Search PubMed⌕ Search

Biomedical subjects

W L Rogers

Publications and source records attributed to W L Rogers.

59 records · Page 4Linked to original sources
PubMedDate not supplied

Comparison of observer performance reading from a video CRT vs. reading from film.

The developing trend for all medical images to be in digital form raises an important question: should diagnostic interpretations be made directly from a CRT or from some form of hard copy recording of the CRT? This question was studied by having two observers read a series of digital images of the thyroid including both conventional scintigrams and computer-generated tomograms. The CRT images were photographed in a carefully controlled fashion. Images were read once from film and a second time directly from the CRT. No significant difference in performance could be found for either display modality based on an ROC analysis. Although based on uncomplicated images and analysis, this result suggests that the decision to read from film or from the CRT can be made on other grounds than observer performance. This important result needs confirmation with more complex images such as ultrasound or CT.

Data Display↗
PubMedDate not supplied

Count-based monitoring of Anger-camera spectra--local energy shifts due to rotation.

This study reports on a spectral monitoring method in which (1) a small source fixed to the camera is used, (2) a narrow, offset window is set on the side of the photopeak, and (3) variations in count rate are measured to assess energy shifts in the vicinity of the source. For one camera model, the count rate drops from 100% to 76% over a rotation of 180 degrees, implying a local energy shift of 1.4 keV. Also looked for are local count-rate variations with rotation for (1) wide-symmetric, (2) 20%-symmetric, and (3) 10%-asymmetric windows. The last is in limited use to partially compensate for Compton scattering. The effects of background and time stability are assessed.

Gamma Cameras↗
PubMedDate not supplied

SPECT instrumentation.

The sensitivity of conventionally collimated SPECT systems is essentially fixed by the number of resolution elements desired. A variety of collimation methods are proposed or in use that distribute sensitivity and resolution differently among the various projection elements, but the effects on image quality have not really been documented. Of the many existing systems, the camera-based systems, which are useful for both head and body imaging, will be most useful in a clinical environment. For brain imaging, it is clear that fan beam collimation offers a large performance advantage over parallel collimation. However, comparison of the various instruments based on specifications alone is difficult if not impossible, and careful 3-dimensional imaging studies are an absolute necessity. In view of the fairly healthy price of dedicated brain instruments, it is interesting to speculate on their role in nuclear imaging. Their cost is from $50,000 to $200,000 less than a multi-headed general purpose system, and they have excellent resolution and sensitivity for brain imaging. They cost from $175,000 to $300,000 more than a single head camera-computer system yet offer 3 to 4 times the resolution-adjusted sensitivity. This suggests that a special purpose instrument would need to be heavily utilized or located (physically or politically) where the body imaging capability of a two or three-headed system would not be used. A good case might be made for locating a dedicated instrument in a neurological ICU in order to avoid transporting critically ill patients out of the unit. The various non-conventional imaging methods show promise for exceeding the sensitivity limit of regular collimators. At present it is speculative as to how much can be gained and whether it will be worth the added complexity and/or cost. Nevertheless, they are very interesting and certainly justify additional research.

Brain↗