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Biomedical subjects

R A Lerski

Publications and source records attributed to R A Lerski.

At least 19 recordsLinked to original sources
PubMed1999

Multicentre magnetic resonance texture analysis trial using reticulated foam test objects.

Texture analysis in magnetic resonance imaging has the ability to provide useful diagnostic information with respect to the discrimination of disease states of a single tissue or the separation of different tissues. However, for widespread use it is necessary to determine how texture measurements carried out in one center relate to those carried out in another. To this end, a multicentre trial has been performed where reticulated foam test objects have been scanned in six European centers according to a fixed protocol. It has been concluded that texture measurements are not transportable between centers. Principal component models calculated from the texture parameters collected in one center do not fit the data collected in another. Further trials are to investigate whether the reticulated foam test objects may be used to normalize tissue texture data collected in different centers.

Europe↗
PubMed1998

The use of reticulated foam in texture test objects for magnetic resonance imaging.

The use of texture analysis in magnetic resonance imaging requires the availability of texture test objects for use in standardisation of in vivo measurement. A series of such objects of varying texture has been developed using reticulated foam, which has an open pore structure. The texture properties of these foams have been compared with in vivo brain and the ability of texture analysis to discriminate the different porosities of foam and brain (white matter) demonstrated.

Brain↗
PubMed1998

Palliation of pain associated with metastatic bone cancer using samarium-153 lexidronam: a double-blind placebo-controlled clinical trial.

PURPOSE: To evaluate the effectiveness and safety of samarium-153 (153Sm) lexidronam (EDTMP) in a double-blind, placebo-controlled study. PATIENTS AND METHODS: Patients with painful bone metastases secondary to a variety of primary malignancies were randomized to receive 153Sm-EDTMP 0.5 or 1.0 mCi/kg, or placebo. Treatment was unblinded for patients who did not respond by week 4, with those who had received placebo eligible to receive 1.0 mCi/kg of active drug in an open-label manner. Patient and physician evaluations were used to assess pain relief, as was concurrent change in opioid analgesia. RESULTS: One hundred eighteen patients were enrolled onto the study. Patients who received 1.0 mCi/kg of active drug had significant reductions in pain during each of the first 4 weeks in both patient-rated and physician-rated evaluations. Pain relief was observed in 62% to 72% of those who received the 1.O-mCi/kg dose during the first 4 weeks, with marked or complete relief noted in 31% by week 4. Persistence of pain relief was seen through week 16 in 43% of patients who received 1.0 mCi/kg, of active drug. A significant correlation (P = .01) was observed between reductions in opioid analgesic use and pain scores only for those patients who received 1.0 mCi/kg 153Sm-EDTMP. Bone marrow suppression was mild, reversible, and not associated with grade 4 toxicity. CONCLUSION: A single dose of 1.0 mCi/kg of 153Sm-EDTMP provided relief from pain associated with bone metastases. Pain relief was observed within 1 week of administration and persisted until at least week 16 in the majority of patients who responded.

Adult↗
PubMed1993

Performance assessment and quality control in MRI by Eurospin test objects and protocols.

As part of its work, the European Concerted Action "Tissue Characterisation by MRS and MRI" (COMAC-BME) has expended considerable effort in the field of magnetic resonance imaging (MRI) quality control. A set of test objects--the Eurospin set--have been designed and rigorously tested in many systems throughout Europe. The full history of this development is described, together with a detailed presentation of the types of measurements that are achievable with such test objects and examples of the results. Further, the principles of more complex Stage II tests (which involve invasive interaction with the system) are introduced. Finally, simplified methods of quantifying the overall performance are discussed and the levels of MRI quality control from acceptance testing to routine quality assurance outlined.

Animals↗
PubMed1993

Trial of modifications to Eurospin MRI test objects.

The original design of the Eurospin test objects (Magn. Reson. Imaging 6:195-199; 1988) for the assessment of magnetic resonance imaging (MRI) image quality, was subjected to re-evaluation at several meetings during the subsequent years, culminating in some changes to the designs. Further, an annulus filled with saline was added to the set with the purpose of simulating the loading of the receiver coils normal in clinical use. All of these modified test objects were circulated among 8 European centres in a detailed experimental trial of their utility. The results are presented, indicating increased success and enhanced functionality of this set of test objects.

Animals↗
PubMed1993

MR image texture analysis--an approach to tissue characterization.

