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C R Meyer

Publications and source records attributed to C R Meyer.

At least 73 records · Page 4Linked to original sources
PubMed1994

Quantitative assessment of surface roughness using backscattered ultrasound: the effects of finite surface curvature.

We have previously described a technique to quantify surface fibrillatory changes in osteoarthritic articular cartilage. In that study, the angular distribution of the scattered acoustic field from an insonifying source directly related to the distribution of surface fibrillatory changes. In the current study, we demonstrate a more sensitive method to quantify surface roughness, the effect of global surface curvature in estimating surface roughness and the utility of using focused transducers in circumventing this potential problem for in vivo work. Phantoms composed of acrylic rods with and without sandpaper grit (about 15 to 72 microns, mean particle size) applied to the surface were scanned. A more robust angular scattering technique to measure the angle dependent data was employed, in which the integrated squared pressure amplitude over a finite time window (mean power) was measured as a function of incident acoustic angle for varying surface roughnesses and radii of curvature. We show that the potential dynamic range for making roughness discriminations diminishes with decreasing radius of curvature of the acrylic rod phantoms using an unfocused transducer. This effect is minimized with use of a focused transducer. Roughness effects are most evident at sufficiently large angles where incoherent scattering dominates. We conclude that the roughness of cylindrically curved surfaces can be quantitatively assessed using a focused ultrasound beam at sufficiently large incident angles, given that the focal spot size is sufficiently smaller than the radius of curvature of the surface.

Cartilage, Articular↗
PubMed1994

Generating a normalized geometric liver model using warping.

RATIONALE AND OBJECTIVES: Automated liver surface determination in abdominal computed tomography scans, currently difficult to achieve, is of interest to determine liver location and size for various medical applications, including radiation therapy treatment planning, surgical planning, and oncologic monitoring. The authors propose to facilitate automation by the addition of a priori shape information in the form of a liver model. METHODS: The normalized geometric liver model is generated by averaging outlines from a set of normal liver studies previously registered using thin-plate spline warping. The model consists of an averaged liver surface, a set of anatomic landmarks, and a deformation function. RESULTS: A liver model is presented and its ability to represent normal liver shapes is demonstrated. CONCLUSIONS: Liver surface warping provides a means of data normalization for model construction and a means of model deformation for representation of liver organ shapes.

Computer Simulation↗
PubMed1994

Staging of mediastinal non-small cell lung cancer with FDG PET, CT, and fusion images: preliminary prospective evaluation.

PURPOSE: To evaluate use of positron emission tomography (PET) with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) in detection of mediastinal lymph node metastases from non-small cell lung cancer. MATERIALS AND METHODS: A prospective trial to compare FDG PET and computed tomography (CT) of the thorax was performed in 23 patients with newly diagnosed or suspected non-small cell lung cancer. Blinded interpretations of CT alone, PET alone, CT and PET together, and fusion images were performed, and the results were compared with pathologic results. RESULTS: Nineteen of 23 patients had non-small cell lung cancer. Prevalence of mediastinal involvement was 41%. In staging disease in the mediastinum, CT alone was 64% sensitive, 44% specific, and 52% accurate, whereas PET alone and fusion images were 82% sensitive, 81% specific, and 81% accurate (P < .05). CONCLUSIONS: FDG PET was more accurate than CT in staging disease in the mediastinum in patients with lung cancer and appears to be the preferred imaging method in this clinical setting.

Carcinoma, Non-Small-Cell Lung↗
PubMed1994

The computerized medical record in action.

Before the advent of the IPS computerized medical record at Burlington, Zallen did not own a computer. Although he learned touch-typing in high school, he emphatically states that he hated it. The average age of the physicians on staff at Burlington is about 40, but few had extensive previous experience with computers. According to Zallen, all have adapted to the CPR with few tears or tirades. The physicians continue to "tweak" the system to customize their own scrapbook and templates. Lahey physicians who work at Burlington part time are using the system, although with more staff help. The CPR is alive and well at Burlington Health Center. HCHP physicians can and do use computers in their daily work, producing quality medical records that are readable and retrievable. Nonetheless, promises that computers will make records more complete and accessible and will improve quality measurement will be mere blather if the CPR doesn't make users' lives easier. My last question to Zallen was "How has this system made your life harder?" After one pensive second, he replied, "I really can't think of anything." To me, that is potent testimony that the CPR is not a techie's fantasy, but rather, a pragmatic, workable answer to the needs of 21st century medicine.

Computer Systems↗
PubMed1993

Cloning, expression, and sequence of an allosteric mutant ADPglucose pyrophosphorylase from Escherichia coli B.

Escherichia coli B mutant strain SG14 accumulates glycogen at 28% of the rate observed for the parent strain. This is due to the presence of an ADPglucose pyrophosphorylase with altered allosteric properties including lower apparent affinities for substrates, the activator, fructose-1,6-bisphosphate, and the inhibitor, AMP. The mutant enzyme also is completely insensitive to activation by NADPH. To clone this mutant, an SG14 library was constructed by insertion of the chromosomal DNA into the PstI site of pBR322. Screening of the library via colony hybridization with a wild-type gene (glgC) probe resulted in the successful isolation of a recombinant plasmid, designated pPJ2, which contained the mutant glgC gene. The enzyme expressed from pPJ2 was partially purified and found to be very similar in kinetic and allosteric properties to the enzyme isolated from the SG14 strain. The mutant glgC gene, a HincII fragment from pPJ2, was then subcloned into pUC118/119 for dideoxy sequencing of both strands. One amino acid change was found in a region that is highly conserved in all known sequences: a single point mutation at the deduced amino acid residue 44 resulted in a change of alanine to threonine. The properties of this mutant are discussed in comparison to other known allosteric mutants.

Adenosine Monophosphate↗
PubMed1993

"Anatometabolic" tumor imaging: fusion of FDG PET with CT or MRI to localize foci of increased activity.

Positron emission tomographic (PET) images of visceral cancers are commonly visualized as "hot spots" of increased activity with relatively little normal anatomy discernable, when 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) is used as the tracer. We describe a method by which computed tomography or magnetic resonance anatomic images can be digitally fused in three dimensions, using a rigid rotate-translate scale model with PET "metabolic" images, to simultaneously display registered anatomic and metabolic information. Such "anatometabolic" fusion images were produced in 10 patients with a variety of visceral cancers. External fiducial markers placed during both the anatomic and the metabolic study, as well as internal anatomic fiducials defined from landmarks observed on reconstructed transmission images, were used to achieve image fusion. The mean error magnitude +/- s.e.m. of fiducial registration in the nine patients with successful realignments was 5.0 +/- 0.8 mm. The mean accuracy in realignment between known anatomic structures seen on both the anatomic study and on the emission PET scan (but not used in realignment) was 6.3 +/- 0.8 mm. Localization of foci of increased FDG uptake to specific anatomic structures was achieved by this method, which represented an enhancement over the rudimentary anatomy available from the emission images alone. Anatometabolic fusion images made using this reasonably simple method should prove useful in the management of patients with cancer and other diseases.

Adult↗