Biomedical subjects
Publications and source records attributed to R N Gibson.
Medical student teaching is an important component of radiology education. Despite the practice of radiology undergoing significant changes during the last two or three decades, the importance of radiology has not translated fully into medical school curricula in Australia and New Zealand. This article reviews the essential components of a quality medical student teaching programme.
This study aimed to assess the ability of CT-i.v. cholangiography to show the perihilar biliary and cystic duct anatomy and to assess the relative performance of axial, maximum intensity projection and surface rendered displays. We also assessed the correlation between serum bilirubin levels and adequacy of biliary opacification. Spiral CT was carried out following infusion of 100 mL of Biliscopin in 181 patients with suspected biliary disease. The display of biliary anatomy was of high quality, with 91% of patients having good opacification of at least first-order bile ducts and 84% having good opacification of at least third-order right and left hepatic ducts. The quality of biliary opacification correlated inversely to serum bilirubin levels, with levels above two to three times the normal value being associated with lower rates of good opacification. Maximum intensity projection and surface rendered reformats aided anatomical interpretation to a similar degree. The relative frequency of types of perihilar branching patterns and cystic duct junctional anatomy correlated closely to those reported from previous anatomical studies.
Bile duct varices are a rare manifestation of portal vein cavernous transformation. They can present as an apparent enhancing, vascular mass in the porta hepatis and are readily diagnosed using ultrasound and CT modalities. Diagnosis is important to avoid unnecessary intervention and concomitant risk of haemobilia.
Renal artery stenosis is a common, progressive cause of hypertension and renal impairment, and is frequently treated with percutaneous transluminal dilatation and stenting. The outcome of this procedure is still being evaluated. The records of 198 consecutive patients who had stents inserted at the Royal Melbourne Hospital were analysed retrospectively, and adequate follow-up information on 148 (75%), in whom a total of 182 renal arteries had been treated was obtained. Technical success was achieved in 144 patients (97%). Complications occurred in 19 patients (13.3%), with major complications occurring in 10 (7.0%) and one death occurring in relation to the procedure. A fall in average systolic blood pressure of 13.2 mmHg (12.1-14.3 mmHg) was seen and a fall in diastolic blood pressure of 10.1 mmHg (9.3-10.9 mmHg), without an increase in the number of antihypertensive drugs used. Renal function remained stable in the majority of patients, particularly those who had minimal baseline renal impairment. Restenosis was common after 6 months, occurring eventually in 29% of screened patients, but was not shown to affect clinical outcomes. Insertion of renal artery stents is a safe and effective treatment for renal artery stenosis.
The purpose of the present paper was to assess whether conventional renal Doppler ultrasound and the commonly used parameters of peak systolic velocity and renal aortic ratio may be an appropriate modality for the follow-up of renal artery stents. A total of 19 arteries in 15 patients was examined with both renal Doppler ultrasound and angiography for the presence or absence of recurrent renal artery stenosis. Disease was considered present on angiography if the arterial diameter was more than 60% stenotic. Doppler criteria for stenosis were either a peak systolic velocity of > 180 cm/s or a renal aortic ratio of > 3.0. Echo enhancement with Levovist (Schering, Berlin, Germany) was used if studies were technically unsuccessful or to improve diagnostic confidence. Renal Doppler ultrasound detected 100% of renal artery stenoses. The specificity was 75%, the positive predictive value was 67% and the negative predictive value was 100%. Echo enhancement improved the technical success rate from 89 to 95% and also increased diagnostic confidence in six examinations. The present limited study suggests that similar renal Doppler parameters as used for the study of unstented renal arteries may be applied to the examination of renal arteries with renal stents in situ. It therefore suggests that Doppler ultrasound may provide an adequate non-invasive means of renal artery stent follow-up, particularly when combined with echo-enhancing agents. Further study is warranted to confirm these initial conclusions.
A case is reported of malignant melanoma presenting as a mass in the head of the pancreas producing obstructive jaundice. On MR imaging the mass displayed signal characteristics not typical of adenocarcinoma but instead exhibited a low signal on T2-weighted images and early phase dynamic enhancement, the combination of which should suggest the possibility of melanoma.
