Search PubMed⌕ Search

Biomedical subjects

D J Lomas

Publications and source records attributed to D J Lomas.

At least 19 recordsLinked to original sources
PubMed2002

Technical developments in bowel MRI.

Magnetic resonance techniques for imaging the gastrointestinal (GI) tract continue to evolve as a result of rapid technical improvement. This review discusses the diagnostic and technical requirements for optimal bowel imaging and to what extent MR is capable of fulfilling these in comparison with established X-ray techniques. New approaches that have recently been demonstrated for the esophagus as well as small and large bowel are described. These developments indicate that MR imaging of the GI tract is likely to make the transition from research development to routine clinical application.

Contrast Media↗
PubMed2002

Interactive body magnetic resonance fluoroscopy using modified single-shot half-Fourier rapid acquisition with relaxation enhancement (RARE) with multiparameter control.

PURPOSE: To develop a technique for interactive fluoroscopic abdominal magnetic resonance imaging (MRI) based on a single-shot half-Fourier rapid acquisition and relaxation-enhanced sequence. MATERIALS AND METHODS: The sequence was modified by incorporating inner-volume excitation, driven-equilibrium signal enhancement, and reduced flip angle refocusing pulses. Contrast control was provided by integrating "on-the-fly" selection of phase encoding view order, fat suppression, and section thickness. The resulting sequence was evaluated with phantom experiments to quantify the signal-to-noise ratio (SNR) effects of the modifications and in healthy volunteers for imaging the bile ducts, stomach, and duodenum using water and gaseous contrast media. RESULTS: Observed SNR relating to driven-equilibrium and flip angle scaling matched theoretical predictions. Volunteer examinations demonstrated the ability of the modified sequence to provide interactive, artifact-free imaging of the abdomen, including switching between conventional proton density-weighted, T2-weighted imaging and "hydrographic" projection imaging. CONCLUSION: Refinement of this technique may provide an abdomino-pelvic imaging capability similar in concept to real-time ultrasound, but with the advantages of MRI.

Abdomen↗
PubMed2001

MR imaging of the wrist: effect on clinical diagnosis and patient care.

PURPOSE: To evaluate the effect of magnetic resonance (MR) imaging of the wrist on clinicians' diagnoses, diagnostic certainty, and patient care. MATERIALS AND METHODS: A controlled observational study was performed. Referring clinicians completed questionnaires about diagnosis and intended management before and after wrist MR imaging. One hundred eighteen consecutive patients referred for MR imaging of the wrist were recruited from the MR imaging units at a regional teaching hospital and a large district general hospital. The main measures were changes in the clinicians' leading and subsidiary diagnoses after MR imaging, their certainty in these diagnoses, and changes in intended patient care. RESULTS: Questionnaires were incorrectly completed for five patients, questionnaires were not returned for three, appointments were canceled for 10, and two could not tolerate the MR examination. Complete follow-up data were available for 98 patients. The clinical diagnosis changed in 55 of 98 patients; in the remaining 43 patients, diagnostic certainty increased in 23. Clinicians reported that MR imaging had substantially improved their understanding of the disease in 67 of 98 patients. The care plan changed in 45 of 98 patients, with a shift away from surgical treatment. Twenty-eight patients were discharged without further investigation. MR imaging was similarly effective in the regional teaching center and the district general hospital. CONCLUSION: MR imaging of the wrist influences clinicians' diagnoses and management plans.

Humans↗
PubMed2001

Colon carcinoma: MR imaging with CO2 enema--pilot study.

Prior to surgery, seven patients with known colonic tumors underwent breath-hold single-shot fast spin-echo magnetic resonance imaging during a CO2 enema. The images were evaluated for depiction of tumor, adjacent structures, and the remaining colon, and findings were compared with findings at surgery. In all seven patients, the tumor was demonstrated, and in four (57%), breach of the muscularis propria was correctly predicted.

Adult↗
PubMed2000

Dual-echo breathhold T(2)-weighted fast spin echo MR imaging of liver lesions.

The purpose of this study was to develop a multi-shot dual-echo breathhold fast spin echo technique (DFSE) and compare it with conventional spin echo (T2SE) for T(2)-weighted MR imaging of liver lesions. The DFSE acquisition (EffTE1/EffTE2/TR = 66/143/2100 ms) imaged 5 sections per 17 s breathhold. T2SE imaging (TE1/TE2/TR = 60/120/2500 ms) required 16:55 (min:s) for 14 sections. Both techniques used a receive-only phased-array abdominal multicoil and provided 192 x 256 effective resolution. The results showed first and second echo relative DFSE/T2SE contrast values for 27 representative lesions (15 consecutive patients) were 1.08 +/- 0.05 and 1.16 +/- 0.09 (mean +/- STD mean), respectively. Corresponding CNR values were 1.12 +/- 0.09 and 0.97 +/- 0.12. Overall DFSE was comparable-to-superior to T2SE for lesion sizing and image artifact. DFSE lesion detection was inferior to T2SE's in several patient studies because of decreased conspicuity of lesions located near multicoil edges and because of poor breathhold-to-breathhold reproducibility and lack of breathholding. However both DFSE (and T2SE) provided lesion detection rated to be of diagnostic quality for all patient studies. In conclusion, we found that DFSE provides diagnostically useful dual-echo T(2)-weighted MR liver images in a greatly decreased acquisition time.

Adult↗
PubMed2000

Massive hepatic fibrosis in Gaucher's disease: clinico-pathological and radiological features.

