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D J Lomas

Publications and source records attributed to D J Lomas.

At least 37 records · Page 2Linked to original sources
PubMed1999

Small bowel MRI using water as a contrast medium.

Magnetic resonance imaging (MRI) of the small bowel has been limited by lack of an adequate luminal contrast medium and problems with image artefacts. In this study we investigate the feasibility of imaging the luminal small bowel using rapid heavily T2w techniques, similar to those used for MR cholangiopancreatography, combined with oral water loading. Eight volunteers were examined after drinking 1-21 of water using serial, multisection, half-Fourier single shot rapid acquisition with relaxation enhancement (RARE) acquisitions. The examinations were continued until the terminal ileum was reached or the water reabsorbed. The results were subjectively assessed for visibility of the small bowel. In all subjects the duodenum, jejunum and ileum were well demonstrated with valvulae conniventes clearly visible. The water column reached the terminal ileum and the caecum in six of the eight subjects but in the remaining two water remained in the small bowel and was ultimately reabsorbed. These preliminary results suggest that with further refinement such an approach may be practical for clinical magnetic resonance imaging of the small bowel.

Adult↗
PubMed1997

Non-invasive cholangio-pancreatography by breath-hold magnetic resonance imaging: preliminary results.

AIMS: A preliminary comparison of a prototype breath-hold magnetic resonance cholangio-pancreatography (MRCP) technique for non-invasive imaging of the pancreatic and biliary ducts with endoscopic retrograde cholangio-pancreatography (ERCP). METHOD: Twenty ERCP and MRCP examinations were performed in 19 patients referred for routine ERCP with suspected biliary or pancreatic abnormalities. The MRCP technique employed a modified heavily T2-weighted thick slice RARE sequence that allowed up to three images to be obtained in a 16 second breath-hold. The examinations were reported independently and the findings compared. RESULTS: MRCP accurately discriminated between patients without obstruction (n = 12) and those with (n = 8) and correctly diagnosed the cause of obstruction (three choledocholithiasis, five malignant stricture). In the 12 patients without obstruction the examinations were concordant in eight. In the remaining four patients MRCP provided more information than the corresponding ERCP study, diagnosing a pseudocyst in one patient and visualizing the entire pancreatic duct in three patients in whom this was not possible at ERCP. CONCLUSIONS: These preliminary results suggest that a breath-hold MRCP technique may allow the selection of those patients with obstructive lesions that require therapeutic ERCP intervention, and may have the potential to reduce the need for diagnostic ERCP examinations.

Adult↗
PubMed1997

Magnetic resonance imaging of the shoulder: assessment of effectiveness.

OBJECTIVES: To quantify how magnetic resonance imaging (MRI) influences clinicians' diagnosis, diagnostic confidence and management plans in patients with shoulder problems. To investigate whether such changes are associated with an improvement in health. METHODS: A prospective observational study on all patients referred to a regional centre for MRI of the shoulder over a 6-month period. Data on diagnosis, diagnostic confidence and proposed management before MRI were compared with diagnoses and actual management after MRI. In addition, short form 36 item (SF-36) health survey data were collected at referral and again 6 months later. RESULTS: In 86 of 99 MRI referrals there was sufficient clinical data for the patient to enter the study. MRI led to previously unsuspected diagnoses in 20 of 59 patients where the clinicians had provided full diagnostic information before and after the examination. When MRI confirmed the clinical diagnosis, significant improvements in clinicians' diagnostic confidence were found (P < 0.001). MRI led to a change in management (P < 0.05) in 44 (62%) of the 71 patients where full management plans were available. Health survey results were available in 62 patients; although there were some improvements in SF-36 scores, these did not reach statistical significance. CONCLUSION: Magnetic resonance imaging of the shoulder significantly influences clinicians' diagnoses and management plans. However, patients do not record a statistically significant improvement in health-related quality of life over 6 months.

Adolescent↗
PubMed1997

Magnetic resonance imaging or arthrography of the shoulder: which do patients prefer?

