🧠 MRI Lesion Load Monitoring Simulator

Baseline MRI & Initial Lesion Count

First scan anchors every future comparison — a lesion census at time zero.

• 5–20: Typical baseline T2 lesions (at first diagnosis)
• 1.5–3T: MRI field strength (standard clinical)
• FLAIR: Key sequence (suppresses CSF signal)
• 6–12 mo: Rescan interval (guideline standard)

Why a baseline matters

Sets the reference count and volume future scans are compared against.

One scan alone cannot show activity — comparison is everything.

T2/FLAIR lesion detection

Bright periventricular spots mark areas of past or current demyelination.

Standardized protocol

Same scanner, slice angle, and sequence improve reliable lesion tracking.

Follow-Up MRI at 6 Months

A second scan reveals whether new lesions accumulated since baseline.

• 6 mo: Follow-up window (first comparison point)
• 1+: New lesion = activity (any new T2 spot counts)
• mm³: Volumetric change tracked (total burden growth)
• ~10:1: Subclinical lesion rate (vs relapses (MRI vs clinic))

Image co-registration

Baseline and follow-up scans align to spot genuinely new lesions.

Cumulative lesion load

Total T2 count/volume climbs — a running ledger of disease burden.

Subclinical activity

Most new lesions cause no symptoms yet still reflect ongoing disease.

Gadolinium-Enhancing Lesions

Contrast dye leaks through a broken blood-brain barrier into active lesions.

• ~3–4 wk: Gd enhancement duration (per active lesion)
• Active: BBB disruption signals (inflammation ongoing)
• Gd+: T1 post-contrast bright spot (marks acute lesion)
• weeks: Enhancement fade (lesion then quiets)

Blood-brain barrier breakdown

Inflammation opens the barrier, letting gadolinium dye leak in.

Gd+ as an activity marker

Enhancing lesions mark currently active, not just old, disease.

Time-limited signal

Enhancement typically resolves within weeks as inflammation settles.

New Lesion Activity Since Baseline

Combined new T2 and Gd findings flag breakthrough disease on therapy.

• 1+ new: Breakthrough definition (T2 or Gd+ lesion)
• New lesion: Therapy review trigger (prompts re-evaluation)
• CUA: Combined unique lesions (new T2 + new Gd, no double count)
• More sensitive: MRI vs relapse detection (MRI wins)

Breakthrough disease activity

New lesions despite treatment suggest the current therapy is underperforming.

Combined unique active lesions

CUA metric merges new T2 and Gd+ counts without double-counting.

Clinical decision point

Repeated new activity often prompts a switch to a stronger therapy.

NEDA — No Evidence of Disease Activity

NEDA means no new lesions, no relapses, no disability progression.

• 3: NEDA-3 criteria (MRI + relapse + disability)
• Brain atrophy: NEDA-4 adds (volume loss rate)
• ~40–60%: 2-year NEDA on therapy (high-efficacy DMTs)
• Switch DMT: Non-NEDA action (escalate therapy)

Defining NEDA

No new/enlarging T2, no Gd+, no relapse, no confirmed disability change.

Treat-to-target strategy

Clinicians increasingly aim for NEDA rather than just fewer relapses.

When NEDA fails

Lesion accumulation without NEDA prompts considering a therapy switch.