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Biomedical subjects

D G Norris

Publications and source records attributed to D G Norris.

At least 55 records · Page 3Linked to original sources
PubMed1993

Fast proton spectroscopic imaging using the sliced k-space method.

The use of one-shot imaging methods for proton spectroscopic imaging (1H-SI) is examined. In particular the acquisition of Kx x Ky x Nt data points by means of Nt excitations, each acquiring a Kx x Ky k-space slice, is advocated. A number of strategies for realising this experiment, and combining it with water suppression and volume-selection are proposed. The practical implementation at 4.7 T for 1H-SI of the rat brain is described. Experimental results from a 32 x 32 spatial matrix with Nt = 64 are presented. Spectra obtained from volumes as low as 3.5 microliters and within measuring times of as little as 3.8 min are shown. In these choline, creatine/phosphocreatine and N-acetylaspartate are all clearly visible.

Animals↗
PubMed1993

Dynamic imaging with T2* contrast using U-FLARE.

Dynamic changes in T2* in the rat brain induced by the injection of Gd-DTPA are monitored using the U-FLARE sequence. Sensitivity to T2* is easily introduced into this sequence and may be freely varied. The images obtained display an adequate spatial resolution and contrast, for a temporal resolution of 1 s. Intensity-time curves and parametric images of regional cerebral blood flow (rCBV) are presented for three different blood pCO2 values. The results presented clearly demonstrate that U-FLARE is a viable method for dynamically measuring changes in T2*, and thus has application in imaging of both perfusion and functional activation.

Animals↗
PubMed1992

On the application of ultra-fast RARE experiments.

The ultra-fast application of the RARE experiment is described in detail, with special emphasis on its multifarious applications with preparation experiments that produce transverse magnetization. The factors affecting the temporal evolution of the magnetization during the experiment are described, and the implications for the slice profile when using a Gaussian refocusing pulse are experimentally examined. The choice of phase-encoding scheme for use with preparation experiments is discussed, as is the use of various phase-encoding schemes to reduce line broadening in the phase-encoding direction if a number of averages are acquired. An explanation for the decomposition of the echo are into two components if the read gradient is imbalanced is given, and the experimental conditions necessary for the coherent addition of these two echo groups are described. An alternative sequence that removes one of these groups from the acquisition window is proposed. The sensitivity of the sequence to flow and motion is investigated, and the drastic loss of signal in this situation explained. The in vivo and in vitro application of preparation experiments leading to the accurate measurement of T1, T2, diffusion constant, and magnetization transfer characteristics is presented. The implementation of zoom-imaging using spin- and stimulated-echo preparation is described, and 3D in vivo spin-echo zoom images are presented. Simple phantom experiments demonstrating the feasibility of chemical-shift selective and spectroscopic imaging are also given.

Animals↗
PubMed1991

Ultrafast low-angle RARE: U-FLARE.

The subsecond application of the RARE technique is described. Two possible methods of implementation are discussed, one in which T2 contrast is manipulated by temporal reordering of the phase-encoding gradient, and the other in which the phase-encoding order is held constant and the contrast is manipulated by means of a spin-echo preparation experiment. In vivo images obtained with the latter method are presented and applications of the sequence discussed.

Animals↗
PubMed1991

The spectrum of eosinophilic gastroenteritis. Report of six pediatric cases and review of the literature.

Eosinophilic gastroenteritis is an inflammatory disease of unknown etiology characterized by infiltration of the gastrointestinal tract with eosinophilic leukocytes, accompanied by varying abdominal symptoms and usually by peripheral blood eosinophilia. We report our experience with six pediatric cases presenting to the Cleveland Clinic Foundation over the past eight years. Unusual findings in our patients included ascitic fluid without eosinophilia and eosinophilic pericarditis (one patient), and eosinophilic cholecystitis (one patient). Endoscopic examination and biopsy helped to establish the diagnosis in all patients. Bone marrow aspiration supported the diagnosis by demonstrating eosinophilia and identifying reactivation of the disease, even in cases without peripheral eosinophilia. All six patients responded promptly to prednisone. Diagnosis is challenging and eosinophilic gastroenteritis may be more common than is recognized. This series of cases significantly expands the spectrum of the disease in children, and documents the usefulness of diagnostic endoscopy in this condition.

