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W M Gedroyc

Publications and source records attributed to W M Gedroyc.

At least 19 recordsLinked to original sources
PubMed2001

The value of MnDPDP enhancement during MR guided laser interstitial thermoablation of liver tumors.

Magnetic resonance (MR)-guided thermal ablation procedures are feasible in modern open low field strength MR scanners. The compromises for rapid imaging in this configuration worsen liver lesino conspicuity. To overcome this, we utilize liver-specific contrast Mangafodipir Trisodium (MnDPDP) to improve lesion recognition and targeting and allow a longer contrast-assisted window. Three observers assessed pre- and post-contrast MR scans of 14 liver ablation patients. They assessed the number of lesions, ease of puncture planning, conspicuity of lesions, gallbladder, vessels, and surrounding bowel. There was a significant improvement in lesion conspicuity and ease of puncture planning when MnDPDP was used. In two of the observers, there was also a significant improvement in the number of lesions seen and in bowel conspicuity. No significant difference was shown in the detection of the gallbladder or vessels. We conclude that the liver-specific contrast agent MnDPDP improves the overall accuracy and safety of MR-guided thermal ablation of liver tumors facilitating this procedure at lower field strengths. J. Magn. Reson. Imaging 2001;13:37-41.

Adult↗
PubMed2001

Dynamic imaging of the pelvic floor using an open-configuration magnetic resonance scanner.

The aims of this study were to develop a noninvasive, erect, gravity-dependent method for assessing movements of the female pelvic floor, to describe the range of movements in pelvic floor ascent and descent in asymptomatic and symptomatic women, and to quantify any differences. A total of 102 women, 28-86 years of age, 35 symptomatic and 67 asymptomatic, were included in the study. They were scanned in a sitting position in an open scanner with good vertical access using fast-gradient echo sequences fast spoiled grass (FSPGR). Measurements of the bladder base, uterocervical junction, and anorectal junction were taken in the sagittal plane. The levator ani (LA) muscle insertion was assessed in the coronal plane with the patients at rest, during maximal strain, and during maximum contraction of the pelvic floor. Premenopausal multiparous women have a significantly lower bladder base (8/0 mm above the baseline; P value = 0.009) and uterocervical junction (15.5/3.5 mm; P value = 0.03) at rest than nulliparous women, and this becomes more apparent on straining. Parity confers a more significant effect on the position and function of the pelvic floor than menopausal status. All pelvic organs are lower at rest and on straining in women with defecation difficulties (0/-24 mm; P value = 0.001). These differences are also seen when comparing women with and without urinary incontinence. Dynamic seated magnetic resonance imaging (MRI) shows that all the pelvic organs are lower at rest and on straining in multiparous women and in those with urinary incontinence than in a group of asymptomatic nulliparous volunteers. This difference is also seen in the position of the bladder base and anorectal junction during pelvic floor contraction. These findings suggest general pelvic floor weakness in women who present with symptoms in one compartment and indicate the need for evaluation of the entire pelvic floor particularly prior to surgery. J. Magn. Reson. Imaging 2001;13:923-929.

Adult↗
PubMed2001

Magnetic resonance angiography: the state of the art.

Three-dimensional contrast magnetic resonance angiography has rapidly advanced over recent years. It is now a highly accurate and safe method of diagnosing vascular abnormalities of the thoracic, abdominal and peripheral vessels. We describe techniques for the examination of the thoracic and abdominal aorta, the renal arteries and the lower limb vessels together with strategies to improve their diagnostic accuracy.

Aortic Diseases↗
PubMed2001

Can interventional MRI provide an insight into the mechanics of a posterior-anterior mobilisation?

