Preoperative segmental localization of hepatic metastases: utility of three-dimensional CT during arterial portography

Accuracy of CT Arterial Portography of the Liver Compared with Findings at Laparotomy

To evaluate the accuracy of CT arterial portography (CTAP) of the liver, CTAP examinations from 111 patients were retrospectively reviewed and compared with the findings at laparotomy. Laparotomy had been performed within 3 weeks after the CTAP examination. In cases of resectable liver tumor, the result from the pathologic examination report was used to calculate the accuracy of CTAP. In cases of nonresectable liver tumor or liver without tumor, CTAP findings were compared with the result of a thorough inspection and palpation of the liver. The right liver lobe and the medial and lateral segments of the left lobe were separately evaluated. Thus, a total of 333 lobes/segments were evaluated. Tumor was found at laparotomy in 80 of 333 lobes or segments. At CTAP a total of 94 lobes were evaluated as positive for tumor growth, 23 of these were falsely interpreted as positive and 9 were falsely interpreted as negative when compared with the findings at laparotomy. However, 3 patients called false-positives later turned out to be true-positives since the lesions were overlooked at operation. A sensitivity of 89%, a specificity of 91%, and an accuracy of 90% was calculated for CTAP. It is concluded that CTAP has a higher accuracy than other radiologic methods and should be considered suitable for preoperative evaluation of potentially resectable liver tumor.

Patient specific anatomy: the new area of anatomy based on computer science illustrated on liver

BACKGROUND

Over the past century, medical imaging has brought a new revolution: internal anatomy of a patient could be seen without any invasive technique. This revolution has highlighted the two main limits of current anatomy: the anatomical description is physician dependent, and the average anatomy is more and more frequently insufficient to describe anatomical variations. These drawbacks can sometimes be so important that they create mistakes but they can be overcome through the use of 3D patient-specific surgical anatomy.

METHODS

In this article, we propose to illustrate such improvement of standard anatomy on liver. We first propose a general scheme allowing to easily compare the four main liver anatomical descriptions by Takasaki, Goldsmith and Woodburne, Bismuth and Couinaud. From this general scheme we propose four rules to apply in order to correct these initial anatomical definitions. Application of these rules allows to correct usual vascular topological mistakes of standard anatomy. We finally validate such correction on a database of 20 clinical cases compared to the 111 clinical cases of a Couinaud article.

RESULTS

Out of the 20 images of the database, we note a revealing difference in 14 cases (70%) on at least one important branch of the portal network. Only six cases (30%) do not present a revealing difference between both labellings. We also show that the right portal fissure location on our 20 cases defined between segment V and VI of our anatomical definition is well correlated with the real position described by Couinaud on 111 cases, knowing that the theoretical position was only found in 46 cases out of 111, i.e., 41.44% of cases with the non-corrected Couinaud definition.

CONCLUSIONS

We have proposed a new anatomical segmentation of the liver based on four main rules to apply in order to correct topological errors of the four main standard segmentations. Our validation clearly illustrates that this new definition corrects the large amount of mistakes created by the current standard definitions, increased by physician interpretation that can vary from one case to another.

Computed tomography: revolutionizing the practice of medicine for 40 years

Computed tomography (CT) has had a profound effect on the practice of medicine. Both the spectrum of clinical applications and the role that CT has played in enhancing the depth of our understanding of disease have been profound. Although almost 90 000 articles on CT have been published in peer-reviewed journals over the past 40 years, fewer than 5% of these have been published in Radiology. Nevertheless, these almost 4000 articles have provided a basis for many important medical advances. By enabling a deepened understanding of anatomy, physiology, and pathology, CT has facilitated key advances in the detection and management of disease. This article celebrates this breadth of scientific discovery and development by examining the impact that CT has had on the diagnosis, characterization, and management of a sampling of major health challenges, including stroke, vascular diseases, cancer, trauma, acute abdominal pain, and diffuse lung diseases, as related to key technical advances in CT and manifested in Radiology.

Horizontal liver cleft: a rare anatomic variant

BACKGROUND

Improvements in hepatobiliary surgical techniques, with increased usage of segmental and subsegmental resection, make accurate preoperative radiological assessment delineation of the liver segments ever more crucial. Conventionally, this is done by drawing imaginary straight planes along the portal and hepatic veins. We herein report a rare case of a horizontal cleft between the superior and inferior liver segments seen on CT.

