PGMI evaluation system

PGMI (Perfect, Good, Moderate, Inadequate) is a method of evaluation of clinical image quality in mammography developed by the United Kingdom Mammography Trainers Group with the support of the Royal College of Radiographers, aimed to ensure the maintenance of a high standard of mammography in Breast Screening and to facilitate a method of external audit.

Criteria for image assessment PGMI based:

1. all breast tissue imaged (fat tissue visualised posterior to glandular tissue) 
2. correct image identification clearly shown
   • date of examination
   • client identification—name and (number and/or date of birth)
   • side markers
   • positional markers
   • radiographer identification
3. correct exposure according to workplace requirements
4. good compression
5. absence of movement
6. correct processing
7. absence of artefactsartifacts
8. no skin folds
9. symmetrical images

Specific positioning criteria for CC view:

• 1. all breast tissue imaged
  • medial border well demonstrated
  • nipple in profile (retro-areolar tissue well separated)
  • nipple in the midline of imaged breast
  • posterior nipple line (PNL) within 1 cm of PNL on MLO view

Specific positioning criteria for MLO view:

• 1. all breast tissue imaged:
  • pectoral muscle shadow to nipple level
  • full width of the pectoral muscle
  • nipple in profile (retro-areolar tissue well separated)
  • infra-mammary fold well demonstrated
  • PNL within 1 cm of PNL on CC view

CC images classification:

P = Perfect images

• CC images meet criteria for image assessment 1−9

G = Good images

• 1. all breast tissue imaged (the axillary portion of breast not to be included at the expense of medial portion)
  • all postero-medial tissue visualised
  • nipple in profile
  • nipple in midline of imaged breast
• 2-6.CC images meet criteria for image assessment 2−6 inclusive for categorisation as G
• 7-9.CC images displaying minor degrees of variation in criteria for imaging assessment 7, 8 and 9 will be accepted for categorisation as G

M = Moderate images (Acceptable for diagnostic purposes)

1. most breast tissue imaged 
   • nipple not in profile but clearly distinguishable from retro-areolar tissue
   • nipple not in midline (significant bias)
2. correct(ed) image identification
3. correct exposure
4. adequate compression
5. absence of movement
6. correct processing
7. artefacts which do not obscure the image
8. skin folds which do not obscure the breast tissue
9. asymmetrical images

I = Inadequate images

1. a significant part of the breast not imaged
2. incomplete or incorrect identification
3. incorrect exposure
4. inadequate compression hindering diagnosis
5. blurred image
6. incorrect processing
7. overlying artefacts
8. skin folds obscuring the image

MLO images classification:

P = Perfect images

• MLO images meet criteria for image assessment 1−9

G = Good images

• 1. all breast tissue imaged
  • pectoral muscle well demonstrated
  • nipple in profile
  • infra-mammary fold (IMF) well demonstrated
• 2 - 6. MLO images meet criteria for image assessment 2−6 inclusive for categorisation as G
• 7 - 9. MLO images displaying minor degrees of variation in criteria for 
• imaging assessment 7, 8 and 9 will be accepted for categorisation as G

M = Moderate images (Acceptable for diagnostic purposes)

1. most breast tissue imaged.
   • pectoral muscle not to nipple level but posterior breast tissue adequately shown
   • nipple not in profile but clearly distinguishable from retro-areolar tissue 
   • IMF not clearly demonstrated but breast tissue adequately shown
2. correct(ed) image identification
3. correct exposure
4. adequate compression
5. absence of movement
6. correct processing
7. artefacts which do not obscure the image
8. skin folds which do not obscure the breast tissue
9. asymmetrical images

I = Inadequate images

1. a significant part of the breast not imaged
2. incomplete or incorrect identification
3. incorrect exposure
4. inadequate compression hindering diagnosis
5. blurred image
6. incorrect processing
7. overlying artefactsartifacts
8. skin folds obscuring the image

Recommended standard

(Image classification in relation to PGMI system to maximize high quality of images and minimise technical repeats)

A minimum of 50% of an audit of 50 randomly selected cases should be graded in: 

• P or G categories (75% desirable) or
• P or G or M categories (97% desirable)

Repeat rate:

<3% of consecutive images to be classified "Inadequate"