Adolescent↗
PubMed1990

A simple method of generating variable T1 contrast images using temporally reordered phase encoding.

A rapid method of generating T1 images by means of an inversion pulse followed by a fast low-angle imaging experiment is presented. The T1 contrast is manipulated by a temporal reordering of the phase-encoding gradient, resulting in an almost completely free choice of T1 contrast, without any extra restriction on the size of the data acquisition matrix. The intrinsic rapidity of the sequence renders it insensitive to motion artifacts and lends itself to multipoint T1 calculations. The method is particularly well suited to high-field imaging.

Animals↗
PubMed1989

Variable excitation angle AFP pulses.

RF pulses employing the principle of adiabatic fast passage are finding increasing application with surface coils. A small modification to existing AFP pulses that allows the excitation angle to be chosen largely independently of B1 strength is described here. Rapid 3D imaging applications of such pulses are presented.

Diagnostic Imaging↗
PubMed1988

Projective Fourier angiography.

The Fourier imaging of flow is discussed, and the limitations of imaging time, spatial and velocity resolution, imposed on this technique when applied in conjunction with ECG synchronization are examined. It is argued that this method is best used in projective format, and in vivo examples are presented. The relative velocity spectrum obtained is largely system independent, and quantification of velocity is implicit in the Fourier technique.

Angiography↗
PubMed1986

Periosteal Ewing's sarcoma.

Ewing's sarcoma is a small cell malignant tumor that usually arises in the medullary cavity of bone. Less frequently, it originates in soft tissue and may secondarily invade underlying bone. The origin of Ewing's sarcoma in a periosteal location without extension into either the bone or adjacent soft tissue has not been clearly documented. Other malignant tumors of bone (e.g., osteosarcoma) appear to have a somewhat better prognosis when confined between periosteum and bone. The case of a patient with a periosteal Ewing's sarcoma who received a radical excision and postoperative chemotherapy and who is without evidence of disease with over 2 years follow-up is reported.

Adolescent↗
PubMed1986

Noninvasive testicular screening in childhood leukemia.

To evaluate the potential of transscrotal ultrasound and magnetic resonance imaging as noninvasive screening methods we studied 8 boys with acute lymphocytic leukemia before testicular biopsy. Ultrasonic images of the testes were performed in 4 patients, including 2 with negative and 2 with positive biopsies, and all images were interpreted as normal. Magnetic resonance images of the testes also were interpreted as normal in 4 patients, including 2 with negative and 2 with positive biopsies, and they were technically inadequate in the remaining 4. The results suggest that neither transscrotal ultrasonography nor magnetic resonance imaging as currently applied may substitute reliably for testicular biopsy as a screen for occult testicular leukemia.

Adolescent↗
PubMed1985

Criteria and definitions for response and relapse in children with brain tumors.

Traditional criteria and definitions for response and relapse are not completely suitable for children with brain tumors. Response and relapse for brain tumors need to be defined using the most objective criteria available, that is, the computed tomography (CT) scan findings. Relapse may also be defined by myelography, cerebrospinal fluid analysis, or biopsy of extraneural disease. Standardization of response and relapse will lead to meaningful comparisons of patients treated with various therapies.

Brain Neoplasms↗
PubMed1981

Transient cortical blindness secondary to vincristine therapy in childhood malignancies.

Three children with malignancies developed severe neurotoxicity, including transient cortical blindness, following chemotherapy regimens. The only drug in common was vincristine sulfate. The clinical courses of these patient are described. All have completely recovered, although one child who was rechallenged with vincristine had a cardiorespiratory arrest, increasing neurotoxicity, and recurrence of blindness. Transient cortical blindness has not previously been attributed to vincristine sulfate therapy, but must be considered as a possible complication of treatment with this agent.

Blindness↗