CASE REPORT

A 74-year-old female patient with a known medical history of ovarian cancer with peritoneal metastasis and retroperitoneal lymphadenopathy was referred to our department for CT to assess disease response after treatment. On contrast-enhanced CT, apart from the ovarian cancer, the liver had a smooth, well-defined horizontally orientated cleft that broadly divided the organ into 2 halves. The cleft contained the right and left main portal veins, and consequently had a curved down-sloping configuration accommodating the curved course of these veins. This liver cleft was present from an earlier CT study performed 3 years ago, and there was no history of preceding liver surgery.

CONCLUSIONS

To the best of our knowledge, this is the first report of the anomaly of a horizontal liver cleft, which may be attributed to early cessation of the embryological formation of the liver. This liver cleft also illustrates the difficulties in liver segmentation using Couinaud's classification.

Liver segmentation: practical tips

The liver segmentation system, described by Couinaud, is based on the identification of the three hepatic veins and the plane passing by the portal vein bifurcation. Nowadays, Couinaud's description is the most widely used classification since it is better suited for surgery and more accurate for the localisation and monitoring of intra-parenchymal lesions. Knowledge of the anatomy of the portal and venous system is therefore essential, as is knowledge of the variants resulting from changes occurring during the embryological development of the vitelline and umbilical veins. In this paper, the authors propose a straightforward systematisation of the liver in six steps using several additional anatomical points of reference. These points of reference are simple and quickly identifiable in any radiological examination with section imaging, in order to avoid any mistakes in daily practice. In fact, accurate description impacts on many diagnostic and therapeutic applications in interventional radiology and surgery. This description will allow better preparation for biopsy, portal vein embolisation, transjugular intrahepatic portosystemic shunt, tumour resection or partial hepatectomy for transplantation. Such advance planning will reduce intra- and postoperative difficulties and complications.

Three-dimensional images of liver tumours reconstructed by Gd-EOB-DTPA-enhanced MRI

The purpose of this study was to evaluate three-dimensional images of liver tumours obtained with gadolinium ethoxybenzyl diethylenetriamine penta-acetic acid (Gd-EOB-DTPA)-enhanced MRI (3D-EOB-MRI) in hepatic surgery. We conclude that 3D-EOB-MRI may be an alternative method for depicting liver tumours adjacent to the hepatic veins and portal branches, and may provide additional information for surgical planning.

Recent advances in liver imaging

Liver surgery remains a difficult challenge in which preoperative data analysis and strategy definition may play a significant role in the success of the procedure. Medical image processing led to a major improvement of patient care by guiding the surgical gesture. From this initial data, new technologies of virtual reality and augmented reality can increase the potential of such images. The 3D modeling of the liver of patients from their CT scan or MRI thus allows an improved surgical planning. Simulation allows the procedure to be simulated preoperatively and offers the opportunity to train the surgical gesture before carrying it out. These three preoperative steps can be used intraoperatively thanks to the development of augmented reality, which consists of superimposing the preoperative 3D modeling of the patient onto the real intraoperative view of the patient and his/her organs. Augmented reality provides surgeons with a transparent view of the patient. This facilitated the intraoperative identification of the vascular anatomy and the control of the segmental arteries and veins in liver surgery, thus preventing intraoperative bleeding. It can also offer guidance due to the virtual improvement of their real surgical tools, which are tracked in real-time during the procedure. During the surgical procedure, augmented reality, therefore, offers surgeons a transparent view of their patient, which will lead to the automation of the most complex maneuvers. The new ways of processing and analyzing liver images have dramatically changed the approach to liver surgery.

Predicting liver failure following major hepatectomy

Pre-operative determination of the risk of liver dysfunction has come under criticism with regards to its usefulness in clinical practice. Opinion is split between centres which use such tests uniformly on all patients and those where clinical judgment alone is used. Published data would not suggest any difference in mortality, morbidity or liver failure rates between these groups. This review outlines and presents the evidence for pre-operative quantification of functional liver remnant volume.

Detection of hepatocellular carcinoma in patients with cirrhosis: added value of coronal reformations from isotropic voxels with 64-MDCT

OBJECTIVE

The purpose of our study was to prospectively assess the added value of isotropic coronal reformations of the liver when using 64-MDCT for the detection of hepatocellular carcinoma (HCC).

SUBJECTS AND METHODS

Seventy-one consecutive patients (60 men, 11 women; mean age, 65 years) suspected of having HCC underwent 64-MDCT with coronal reformations. A multiphasic CT protocol that included unenhanced, hepatic arterial, portal venous, and equilibrium phases was performed. Three independent, blinded readers interpreted the transverse scan alone, the coronal scan alone, and the combined transverse and coronal scans for the presence of HCC. Sensitivity, positive predictive value, area under the receiver operating characteristic curve (A(z)), and interpretation time were calculated for each reading session.

