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Biomedical subjects

R M Summers

Publications and source records attributed to R M Summers.

At least 37 records · Page 2Linked to original sources
PubMed1996

A Fourier based algorithm for tracking SPAMM tags in gated magnetic resonance cardiac images.

A method is described for automatically tracking spatial modulation of magnetization tag lines on gated cardiac images. The method differs from previously reported methods in that it uses Fourier based spatial frequency and phase information to separately track horizontal and vertical tag lines. Use of global information from the frequency spectrum of an entire set of tag lines was hypothesized to result in a robust algorithm with decreased sensitivity to noise. The method was validated in several ways: first, actual tagged cardiac images at end diastole were deformed known amounts, and the algorithm's predictions compared to the known deformations. Second, tagged, gated images of the thigh muscle (assumed to have similar signal to noise characteristics as cardiac images, but to not deform with time) were created. Again the algorithmic predictions could be compared to the known (zero magnitude) deformations and to thigh images which had been artificially deformed. Finally, actual cardiac tagged images were acquired, and comparisons made between manual, visual, determinations of tag line locations, and those predicted by the algorithm. At 0.5 T, the mean bias of the method was < 0.34 mm even at large deformations and at late (noisy) times. The standard deviation of the method, estimated from the tagged thigh images, was < 0.7 mm even at late times. The method may be expected to have even lower error at higher field strengths.

Algorithms↗
PubMed1996

Virtual bronchoscopy: segmentation method for real-time display.

Computed tomography (CT) data sets obtained in 14 patients were used in a segmentation method for virtual bronchoscopy (VB). The method constrained the distance of propagation of a region-growing algorithm. The resulting three-dimensional bronchial model was a faithful representation of the source CT data and could be manipulated in real time at frame rates of one to two frames per second. Preliminary data showed that 90% of bronchi (up to third order) measureable on multiplanar CT reformations were also measurable at VB. The bronchial diameters measured at VB were within 1 mm of those measured on multi-planar reconstructions of the CT data.

Adult↗
PubMed1996

Caries experience, tooth loss and oral health-related behaviours among Bangladeshi women resident in West Yorkshire, UK.

Several studies have reported high levels of caries experience among young Muslim Asian children, but there has been little corresponding information on adult dental health or related health behaviours. This paper presents the results of a questionnaire together with clinical oral findings among first generation Bangladeshi women aged over 25 years. The majority chewed betel quid with tobacco, were of rural origin, used traditional oral hygiene practices and had never visited a dentist. Of the 247 examined, only one was edentulous. A very low level of caries experience was recorded, a mean DFT score of 1.87 at 25-34 years of age, with an average of 1.05 missing teeth. Coronal caries experience was found to be independent of oral hygiene methods, including the use of fluoride toothpaste, or the frequency of betel quid chewing. It was concluded that Bangladeshi adult women have considerably lower levels of caries experience and tooth loss than United Kingdom adults as represented in recent national surveys.

Adult↗
PubMed1995

MR microscopy of the rat carotid artery after balloon injury by using an implanted imaging coil.

Neointimal hyperplasia after angioplasty was followed in vivo in rats by using MR microscopy and surgically implanted RF imaging coils. By using an inductively coupled pick-up coil, the arteries were imaged 4 days before and 3, 7, and 14 days after angioplasty with a 3DFT spin echo sequence. Eight of 10 angioplastied rats showed moderate to severe stensois based MR measures of lumen diameter reduction from baseline images. There was a good correlation between total wall thickness between MR and hematoxylin and eosin (H&E)-stained sections obtained on the last day. Arteries in the intact and sham groups remained unchanged from baseline measurements. Because this imaging technique examines the artery under in vivo conditions of arterial pressure and flow, it promises to be a useful tool for evaluating pharmacological and mechanical methods of reducing the incidence of vascular stenosis.

Angioplasty, Balloon↗
PubMed1994

The use of tobacco and betel quid ('pan') among Bangladeshi women in West Yorkshire.

The high prevalence of oral cancer in South Asia has been linked to tobacco use particularly in conjunction with chewing betel quid or 'pan'. However, it is not known whether and to what extent these habits are practised by Asian people in the United Kingdom. Home based interviews using semi-structured questionnaires were undertaken among 296 first generation Bangladeshi women resident in inner-city Leeds and Bradford, West Yorkshire. 'Pan' was reportedly chewed by 282 (95 per cent) of the women, of whom 174 (62 per cent) added tobacco in leaf form, and 75 (27 per cent) as a component of zarda. Those who consumed more 'pans' daily were significantly older, less literate, had a lower educational attainment, and were more likely to believe that chewing betel quid was beneficial. Cigarette smoking was practised by 9 per cent, this group being older and having lived in the UK longer. Burnt tobacco leaves were used as an oral hygiene aid by 20 per cent. Over half (58 per cent) of the sample had never visited a dentist, the majority deeming it unnecessary. The use of tobacco and 'pan' imply an increased risk for oral cancer and precancer. Since 'pan' chewing is a traditional custom, health promotion within these communities would require a sensitive approach. Health personnel likely to be consulted by Asian groups who chew 'pan' should be aware of the danger to oral health posed by this practice.

