Hepatic lesion characterization in cirrhosis: significance of arterial hypervascularity on dual-phase helical CT.

OBJECTIVE: Our goal was to evaluate the diagnostic significance of the presence and pattern of arterial hypervascularity in lesions detected on dual-phase helical CT in cirrhotic patients. MATERIALS AND METHODS: Fifty-eight lesions greater than 1 cm in size were prospectively identified in 26 patients with end-stage liver disease who had undergone dual-phase helical CT for preoperative liver transplantation evaluation. All 26 patients had diagnoses proven by histologic evaluation or by clinical criteria. All arterial phase scans were retrospectively reviewed and lesions were categorized for the presence and pattern of arterial hypervascularity. Radiologic findings were correlated with histopathologic data. RESULTS: Thirty-seven of the 58 lesions had hypervascular components on arterial phase scans. All 37 of these lesions were found to represent hepatocellular carcinoma (HCC) (positive predictive value, 100%). Of the 21 remaining hypovascular lesions, 17 were HCC and four were benign (positive predictive value, 81%). Of the nine patients in whom all lesions were hypovascular, six had HCC (positive predictive value, 66%). The value of the presence of arterial hypervascularity for diagnosing HCC was statistically significant (p < .05). However, the presence or absence of arterial hypervascularity and the specific enhancement pattern revealed by helical CT did not correlate with histologic grading. CONCLUSION: The presence of hypervascularity in hepatic masses found in cirrhotic patients is highly predictive of malignancy.

Percutaneous nephrostomy: placement under CT and fluoroscopy guidance.

OBJECTIVE: The purpose of this paper is to present our experience with CT- and fluoroscopy-guided percutaneous nephrostomy tube (PNT) placement and to describe the technique of placement with patients in the supine-oblique position. MATERIALS AND METHODS: A CT scanner was coupled with a ceiling-mounted C-arm for fluoroscopy at the CT table, PNT was done with CT localization and fluoroscopic control. We attempted 148 placements in 129 patients, with most patients in the supine or the supine-oblique position. RESULTS: Successful PNT placement was achieved in 144 (97%) of 148 kidneys. In the native kidney group, 101 (81%) of 124 PNTs were placed with the patients in the supine-oblique position. We experienced no major complications, three (2%) minor complications, and two (1%) catheter dislodgments. CONCLUSION: CT-fluoroscopy control allows routine PNT placement with patients in the supine or the supine-oblique position and is associated with the lowest complication rate to our knowledge.

Local staging of pancreatic cancer: criteria for unresectability of major vessels as revealed by pancreatic-phase, thin-section helical CT.

OBJECTIVE: This study was conducted to determine the criteria for unresectability of major peripancreatic vessels in patients with pancreatic carcinoma as revealed by optimally enhanced, pancreatic-phase thin-section helical CT. SUBJECTS AND METHODS: Twenty-five patients with pancreatic adenocarcinoma who underwent local dissection during curative or palliative surgery also underwent preoperative pancreatic-phase thin-section helical CT (40- to 70-sec delay, 2.5- to 3-mm collimation). Tumor involvement of the portal and superior mesenteric veins and the celiac, hepatic, and superior mesenteric arteries was prospectively graded on a 0-4 scale based on circumferential contiguity of tumor to vessel. Subsequent surgical results were then correlated with the CT grades. RESULTS: At surgery, definitive evaluation was possible for 80 vessels. Forty-eight of 48 vessels graded 0 and three of three vessels graded 1 were resectable. Four of seven vessels graded 2, seven of eight vessels graded 3, and 14 of 14 vessels graded 4 were unresectable. A threshold of between grades 2 and 3, which corresponded to tumor involvement of one-half circumference of the vessel, yielded the lowest number of false-negatives and an acceptable number of false-positives for unresectability. Such a threshold would have yielded a sensitivity of 84%, a specificity of 98%, a positive predictive value of 95%, and a negative predictive value of 93% for unresectability of the vessels studied. CONCLUSION: A grading system for tumor involvement of the major vessels in patients with pancreatic adenocarcinoma can be based on the degree of circumferential contiguity of tumor to vessel. Involvement of vessel to tumor that exceeds one-half circumference of the vessel is highly specific for unresectable tumor.