RESULTS

Seventy-six HCC nodules were confirmed in 48 patients using histopathologic analysis or follow-up with long-term CT, MRI, or both (mean follow-up time, 12 months; range, 12-15 months) as the reference standard. Mean sensitivity, positive predictive value, and A(z) value for HCC detection were, respectively, 84% (191/228 readings), 91% (191/210 readings), and 0.85 for the transverse scan alone; 83% (189/228 readings), 93% (189/203 readings), and 0.86 for the coronal scan alone; and 87% (198/228 readings), 93% (198/213 readings), and 0.87 for combined interpretation of transverse and coronal scans. No comparisons were statistically significant. Forty-eight false-positive interpretations were recorded (19 for the transverse, 14 for the coronal, and 15 for the combined interpretation sets). The reading session in which combined transverse and coronal scans were available for interpretation showed significantly superior reader confidence for HCC detection as well as longer interpretation times (p<0.05 for both comparisons). The average reading time for the combined interpretation of transverse and coronal image sets (mean, 12.1+/-0.8 minutes) was significantly longer than for the transverse image set (7.4+/-1.5 minutes) or the coronal image set (7.1+/-1.3 minutes) (p<0.01).

CONCLUSION

With 64-MDCT, the addition of isotropic coronal reformations to transverse images significantly improved reader confidence for the detection of HCC, with no statistically significant improvement in sensitivity, positive predictive value, or diagnostic accuracy (as determined by the A(z) value). This improvement comes at the cost of a longer interpretation time.

A new and simple practical plane dividing hepatic segment 2 and 3 of the liver: evaluation of its validity

Objective

The conventional method of dividing hepatic segment 2 (S2) and 3 (S3) is subjective and CT interpretation is unclear. The purpose of our study was to test the validity of our hypothesis that the actual plane dividing S2 and S3 is a vertical plane of equal distance from the S2 and S3 portal veins in clinical situations.

Materials and Methods

We prospectively performed thin-section iodized-oil CT immediately after segmental chemoembolization of S2 or S3 in 27 consecutive patients and measured the angle of intersegmental plane on sagittal multiplanar reformation (MPR) images to verify its vertical nature. Our hypothetical plane dividing S2 and S3 is vertical and equidistant from the S2 and S3 portal veins (vertical method). To clinically validate this, we retrospectively collected 102 patients with small solitary hepatocellular carcinomas (HCC) on S2 or S3 the segmental location of which was confirmed angiographically. Two reviewers predicted the segmental location of each tumor at CT using the vertical method independently in blind trials. The agreement between CT interpretation and angiographic results was analyzed with Kappa values. We also compared the vertical method with the horizontal one.

Results

In MPR images, the average angle of the intersegmental plane was slanted 15 degrees anteriorly from the vertical plane. In predicting the segmental location of small HCC with the vertical method, the Kappa value between CT interpretation and angiographic result was 0.838 for reviewer 1 and 0.756 for reviewer 2. Inter-observer agreement was 0.918. The vertical method was superior to the horizontal method for localization of HCC in the left lobe (p < 0.0001 for reviewers 1 and 2).

Conclusion

The proposed vertical plane equidistant from S2 and S3 portal vein is simple to use and useful for dividing S2 and S3 of the liver.

Impact of preoperative planning using virtual segmental volumetry on liver resection for hepatocellular carcinoma

BACKGROUND

Accurate assessment of resection volume and vascular anatomy is mandatory in preoperative planning for safe and curative hepatectomy to treat cancer. Accordingly, we examined feasibility and accuracy of a preoperative three-dimensional (3D) computed tomography (CT) scan based simulation in patients with impaired liver function undergoing hepatectomy for hepatocellular carcinoma (HCC).

METHODS

Hepatectomy simulation software was programmed to reconstruct detailed 3D vascular structure and calculate liver volume based on hepatic circulation. In 113 patients with HCC, liver resection volume was estimated preoperatively by both simulation and conventional planimetry. For validation, predicted resection volumes were compared with actual resected specimen weights. The resection margin as estimated by the simulation was compared with the margin in the specimen.

RESULTS

Simulation showed higher correlation and smaller discrepancy (r = 0.96; 9.3 ml) between predicted and actual liver resection volume than conventional planimetry (r = 0.74; 174 ml). Simulation showed correlation (p < 0.01) between estimated and actual segmental volume, which was not measurable by planimetry. Simulation showed a correlation (r = 0.84) between predicted and actual margin, with a difference of 1.6 mm.

CONCLUSIONS

Hepatectomy simulation in 3D predicted segmental liver volume and the resection margin accurately. This virtual method should contribute to preoperative planning to achieve safe, curative resection in HCC patients, whose hepatic function is compromised.