110 consecutive patients were asked about their degree of anxiety (SAI scores), pain (VAS scores) and preferences at various stages before and after imaging in order to determine whether patients with shoulder problems prefer MRI or shoulder arthrography. 88 patients underwent MRI, 42 arthrography and 19 both. Mean levels of anxiety were slightly higher for patients undergoing MRI than those having arthrography, but this difference was not statistically significant. There was a statistically significant (p < 0.03) reduction in anxiety after arthrography, but not following MRI. Pain scores fell for both patient groups while at rest during the imaging procedure compared with their pre-imaging baseline measurement. This was statistically significant (p < 0.03) for MRI, but not for arthrography. A significantly higher proportion (p < 0.001) of patients found MRI unpleasant or extremely unpleasant (20/77) compared with arthrography (3/41). Of the 25 patients who expressed a preference on the basis of past or current experience, 11 preferred MRI and 14 arthrography (NS). There was no significant difference in the proportion of patients who would not allow the test to be repeated (29/73 for MRI, 15/39 for arthrography): Although there were minor differences in both the anxiety and pain experienced by patients undergoing MRI and arthrography, this study did not reveal any firm preference for either investigation.

Adolescent↗
PubMed1996

Magnetic resonance imaging of transverse acoustic strain waves.

We describe a phase contrast based MRI technique with high sensitivity to cyclic displacement that is capable of quantitatively imaging acoustic strain waves in tissue-like materials. A formalism for considering gradient waveforms as basis functions to measure arbitrary cyclic motion waveforms is introduced. Experiments with tissue-like agarose gel phantoms show that it is possible to measure small cyclic displacements at a submicron level by an appropriate choice of the applied gradient basis function and to use this capability to observe the spatial and temporal pattern of displacements caused by acoustic strain waves. The propagation characteristics of strain waves are determined by the mechanical properties of the media. It is therefore possible to use this technique to noninvasively estimate material properties such as elastic modulus.

Acoustics↗
PubMed1996

Magnetic resonance imaging of the knee: assessment of effectiveness.

OBJECTIVES: To quantify how magnetic resonance imaging (MRI) influences clinicians' diagnoses, diagnostic confidence and management plans in patients with knee problems. To investigate whether these changes can bring about an improvement in health. METHODS: This was a prospective observational study on all patients referred to a regional unit for MRI of the knee over a 6-month-period. Data on diagnosis, diagnostic confidence and proposed management before MRI was compared with diagnoses and actual management after MRI. In addition, short form 36 item (SF-36) health survey data was collected at referral and again 6 months later. RESULTS: Three hundred and thirty-two patients were entered into the study. MRI led to previously unsuspected diagnosis in 69 of 269 patients with available data. When MRI confirmed the clinical diagnosis, significant improvements in clinicians' diagnostic confidence were found (P < 0.01 for medical meniscus, P < 0.05 lateral meniscus, P < 0.05 anterior cruciate). MRI led to a change in management in 180 (63%) of 288 patients (where data available). There was a significant shift away from surgical management after MRI (P < 0.01). SF-36 results were available in 206 patients. There was a significant improvement over time in five of the eight SF-36 scales (four at P < 0.001, one at P < 0.01). CONCLUSIONS: Magnetic resonance imaging significantly influences clinicians' diagnoses and management plans. These patients, examined by MRI, also recorded an improvement in health related quality of life.

Adolescent↗
PubMed1996

Magnetic resonance imaging of the knee: diagnostic performance studies.

OBJECTIVES: To review and reassess the published diagnostic performance statistics for MRI of the menisci and cruciate ligaments. To illustrate the potential sources and effects of bias in the evaluation of this widely accepted diagnostic technique. METHODS: Published evaluations of knee MRI were identified from the literature. Criteria for inclusion in the review were a total sample size > or = 35, arthroscopic correlation of MRI findings and presentation of complete results. Diagnostic performance statistics were then recalculated for each published study. RESULTS: Twenty-two studies were identified with sample sizes between 35 and 1014. The overall sensitivity for MRI of the menisci and cruciates was 0.88 (95% confidence interval 0.86-0.90). The overall specificity was 0.94 (0.93-0.94). Sampling error varied widely amongst studies and was rarely quantified. CONCLUSIONS: Diagnostic performance statistics are widely used. It is still not well appreciated that these are subject to sampling error. Such errors make meaningful comparisons between published studies more difficult. Nevertheless, the results for meniscal and cruciate lesions are consistently high and support the use of MRI for these common problems. The diagnostic performance of other applications of MRI should be subjected to similar critical review.

