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Biomedical subjects

S C Bushong

Publications and source records attributed to S C Bushong.

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

Dosimeter placement in the Rando phantom.

Each section of the Alderson Rando phantom contains a tissue-equivalent plastic coating layer approximately 2 mm thick, applied to both faces. This compensates for material removed in the sawing process. Conventional use of thermoluminescent dosimeters positions them totally or partially within the coating layer. Analysis shows that, in the lung region, dosimeters placed in this layer received a dose averaging 39% lower than those placed at midsection. Where bony structures interfere, some dosimeters in the coating layer received an 18% higher dose than those at midsection. Therefore, positioning dosimeters at the center of a section is recommended.

Models, Structural↗
PubMedDate not supplied

Single-step calculation of the MTF from the ERF.

A method is presented whereby the modulation transfer function can be calculated directly from the edge response function without having to find the line spread function as an intermediate step.

Energy Transfer↗
PubMedDate not supplied

Multivariate analysis of TLD orientation effects.

The effect of orientation on extruded thermoluminescent dosimeters has been investigated. TLD's placed on the surface and within a phantom were exposed separately to five diagnostic beam qualities and to 60Co gamma rays. The resulting data were subjected to analysis of variance and examined for significant correlations. The response of dosimeters on the phantom surface varied with orientation and was energy dependent. In the phantom and with 60Co, no orientation effects were observed.

Analysis of Variance↗
PubMedDate not supplied

A precise CT phantom alignment procedure.

Two of the AAPM CT performance phantom inserts require precise alignment. We present a method for aligning an insert which makes use of the partial volume effect. We demonstrate that the procedure is sensitive to tilts of less than one degree and, using the slice thickness insert, allows reproducible positioning.

Humans↗
PubMedDate not supplied

CT quality assurance: computer assisted slice thickness determination.

The precise slice geometry of a CT scanner is an important, albeit tedious to determine, characteristic. A series of computer programs have been developed to analyze the slice thickness insert of the AAPM phantom. Without operator assistance they generate the beam profiles and slice thicknesses at three points in the scan field. A representative analysis is done on an AS&E scanner with slice thickness settings of 2 to 10 mm. The resulting discrepent measured thicknesses, ranging from 3 to 8 mm, indicate the need to perform such slice thickness measurements as part of a regular quality assurance program.

Computers↗
PubMedDate not supplied

Computer assisted MTF determination in CT.

A series of computer programs have been written to analyze a scan of the AAPM CT performance phantom resolution insert with little operator assistance. A representative analysis is done on a scan from an AS&E scanner as an example. Its point spread function, edge response function and modulation transfer function are presented.

Computers↗
PubMedDate not supplied

CT alignment probe for the dose profile insert.

One of the most accepted methods of characterizing the dose in computed tomography (CT) is by measuring the dose profile. Thermoluminescent dosimeters (TLD's) arranged in a stack are scanned in a plexiglass phantom. Unfortunately with this system there is no assurance that the scan properly intercepts the stack. Mispositioning will not be apparent until the TLD's are read, entailing at least a 24 h delay before rescanning. We have designed a simple alignment probe that insures that the scan will be centered on the stack to within 1 mm.

Humans↗
PubMedDate not supplied

An improved method for determining CT image slice thickness.

One of the important characteristics of a computed tomography scanner is the image slice thickness. Most phantoms designed to measure this parameter do so with a ramp or tilted wire. Such a phantom must be precisely aligned to avoid possible significant inaccuracy. We present here a procedure for measuring the image slice thickness using a phantom containing two crossed ramps. The procedure produced consistent and accurate measurements of slice thickness without having to carry out a time consuming alignment procedure.

Humans↗
PubMedDate not supplied

Radiation dose in neurological computed tomographic scanning.

Patient dose and dose distribution during neurological computed tomography examinations were determined with five different computed tomography scanners. Maximum intracranial doses ranged from 1.17 to 2.67 rads. Doses to the lens of the eye ranged from 0.23 to 2.81 rads. These levels are considered and compared with patient doses reported for other computed tomography studies and for conventional tomographic examinations. In general, patient dose during computer tomographic examinations is less than one quarter of that during conventional tomography of the head.

Brain↗