Dual-phase 3D MDCT angiography for evaluation of the liver before hepatic resection

OBJECTIVE

We sought to evaluate the accuracy of dual-phase MDCT angiography for assessing the liver before hepatic resection and to compare 2D and 3D images for quality and arterial branch visualization.

MATERIALS AND METHODS

Sixty-three patients with colorectal metastases (n = 30), hepatocellular carcinomas (n = 13), giant hemangiomas (n = 5), and other lesions (n = 15) underwent dual-phase MDCT using either a LightSpeed QX/i 4-MDCT (n = 31) or LightSpeed QX/i Ultra 8-MDCT (n = 32) scanner. Contrast material (150 mL of Isovue 370 [iopamidol]) was injected at a rate of 5 mL/sec. The arterial phase images were rendered on a workstation to obtain 3D MDCT angiograms that were assessed by two reviewers who were blinded to the surgical findings. Arterial anatomy was categorized according to the Michels classification. The reviewers assessed the 2D and 3D images for quality, arterial branch visualization, and differences between the 4- and 8-MDCT images. In the 43 patients who underwent resection, imaging findings were correlated with intraoperative findings.

RESULTS

The anatomy of hepatic arteries in the 63 patients was classified as follows: Michels type I, 51 patients (80.9%); type III, four patients (6.3%); type V, five patients (7.9%); and types VII, VIII, and IX, one patient (1.6%) each. In 40 (93%) of 43 patients, the surgical findings concurred with MDCT findings. Three discrepancies were due to failure to identify small accessory left hepatic arteries. Branch visualization and image quality of the 2D images were superior to those of the 3D images. No significant difference was found between the 4- and 8-MDCT images in branch visualization and image quality.

CONCLUSION

Three-dimensional MDCT angiography is accurate for classification of hepatic arterial anatomy before hepatic resection. Although 2D data sets show small arteries to better advantage than 3D MDCT angiograms, the 3D MDCT angiograms provide a useful overview of hepatic anatomy.

Relation between hepatic and portal veins in the right paramedian sector: proposal for anatomical reclassification of the liver

Although a right liver graft without a middle hepatic vein resulted in potential venous congestion in the right paramedian sector, the details of the hepatic venous distribution in the right paramedian sector have not been established. In this study, the ramification patterns of the hepatic veins draining the right anterosuperior segment (S8) and the relation between the hepatic and portal veins were assessed using multislice computed tomography in 44 patients without lesions in the liver. All 52 drainage veins of the ventral area of S8 joined the middle hepatic vein, and all 48 drainage veins of the dorsal area joined the right hepatic vein. The hepatic vein crossing between the ventral and dorsal areas was observed in each patient examined. Therefore, we propose a reclassification wherein the right paramedian sector is divided into ventral and dorsal segments. This new classification may contribute to the development of new and safer surgical procedures, including more limited resection and right lobe adult living donor liver transplantation to avoid graft congestion.

Limitations and pitfalls of Couinaud's segmentation of the liver in transaxial Imaging

The segmental anatomy of the human liver has become a matter of increasing interest to the radiologist, especially in view of the need for an accurate preoperative localization of focal hepatic lesions. In this review article first an overview of the different classical concepts for delineating segmental and subsegmental anatomy on US, transaxial CT, and MR images is given. Essentially, these procedures are based on Couinaud's concept of three vertical planes that divide the liver into four segments and of a transverse scissura that further subdivides the segments into two subsegments each. In a second part, the limitations of these methods are delineated and discussed with the conclusion that if exact preoperative localization of hepatic lesions is needed, tumor must be located relative to the avascular planes between the different portal territories.

Multiplanar reformat display technique in abdominal multidetector row CT imaging

The purpose of this study was to evaluate the image quality and diagnostic value of multiplanar reformat (MPR) of abdominal CT performed with multidetector row spiral technique (MDCT). Forty-five patients were referred for an abdominal MDCT angiography. No significant differences in image quality and in the number of lesions detected were found between axial and MPR images (t-test, P>.90 and chi-square, P>.95). Additional diagnostic value to axial images could be obtained with MPR display.

Intrahepatic portal venous variations: demonstration by helical CT during arterial portography

PURPOSE

We assessed the prevalence and types of intrahepatic portal venous variations by helical computed tomography performed with arterial portography (CTAP).

METHODS

In 192 patients without evidence of vascular invasion or distortion, CTAP images were reviewed retrospectively to identify portal venous variations.