In a review of 49 carotid arteries that had been assessed by ultrasound and angiography, two Doppler criteria were compared for accuracy in grading internal carotid artery (ICA) stenosis. The Seattle criteria for Doppler spectral analysis and the internal-to-common carotid artery peak systolic velocity ratio were of similar accuracy. When used in combination, there was an increase in sensitivity compared with the use of a single criterion. The velocity ratio had a higher sensitivity for detection of high-grade stenosis, but it tended to overestimate the grade of stenosis more than the Seattle criteria. To increase the sensitivity for detection of severe stenosis, the criteria should be used together and the higher grade of stenosis should be taken if there is a mismatch in assessment.
Magnetic resonance cholangiopancreatography (MRCP) is a non-invasive imaging method for examining the biliary and pancreatic ducts. The technique uses heavily T2-weighted imaging, which produces high signal from bile and other static fluids by virtue of their long T2 time, while suppressing background signal. Fast scanning techniques, particularly half-Fourier fast spin-echo techniques, are continuing to improve image resolution and allow scans within short breath-holds, reducing the effects of respiratory movement. The MRCP method has reached a level of resolution and reliability where it may well largely replace diagnostic endoscopic retrograde cholangiopancreatography (ERCP) in the near future. A review of MRCP techniques and imaging findings is presented with emphasis on half-Fourier imaging, with reference to potential clinical indications and limitations. Use of MRCP shows a high sensitivity and specificity for detection of biliary dilatation, calculi, strictures and anatomical variants. Experience with MR imaging of the pancreatic duct is less extensively described in the literature, but pancreatic duct dilatation, calculi and anatomy can now be reliably detected. However, as experience with MRCP increases, some sources of errors and limitations are becoming apparent, with image artefacts, and gas, blood or sludge within ducts potentially mimicking stones or strictures.
OBJECTIVE: The aim of this study was to determine the accuracy of direct and indirect parameters for the diagnosis of renal artery stenosis and to determine the most useful thresholds for these parameters. SUBJECTS AND METHODS: One hundred twenty-five arteries in 63 patients were examined with renal Doppler sonography and angiography for the presence or absence of renal artery stenosis. Arteries were considered stenosed on angiography if there was a diameter reduction of greater than 60%. Renal Doppler sonographic measures of peak systolic velocity, renal aortic ratio, acceleration time, and acceleration were recorded and compared with the angiographically determined presence or absence of disease. RESULTS: Doppler examination was technically successful in 87% of kidneys and 76% of patients. Receiver operating characteristic analysis showed the optimal peak systolic velocity threshold to be 180 cm/sec and the optimal renal aortic ratio threshold to be 3.0. An acceleration time greater than 70 msec and an acceleration less than 300 cm/sec2 yielded sensitivities of 41% and 56%, respectively, and specificities of 85% and 62%, respectively. Combining a renal aortic ratio of greater than 3.0 or peak systolic velocity greater than 180 cm/sec provided the best combination of parameters with a sensitivity and sensitivity at 85% and 76%, respectively. CONCLUSION: The most accurate use of parameters was found to be a combination of either peak systolic velocity greater than 180 cm/sec or renal aortic ratio greater than 3.0. Indirect parameters were not found to be useful in predicting the presence or absence of renal artery stenosis.
The use of renal artery Doppler ultrasound for the diagnosis of renal artery stenosis is a well-established technique in selected populations, but the technical failure rate of the examination leading to incomplete studies is a major drawback. The results of ultrasound contrast-enhanced renal artery Doppler for renal artery stenosis, using the echo-enhancing agent, Levovist, are reported here. Sixteen patients (22 arteries) were examined with Levovist. The technical success rate of these examinations was 91%, and all four renal artery stenoses were correctly identified. It is concluded that the use of ultrasound contrast (Levovist) increases the technical success rate of renal artery Doppler ultrasound in this setting, with similar accuracy to unenhanced Doppler examinations.
