Summary of key design decisions, associated methodological considerations and clinical implications
| Design decisions | Methodological considerations | Clinical implications |
|---|---|---|
| Defining a region of interest | Is there a good evidence base for atrophy in the region? | Dictates utility and interpretation in certain clinical populations |
| Should the region be rated in >1 imaging plane? | Requires three-dimensional or multiple image acquisitions and increases time to perform rating | |
| Is there an imaging landmark to allow consistent slice selection? | Improves test-retest reliability | |
| Displaying a region of interest | Is the MR contrast appropriate and in common clinical use? | Affects the appearance of atrophy and the sensitivity to artefacts |
| Is the appearance of the region badly affected by patient positioning? | Difficult to rate certain regions or to reliably assess symmetry if the head is tilted | |
| Defining scale increments | How much variation can reliably be captured? | Truncated use of the scale may result in decreased diagnostic value |
| Is there a reliable cut-off between normal and abnormal scan appearance? Should the cut-off be adjusted for age? | Affects clinical interpretation | |
| Providing training material | How is each scale increment best described and are there reference images available to demonstrate these features? | Provides a useful framework for scoring |
| Are there expert raters available to provide training sets? | Provides confidence in ratings and a means of audit | |
| Validating the scale | What is the inter-rater/intra-rater reliability and how should it be measured? | Determines suitability for use in clinical practice and comparison with other scores |
| Do the scores correlate with clinical measures or other measures of atrophy? | Validates clinical relevance | |
| Is there a diagnostic gold standard available for comparison? | Provides validation of diagnostic value |