OBJECTIVES: A pilot study aimed to investigate if interventional MRI could detect changes in the spine and surrounding soft tissues as a result of a posteroanterior mobilisation, and to determine if such an effect was specific to the level of application. DESIGN: A prospective pilot study to investigate the kinematics of cervical spine mobilisation. BACKGROUND: Posteroanterior mobilisation is a manual physiotherapy technique that is commonly used as an examination tool and a form of conservative treatment. The efficacy of this technique is controversial and little is known regarding the underlying mechanisms. METHODS: Five control subjects were recruited and written informed consent obtained. Subjects were scanned, using a General Electric Signa SP10 Open Interventional MRI scanner, in the prone position with their necks in either a neutral or flexed position. In each position a posteroanterior mobilisation to the 2nd and 6th cervical vertebrae was performed. Sagittal images of the spine were obtained prior to, during and following the mobilisation. RESULTS: Clear images of vertebral position could be obtained during the application of a posteroanterior mobilisation. Measurements of intervertebral angulation and translation demonstrated little if any motion during the application of a posteroanterior mobilisation, in both a flexed and neutral position. Changes were seen in terms of soft tissue compression and in some instances overall angulation of the cervical spine. CONCLUSIONS: Interventional MRI can produce images of posteroanterior mobilisation. Dynamic imaging of the procedure produced images of unsuitable quality for analysis. The quasi-static images of suggested that the application of a posteroanterior mobilisation to the cervical spine produces minimal if any intervertebral motion, but significant soft tissue deformation of the overlying structures. RELEVANCE STATEMENT: Posteroanterior mobilisation is frequently used in the assessment and management of spinal problems, but the efficacy of the technique remains controversial. This is hampered by the fact that little is known about the mechanisms involved during such a procedure.

Adult↗
PubMed2001

Assessment of spinal kinematics using open interventional magnetic resonance imaging.

Assessment of spinal intersegmental motion has been a focus for research and has depended on radiographic techniques. Radiographic techniques are limited because of ionizing radiation exposure, magnification errors, and image quality. Interventional magnetic resonance scanners, however, allow dynamic imaging in the scanner in different positions. Twelve healthy subjects were scanned using a General Electric Signa SP10 open interventional magnetic resonance scanner. Subjects were scanned while they were in the supine position and during sitting in flexed and extended positions. Measurements of lumbar curvature and intersegmental motion were made from the sagittal images obtained. The results showed that it was possible to obtain repeatable measures of intersegmental rotation and translation from open magnetic resonance images of the spine in flexed and extended positions. These measures of motion are in agreement with previous data and suggest that the greatest motion occurs at the L4-L5 level. The use of interventional magnetic resonance imaging for assessing lumbar intersegmental mobility seems promising.

Adult↗
PubMed2000

Magnetic resonance-guided percutaneous laser ablation of uterine fibroids.

Laser ablation of uterine fibroids using a percutaneous approach under local anesthetic in an open magnetic resonance (MR) scanner was performed in 12 symptomatic women awaiting hysterectomy. Accurate laser fiber placement was assisted by the use of an MR needle tracking system, as well as laser heat dissipation monitored during treatment by a real-time imaging processor. This day case procedure was well tolerated by all women, with eight women subsequently declining their planned surgery. Follow-up measurements of treated fibroid volume by MRI demonstrated a mean decrease of 37.5% at 3 months. This novel minimally invasive approach offers an alternative to surgery for women with fibroids, but longer follow-up is required to ascertain maximal fibroid shrinkage and to compare outcome with traditional surgery.

Adult↗
PubMed2000

MRI of the claustrophobic patient: interventionally configured magnets.