The role and value of texture analysis in the quantification of medical images is reviewed and the various methods described. The promise in magnetic resonance imaging is discussed and the coordinated research programme being carried out within the framework of the European Economic Community Concerted Action on Tissue Characterization by MRS and MRI is outlined. Tissue characterization of the human brain has been performed by texture analysis of proton relaxation time images using a standard MR whole body imager operating at 1.5 T and the results are presented.

Brain↗
PubMed1989

A test material for tissue characterisation and system calibration in MRI.

A tissue-equivalent test material for MRI has been produced from a polysaccharide gel, agarose, containing gadolinium chloride chelated to EDTA. By varying the amounts of each constituent, the T1 and T2 of the material can be varied independently. As a result, the entire range of in vivo tissue relaxation times can be covered. Through the mathematical modelling of the 1H relaxation theories for both the gel and chelated paramagnetic ion, it has been possible to create a material with relaxation properties and behaviour predictable as functions of both the Larmor frequency and temperature. The similarity of the material to in vivo tissues, in terms of its biological and physical NMR characteristics, makes it an excellent tissue-equivalent substance, in addition to being an accurate calibration standard for routine MRI.

Edetic Acid↗
PubMed1988

Quantitative magnetic resonance imaging in assessment of the blood-retinal barrier.

Application of magnetic resonance imaging (MRI) in two-dimensional quantitative assessment of blood-retinal barrier dysfunction was investigated in rabbits using a 0.1 T (4.25 MHz) resistive system. Reliable and consistent measurements of vitreous T1 were obtained repeatedly, in slices of width 5 mm and X-Y resolution of 1.2 mm. Calibration of reduction of T1 in eyes after injection of gadolinium-DTPA (Gd-DTPA) was performed, resulting in a dose-related response of relaxation rate (1/T1) to the dose of Gd-DTPA injected. Follow-up scans of injected eyes demonstrated a gradual spread of the T1 "hot-spot" as the contrast agent diffused through the vitreous. T1 rose gradually to basal levels by 72 hr. No local effect of Gd-DTPA was found by ophthalmoscopy. Xenon arc photocoagulation of rabbit retina reduced T1 from 1638 +/- 54 (n = 6, mean +/- SD) ms to 1408 +/- 118 (n = 4) msec (P less than 0.01) throughout the vitreous 5-7 hr after treatment. In treated rabbits receiving 1.0 mmol/l Gd-DTPA intravenously, T1 adjacent to lesions 90-120 min after injection was further reduced in a 63 microliter voxel to 670 +/- 50 ms (mean +/- SD, n = 5) with a minimum pixel value of 285 +/- 52 ms. It was estimated that this represented leakage into vitreous of 8.3 nmol Gd-DTPA. Plasma Gd-DTPA concentrations declined rapidly, with half-life of 20-40 min. The findings indicate that MRI is a technique with the potential for repeated quantitative three-dimensional assessment of blood-retinal barrier dysfunction.

Animals↗
PubMed1986

Practical aspects of ghosting in resistive nuclear magnetic resonance imaging systems.

The concept of 'ghosting' in NMR images is discussed and it is demonstrated that, among other things, any external modulation of the NMR signal can produce such effects. A simple theoretical model, based on elementary Fourier modulation theory is presented for saturation recovery imaging sequences. Both amplitude (AM) and frequency (FM) modulations are considered. The predictions of the theory with regard to the positions and amplitudes of the ghosts produced by such modulations are outlined. Appropriate AM and FM conditions are generated experimentally on a 0.1 T resistive NMR system and measurements on the concomitant ghost images verify the theoretical predictions. Some practical implications of the phenomenon, with particular relevance to resistive magnet systems, are highlighted.

Humans↗
PubMed1982

Ultrasonic characterisation of diffuse liver disease - the relative importance of frequency content in the A-scan signal.

Successful methods of ultrasonic characterisation of alcohol-induced diffuse liver disease using texture analysis (Lerski et al. 1979, 1980a, b) have studied the radiofrequency (RF) A-scan ultrasonic signal. In the present paper the Fourier spectra of such signals have been partitioned and a statistical analysis implemented to determine the diagnostic usefulness of certain frequency groups present in the signal. Although this method has not, of itself, been found to compared favourably with texture analysis it has shown that useful information is present in the high frequency portion of the frequency spectra. This information would not be available if the smoothed and denodulated A-scan signal were studied.

Fatty Liver, Alcoholic↗