Evaluation of a parallel hole grid for bedside chest imaging.
OBJECTIVE
The application of a new parallel hole grid designed for bedside radiography is investigated. This grid is constructed of sheets of holes and is designed to have more tolerance to positioning errors than conventional grids.


METHODS
The parallel hole grid is compared to conventional 6:1 and 12:1 grids using phantoms. The contrast improvement, scatter fractions, exposure, and tolerance to positioning errors are measured.


RESULTS
The parallel hole grid has much more tolerance to positioning errors than conventional grids. The contrast improvement and scatter rejection are significantly less than those obtained with a conventional 6:1 ratio grid. Compared with nongrid techniques, the parallel hole grid provides 13% to 20% higher lung contrast.


CONCLUSIONS
The parallel hole grid may be used for bedside imaging without the need for accurate alignment. The parallel hole grid requires approximately 2.7 times the entrance exposure of a nongrid technique. Lung contrast improvement is approximately half of that from an accurately aligned 6:1 conventional grid. For grid angulation greater than 8 degrees, the parallel hole grid provides higher contrast than the 6:1 grid.
Department of Radiological Sciences and Technology, Massachusetts General Hospital, Boston 02114.
L T
LT
Niklason
H P
HP
Chan
D015502:Absorptiometry, Photon; D000535:Aluminum; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D020366:Methylmethacrylate; D008768:Methylmethacrylates; D008961:Models, Structural; D010362:Patients' Rooms; D011137:Polystyrenes; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D013902:Radiography, Thoracic / Q000295:instrumentation*; D012542:Scattering, Radiation; D014963:X-Ray Intensifying Screens
D008768:Methylmethacrylates; D011137:Polystyrenes; D020366:Methylmethacrylate; D000535:Aluminum