Classifying Imaging Findings

Classifying Imaging Findings

Applies standardized classification systems (BI-RADS, LI-RADS, TI-RADS, Lung-RADS, PI-RADS) to imaging findings.

Why This Skill Exists

Radiology classification systems translate complex imaging findings into standardized categories with defined management pathways. These systems — BI-RADS (breast), LI-RADS (liver), TI-RADS (thyroid), Lung-RADS (lung cancer screening), PI-RADS (prostate), and others — are mandated by the ACR for their respective organ systems and represent decades of evidence-based development. Incorrect classification directly impacts patient management: an under-classified breast lesion may delay cancer diagnosis; an over-classified thyroid nodule may lead to unnecessary biopsy. Medicare and many commercial payers require appropriate RADS classification for reimbursement. The Joint Commission and ACR accreditation programs audit classification accuracy as a quality metric.

Each classification system uses specific imaging features scored against defined criteria to produce a category that maps to a management recommendation. Radiologists must understand the precise criteria, applicable modality, and patient-population requirements for each system. This skill consolidates the major RADS systems into a single reference with their scoring rubrics, management algorithms, and common pitfalls.

Checkpoint A: Pre-Draft Intake (Mandatory)

1. Which classification system is required? (Default: Determine from organ system and modality)
2. What imaging modality was used? (Default: Identify — CT, MRI, US, mammography, PET/CT)
3. Is the patient in a screening or diagnostic population? (Default: Diagnostic)
4. What is the patient's relevant risk history? (Default: Average risk — update with actual history)
5. Are prior studies available for comparison? (Default: No priors)
6. Is the patient in the appropriate population for this classification system? (Default: Verify eligibility)

Documents to Request

• Current imaging study with all sequences/phases
• Prior imaging in the same modality for comparison
• Relevant clinical history (cancer history, risk factors, cirrhosis status, PSA levels)
• Prior biopsy results if applicable
• Requisition with clinical indication

Step 1: Select the Appropriate Classification System

Critical rule: Never apply a classification system outside its intended population (e.g., LI-RADS only applies to patients at risk for HCC, not all liver lesions).

Step 2: Apply the Classification Criteria

BI-RADS (Breast Imaging)

LI-RADS (Liver — HCC Risk Population Only)

LI-RADS major features: arterial-phase hyperenhancement (APHE), nonperipheral "washout," enhancing "capsule," size, threshold growth (≥50% increase in ≤6 months).

Lung-RADS v1.1 (LDCT Screening Only)

PI-RADS v2.1 (Prostate MRI)

Zone-specific dominant sequence: T2W for transition zone; DWI/ADC for peripheral zone.

Step 3: Document the Classification

For every classified finding, the report must include:

1. Finding description — size, location, morphologic features
2. Scoring features — itemize each criterion used (e.g., TI-RADS points per category)
3. Assigned category — explicit category with system version (e.g., "BI-RADS 4B per 5th edition")
4. Management recommendation — per the classification algorithm
5. Comparison — change from prior classification if available
6. Caveats — any features that could upgrade/downgrade the category

Documentation Template

[Organ] [Location]: [Size] [descriptor]
- Features: [list scored features]
- Classification: [System] [Category] ([version])
- Recommendation: [Management per algorithm]
- Prior: [Change from prior or "no prior comparison"]

Step 4: Handle Edge Cases and Discordance

Checkpoint B: Post-Draft Alignment (Mandatory)

1. Is the correct classification system applied for the organ, modality, and population?
2. Are all individual scoring features documented?
3. Does the assigned category match the scoring criteria exactly?
4. Is the management recommendation consistent with the assigned category?
5. Are edge cases and limitations explicitly documented?

Quality Audit

• Classification system version is stated (e.g., LI-RADS v2018, BI-RADS 5th ed.)
• Patient eligibility for the classification system is confirmed
• Each scored feature is individually documented
• Total score/category is stated explicitly
• Management recommendation matches the assigned category
• Finding is measured in the correct axis per system requirements
• Comparison with prior classification is included when available
• Multiple lesions are each individually classified
• Lesions below size thresholds are handled per system-specific rules
• Caveats and technical limitations are noted
• Report avoids applying classification systems outside their intended population
• Category assignment is not modified based on clinical suspicion (classifications are imaging-based)
• The specific management pathway is spelled out (not just the category number)

Guidelines

1. Always state the classification system version — criteria change between editions and versioning prevents ambiguity.
2. Never apply LI-RADS to patients without established HCC risk factors (cirrhosis, chronic HBV, prior HCC).
3. Lung-RADS applies exclusively to low-dose CT lung cancer screening; do not use it for diagnostic CTs or incidental nodules.
4. For BI-RADS, always document density category (A through D) separately from the assessment category.
5. PI-RADS scoring uses a zone-specific dominant sequence — misapplying T2W as the dominant sequence in the peripheral zone is a common error.
6. When a lesion's features straddle two categories, assign the higher category and document the reasoning.
7. TI-RADS requires itemized point scores for all five feature categories — do not skip features or assign a level without documentation.
8. If a classification system does not apply, describe findings using standardized descriptors without forcing a RADS category.