RESULTS

Of the 192 patients examined, 10 (5.2%) had trifurcation, 5 (2.6%) had a right posterior segmental branch arising from the main portal vein, 5 (2.6%) had an absence of the horizontal segment of the left portal vein, and 1 (0.5%) had an absence of the left lateral segmental portal branch. Of the patients without a horizontal segment, two had a right-sided ligamentum teres associated with malposition of the gallbladder, while another had complete ramification of intrahepatic portal branches from an umbilical vein-like segment. In the patient missing the left lateral segmental branches, the right portal vein segments were subcapsularly located.

CONCLUSION

Variations of the intrahepatic portal veins can be recognized on CTAP imaging. tomography-Portal vein, computed tomography.

Hepatic MR imaging with a dynamic contrast-enhanced isotropic volumetric interpolated breath-hold examination: feasibility, reproducibility, and technical quality

PURPOSE

To evaluate the feasibility, reproducibility, and technical quality of a dynamic contrast material-enhanced isotropic three-dimensional (3D) volumetric interpolated breath-hold hepatic magnetic resonance (MR) imaging examination.

MATERIALS AND METHODS

Fifty patients underwent 3D spoiled gradient-echo imaging (4.2/1.8 [repetition time msec/echo time msec]; flip angle, 12 degrees; interpolation in three directions; intermittent fat saturation; pixel size </= 2.5 mm in all dimensions) before and dynamically after administration of gadopentetate dimeglumine, with the first enhanced acquisition timed for hepatic arterial dominance by using a test bolus of contrast material. Qualitative and quantitative measures of image quality were determined. Patterns of arterial and venous anatomy were assessed. Ten patients (20%) underwent repeat imaging within 6 months, and reproducibility was evaluated.

RESULTS

Hepatic contrast-to-noise ratios for nonenhanced and arterial, portal venous, and equilibrium phase studies averaged 13.0 +/- 12.6 (SD), 17.4 +/- 11.8, 30.4 +/- 16.2, and 28.6 +/- 21.1, respectively. During arterial phase, the liver enhanced a mean of 29% of the maximal enhancement as measured during portal venous phase. Hepatic vascular anatomic variants were comparable in distribution to those cited in published articles. Repeat studies were not significantly different in image quality when compared with original studies.

CONCLUSION

High-quality arterial phase 3D volumetric interpolated breath-hold images can be obtained reliably and reproducibly when timed by using a test dose of contrast material.

Anatomy of the right anterosuperior area (segment 8) of the liver: evaluation with helical CT during arterial portography

PURPOSE

To evaluate the segmental anatomy of the right anterosuperior area (segment 8) of the liver by using helical computed tomography during arterial portography (CTAP).

MATERIALS AND METHODS

Twenty-seven patients without lesions at segment 8 underwent helical CTAP. Three-dimensional portograms were reconstructed to verify the course of the portal veins. The number of subsegmental branches, in addition to the branching point and the distribution in segment 8, was assessed.

RESULTS

In 25 (93%) patients, the dorsal branch of segment 8 gave rise to dorsally directed branches posterior to the right hepatic vein. In only four (25%) of 16 patients in whom the medial branch of segment 8 arose near the porta hepatis, the long paracaval portal branch of the caudate lobe extended upward above the interval between the middle and right hepatic veins.

CONCLUSION

In most of the patients, the dorsal branches of segment 8 supplied the dorsocranial area of the right lobe posterior to the right hepatic vein. The paracaval portion of the caudate lobe was limited to below the interval between the middle and right hepatic veins in the majority of patients who showed medial branches of segment 8 arising near the porta hepatis. Recognition of this vascular anatomy is clinically important for preoperative evaluation of hepatic tumors in segment 8 because it may contribute to a safer surgical approach.

Computed tomography scan of the liver

Computed tomography (CT) examination of the liver has continually been improving our understanding and assessment of liver disease since its introduction into clinical practice. The hallmark of the advances in CT imaging has undoubtably been helical CT, which made a great impact on body imaging with its many advantages, the most important being optimization of multiphasic enhanced studies, CT hepatic angiography (CTHA), and CT arterial portography (CTAP). Various applications and protocols of CT imaging rendering advantages and drawbacks to the technique are highlighted in this review article.

The changing role of radiology in imaging liver tumors: an overview

The surgical and the radiological advances in liver tumors in last two decades have made some malignant tumors operable which were considered inoperable and have completely changed the expectations from radiology. However, accurate staging, that is performed by imaging modalities, has critical importance in the selection of patients who can benefit from resection. Radiologists and referring physicians, therefore, should be aware of the current concepts in imaging liver tumors. This report updates both the changing role of radiology in hepatic neoplasms and the appropriate use of radiological modalities in liver tumors.