Adult↗
PubMed1992

Case report 712: Hemorrhagic synovial cyst arising from right L2-3 facet joint.

Synovial cysts are a common complication of osteoarthritis in the lumbar spine, causing pain and neurological symptoms. However with early diagnosis a good clinical result can be expected. This report describes a documented case of hemorrhage into a synovial cyst demonstrated on both MR and CT imaging and summarizes the relevant diagnostic features. The sites of origin of such a synovial hemorrhagic cyst are described and its relationship to an arthritic facet joint is stressed.

Hemorrhage↗
PubMed1992

Laminar submerged jets by color Doppler ultrasound. A model of the ureteral jet phenomenon.

RATIONALE AND OBJECTIVES: The authors developed and tested a technique to noninvasively measure ureterovesical junction (UVJ) pressure gradients. Such a technique could be used to evaluate ureteral reflux and obstruction. METHODS: Color Doppler ultrasound measurements of an in vitro model of the ureteral jet were performed. RESULTS: The authors show that the orificial rate of momentum transfer of the ureteral jet (from which the intraluminal pressure in the ureter can be calculated) can be determined to within 45% to 94% of its true value depending primarily on the flow sensitivity of the color flow imager. Marked improvement in the momentum calculation (> 80%) is achieved when a low-flow sensitivity is used. CONCLUSION: Such noninvasive measurements could replace more invasive techniques (eg, the Whitaker test or cystoscopy with or without ureteral cannulation), which seriously perturb the system of interest.

Humans↗
PubMed1991

Sodium nuclear magnetic resonance imaging of neuroblastoma in the nude mouse.

The average concentration of sodium is known to be elevated in some tumors relative to normal tissues, and necrosis is suspected of being a possible cause. We have performed in vivo sodium-23 magnetic resonance imaging (MRI) of IMR-5 neuroblastoma in the athymic nude mouse on a 1.9-Tesla, small-bore animal imaging system. We compared the sodium images with histologic analysis for necrosis and with proton images, chemical measurements of water and blood content, and sodium and potassium concentrations. We found that the sodium concentrations determined by MRI were proportional to the fraction of the tumor tissue that was necrotic. Correlation coefficients varied from 0.65 to 0.78, depending upon how the data were selected. With further refinement it is possible that the sodium concentration measurements determined noninvasively by MRI may have applications as part of clinical diagnosis and staging of soft tissue tumors.

Animals↗
PubMed1988

Sodium NMR imaging of lung water in rats.

Coronal proton and sodium images of control rats and rats with either increased permeability edema produced by intravenous alloxan (300 mg/kg) or increased pressure edema produced by saline infusion (2 ml/min) were obtained. Axial chest CT images were used to monitor the development of pulmonary edema. Immediately after the imaging session compartmental lung water was measured gravimetrically. The sodium and proton imagings were done sequentially in a 31-cm-bore 1.9-T magnet without moving the animal. The anatomical boundaries of the lung on the proton images were transferred to the sodium images for calculation of the average sodium signal intensity which was determined by extrapolating the mean values from five echoes to time zero. The sodium signal intensity was correlated (r = 0.7) with the total water fraction. There was poor correlation (r = 0.56) with the extravascular water due to confounding by the sodium vascular signal.

Animals↗
PubMed1988

Dextran-magnetite: a contrast agent for sodium-23 MRI.

Dextran-magnetite, a superparamagnetic compound, is a powerful relaxation reagent for sodium. Administered intravenously, it is confined mainly to the vasculature and eliminates the signal from plasma sodium, a significant component of the tissue sodium signal. Applications of dextran-magnetite for in vivo sodium imaging of a normal rat and rats with a tumor and experimentally induced peripheral edema are shown. Our results indicate that dextran-magnetite may be useful for improving tumor detection and for imaging of edema. To our knowledge, this is the first report of a contrast agent suitable for sodium magnetic resonance imaging.

Adenocarcinoma↗
PubMed1987

The flip-angle effect: a method for detection of sodium-23 quadrupole splitting in tissue.

A method is presented for the detection of quadrupole splitting in tissue, where the spectral line splittings are typically unobservable. The method used is a study of the rate of rotation of the flip angle as a function of radiofrequency (rf) amplitude. Our results with samples of skeletal muscle and cat brain indicate the absence of quadrupole splitting.

Animals↗
PubMed1986

A computer simulation of nuclear magnetic resonance imaging.

