Imaging Protocol

This page describes the image capture methodology, quality control system, and standardisation requirements for alopecia clinical trials using Legit.Health.

Smartphone-based capture

Legit.Health uses standard smartphone cameras for image acquisition. No specialised photography equipment is required.

Traditional clinical photography often relies on systems like Canfield VISIA, which require per-site hardware, per-site calibration, and significant rental or purchase costs. Smartphone-based capture eliminates these costs while maintaining the image quality needed for AI scoring.

The Legit.Health mobile application guides investigators through the capture process with visual perspective silhouettes, real-time DIQA quality checks, and immediate feedback on image adequacy.

Standard 4-quadrant protocol

The default imaging protocol follows the SALT methodology (Olsen et al., 2004), which assesses alopecia severity by evaluating hair loss across four scalp quadrants. Four photographs are captured, one for each quadrant:

Left side

Right side

Top of scalp

Back of scalp

This protocol ensures complete scalp coverage. Each quadrant is captured as a separate image, and the four images are combined using SALT-standard anatomical weights to produce the total score.

Capture technique

Distance and positioning

• Camera distance: 20–30 cm (7–12 inches) from camera to scalp
• Patient position: Seated (required for the top-of-scalp perspective)
• Angle: Camera held directly above or to the side of the relevant quadrant, perpendicular to the scalp surface

Quadrant-specific instructions

Quadrant	Camera position	Patient instruction
Top	Directly above the patient's head	Look straight ahead, chin level
Back	Behind the patient, level with the occiput	Tilt head slightly forward
Left	To the patient's left, level with the ear	Turn head slightly to the right
Right	To the patient's right, level with the ear	Turn head slightly to the left

Alternative perspective protocols

The 4-quadrant protocol is the default, but Legit.Health supports configurable alternatives:

Protocol	Perspectives	Use case
Standard 4-quadrant	4 views: Left side of scalp, Right side of scalp, Top of scalp, Back of scalp	Standard SALT protocol capturing all four scalp quadrants. Provides full scalp coverage for total SALT score calculation. Patient must be seated for the top perspective.
Custom	Any combination of perspectives	Any combination of scalp perspectives, defined in collaboration with the sponsor during protocol design. Can include additional close-up views for detailed lesion tracking.

DIQA: Dermatology Image Quality Assessment

What is DIQA?

DIQA (Dermatology Image Quality Assessment) is an AI-powered image quality assessment algorithm that evaluates every captured image in real time before it is accepted for analysis. It was developed by Legit.Health and published in the Journal of the American Academy of Dermatology (Hernández Montilla et al., 2023).

What DIQA evaluates

Quality dimension	What it checks	Why it matters
Focus	Sharpness of the image; absence of motion blur	Out-of-focus images can obscure small lesions, leading to undercounting
Lighting	Adequate, even illumination; absence of harsh shadows or glare	Poor lighting creates shadows that mimic or hide lesions
Framing	Correct anatomical region captured at the required angle	Incorrect framing means the AI analyses the wrong area
Resolution	Sufficient pixel density for lesion detection	Low resolution makes small features undetectable

How it works in the workflow

1. The investigator captures an image through the mobile application
2. DIQA evaluates the image immediately (sub-second processing)
3. If the image passes: it is accepted and queued for AI scoring
4. If the image fails: the investigator receives immediate feedback explaining the quality issue and must recapture

Configurable thresholds

The DIQA pass/fail threshold is configurable per study protocol. Sponsors can choose stricter thresholds for pivotal studies (rejecting more images to ensure the highest quality) or more lenient thresholds for real-world evidence studies.

Site instructions and standardisation

Patient preparation

• Remove all headwear: Hats, turbans, scarves, and headbands obscure scalp regions and prevent accurate hair loss assessment
• Remove hair accessories: Pins, clips, beads, and decorative items can cover areas of hair loss or create shadows
• Remove wigs, extensions, and hairpieces: Artificial hair completely masks the underlying hair loss pattern
• Ensure natural hair position: Hair should not be styled to cover areas of loss; the AI needs to see the true extent of alopecia
• Keep facial hair consistent: Maintain the same facial hair style throughout the study to minimise variability between visits
• Patient must be seated: Seated position is required to capture the top-of-scalp perspective consistently

Environmental conditions

• Patient positioning: Seated comfortably on a stool or chair without a headrest, remaining still during capture
• Background: Neutral, non-reflective background to reduce artefacts
• Lighting: Well-lit environment with even illumination. Natural light or the smartphone flash can be used. Avoid harsh directional lighting that creates deep shadows on the scalp.

Consistency across visits

The most important principle is consistency: the same lighting conditions, the same distance from camera to scalp, the same angles, and the same patient preparation at every visit. Consistent capture conditions ensure that score changes between visits reflect actual clinical changes (hair regrowth or further loss), not variations in image acquisition.

Key standardisation points

• The patient should always be seated in the same position
• Hair should never be styled to cover areas of loss
• All headwear, accessories, wigs, and extensions must be removed before every visit
• If the patient has remaining hair, it should be in a natural, unstyled position to avoid obscuring patches of alopecia