Three-dimensional imaging of liver tumors using helical CT during intravenous injection of contrast medium

PURPOSE

The goal of this work was to determine whether 3D reconstruction of images from CT during intravenous injection of contrast medium, performed in tandem with advanced rendering algorithms, could accurately depict major anatomic structures and hepatic tumors.

METHOD

Thirty-one patients (22 with hepatocellular carcinoma, 8 with metastatic lesions, and 1 with intrahepatic cholangiocarcinoma) underwent CT imaging. Twenty-three of the 31 patients underwent needle biopsy or surgery, yielding a histologic diagnosis. The remaining eight patients were diagnosed from imaging findings and laboratory data. We compared the ability of maximum intensity projection (MIP) and volume-rendered technique (VRT) images to depict the hepatic veins and intrahepatic portal veins.

RESULTS

Both MIP and VRT depicted the course of vessels up to the second or third branches. The techniques did not significantly differ. In this regard, in most cases, visualization of the liver surface and tumor was excellent with VRT images.

CONCLUSION

Volume-rendered 3D-CT images during intravenous injection without the MIP technique produced 3D images of high quality with excellent visualization of tumors and their relationships to vital structures.

Pre-surgical localization of ectopic parathyroid glands using three-dimensional CT imaging, 99Tcm sestamibi, and 99Tcm tetrofosmin imaging

We describe two patients with ectopic parathyroid glands evaluated with 99Tcm sestamibi, 99Tcm tetrofosmin, and three-dimensional computed tomography (3D-CT). Radionuclide images of the neck were acquired at 10 min, and at 2-3 h after radiopharmaceutical injection, and showed intense uptake in the ectopic parathyroid tissue. These patients also underwent contrast enhanced CT imaging with 3D reconstructions which were evaluated for ability to visualize critical anatomical structures, e.g. blood vessels and parathyroid glands. Based on 3D-CT images, surgical planning was altered in one of the two patients studied. In conclusion, reconstructed 3D-CT images provided useful anatomical localization of ectopic parathyroid glands identified on 99Tcm sestamibi and 99Tcm tetrofosmin imaging. This anatomical information aided surgical planning of gland resection.

The watershed between right and left hepatic artery territories: findings on CT scans after transcatheter oily chemoembolization of hepatic tumors. A preliminary report

The goals of this study were to delineate the boundary between the right and left hepatic artery territories by computed tomography (CT), to compare this boundary with the middle scissura of Couinaud's segmental anatomy, and to discuss the clinical implications of these findings. The 18 patients who underwent transcatheter oily chemoembolization (TOCE) of liver tumors via the right or left hepatic artery, were examined with an immediate postembolization CT scan. We measured the orientation of the watershed line between the right and left hepatic artery territories and the orientation of the middle scissura on other available sectional imaging modalities, and then compared the middle scissura with the arterial watershed line. A part of segment IV was fed by the right hepatic artery in two of 18 (11.1%) patients. Moreover, one of 4 segment IV lesions was embolized via right hepatic artery infusion. Thus, in 11.1% of cases there was no coincidence between the arterial watershed line and the middle scissura. Some segment IV lesions may be fed and therefore embolized only via right hepatic artery infusion in TOCE for liver tumor.

[Preoperative portal embolization: an effective means for inducing hypertrophy of the healthy liver and increasing indications for hepatic resection]

AIM OF THE STUDY

The aim of the preoperative portal embolization is a redistribution of the portal venous blood flow in an attempt to induce hypertrophy of the future remnant liver in order to perform a curative liver resection.

MATERIAL AND METHODS

Preoperative portal embolization was performed in a group of 43 patients. The volumetric ratio (future remnant liver/total liver-tumor) was 20%. Liver metastases were present in 40 patients and primary liver tumor in three. Twenty-four patients had received chemotherapy prior to the preoperative portal embolization. Required operative procedures were right hepatectomy (n = 15), right hepatectomy extended to the segment IV (n = 24) or atypical resection (n = 4). Preoperative portal embolization was performed under percutaneous transhepatic approach with a Blue Histoacryl and Lipiodol Ultra Fluide mixture. Liver volumetric measurements were obtained with 3D color encoded computed tomography, before portal embolization and before surgery.

RESULTS

Hypertrophy of the future remnant liver was 83 +/- 58% after a mean 32-day interval between portal embolization and surgery. The tolerance of portal embolization was excellent. Thirty-six hepatectomies were performed as initially planned; seven were cancelled for emergence of metastases (distant in six patients and intrahepatic in one).

CONCLUSION

Pre-operative portal embolization is a safe and effective procedure which increases the possibilities of curative resection in the liver tumors.