A modular, user-friendly computer simulation of NMR imaging was created for the DEC VAX computer. This simulation is novel in that complex imaging phenomena, such as chemical shifts and flow, may be easily studied. Other features include spin warp and backprojection imaging, movie generation, and simulation of image contrast, composite pulse sequences, motion artifacts, aliasing, selective excitation, field inhomogeneity, noise and signal averaging. The simulation incorporates fast Fourier transform and graphics modules for processing and display of one- and two-dimensional images. Examples which illustrate features of the program are shown. The simulation is a useful tool for both the sophisticated and the beginning user of NMR imaging. It serves as a drawing board for studying MRI phenomena and a teaching program for demonstrating basic techniques.

Adipose Tissue↗
PubMed1986

Respiratory effects in two-dimensional Fourier transform MR imaging.

Respiratory and other regular motions during two-dimensional Fourier transform magnetic resonance imaging produce image artifacts consisting of local blurring and more or less regularly spaced "ghost" images propagating along the direction of the phase-encoding magnetic field gradient. The patterns of these ghost artifacts can be understood in terms of the technique of image production and basic properties of the discrete Fourier transform. This understanding permits, without respiratory gating, production of images of improved quality in body regions in which there is significant respiratory motion. In particular, the ghosts can be maximally separated from the primary image by choosing intervals between phase-encoding gradient pulse increments that are equal to one-half the respiratory period; they can be minimally separated by choosing an interval equal to the respiratory period. Increasing the number of signal averages between each phase-encoding increment decreases the intensity of the ghosts.

Abdomen↗
PubMedDate not supplied

Challenges for computer-aided diagnosis for CT colonography.

Computer-aided diagnosis for computed tomographic colonography is in its infancy but has the potential to improve sensitivity and decrease costs for colonic polyp detection. This article reviews the current state of research in this nascent field and explores major challenges and avenues for future work.

Colon↗
PubMedDate not supplied

Pelvic CT findings after radical prostatectomy.

OBJECTIVE AND METHODS: To evaluate the spectrum of pelvic CT findings in patients who have had radical prostatectomy, we retrospectively evaluated the pelvic CT of 17 patients after surgery for prostate cancer. All patients were thought to be clinically free of local recurrence of carcinoma. RESULTS: The bladder base was retropubic in 100%, the levator sling was well delineated in its entirety in only 88%, and fat was clearly demonstrated between the rectum and bladder base in only 44%. Unsuspected findings in this group included soft tissue density structures in the resected bed of the seminal vesicles (88%) and a transversely oriented, soft tissue density bar between the bladder base and rectum (53%). A variety of symmetric abnormalities are commonly seen on postprostatectomy pelvic CT. CONCLUSION: Seminal vesical-like soft tissue structures are routinely visualized, and a horizontal bar of soft tissue in the rectovesical space is commonly demonstrated. These structures should not be confused with local tumor recurrence.

Aged↗
PubMedDate not supplied

Gadolinium-enhanced 3D MRA prior to isolated hepatic perfusion for metastases.

PURPOSE: Isolated hepatic perfusion (IHP) is a new treatment for patients with isolated unresectable liver metastases, which can result in a partial or complete response in approximately 75% of patients. Preoperative knowledge of hepatic arterial anatomy is important to adequately perfuse the liver. Digital subtraction angiography (DSA) is currently used to identify the hepatic arterial anatomy. The purpose of this study was to determine if MR angiography (MRA) could replace DSA prior to IHP. METHOD: Twenty-seven patients scheduled to undergo IHP underwent MRA with a contrast-enhanced 3D time-of-flight gradient echo sequence. Both maximal intensity projections (MIPs) and source coronal images were used to evaluate the images. The results of the MRA were interpreted by two readers who were blinded to the surgical results. The first 17 patients also underwent DSA, and a separate comparison was made with those results. Anatomy was characterized as either normal hepatic arteries (NHAs), normal vasculature with an accessory left hepatic artery (aLHA), or a replaced right hepatic artery (rRHA). RESULTS: MRA correctly detected all 22 patients with NHAs but also identified 6 aLHAs, of which only 2 were confirmed surgically. MRA correctly detected all five rRHAs. MIP images alone accurately depicted the hepatic arterial anatomy in only 9 of 27 (33%), usually because significant vessels were not visualized or their origin could not be determined. Source coronal images were required to accurately determine the anatomy in all patients. Among the 17 patients who underwent DSA, MRA detected 14 of 14 with NHA and 3 of 3 with rRHA. Six aLHAs were identified by MRA and five were confirmed by DSA. CONCLUSION: Enhanced 3D MRA is an accurate method of depicting the hepatic arterial supply. In comparison to surgery, MRA overestimates the number of aLHAs, but this may be because these small vessels are not detected at surgery. Based on the results of this study, DSA has been replaced by MRA in the planning of IHP at our institution. A better display of MRA images is needed as MIP images were usually insensitive for the small caliber arteries supplying the liver.

Angiography, Digital Subtraction↗