ACR Electronics L-32 FIELD MARKER LIGHTING SYSTEM Informacje Techniczne Pobierz pdf (Strona 31)

II-6. Radiation Beam Restriction and Alignment

This section

describes

the

evaluation of the

collimator's ability to automatically restrict the x-ray

field size to the size of the selected portion of the

image receptor.

This parameter

should be evaluated at

least annually or after any repair or adjustment to 1)

collimator drive motors or

blades, 2)

collimator

electronics, 3) image

intensifier tower

SID sensing

device, or 4) cassette holder within spot film device.

In addition, this section evaluates the alignment of the

x-ray beam central ray with the center of the image

receptor.

Misalignment can occur due to:

(a) Incorrect positioning of the fluoroscopic

tower with respect to the focal spot,

(b) Incorrect positioning of the image

intensifier within the fluoroscopic tower.

the conventional spot film device,

(d) Incorrect centering of the photospot camera, or

(e) Incorrect centering of the television camera

or monitor.

Alignment should be evaluated at least annually or after

any repair or adjustment which could affect alignment in

a-e above.

II-6-A. Test Method

The following

used to evaluate

test method (Reference #11) may be

x-ray beam

alignment and

beam

restriction.

The outline is listed here to illustrate

the scope of this testing procedure.

The only test

equipment required are commercially available ready pack

direct exposure film and a beam restriction test tool.

This test-tool

simply

consists

of a 1/2" Aluminum

attenuating block 8" x 8" in cross section on 1/2" legs.

An orthogonal set

of slide channels are

cut into the

block to accept radiopaque bars made of brass.

Fluoroscopic Mode

1) Adjust the tower vertically to result in the

minimum SID.

2) Place the test tool on the tabletop and

select the image intensifier's largest field

of view.

Record the distance from the top

of the test tool to the level of the cas-

sette in the spotfilmer.

Record the

distance from the tabletop to the top of

the test tool.

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 60 61

Komentarze do niniejszej Instrukcji

Brak uwag

ACR Electronics L-32 FIELD MARKER LIGHTING SYSTEM Informacje Techniczne Strona 31

Komentarze do niniejszej Instrukcji