Focal nodular hyperplasia of the liver: assessment of hemodynamic and angioarchitectural patterns with gadolinium chelate-enhanced 3D spoiled gradient-recalled MRI and maximum intensity projection reformatted images

PURPOSE

Our goal was to determine the relative merits of gadolinium chelate-enhanced 3D spoiled gradient-recalled (GRE) MRI versus maximum intensity projection (MIP) reformatted images in assessing the morphologic, hemodynamic, and angioarchitectural patterns of focal nodular hyperplasia (FNH) of the liver.

METHOD

Ten consecutive patients with 10 FNHs had prospectively gadolinium chelate-enhanced 3D spoiled GRE MRI (TR/TE/FA = 10.1/1.9/30) of the liver at 1.5 T. Gadolinium chelate-enhanced 3D spoiled GRE source images and MIP reformatted images were separately analyzed with respect to morphologic and hemodynamic features and angioarchitectural patterns by two independent readers.

RESULTS

Gadolinium chelate-enhanced 3D spoiled GRE source images and MIP reformatted images showed the most intense degrees of enhancement of FNH during the arterial phase of hepatic parenchymal enhancement in all cases. Gadolinium chelate-enhanced 3D spoiled GRE source images were superior to MIP reformatted images for the assessment of morphologic features of FNH (p < 0.02). MIP reformatted images were superior to the corresponding source images for showing the main branches of the hepatic artery, an arterial branch going to the FNH, and a small artery within the FNH radiating to peripheral areas (p < 0.05). There was excellent agreement between the two observers for analysis of the MIP reformatted images (p < 0.05).

CONCLUSION

The combination of gadolinium chelate-enhanced 3D spoiled GRE source images and MIP reformatted images allows the analysis of morphologic, hemodynamic, and angioarchitectural patterns of FNH of the liver. Further study and comparison with currently applied strategies will determine the value of these two techniques for diagnosing FNH of the liver.

Delineation of segmental liver anatomy. Comparison of ultrasonography, spiral CT and MR imaging for preoperative localization of focal liver lesions to specific hepatic segments

PURPOSE

The purpose of this study was to determine the ability of noninvasive imaging methods to localize focal liver lesions to specific hepatic segments.

MATERIAL AND METHODS

In a prospective study we evaluated 24 patients with hepatic masses with ultrasonography (US), spiral CT and MR imaging.

RESULTS

The primary segmental location of the lesions was correct with US in 15 of 24 patients (63%), with CT in 21 of 24 patients (88%) and with MR imaging in 17 of 22 patients (77%). The full extent of the lesions was correctly described with US in 9 of 24 patients (38%), with CT in 16 of 24 patients (67%) and with MR in 12 of 22 patients (55%).

CONCLUSION

Among the noninvasive imaging methods, CT provides the best information for determining the segmental location and planning the surgical approach to hepatic resections.

[Spiral scanners: principles and clinical prospects]

Helical computed tomography (CT) involves continuous patient shifting during X-ray source rotation and data acquisition. As a result, a volume data set is obtained in a short period of time. An entire examination can be completed in a single breath hold, without additional radiation exposure, optimizing enhancement with intravenous contrast material. By overcoming some of the constraints of conventional CT, helical CT has advanced prospects, including multiplanar reconstruction and CT angiography, as reviewed in this article. There are undergoing studies to confirm these preliminary findings: its clinical applications are currently evolving.

Three-dimensional helical CT of intrahepatic venous structures: comparison of three rendering techniques

OBJECTIVE

To define the advantages and disadvantages of various rendering techniques to obtain three-dimensional (3D) displays of intrahepatic venous structures with helical CT data.

MATERIALS AND METHODS

After rapid preprocessing segmentation of the liver, helical CT data (8 mm slice thickness overlapped every 4 mm) from 10 patients were reconstructed using maximum intensity projection (MIP), volume rendering, and surface rendering algorithms. Three-dimensional imaging was evaluated blindly and independently by three observers for presence of artifacts and overall quality.

RESULTS

Three-dimensional displays showed the hepatic veins and fifth order portal branches with the volume and MIP rendering techniques. Best overall quality in the 3D representation of the liver was achieved with the MIP technique (p < 0.05). Small details in venous anatomy and portal involvement by tumor were better imaged with the MIP technique. "Stair-step" artifacts markedly degraded the 3D displays obtained with the surface rendering technique, making it inappropriate for imaging the intrahepatic venous structures.

CONCLUSION

Maximum intensity projection appears to be an adequate technique to perform 3D imaging of intrahepatic venous structures with helical CT data when 8 mm slice thicknesses overlapping every 4 mm are used. However, optimization of imaging protocols needs to be done and compared in a larger series.

