ACR Electronics L-32 FIELD MARKER LIGHTING SYSTEM Informações Técnicas descarregar pdf (Página 35)

II-6-E. Alternate Test Methods

The test method briefly described in II-6-A is only

one of many.

While the test equipment required for this

method is minimal, many

images must be

processed to completely

verify

exposed and

device and imaging chain.

a conventional spot film

Lin has described in detail

the design and use

of more expensive test tools which

drastically reduce the time required to complete the

testing (References #5

and

#12).

Hendee

and

Rossi

(Reference #11) also suggest alternate test tools which

reduce testing time.

Reference #4 by Gray et. al. is

another source of alternate test methods.

II-7. Radiation Output and Beam Characteristics

With the exception of the paragraph on mammography

units,

all the general comments in Section I-7 apply also

to fluoroscopic x-ray beams.

II-7-A. Determination of HVL

The

HVL

of the fluoroscopic x-ray beam should be

measured at least annually,

ray tube assembly,

after replacement of the x-

after generator

recalibration, or

change in the added filtration.

The measurement should

be made in

"good geometry" (Reference #7). The effects

of high voltage cable capacitance on the measured HVL on

three phase units (Reference #21) can be eliminated by

collecting data with the rate mode of the dosimeter.

On single phase units the measured HVL decreases as

the fluoroscopic tube current increases due to the cable

capacitance of the high voltage cables (Reference #22).

HVL measurements obtained with the dosimeter in the rate

mode on these units do not avoid this

effect; these HVL

compliance measurements should

use

the

maximum

fluoroscopic tube current setting.

Comparison of fluoroscopic measured HVLs from survey

to survey are meaningless

kVp, and on

unless the chosen geometry,

single phase units, tube current remain

constant.

CAUTION: During measurement of the HVL of a fluoroscopic

beam, an appropriate attenuator should be attached to the

face of the

image

intensifier

avoid excessive

radiation rates at its input.

Failure to do this could

damage the image intensifier television chain during HVL

measurements. See Section

II-5-A for

thicknesses of this attenuator.

suggested

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 60 61

Comentários a estes Manuais

Sem comentários

ACR Electronics L-32 FIELD MARKER LIGHTING SYSTEM Informações Técnicas Página 35

Comentários a estes Manuais