PURPOSE: To assess the safety and efficacy of percutaneous retrograde transjejunal cholangiography and biliary intervention for benign and malignant disease. MATERIALS AND METHODS: The clinical and radiographic records of 43 patients (31 with benign and 12 with malignant disease) who had undergone percutaneous retrograde transjejunal biliary intervention over a 10-year period at a single institution were reviewed. One hundred eighty-one procedures were performed via a fixed Roux-en-Y loop and 15 via an unfixed loop. RESULTS: Percutaneous retrograde transjejunal cholangiography was attempted on 196 occasions (143 for benign and 53 for malignant disease). Primary successful access was obtained in 181 (92.3%). Adjunctive percutaneous transhepatic cholangiography improved successful access in an additional seven procedures, to 188 (95.9%). Interventions included stricture dilation, stone extraction, stent insertion, and brachytherapy. The mean number of biliary interventions and the mean interval between them were 3.1 interventions and 5.9 months in the benign group and 3.6 interventions and 3.8 months in the malignant group. The complication rate was 4.1%, with no deaths or episodes of biliary sepsis. CONCLUSION: Percutaneous transjejunal biliary access allows repeated interventions over many years with a low morbidity. Routine superficial fixation of Roux-en-Y loops is recommended for all biliary-enteric anastomoses to allow use of this safe and effective approach for any subsequent biliary intervention.
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The validity and clinical relevance of Doppler flowmetry in measuring changes in regional blood flow are uncertain. In the present study we compared changes induced ketanserin in regional splanchnic blood flow as measured by Doppler flowmetry with changes in conventionally measured systemic and in hepatic haemodynamic indices estimated pharmacokinetically using indocyanine green. Fourteen patients with alcoholic cirrhosis and portal hypertension were evaluated. On multivariate analyses, significant associations were noted for only three indices: changes in estimated hepatic blood flow were predicted jointly by changes in flow in the main and right portal veins and hepatic artery (R2 = 0.80); changes in intrahepatic shunting (indocyanine green extraction) were predicted by changes in flow in the main and right portal veins (R2 = 0.55); and changes in sinusoidal perfusion (indocyanine green clearance) were significantly predicted by changes in main portal vein flow alone (R2 = 0.76). These data support the validity of Doppler flowmetry in quantifying change in regional blood flow, but highlight the limitations in its clinical application and interpretation. The association of changes in main portal vein flow with changes in sinusoidal perfusion has clinical potential but requires confirmation using other modulating drugs.
The main trunks of both coeliac and superior mesenteric arteries were sheared off the abdominal aorta by an anterior dissection that spared the renal arteries. Both vessels were cannulated and a Walstent inserted across the false lumen to restore normal coeliac and superior mesenteric perfusion. This produced a successful haemodynamic and angiographic result with improvement in the patient's clinical condition.
The replacement of venography with ultrasound in investigation of lower limb deep venous thrombosis (DVT) is a trend that generally has been appropriate. However, there is substantial variation in reported accuracies related to different clinical contexts, operator experience and sophistication of equipment. The best and most consistent results are for suspected acute femoropopliteal thrombosis, while there is variation in accuracy and diagnostic approach for below knee thrombosis. Potential exists for substantial diagnostic inaccuracy for suspected recurrent DVT, in surveillance of high-risk patients and in patients with possible pulmonary embolism. The choice of ultrasound over contrast venography should take account of local expertise and accuracy, availability of resources, clinical indication for investigation and cost-effectiveness.
Focal nodular hyperplasia (FNH) is a rare, benign, hepatic mass lesion that is usually found in young adult females. It is sometimes an incidental finding on abdominal sonography or computed tomography. Its appearance on these studies is not characteristic however, thereby creating a diagnostic problem. This report is of a case which showed a centrifugal, spokewheel pattern of pulsatile blood supply on colour Doppler US. This finding, we suggest, is sufficiently diagnostic to avoid the need for further investigation in some patients, and to direct further imaging more appropriately in others.
An ultrasound phantom is described which allows practice of ultrasound-guidance of needle placement over variable depths and into targets of variable size. The phantom mimics a solid organ in its echogenicity and can be cheaply and easily made from resources of the domestic kitchen.