Biomedical subjects
Publications and source records attributed to W M Gedroyc.
Percutaneous laser ablation of uterine fibroids with magnetic resonance thermal monitoring causes shrinkage of treated areas by 37.5% 3 months later. This technique may provide an alternative to open surgery.
A minimally invasive technique for performing magnetic resonance (MR)-guided laser interstitial thermoablation (LITT) for inoperable renal tumors is described. Three patients were treated using a percutaneous technique with real-time MR guidance in an open access interventional MR scanner. Laser therapy was delivered using a neodymium-YAG source via a water-cooled applicator system. Thermal lesions were monitored in real time using a color thermometry sequence. All patients were discharged the following day with no complications. Follow-up with gadolinium-enhanced MRI in a conventional high-field system confirmed necrosis in targeted tissue, and further treatment is planned for one patient. We concluded that LITT can be useful in treating inoperable renal malignancy and merits further evaluation. J. Magn. Reson. Imaging 1999;10:545-549.
BACKGROUND/AIMS: Primary and secondary liver tumours are a common clinical problem, with a poor prognosis in most cases. Surgical resection offers the best outcome, but is only appropriate for the minority. Thermal ablation techniques have been described, but the lack of an optimal means of monitoring has limited their use. We undertook a pilot study to assess the feasibility and safety of an integrated MR-guided laser thermoablation technique under local anaesthesia using a real-time colourisation thermal monitoring technique in a newly developed open MR scanner. METHODS: Liver tumours were punctured after the administration of intravenous Mangafodipir trisodium (MnDPDP) using real-time MR image guidance under local or general anaesthesia, and treated using a water-cooled interstitial fibre and a Nd-YAG laser source. Twenty-seven procedures were performed in 12 patients. Therapy was monitored using a real-time MR colourisation sequence. Thermoablation was followed by a colour change in a region of interest. RESULTS: Thermal lesions of mean size 3 cm in diameter were produced with a maximum size of 5 cm. Eight out of 12 patients were discharged the next day with few significant complications. Repeat procedures have been performed in seven of 12 patients. Two patients with lesions of 3 cm diameter have had complete tumour ablation with only one procedure. CONCLUSION: Percutaneous laser thermoablation for liver tumours performed as an integrated one-step technique in an open configuration MR scanner is described. It can be safely performed under local anaesthesia in the majority of patients, with few side effects. MR control shows the site and size of the evolving thermal lesions, allowing appropriate action to be taken in terms of further burns, time of application and power applied.
We present the first study in vivo of meniscal movement in normal knees under load. Using an open MR scanner, allowing imaging in physiological positions in near to real-time, 16 young footballers were scanned moving from full extension to 90 degrees flexion in the sagittal and coronal planes. Excursion of the meniscal horns, radial displacement and meniscal height were measured. On weight-bearing, the anterior horn of the medial meniscus moves through a mean of 7.1 mm and the posterior horn through 3.9 mm, with 3.6 mm of mediolateral radial displacement. The height of the anterior horn increases by 2.6 mm and that of the posterior horn by 2.0 mm. The anterior horn of the lateral meniscus moves 9.5 mm and the posterior horn 5.6 mm, with 3.7 mm of radial displacement. The height of the anterior horn increases by 4.0 mm, and that of the posterior horn by 2.4 mm. In non-weight-bearing, the anterior horn of the medial meniscus moves 5.4 mm and the posterior horn 3.8 mm, with 3.3 mm of radial displacement. The anterior horn of the lateral meniscus moves 6.3 mm, and the posterior horn 4.0 mm, with 3.4 mm of radial displacement. The most significant differences between weight-bearing and non-weight-bearing were the movement and vertical height of the anterior horn of the lateral meniscus.
The development of minimally invasive surgical and interventional techniques has created a need for more accurate and sensitive image guidance and monitoring. Magnetic resonance imaging, with its superior soft tissue discrimination and multiplanar facilities, seems the obvious choice for an ideal image-guidance tool. Until recently, the employment of MRI in this role has been prevented by the physical constraints of conventional, closed-configuration machines. The problem has now been overcome by the development of an open design allowing both horizontal and vertical access to the patient in the scanner so that procedures can be performed concurrent with image acquisition. This configuration, together with the use of fast gradient echo sequences which can scan at speeds close to real time, means that a wide range of interventional procedures can be performed with on-line image guidance and monitoring. In addition, the versatility of the open design means that patients can assume physiological positions to allow dynamic joint imaging to be performed. This opens up a whole new field in the understanding of joint pathophysiology. This review article discusses these recent technological developments and their clinical applications. In particular, the potential role in guidance of biopsies, monitoring of thermal ablation techniques and applications in endoscopic surgery is outlined.
Renal artery stenosis is a common cause of renal impairment which in many cases may be potentially reversible. The diagnosis and follow-up of this condition is commonly carried out using the relatively invasive technique of intra-arterial angiography. Magnetic resonance angiography (MRA) is emerging as a possible alternative technique to conventional angiography. We have studied 60 patients who were referred for investigation of possible renal artery stenosis using both 3-D phase contrast MRA techniques and conventional digital arteriography. Studies were assessed prospectively and conventional angiography was assumed to be the gold standard for the purposes of this study. Calculated sensitivity and specificity results were 84% and 91% respectively, for 3-D phase contrast MRA of the renal arteries. We conclude that 3-D phase contrast MRA is a very promising technique for the noninvasive investigation of renal artery stenosis with high sensitivity and specificity levels acting as a screening test in the future for patients with this potential diagnosis, diminishing the amount of conventional angiograms that are performed.
