttherapeutic evaluation of tumors and to the determination of the appropriate time for reembolization therapy.     

Efficacy of cone-beam computed tomography during transcatheter arterial chemoembolization for hepatocellular carcinoma

Cone-beam computed tomography (CBCT) using a flat-panel detector is an alternative method of obtaining cross-sectional images. This technique is now being used during transcatheter arterial chemoembolization (TACE) for inoperable hepatocellular carcinoma (HCC). Several CBCT techniques are performed to detect HCC lesions: CBCT during portography (CBCTAP), CBCT during hepatic arteriography (CBCTHA), CBCT after iodized oil injection (LipCBCT), CBCT during arteriography (CBCTA) of extrahepatic collaterals. Almost all HCC lesions can be detected using these CBCT images. Three-dimensional arteriography using maximum intensity projection from CBCTHA images can identify the tumor-feeding branch. In particular, this technique is useful when the tumor stain cannot be demonstrated on arteriography. In addition, dual-phase CBCTHA can improve the diagnostic accuracy for hypervascular HCCs because corona enhancement can be detected around the tumor. To monitor the embolized area during TACE, selective CBCTHA or LipCBCT at the embolization point is useful. Two sequential CBCT scans without and with contrast material injection is also useful to confirm each embolized area of two vessels. Furthermore, CBCTA can prevent nontarget embolization. Although the image quality of CBCT is low compared to that of conventional CT, CBCT provides useful information that helps perform TACE for HCCs safely and effectively.     

Imaging well-differentiated hepatocellular carcinoma with dynamic triple-phase helical computed tomography

To investigate the imaging appearance of well-differentiated hepatocellular carcinoma (HCC) on dynamic CT, a total of 38 histopathologically proven well-differentiated HCC were included in a retrospective study. We reviewed the contrast-enhanced dynamic CT of all 38 tumours for attenuation of each tumour in unenhanced scan, arterial-dominant and delayed portal venous phases. Our results showed that dynamic CT identified 26 (68.4%) out of the 38 lesions. The remaining 12 lesions were isodense compared with surrounding liver parenchyma in each dynamic CT phase. There was no statistically significant difference between the mean size of tumours detected by dynamic CT and that of tumours not detected by dynamic CT (p = 0.1). Of a total of 38 tumours, most were isodense (n = 19) or hypodense (n = 16) in unenhanced scan, mostly hyperdense (n = 18) or isodense (n = 15) in arterial-dominant phase and mostly isodense (n = 22) or hypodense (n = 15) in delayed portal venous phase. Enhancement of tumour was observed in 19 (50.0%) of 38 lesions. In conclusion, the ability of dynamic CT to detect well-differentiated HCC is poor, and negative CT findings cannot exclude the presence of well-differentiated HCC, especially if there is well-grounded clinical suspicion for HCC.     

Detection of hepatocellular carcinoma: comparison of dynamic three-phase computed tomography images and four-phase computed tomography images using multidetector row helical computed tomography

PURPOSE: The purpose of our study was to assess the value of additional early arterial phase computed tomography (CT) imaging in the detection of hepatocellular carcinoma (HCC) by comparing three-phase and four-phase imaging by using multidetector row helical CT. METHODS: Twenty-five patients with 33 HCCs underwent four-phase helical CT imaging. The diagnosis was established by pathologic examination after surgical resection in 19 patients and by biopsy in six. Four-phase CT imaging comprises early arterial, late arterial, portal venous, and delayed phase imaging obtained 25 seconds, 45 seconds, 75 seconds, and 180 seconds after the start of contrast material injection using multidetector row helical CT. Three-phase CT images (late arterial, portal venous, and delayed phase) and four-phase CT images (early arterial, late arterial, portal venous, and delayed phase) were interpreted independently for the detection of HCC by three blinded observers on a segment-by-segment basis. Sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve (Az) for three-phase CT images and four-phase CT images were calculated. The enhancement pattern of HCC was analyzed on early arterial and late arterial phase imaging. RESULTS: The mean sensitivity of three- and four-phase CT images was 94% and 93%, respectively. The differences between sensitivities were not statistically significant (all p > 0.05). The mean specificities of three- and four-phase CT images were 99% and 98%, respectively. The differences between the specificities were not statistically significantly (all p > 0.05). Neither were the mean areas under the ROC curve for four-phase CT images (Az = 0.976) and three-phase CT images (Az = 0.971) statistically significant (p > 0.05). On early arterial phase imaging, 16 HCCs were hyperattenuating and 17 HCCs were isoattenuating. On late arterial phase imaging, 24 HCCs were hyperattenuating and nine HCCs were isoattenuating. CONCLUSIONS: Additional early arterial phase imaging did not improve the detection of HCC compared with three-phase CT images, including late arterial, portal venous, and delayed phase imaging.     

