Standard Practice for Determining Low-Contrast Visual Acuity of Radiographic Interpreters

Importancia y uso:

4.1 This practice is used to evaluate the ability of a radiographic interpreter to discriminate low contrast slit images in a radiographic interpretation environment. A radiographic viewer, as described in Specification E1390, and a viewing environment, as described in Guide E94, are strongly recommended. The minimum acceptable test score in any given application depends on the requirements of the application. Using parties should develop and maintain records of their test results to guide the establishment of acceptable test scores for their applications. (See Note 1.)

Note 1: During round robin testing with experienced radiographic interpreters, 76 % of the interpreters achieved a score of 85 % or higher, and 95 % achieved a score of 80 % or higher. The average score was 90.7 %, and the standard deviation was 6.7 %. In a second study from 2017, with both certified radiographers and uncertified personnel, the average and standard deviation among certified radiographers was 90.4 ± 4.0 % and among uncertified personnel was 88.4 ± 4.9 %. It was found that on each test page there are 3 or 4 images where the average score for each was less than 80 % correct and the remainder of the images all individually scored greater than 80 % on average. A limited number of the general public was examined, and the average score among these was 75.0 ± 3.3 %.

4.2 Administration of the Test 

4.2.1 The test procedure described in this practice is intended to determine the ability of a radiographic interpreter to detect low contrast images in a low light level environment. Appropriate dark adaptation time should be permitted. A minimum of 1 min is recommended; however, longer dark adaptation times may be required by some users.

4.2.2 The test shall be administered by or under the direction of a test administrator (see 3.2.4). The individual being tested shall not know the identification of the plate or orientation prior to the test.

4.2.3 The interpretation of each of the 25 image areas on a plate is recorded on an answer sheet, Fig. 2, by drawing a line corresponding to the location and orientation of the slit image in that image area. Where no line image is detected, a circle should be drawn on the answer sheet in the area corresponding to the image area in which no slit image was detected. An example score sheet is given in Fig. 3, illustrating typical line locations and orientations and illustrating the method for marking answers. The markings shown in the sample score sheet are not taken from any of the actual test plates; however, they illustrate typical distributions of slit images. Fig. 2 of this practice may be photocopied to provide answer sheets, or the using organization may generate their own suitable answer sheet. In any case, the answer sheet must have provisions for recording both the location and orientation of the indication in each of the 25 image locations.

FIG. 2 Visual Acuity Test Score Sheet

FIG. 3 Example of Completed Visual Acuity Test Score Sheet

4.2.4 The order in which the indications are marked is not important. The reader may mark the indications in order, or may mark the easier images and return to the more difficult images.

4.2.5 Once the score sheet is completed, the test administrator shall determine the identity and orientation of the plate that was read and score the answers using the appropriate answer key.

Subcomité:

E07.02

Volúmen:

03.04

Número ICS:

19.100 (Non-destructive testing)

Palabras clave:

dark adaptation; nondestructive testing; radiographic interpreter; radiography; radiology; slit image; visual acuity;