Hepatomegaly is frequent in patients with type 1 Gaucher's disease and is associated with infiltration of the liver with pathological macrophages. Most patients suffer no significant clinical consequences, but a few develop portal hypertension which may progress to parenchymal liver failure. We describe four patients with Gaucher's disease who have developed portal hypertension. We have reviewed their clinical histories and all available histological and radiological material. All had severe Gaucher's disease with multi-organ involvement, and had undergone splenectomy in childhood. Histologically, this advanced liver disease was characterized by a picture of extreme and advanced confluent fibrosis occupying the central region of the liver. This massive fibrosis is associated with characteristic radiological appearances. The liver histology in these cases is highly unusual and virtually unknown in other conditions. Our studies indicate that without specific treatment the liver disease is progressive and rapidly fatal. However, institution of enzyme replacement therapy with imiglucerase may have beneficial effects even when the condition is far advanced.

Adolescent↗
PubMed2000

High resolution magnetic resonance imaging of atherosclerosis and the response to balloon angioplasty.

OBJECTIVE: To explore the use of high resolution magnetic resonance imaging (MRI) of the popliteal artery in defining atheroscelerotic lesions and to monitor the remodelling response to balloon angioplasty. METHODS: Four patients (aged 49-67) with symptomatic discrete popliteal artery stenoses, as demonstrated by conventional angiography, underwent balloon angioplasty. MRI of the diseased vessel was performed before and one week, one month, three months, and six months after therapeutic balloon angioplasty. Cine phase contrast MRI was used to estimate blood flow just proximal to the lesion before and after angioplasty. RESULTS: In all patients the extent of the atherosclerotic plaque could be defined, such that even in segments of vessel which were angiographically "normal", atherosclerotic lesions with cross sectional areas ranging from 49% to 76% of potential lumen area were identified. Following angioplasty, plaque fissuring and local dissection were easily identified and serial changes in lumen diameter, blood flow. and lesion size could be documented. CONCLUSIONS: High resolution MRI can define the extent of atherosclerotic plaque in the peripheral vasculature and demonstrate the changes that occur with remodelling and restenosis following angioplasty. As a safe, reproducible technique MRI is ideal for assessing plaque and monitoring intervention, but further technological developments will be needed if similar or better images are to be achieved in other vascular beds.

Aged↗
PubMed2000

Magnetic resonance cholangiopancreatography.

Magnetic resonance imaging can now offer a robust and non-invasive diagnostic alternative to the established imaging investigations of the biliary and pancreatic ducts. This article briefly reviews the underlying principles, technique, pitfalls and clinical applications.

Bile Duct Diseases↗
PubMed1999

MR cholangiopancreatography: prospective comparison of a breath-hold 2D projection technique with diagnostic ERCP.

The aim of this study was to compare prospectively a breath-hold projection magnetic resonance cholangiopancreatography (MRCP) technique with diagnostic endoscopic retrograde cholangiopancreatography (ERCP). Seventy-six patients with suspected strictures or choledocholithiasis were referred for MRCP and subsequent ERCP examination, which were performed within 4 h of each other. The MRCP technique was performed using fat-suppressed rapid acquisition with relaxation enhancement (RARE) projection images obtained in standardised planes with additional targeted projections as required by the supervising radiologist. Two radiologists (in consensus) assessed the MRCP results prospectively and independently for the presence of bile duct calculi, strictures, non-specific biliary dilatation and pancreatic duct dilatation, and recorded a single primary diagnosis. The ERCP was assessed prospectively and independently by a single endoscopist and used as a gold standard for comparison with MRCP. Diagnostic agreement was assessed by the Kappa statistic. The MRCP technique failed in two patients and ERCP in five. In the remaining 69 referrals ERCP demonstrated normal findings in 23 cases, strictures in 19 cases, choledocholithiasis in 9 cases, non-specific biliary dilatation in 14 cases and chronic pancreatitis in 4 cases. The MRCP technique correctly demonstrated 22 of 23 normal cases, 19 strictures with one false positive (sensitivity 100 %, specificity 98 %), all 9 cases of choledocholithiasis with two false positives (sensitivity 100 %, specificity 97 %), 12 of 14 cases of non-specific biliary dilatation and only 1 of 4 cases of chronic pancreatitis. There was overall good agreement for diagnosis based on a kappa value of 0.88. Breath-hold projection MRCP can provide non-invasively comparable diagnostic information to diagnostic ERCP for suspected choledocholithiasis and biliary strictures and may allow more selective use of therapeutic ERCP.

Adult↗
PubMed1999

Vesicouterine fistula: MRI diagnosis.

A case of vesicouterine fistula in a young woman following caesarean section is presented. The diagnosis was established successfully using heavily T2-weighted MRI which clearly demonstrated fluid within the fistula, obviating the need for conventional radiographic contrast examination.

Adult↗
PubMed1999

How reliable is modern breast imaging in differentiating benign from malignant breast lesions in the symptomatic population?

AIM: To assess the ability of mammography and ultrasound individually and in combination to predict whether a breast abnormality is benign or malignant in patients with symptomatic breast disease. MATERIALS AND METHODS: Patients included were those in whom histological confirmation of the abnormality following surgical excision was available. Mammographic and ultrasound appearances were prospectively classified using a four-point scale (1 = no significant lesion, 2 = benign lesion, 3 = possibly malignant, 4 = probably malignant). RESULTS: Histological confirmation following surgical excision was available in 559 patients, of which 303 were benign and 256 were malignant. The imaging classification was correlated with histology in these 559 lesions. In predicting final histology, the sensitivity and specificity of mammography alone were 78.9 and 82.7%, respectively, of ultrasound alone were 88.9 and 77.9%, respectively, and of mammography and ultrasound in combination were 94.2 and 67.9%, respectively. Only one patient had both a mammogram and ultrasound reported as normal (category 1 for both tests) in whom subsequent histology revealed a carcinoma (0.4% of all carcinomas). CONCLUSION: We found that the extensive use of ultrasound increases the cancer detection rate in this selected population by 14%.

Adult↗
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↗