Comparison of cerebral blood flow between perfusion computed tomography and xenon-enhanced computed tomography for normal subjects: territorial analysis

OBJECTIVE: The purpose of this study was to clarify the difference between cerebral blood flow (CBF) by perfusion computed tomography (CT) and that by xenon-enhanced CT (Xe-CT) through simultaneous measurement. METHODS: Xenon-enhanced CT and perfusion CT were continually performed on 7 normal subjects. Ratios of CBF by perfusion CT (P-CBF) to CBF by Xe-CT (Xe-CBF) were measured for 5 arterial territories; 3 were territories of 3 major arteries (the anterior [ACA], middle [MCA], and posterior [PCA] cerebral arteries), and the other 2 were areas of the thalamus and putamen. RESULTS: The ratios were 1.30 +/- 0.10, 1.26 +/- 0.15, 1.61 +/- 0.15, 0.801 +/- 0.087, and 0.798 +/- 0.080 for the ACA, MCA, PCA, thalamus, and putamen, respectively. Although a good correlation was observed between P-CBF and Xe-CBF for each territory, the ratios were significantly different (P < 0.0001) between 3 territory groups (group 1: ACA and MCA, group 2: PCA, and group 3: thalamus and putamen). CONCLUSIONS: The difference in the ratio of P-CBF to Xe-CBF between the 3 territory groups was considered to result principally from the features of P-CBF. To evaluate P-CBF properly, its territorial characteristics should be taken into account.     

Contrast-enhanced computed tomography and ultrasound for the evaluation of tumor blood flow

OBJECTIVE: We evaluated implanted rat mammary adenocarcinoma tumors during a 5-week period using ultrasound, computed tomography (CT), and histology. MATERIALS AND METHODS: Contrast-enhanced ultrasound with a destruction-replenishment imaging scheme was used to derive estimates of blood volume and flow. These ultrasound-derived measures of microvascular physiology were compared with contrast-enhanced CT-derived measures of perfusion and vascular volume made by the Mullani-Gould formula and Patlak analysis, respectively. RESULTS: The tumor cross-sectional area and necrotic core cross-sectional area determined by the 3 methods were correlated (r>0.8, P<0.001, n=15). The spatial integral of perfusion estimated by CT correlated with the spatial integral of flow from ultrasound (P<0.05). The contrast-enhanced tumor area calculated from the ultrasound analysis was highly correlated with the contrast-enhanced area estimated by CT images (r=0.89, P<0.001, n=15). However, the fraction of the tumor area enhanced by the CT contrast agent was significantly larger than either the fraction enhanced by ultrasound contrast agent or than the viable area as estimated from histology slides. CONCLUSION: Destruction-replenishment ultrasound provides valuable information about the spatial distribution of blood flow and vascular volume in tumors and ultrasound analysis compares favorably with a validated contrast-enhanced CT method.     

Flat panel computed tomography for non-invasive flow measurement: initial results in in-vitro studies

The purpose was to evaluate the feasibility of flat panel computed tomography (FPCT) for quantifying flow by analyzing contrast changes along the z-axis in an in-vitro setting. Contrast material was injected in a 3-mm silicone tube at flow rates of 0.1, 0.2, 0.5 and 1.0 ml/s using a commercially available injector pump. FPCT scans of this phantom were performed with a gantry rotation time of 3 s. From this data 41 phases were reconstructed at different points in time using a full and a partial gantry rotation. The differences in the contrast material arrival time and the contrast enhancement along the z-axis were recorded. Flow was calculated from this data and compared to the injector settings. There was a good agreement between the injector settings and the calculated flow rates, but agreement decreased with increasing flow rates. Absolute (percent) mean deviation between the injector settings and calculated flow values was 0.0230 ± 0.0489ml/s (3.7243 ± 4.7817%) using the full gantry rotation. Repeated-measurement ANOVA failed to show significant differences between the various techniques (p = 0.9726). FPCT allows for computing flow. While preliminary results indicate a good agreement at low flow rates, further studies are needed to assess this technique for higher flow rates.     