Internal double-J stents are used to maintain ureteral patency and require replacement within 4-6 months. We present our experience with 15 consecutive patients who had 35 internal ureteral stents retrieved and in whom 27 were successfully replaced, retrogradely under fluoroscopic control. The double-J stents were retrieved using an Amplatz gooseneck snare. Replacement was more successful in female patients, and was technically more difficult via an ileal conduit or transplant ureter. We found this new technique to be straightforward and well tolerated by the patients. The procedure was performed on an outpatient basis, and no serious complications were reported. This technique is considerably cheaper than cystoscopic replacement under epidural or general anaesthesia, and is recommended for the retrieval and replacement of internal ureteral plastic stents in most patients.
Stenosis of renal transplant arteries is a common cause of graft dysfunction and hypertension. Conventionally it is investigated by intraarterial digital subtraction angiography (IA DSA). Recently three-dimensional phase contrast magnetic resonance angiography (MRA) has been used successfully as a non-invasive method of assessing renal transplant arteries. We report three cases where MRA was superior to IA DSA in the detection of renal transplant artery stenosis.
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Magnetic resonance angiography has very exciting potential for the investigation of renal artery stenosis. This article discusses what exact techniques are optimal and current information suggests that 3-D phase contrast sequences are probably the best that are currently available for this role. Magnetic resonance imaging techniques provide instantly recognizable images and generally are more acceptable than other modalities. In addition, the current study suggests a very promising sensitivity and specificity for the determination of renal artery stenosis.
In three patients undergoing three-dimensional phase contrast magnetic resonance angiography (MRA) for evaluation of renal transplant arteries, a convincing stenosis was demonstrated that was not present on conventional angiograms. In each patient there was a stainless steel surgical clip in the soft tissues adjacent to the renal artery. Although the clip artefact was easily recognized on the acquired tomographic magnetic resonance slices, it was completely indistinguishable from a true stenosis on the final projection images. This may limit the use of MRA in post-surgical vascular evaluation unless review is made of the phase contrast images.
Stenosis of the artery of transplanted kidneys is an important cause of graft dysfunction. Diagnosis and follow-up of this condition normally requires intra-arterial digital-subtraction angiography (IADSA), which is invasive and may cause complications. A possible alternative to IADSA is magnetic resonance angiography (MRA), and we have assessed this technique in 50 renal transplant patients who were referred for investigation of possible renal arterial stenosis. In every patient, MRA was compared prospectively with conventional IADSA. Compared with IADSA, MRA had a sensitivity of 83% and a specificity of 97%, and when all images were graded retrospectively for severity of stenosis, the two techniques showed a significant correlation (r = 0.74, p less than 0.001). MRA can provide an accurate image of the renal transplant artery in a non-invasive manner with a high sensitivity and specificity.
Eight patients with the middle aortic syndrome are described. They were aged 2 months to 14 years at diagnosis; follow up was one to 11 years. Clinical presentations included asymptomatic hypertension (n = 5), severe headache, nose bleed, and chest pain (n = 1), and cardiac failure (n = 1). All had severe hypertension requiring multiple drug treatment. Diminished peripheral pulses were not helpful in the diagnosis, which is made on aortography. Associated clinical findings were Williams' syndrome (n = 3) and appreciable eosinophilia (n = 3). The differential diagnosis includes Takayasu's arteritis, fibromuscular dysplasia, and neurofibromatosis. Blood pressure was adequately controlled by medical treatment in six patients. Surgical angioplasty was performed in two. One patient remained normotensive without drug treatment 21 months after operation; the other died of sepsis and uncontrollable haemorrhage in the postoperative period. Medical treatment is satisfactory in most cases: surgery should be reserved for those in whom blood pressure cannot be controlled without unacceptable side effects of drug treatment. Although rare, the middle aortic syndrome should be considered in the differential diagnosis of hypertension when commoner causes have been excluded. Aortography is necessary for diagnosis.
Techniques developed for removal of stones from normally sited kidneys can be safely employed in the transplanted kidney. We describe our experience in removing stones, stent material and organised blood clot from renal transplant collecting systems, using modified percutaneous techniques.
Distorted, clubbed calices associated with focal renal scars or areas of more diffuse parenchymal loss make up the accepted urographic diagnostic criteria of chronic reflux nephropathy. It is widely believed that this diagnosis should not be suggested in the absence of the above findings and that scarring with normal calices indicates a vascular aetiology. This study describes five children with marked renal parenchymal loss all of whom have normal or near normal calices underlying the areas of parenchymal thinning and all of whom show severe vesico-ureteric reflux on micturating cystography. We suggest that these patients represent examples of true reflux nephropathy and that normal or near normal caliceal patterns may be seen underlying areas of renal parenchymal damage in this condition. No localised scars were seen in association with normal calices and we suggest that the marked tissue distortion caused by localised indented scars plays a significant part in producing the caliceal appearances more usually seen in reflux nephropathy. Other possible mechanisms responsible for the maintenance of relatively normal caliceal architecture are also discussed.
Sponge kidney has characteristic plain film and urographic findings which are generally regarded as being limited to the medullary pyramids. We describe two groups of patients with renal changes of medullary sponge kidney who show additional renal abnormalities. In the first group there were multiple cortical cysts; in the second there were cavities deep in the medulla, many of which communicated with the calices. Neither of these findings has been described before and we suggest that the spectrum of changes associated with this condition is wider than has previously been appreciated.
The use of renal stents in renal transplants is becoming increasingly popular and has been routine practice at this institution for the past 4 years. Despite this procedure, however, obstruction of the transplant ureter still occurs and we describe 7 patients who developed renal obstruction in the presence of a stented transplant ureter. The underlying causes of these findings are discussed together with suggested recommendations for optimum radiological assessment of transplant ureteric stents. The implication of these observations is that urine may flow down stented ureters between the ureter and the stent rather than down the stent lumen.