The aim of this study was to determine whether or not claustrophobic patients would tolerate a scan in an open configuration interventional magnetic resonance (iMR) imaging unit, when they had failed to complete a diagnostic scan in a conventional MRI system. 50 claustrophobic subjects were entered into the study. Their response to the iMR environment was compared with their previous experience in an MRI scanner by means of a two-stage questionnaire. Part 1 was completed before their iMR scan and Part 2 following their attempt at imaging in the iMR unit. 60% (n = 30) of the participants were female and 40% (n = 20) were male, age range 25-71 years (mean 49.5 years). 48% (n = 24) were lumbar spine studies and 28% (n = 14) were studies of the head. 24% (n = 12) underwent scanning of other anatomical regions. 94% (n = 47) of participants underwent successful MRI in the interventional magnet without extra sedation. 6% (n = 3) failed to complete a diagnostic scan in the iMR machine. The GE Signa 0.5 T SP magnet allows successful MRI in 94% of the claustrophobic population who have failed to complete a scan in a conventional diagnostic machine.

Adult↗
PubMed2000

Upright dynamic MR defaecating proctography in an open configuration MR system.

We describe our experience evaluating an MR proctography technique using an open 0.5 T MR system. Evacuation of a gadolinium-containing rectal contrast agent was dynamically imaged in the upright position using a fast gradient echo sequence. Anatomical and functional abnormalities were documented. Results from 40 patients who underwent this technique are reported. The method is proposed as an alternative to conventional fluoroscopic proctography.

Adult↗
PubMed2000

Prevalence of renal artery stenosis in subjects with type 2 diabetes and coexistent hypertension.

OBJECTIVE: To assess the prevalence of renal artery stenosis (RAS) in subjects with type 2 diabetes and coexistent hypertension by using magnetic resonance angiography (MRA) of the renal arteries, to assess clinical and biochemical predictors of RAS, and to assess the hemodynamic significance of RAS, by using the captopril test (a measure of the response of plasma renin activity to a single oral dose of captopril). RESEARCH DESIGN AND METHODS: A total of 117 subjects with type 2 diabetes and coexistent hypertension between 40 and 70 years of age and with creatinine concentrations < 150 micromol/l were recruited from two inner-city general diabetes clinics. All subjects underwent MRA of the renal arteries. In a subgroup of 85 subjects, data concerning possible clinical and biochemical predictors of RAS were collected, and the captopril test was performed. For comparison of a continuous variable between subjects with a positive MRA and those with a negative MRA, the Mann-Whitney test was used. For comparison of a discrete variable between subjects with a positive MRA and those with a negative MRA, Fisher's exact test was used. RESULTS: The prevalence of RAS detected by using MRA in 117 hypertensive type 2 diabetic subjects was 17%; 19 subjects had unilateral RAS, and only 1 subject had bilateral RAS. A femoral bruit was significantly more common in subjects with a positive MRA versus subjects with a negative MRA (21 vs. 0%; Fisher's exact test P < 0.005); however, other clinical features of atherosclerotic disease were not statistically associated. Greater duration of hypertension and treatment with statins were features of subjects with RAS (P < 0.05). The captopril test was negative in all subjects, although the antihypertensive response to oral captopril was significantly greater in subjects with RAS detected by MRA. CONCLUSIONS: RAS is common in hypertensive type 2 diabetic subjects. The presence of a femoral bruit is a useful predictive clinical marker. The captopril test is not useful in predicting the hemodynamic significance of RAS in this patient group.

Aged↗
PubMed1999

MR-guided laser thermoablation of inoperable renal tumors in an open-configuration interventional MR scanner: preliminary clinical experience in three cases.

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.

Aged↗
PubMed1999

MRI guidance of infra-red laser liver tumour ablations, utilising an open MRI configuration system: technique and early progress.

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.

Adult↗
PubMed1999

Meniscal movement. An in-vivo study using dynamic MRI.

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.

Adolescent↗
PubMed1997

Interventional magnetic resonance imaging.

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.

Animals↗
PubMed1995

Magnetic resonance angiography of renal artery stenosis.

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.

Adult↗
PubMed1995

Retrograde radiological retrieval and replacement of double-J ureteric stents.

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.

Female↗
PubMed1995

Case report: renal transplant artery stenosis--three cases where magnetic resonance angiography was superior to conventional arteriography.

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.

Adult↗