Anterior Cruciate Ligament↗
PubMed1996

MR sialography. Work in progress.

PURPOSE: To develop a noninvasive method for demonstrating the main salivary gland duct systems. MATERIALS AND METHODS: The authors developed a magnetic resonance (MR) imaging protocol that uses a heavily T2-weighted (echo time, 750 msec), fat-suppressed pulse sequence and rapid acquisition with relaxation enhancement. The technique was optimized to depict fluid within a two-dimensional thick slab. A preliminary evaluation was performed by examining the major salivary gland ducts in 10 asymptomatic volunteers and three symptomatic patients with known salivary duct abnormalities. RESULTS: The main parotid gland ducts were clearly demonstrated in all volunteers. The submandibular ducts were visible in all cases, although not always on projection images. In the three patients, the MR technique clearly demonstrated bilateral sialectasis, a calculus obstructing the left submandibular duct, and a fluid-filled ranula, respectively. CONCLUSION: Preliminary work indicates that this MR technique can successfully demonstrate both normal and abnormal parotid and submandibular gland duct systems and has several advantages over conventional x-ray sialography.

Adolescent↗
PubMed1995

Magnetic resonance elastography by direct visualization of propagating acoustic strain waves.

A nuclear magnetic resonance imaging (MRI) method is presented for quantitatively mapping the physical response of a material to harmonic mechanical excitation. The resulting images allow calculation of regional mechanical properties. Measurements of shear modulus obtained with the MRI technique in gel materials correlate with independent measurements of static shear modulus. The results indicate that displacement patterns corresponding to cyclic displacements smaller than 200 nanometers can be measured. The findings suggest the feasibility of a medical imaging technique for delineating elasticity and other mechanical properties of tissue.

Acoustic Stimulation↗
PubMed1995

Non-invasive measurement of azygos venous blood flow using magnetic resonance.

Monitoring treatment efficacy in patients with portal venous hypertension has been limited by the difficulty of direct or indirect assessment of portal vein pressure. The majority of currently available haemodynamic tests, such as hepatic vein wedge pressure or azygos vein flow measurement by thermodilution catheter, are invasive which has restricted their application. We describe a non-invasive cine phase contrast magnetic resonance technique for quantitative measurements of bulk volume flow and for demonstrating flow changes during the cardiac cycle in the azygos vein. The technique was used to analyse the azygos vein flow in seven adult volunteers and five patients with biopsy-confirmed chronic liver disease, portal hypertension and endoscopically proven oesophageal varices. In the volunteers the mean volume flow rates varied between 81 and 241 ml/min with a mean for the group of 171 ml/min. The patients had a significantly higher mean volume flow rate of 628 ml/min (p < 0.01), with a range of 339 to 945 ml/min. These preliminary results suggest that cine phase contrast magnetic resonance angiography is a practical non-invasive method for measuring absolute azygos vein flow, and may provide a non-invasive method of monitoring portal hypertension.

Adult↗
PubMed1995

Comparison of breath-hold fast spin-echo and conventional spin-echo pulse sequences for T2-weighted MR imaging of liver lesions.