Three-dimensional perfusion imaging of hepatocellular carcinoma using 256-slice multidetector-row computed tomography

Purpose  The aim of this study was to evaluate the clinical capability of three-dimensional (3D) perfusion imaging of hepatocellular carcinoma (HCC) by performing dynamic scanning using a 256-slice multidetector-row CT (MDCT) scanner. Materials and methods  Two patients with HCC were examined in this study. They were scheduled to undergo transcatheter arterial infusion therapy using an arterial infusion reservoir system. The CT system used was a newly developed prototype scanner of 256-slice MDCT. Dynamic CT scanning was performed with intraarterial injection via the reservoir route, and perfusion analysis was done based on the 3D data. Results  The blood flow volume per unit volume in the tumors was significantly increased compared with that in normal hepatic parenchyma. Using a 3D workstation, 3D perfusion images could be displayed by fusing CT images with perfusion images about blood flow volume. Conclusion  Three-dimensional perfusion images, which enable 3D evaluation of perfusion in HCCs, can be generated using 256-slice MDCT.     

Evaluation of the vascular pattern of hepatocellular carcinoma with dynamic computed tomography and its use in identifying optimal temporal windows for helical computed tomography

The aim of this work was to study the vascularization of hepatocellular carcinoma (HCC) by means of dynamic CT and to demonstrate the existence of optimal temporal windows for visualization of HCC in order to develop new protocols for helical CT of the liver. We studied, by means of dynamic CT, 42 histologically proved HCCs in 30 patients after injecting contrast medium (100 ml, 3 ml/s). We performed a time–density analysis of the aorta, liver, portal vein, spleen and lesion. We identified three temporal curves of attenuation of the neoplastic tissue. Curve 1 was three-phasic: hyperattenuation, isoattenuation and hypoattenuation; curve 2 was two-phasic: hyperattenuation and isoattenuation; curve 3 was two-phasic: isoattenuation and hypoattenuation. Thirty-two lesions were homogeneous (curve 1 in 22 cases, 68.7 %; curve 2 in 7 cases, 21.8 %; curve 3 in 3 cases, 9.4 %), whereas 10 lesions were non-homogeneous. Two optimal temporal windows were identified: the first, with predominantly hyperattenuating lesions (range 29–65 s, 90.4 % sensitivity); the second, with predominantly hypoattenuating lesions (range 132.1–360 s, 76.1 %). There is an interposed time range of reduced visualization (range 62–127 s, 54.7 %) in which lesions are isoattenuating. Combined CT study during the first and second temporal windows improves the detection of HCCs especially for homogeneous and small lesions. The intermediate isoattenuation time range does not increase lesion detection rate. Received: 22 March 1996; Revision received 3 September 1996; Accepted 21 March 1997     

"Scar sign" on computed tomography and sonography in fibrolamellar hepatocellular carcinoma

Demonstration by computed tomography of a central linear or stellate low-attenuation region within a focal liver mass has been reported to be suggestive of focal nodular hyperplasia in appropriate clinical settings. We present a case of a focal liver mass with typical central scarring in which the ultimate diagnosis was fibrolamellar hepatocellular carcinoma.     

Dual input computed tomography perfusion in evaluating the therapeutic response of transarterial chemoembolization for hepatocellular carcinoma

Objective

To assess diagnostic role of multi-detector computed tomographic perfusion in evaluating the therapeutic response of trans-arterial chemo-embolization in hepatocellular carcinoma.

Radiological assessment of hepatic vein invasion by hepatocellular carcinoma using combined computed tomography hepatic arteriography and computed tomography arterial portography

Purpose

The aim of this study was to elucidate computed tomography hepatic arteriography (CTHA) and CT arterial portography (CTAP) findings characteristic of hepatocellular carcinoma (HCC) with large hepatic venous invasion (HVI) and then to examine whether the presence of minute HVI can be diagnosed based on each finding.

Materials and methods

Combined CTHA and CTAP of 106 HCCs were examined. Two radiologists analyzed the radiological findings of five nodules with large HVI (group vv2). The remaining 101 nodules were classified into two groups: group vv1, positive minute HVI; group vv0, negative HVI. They examined whether each finding observed in group vv2 could be detected in groups vv1 and vv0.

Results

Analysis of group vv2 identified (a) tumor thrombus, (b) early inflow of the contrast into the hepatic vein proximal to the invaded site, and (c) partially decreased portal venous flow in the peripheral parenchyma subject to the involved hepatic vein. Findings (b) and (c) were observed in 16% of group vv1. A significant difference in frequency of finding (c) was obtained between groups vv1 and vv0. The positive and negative predictive values of finding (c) were 66.7% and 77.9%, respectively.

Conclusion

Findings (b) and (c), especially the latter, may partly contribute to the radiological diagnosis of minute HVI.