Helical CT angiography for examination of living renal donors.

OBJECTIVE: This prospective study was intended to determine if helical CT arteriography plus conventional radiography is sufficiently accurate to replace and less costly than excretory urography and conventional renal arteriography, the techniques currently used to examine living renal donors. SUBJECTS AND METHODS: Patients underwent CT arteriography with a helical CT scanner. Conventional radiographs were obtained during the pyelographic phase to evaluate the urothelium. Findings on CT arteriograms were compared with findings on conventional arteriograms and at surgery. RESULTS: Of 57 patients who underwent CT arteriography, 46 also underwent conventional arteriography and 40 underwent surgery. For those 46 patients, we found agreement between results of CT arteriography and conventional arteriography in 89% of kidneys. For those 40 patients, we found agreement between results of CT arteriography and findings at surgery in 90% of kidneys and agreement between results of conventional arteriography and findings at surgery in 87% of kidneys. Of the 57 patients, six (11%) had findings on CT angiograms that precluded further consideration for donation. CONCLUSION: Eight to ten percent of renal arteries are not seen on renal arteriograms when compared with findings at surgery. Our results indicate that CT arteriography is as accurate as conventional arteriography at revealing the number of vessels that perfuse and drain the kidneys and can replace conventional arteriography. Use of CT angiography plus conventional radiography instead of excretory urography and conventional arteriography can result in a 35-50% reduction in cost of the imaging studies in potential renal donors.

Two-phase helical CT for pancreatic tumors: pancreatic versus hepatic phase enhancement of tumor, pancreas, and vascular structures.

PURPOSE: To quantitatively evaluate and validate a two-phase helical computed tomographic (CT) protocol for evaluation of pancreatic tumors. MATERIALS AND METHODS: Twenty-seven patients with pathologically proved pancreatic adenocarcinomas prospectively underwent two-phase CT examination with helical acquisition during the pancreatic phase (40-70 seconds after infusion of intravenous contrast material at 3 mL/sec) and the hepatic phase (70-100 seconds after infusion). Mean CT attenuation values of tumor, bordering pancreas, and all major peripancreatic vessels were obtained for both time intervals. RESULTS: Mean tumor-pancreas contrast was significantly greater during the pancreatic phase (67 HU +/- 19) than the hepatic phase (39 HU +/- 16) (P < .001) This was the result of both greater enhancement of normal pancreas and lower tumor enhancement during the pancreatic phase. Opacification of all vascular structures, including the portal vein, was also greater during the pancreatic phase (P < .001). CONCLUSION: Two-phase helical CT with pancreatic phase acquisition provides statistically significantly better pancreatic, arterial, and portal venous enhancement than that of hepatic phase imaging, with improved tumor-pancreas contrast.

Helical computed tomography for abdominal imaging.

Significant technologic advances have taken place in computed tomography (CT). Current-generation conventional CT scanners are able to image a slice of tissue in as little as 2 to 3 seconds and can acquire several consecutive images. Although it is a substantial improvement from the CT of 5 years ago, there remain practical limits to the utility of conventional CT imaging within the abdomen. Recently, a new type of CT gantry design ("slip-ring") and faster computers have contributed to the development of a new generation of CT scanners, the "helical" or "spiral" CT scanners.

Proximal fetal cerebral ventricle: description of US technique and initial results.

PURPOSE: To establish adequacy and ease of visualization of the proximal ventricle, normal range of measurements of the proximal ventricle, and distance of the proximal choroid plexus from the lateral ventricular wall. MATERIALS AND METHODS: With use of an angled technique, ultrasound (US) evaluation of the proximal fetal ventricle was attempted in 439 fetuses during routine obstetric US examination. Ease of examination, additional time required, mean measurements, and standard deviation (SD) were calculated. RESULTS: Visualization and measurement of the proximal ventricle were performed without difficulty in 77% of cases and with difficulty in 19%, and were impossible in 4%. Average additional time required was 4.2 minutes. The upper limit of normal for the midportion of the proximal ventricle was 8 mm (mean + 2.5 SD). In no normal pregnancy was the proximal ventricle separated from the choroid plexus by greater than 3 mm. CONCLUSION: Visualization and measurement of the proximal fetal cerebral ventricle can be performed during routine obstetric US examination in little additional time and can be used to detect abnormalities that might otherwise be overlooked because of fetal position.