PURPOSE: To evaluate a breath-hold fast spin-echo (SE) technique for T2-weighted magnetic resonance (MR) imaging of liver lesions. MATERIALS AND METHODS: A fast SE technique was developed that enabled six sections to be imaged per 16-second breath hold with a single echo. Resulting images were compared with those obtained with the first echo of a conventional dual-echo T2-weighted SE sequence (16 minutes 55 seconds for 18 sections). Thirty-one patients with malignant focal hepatic lesions were studied prospectively. The images were compared quantitatively and qualitatively. RESULTS: Quantitatively, the contrast and contrast-to-noise ratios for the fast SE images were 20% +/- 5 and 19% +/- 8 greater, respectively, than those for the conventional T2-weighted SE images of the 54 representative lesions. Qualitatively, fast SE images had less image artifact, enabled comparable or better lesion sizing, and greatly improved depiction of extrahepatic structures compared with conventional T2-weighted SE images. CONCLUSION: The fast SE technique with breath holding provides diagnostically useful liver images in a greatly decreased acquisition time.

Adult↗
PubMed1995

Errors at knee magnetic resonance imaging: true or false?

Amongst a series of 332 patients undergoing a prospective evaluation of the influence of magnetic resonance imaging (MRI) on diagnosis and outcome, arthroscopic correlation became available in 92 knees (91 patients). The MRI report, the arthroscopic findings and the patient's case notes were reviewed by a consensus panel. With respect to the menisci and cruciate ligaments, the formal radiological report was at variance with the arthroscopic findings in 22/349 sites where there had been no previous surgery (10 medial meniscus, six lateral meniscus and six anterior cruciate ligament). 12 of these 22 errors were considered, on review, to be genuine MRI errors. However, considerable controversy remains as to whether the other 10 "errors" were true or false. There are several factors which contribute to such controversy. These include technically difficult arthroscopies, delays between MRI and arthroscopy, and ambiguities in the wording of both the referral letter and the radiological report. These factors should be considered when evaluating the diagnostic performance of both MRI and arthroscopy.

Adolescent↗
PubMed1994

A comparison of MR and duplex Doppler ultrasound for vascular assessment prior to orthotopic liver transplantation.

A prospective blinded comparison of duplex Doppler ultrasound (DDU) and a magnetic resonance angiography (MRA) 2-D time-of-flight technique was performed to assess the hepatic vasculature in 23 adult patients referred for orthotopic liver transplantation. Both techniques confirmed patency of the inferior vena cava in all patients, demonstrated a complete portal vein occlusion in one patient, and accurately defined the vascular and organ anatomy in a patient with situs inversus. The results were confirmed at surgery in 18 of the patients who have subsequently undergone liver transplantation. In one patient a partial portal vein thrombosis was found at surgery which was not detected by either imaging technique. MRA was more sensitive overall in detecting porto-systemic collaterals (31 locations in 17 patients) compared with ultrasound (24 locations in 17 patients), although ultrasound detected more patients with recanalized para-umbilical veins (DDU: 10 patients; MRA: 8 patients). These results indicate that a simple MRA technique can equal duplex Doppler ultrasound for the non-invasive assessment of patency of the hepatic vasculature and should be considered when DDU examination is equivocal or technically inadequate. MRA may provide additional information on the presence and size of porto-systemic collaterals which may be of value in monitoring portal hypertension.

Adult↗
PubMed1994

Magnetic resonance.

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Echo-Planar Imaging↗
PubMed1993

Artifacts in the ascending aorta on computed tomography: another measure of aortic distensibility?

The appearance of the ascending aorta was studied in 53 patients undergoing computed tomography on a modern system capable of routine 1 second data acquisition times. Motion artifact caused a blurred aortic outline in 48 patients; the extent was objectively and subjectively assessed. The maximum and minimum cross-sectional aortic areas were measured at the margins of the blur. The area of the blur, expressed as a fraction of the minimum aortic cross-sectional area, decreased with age (P < 0.001) and was significantly smaller in the 13 patients with known cardiovascular problems (P < 0.05). These findings were substantiated by the subjective gradings which showed less marked artifacts amongst elderly patients (although this observation did not reach statistical significance). Artifacts were less prominent in 16 patients with evidence of aortic wall calcification, both on subjective grading (P < 0.05) and formal area measurements (P < 0.05). These observations lead us to believe our postulation that this artifact is an indicator of aortic distensibility and thus, indirectly, of cardiovascular status.

Adolescent↗