The current state of the art in three dimensional oncologic imaging: an overview

PURPOSE

To provide an overview of the methods and clinical applications of three dimensional (3D) medical imaging in the oncologic patient.

METHODS AND MATERIALS

We briefly outline the techniques currently used to create 3D medical images with an emphasis on their strengths and shortcomings as they relate to oncologic imaging and radiation therapy planning. We then discuss some of the most important and promising oncologic applications of 3D imaging and suggest likely future directions in this rapidly developing field.

RESULTS

Since the first application of 3D techniques to medical data over a decade ago, 3D medical images have evolved from relatively crude representations of musculoskeletal abnormalities to detailed and accurate representations of a variety of soft tissue, vascular, and oncologic pathology. The rapid development of both computer hardware and software coupled with the application of 3D techniques to a variety of imaging modalities have expanded the clinical applications of this technology dramatically.

CONCLUSIONS

3D medical images are clinically practical tools for oncologic evaluation and effective radiation therapy planning.

Planning of liver surgery using three dimensional imaging techniques

In the simplified Couinaud classification, in which the liver is divided into eight segments, each supplied by a central vasculo-biliary sheath, little attention is given to the high prevalence of anatomical variations which occur, especially in the right hemiliver. Using volumetric acquisition techniques, such as magnetic resonance imaging or spiral computed tomography scanning, detailed insight into the individual segmental anatomy can now be obtained in a non-invasive manner. The significance of this anatomical insight lies in the planning of anatomical resections, whereby the relationship between tumour and individual segmental anatomy can be depicted in a three-dimensional format. As such, three dimensional (3D) liver imaging helps to design an individualised resection, tailored to the topographical relationship between individual segmental anatomy and tumour tissue present. Three dimensional liver imaging is of most practical value if a resection of one or more segments or sectors is considered, especially in the right hemiliver. In these cases, 3D liver imaging can demonstrate the precise location of the scissuras to the surgeon pre-operatively.

3-D reconstruction of hepatic neoplasms: a preoperative planning procedure

Three-dimensional display of intrahepatic vascular structures, tumour(s) and liver surface offers the possibility of perceiving the complex individual anatomy in a coherent fashion. Since this presentation of anatomical structures can be varied at will, the resulting interactive dynamic display of the 3-D data sets can be considered an example of Virtual Reality; the surgeon experiences the interactive 3-D display as a realistic presentation of the patient's surgical anatomy. Three-dimensional display offers the possibility of planning a specific resection in detail, tailored to the individual anatomy. The benefits and problems of various surgical approaches can be worked out in detail, and potential hazardous phases in the operation can be anticipated, thus minimizing unexpected complications. However, because the generation of detailed 3-D renderings takes considerable time investment by an experienced operator it is important to select patients, in whom such an effort is warranted. In our experience, 3-D display of the liver is most likely to be of benefit in the presence of central tumours, or if segmental resections are considered.

Involvement of superior mesenteric vessels and portal vein in pancreatic adenocarcinoma: detection with CT during arterial portography

A prospective study was designed to determine the utility of computed tomography (CT) during arterial portography (CTAP) in the detection of superior mesenteric vessels and portal vein involvement in patients with pancreatic adenocarcinoma. Eighteen patients with adenocarcinoma of the head of the pancreas and eight patients with benign pancreatic disease were investigated with CTAP, dynamic contrast-enhanced CT, and angiography. Appropriate review was made to determine presence or absence of superior mesenteric vessels and portal vein involvement. Final diagnosis was obtained in all cases by surgical explorations. The overall accuracy rate for detecting or excluding superior mesenteric vessels and portal vein involvement was 96% (25 of 26 patients) with CTAP, 88% (23 of 26 patients) with dynamic contrast-enhanced CT, and 85% (22 of 26 patients) with angiography. No statistically significant difference in accuracy was found among the three techniques. Our results suggest that the use of CTAP is not indicated in the preoperative detection of superior mesenteric vessels and portal vein involvement in patients with pancreatic adenocarcinoma.

Spiral CT of the liver: current applications

Spiral CT allows rapid imaging of the liver resulting in improved contrast dynamics compared with conventional CT techniques. Improved lesion detection has been shown with spiral CT by using overlapping reconstruction intervals and by eliminating respiratory misregistration. Vascular and parenchymal abnormalities, including portal venous thrombosis or cirrhosis with development of collateral vessels, are readily appreciated using spiral technique. Combining spiral CT and portography enhances lesion detection by maintaining high levels of hepatic contrast enhancement for the duration of the liver scan.