Storage Phosphor Screens Research Articles

Triazolam-induced modulation of muscarinic acetylcholine receptor in living brain slices as revealed by a new positron-based imaging technique.

The effect of triazolam, a potent benzodiazepine (BZ) agonist, on muscarinic acetylcholinergic receptor (mAChR) binding was investigated in living brain slices by use of a novel positron-based imaging technique. Fresh rat brain slices were incubated with [11C]N-methyl-4-piperidylbenzilate ([11C]NMPB), a mAChR antagonist, in oxygenated Krebs-Ringer solution at 37 degrees C. During incubation, time-resolved imaging of [11C]NMPB binding in the slices was constructed on the storage phosphor screens. Addition of triazolam (1 microM) plus muscimol (30 microM), a GABA(A) receptor agonist, to the incubation mixture decreased the specific binding of [11C]NMPB. Ro15-1788, a BZ receptor antagonist, prevented this effect, indicating that the effect was exerted through the GABA(A)/BZ receptor complex. These results demonstrated that stimulation of the GABA(A)/BZ receptor lowers the affinity of the mAChR for its ligand, which may underlie the BZ-induced amnesia, a serious clinical side effect of BZ. No such effect in the P2-fraction instead implies that the integrity of the neuronal cells and/or their environment is prerequisite for the modulation of mAChR by GABA(A)/BZ stimulation.

Detection and quantitation of unlabeled nucleic acids in polyacrylamide gels.

A method for the detection and quantitation of unlabeled nucleic acids in polyacrylamide gels is presented. The technique is a variation on UV shadowing. The technique is based on the observation that some storage phosphor screens (Kodak in this case) are sensitive to UV light in the range where nucleic acids absorb most strongly. Nucleic acid present in a gel resting on the screen absorbs the UV light and casts an ultraviolet shadow on the storage phosphor screen. The amount of nucleic acid in a particular area of the polyacrylamide gel is inversely proportional to the average pixel intensity in the corresponding area of the image. The technique therefore provides an electronic record of the gel in addition to the ability to quantitate the amount of nucleic acid present in any particular band. The storage phosphor screen images are erased by visible light. If the passage of that light to the screen is blocked by the presence of solid objects or images, the reverse process can be achieved, i.e., the recording of positive images by visible light etching of a uniformly charged background. By this method, we are able to transform old autoradiographic data into digital form for easy storage, computerized manipulation and distribution.

In vitro positron emission tomography (PET): use of positron emission tracers in functional imaging in living brain slices

Positron-emitting radionuclides have short half-lives and high radiation energies compared with radioisotopes generally used in biomedical research. We examined the possibility of applying positron emitter-labeled compounds to functional imaging in brain slices kept viable in an oxygenated buffer solution. Brain slices (300 μm thick) containing the striatum were incubated with positron emitter-labeled tracers for 30–45 min. The slices were then rinsed and placed on the bottom of a Plexiglas chamber filled with oxygenated Krebs-Ringer solution. The bottom of the chamber consisted of a thin polypropylene film to allow good penetration of β+ particles from the brain slices. The chamber was placed on a storage phosphor screen, which has a higher sensitivity and a wider dynamic range than X-ray films. After an exposure period of 15–60 min, the screen was scanned by the analyzer and radioactivity images of brain slices were obtained within 20 min. We succeeded in obtaining quantitative images of (1) [18F]fluoro-deoxyglucose uptake, (2) dopamine D2 receptor binding, (3) dopa-decarboxylase activity, and (4) release of [ 11 C]dopamine preloaded asl-[11C]DOPA in the brain slice preparation. These results demonstrate that positron emitter-labeled tracers in combination with storage phosphor screens are useful for functional imaging of living brain slices as a novel neuroscience technique.

Digital storage phosphor radiography for treatment verification in radiotherapy.

The potential of digital storage phosphor radiography (SR) to improve image quality of portal radiographs is evaluated. Conventional film radiographs (FR) and corresponding SR verification images of an anthropomorphic phantom and various irradiation ports of patients were obtained with high-energy photon beams. For both techniques conventional films and storage phosphor screens were placed into a cassette with steel screens. Images were evaluated according to contrast and spatial resolution, delineation of anatomical structures, position of shielding blocks and accuracy of field alignments. Evaluation of 33 pairs of SR and FR portal images yielded a superior contrast resolution of SR in 47% (contrast air-soft tissue) and 37% (bone-soft tissue). Thus SR allows quick and easy detectability of anatomical structures as well as a better definition of block positions and field alignments. Shorter exposure times for computed images may result in a reduction of motion artefacts. SR images are indispensable in modern radiation therapy units, as they are instantly available in a computerized network for further image processing and analysis.

Storage-phosphor digital radiography in genitourinary radiology

A digital-projection radiography system with potential applications in genitourinary imaging is presented. The system replaces the traditional film-screen combinations by storage phosphor screens but continues to use cassettes in conventional X-ray equipment. Technical features such as consistently optimal image brightness and contrast across an extremely wide exposure range and edge-enhancement capabilities overcome deficiencies seen with conventional film-screen systems, such as improper exposure and poor contrast discrimination. Images obtained with a dual-energy radiation spectrum selectively demonstrate soft-tissue- or bone-equivalent structures and diminish the obscuring effect of bowel gas. Problems resulting from the singular reliance on film as a display and storage medium in conventional radiography are resolved in digital radiography by fast and simultaneous electronic access to images that can be displayed on high-resolution monitors or laser-printed films. The basic technical features of storage-phosphor digital imaging as compared to conventional radiography are described. A summary of recently published results relevant to genitourinary examinations is given and radiographic examples are presented.