A new holder and surface MRI coil for the examination of the newborn infant hip.

A special holder was developed for examination of the infant hip joint using MRI. This holder allows the infant hip joint to be examined both in a neutral position and in various defined functional positions. A special integrated surface coil, also developed for this purpose, provides the high spatial resolution required for assessment of the fine joint structures. Thirty infants were examined and the new device has proved useful in advanced hip dysplasia, therapy-resistant subluxation and luxation, and for operative therapy planning (reconstruction of the acetabular roof, redirectional osteotomies). Interpretation errors due to misprojection can be eliminated to a large extent since the holder allows standardized and reproducible positioning.

[Stereolithographic model construction based on 3-dimensional reconstructed CT sectional image sequences]. / Stereolithographische Modellfertigung auf der Basis dreidimensional rekonstruierter CT-Schnittbildfolgen.

Techniques for 3D reconstruction of medical objects and production of models by CAM have been markedly improved. Milling tools have limited abilities to reproduce complex anatomical structures. Even if 5-axis milling systems are used, the problem of collisions between tool and object is not yet under control. An alternative is offered here by stereolithography. We performed a computed tomography (Somatom DRH, Siemens/Erlangen) of a child with extensive maxillary bone defect after surgical treatment of a congenital tumour. The bone defect was covered by an alloplastic implant. 3D reconstructions were performed by the aid of a conventional personal computer. Generated 3D volume data sets were transferred to a stereolithography system (3D Systems GmbH, Darmstadt/FRG). The produced model revealed high accuracy of the anatomical structures. Intraoperatively, the alloplastic prosthesis was removed and the shape of the new implant could be designed using the stereolithographic model.

Biomechanics of valvular plane displacement of the heart.

There has been no consensus concerning the particular movement of the valvular plane of the heart (VPM). As shown in this study involving a mathematical model based upon the momentum equation and experiments on a specially designed artificial heart pump, the VPM not only results from the shortening of the heart, but also from blood flow within the heart and large blood vessels, from the forces caused by the muscle movements, and from the elastic properties of the heart's suspension. The results of the calculations and the experiments confirm the effect of the so-called valve mechanism and its influence on the economic beating action of the heart.

[CO2 angiography: studies of gas filling of vessels and assessing the factors of influence on the injection process with a cardiovascular model]. / CO2-Angiographie: Untersuchungen zur Gasausfüllung der Gefässe und Erfassung von Einflussfaktoren auf den Injektionsvorgang am Kreislaufmodell.

Following the advent of digital subtraction angiography (DSA), carbon dioxide gas has become a useful contrast agent for arterial angiography. Former manual injection methods had precluded accurate dosing and reproducibility. An original gas injector was therefore developed and tested in a circulatory system model. This permitted an accurate evaluation of vascular gas-filling. it also proved possible to measure the injection parameters taking different influencing factors into account. It was shown that vessels up to 10 mm in diameter are virtually completely filled with gas. In vessels larger than 10 mm in diameter, a residual fluid level remains, which in turn reduces the possibility for complete vessel imaging. The injection flow is dependent primarily on the vascular circulation rate, vessel diameter and the inclination of the vessel. With respect to other factors examined, neither catheter size, number of holes nor the direction of the injection have any relevant influence.

MR-anatomy of infants hip: comparison to anatomical preparations.

The correlation between anatomical preparations and MRI images of the most important structures of newborn hips in coronal and axial orientation was performed in 18 post mortem babies. T1-weighted images present a good differentiation between cartilage, bone, ligaments and surrounding soft tissues. Coronal images give the best opportunity to study the clinically important structures of the roof of acetabulum including the labrum and the ground of the acetabulum. The latter is shown in a more detailed way by MRI than by sonography. Axial images allow additional examinations of the ventral and dorsal parts of the joint. By using both coronal and axial images the exact determination of the centering of the femur head in the hip joint is possible.

[Arterial DSA using CO2 as a contrast medium: improvement of picture quality using a novel gas injector in an animal experiment]. / Arterielle DSA mit CO2 als Kontrastmittel: Verbesserung der Bildqualität mit einem neuartigen Gasinjektor im Tierexperiment.

The use of CO2 as contrast medium for DSA requires accurate and reproducible doses of the gas. This cannot be achieved by manual injection or by using injectors designed for liquid contrast media. For this reason a new gas injector has been developed which meets these requirements despite the compressibility of gas. The suitability and ease of use of the injector has been confirmed in experiments on 15 dogs. At the same time optimal volumes for different vessels with varying diameters have been determined. It has been shown that the injection parameters (gas speed and volume) in small vessels up 10 mm. diameter are not critical. With increasing vessel diameter accurate gas dose becomes important in order to perform optimal angiograms safely.

[CO2 angiography: development and trial of an animal experimental gas dosage device]. / CO2-Angiographie: Entwicklung und Erprobung einer tierexperimentell einsetzbaren Gas-Dosiervorrichtung.

Gas have long been used in radiological examinations, in particular for the diagnostic evaluation of gastrointestinal diseases. However, not until the introduction of digital subtraction angiography was carbon dioxide also used with success for angiography of arteries. In order to advice exact and reproducible dosage of the gas with freely selectable injection parameters, a carbon dioxide gas metering device was developed. The principle of gas metering is based on the measurement of the pressure gradient of the gas across a defined pneumatic resistance. The gas metering devices was tested in 15 animal experiments to produce survey and selective angiograms.

[Paget's disease of bone: MR characteristics at 1.5 T]. / M. Paget des Skeletts: MR-Charakteristika bei 1,5 T.

Thirteen patients with confirmed Paget's disease were examined using a 1.5 T MR tomograph. Five patients had polyostotic and eight patients monostotic forms of the disease. The results of these MR examinations were compared with the results of MR examinations performed on patients with osseous changes of different origin (metastases of breast cancer and prostate cancer, osteomyelitis, bone marrow infiltration due to acute lymphatic leukaemia and plasmocytoma). MR tomography permits evaluation of bone marrow space, osseous changes, and the surrounding soft tissue. Areas of sclerotic bone, thickened corticalis and bands of connective tissue in the marrow space were recognised as structures with no signal in T1- and T2-weighted images. The red and yellow marrows showed normal signal intensity patterns, although they were often reduced in size.

[Hyaline articular cartilage in MR tomography of the knee joint at 1.5 T]. / Der hyaline Gelenkknorpel in der MR-Tomographie des Kniegelenkes bei 1,5 T.

MRI is a new method for imaging the knee joint. There is still some uncertainty regarding the extent and the signal from hyaline articular cartilage. MRI images were therefore compared with anatomical and histological preparations of the knee joint and the difference between MRI and the anatomical sections have been determined. It was shown that demonstration of hyaline cartilage was obscured by an artifact. Further investigations are required to determine the cause of this artifact and to achieve accurate imaging of hyaline cartilage by MRI.

[Initial experiences with CO2 as a gaseous contrast medium in digital subtraction angiography]. / Erste Erfahrungen mit CO2 als gasförmiges Kontrastmittel in der DSA.

Electronic contrast enhancement allows the use of CO2 as a contrast material for studying the vascular system with DSA. Its use, safety and the information provided were studied in 40 patients and in 5 animal experiments and the results were compared with iodine-containing contrast media. The available results indicate that CO2 is a safe negative contrast medium for peripheral arteriography and that it provides angiograms with a picture quality comparable to those of iodinated contrast media in the extremities. The method can therefore be used to advantage in patients with allergies to the iodinated contrast media and in patients with renal failure.