Multi-Wavelength PBM / Class IV Laser Tissue Dosimetry Calculator
Beer-Lambert depth model using the diffusion effective attenuation coefficient μeff = √(3·μa·(μa+μs′)). Edit any field — results recompute live. Built from a 3-model council (Claude Opus 4.8, GPT 5.5, Gemini 3.1 Pro).
Treatment Inputs
Treatment Outputs
Off skin: standoff gap. Beam diverges across the gap, enlarging the spot and lowering surface irradiance (inverse-area). Pressure: compressing tissue blanches blood/water and displaces interstitial fluid, lowering μa & μs′ and thinning the path — deepening penetration.
Total Power per Wavelength (W)
1270 nm directly excites molecular oxygen to singlet oxygen (no photosensitizer). It sits in a water-absorption region — shallow (~2–3 mm) (Biomed. Opt. Express 2019; Krasnovsky 2011).
Tissue Optical Model
Coefficients drive penetration depth — the biggest source of variation between models. Skin = shallow/conservative; muscle = deep/optimistic. Edit any cell to override (switches to Custom).
λ (nm)
μa (cm⁻¹)
μs′ (cm⁻¹)
Per-Wavelength Summary
λ
Power (W)
μeff (cm⁻¹)
Surface I₀ (mW/cm²)
Surface fluence (J/cm²)
Total energy (J)
1/e depth (mm)
Max penetration —1% depth (mm)
Total delivered energy (all λ):
Irradiance vs Depth (mW/cm²) — 0 to 7 cm in 0.5 cm steps
Green cell = ≥1 mW/cm² (commonly cited minimum target irradiance); amber = 0.01–1; grey = sub-threshold. I(z)=I₀·e−μeff·z. Total row = sum of each wavelength column across all depth steps.
Fluence (Dose) vs Depth (J/cm²)
Fluence(z) = surface fluence × e−μeff·z. Surface fluence = total joules / treatment area = I₀ × beam-on time. Total column = combined all-wavelength fluence at each depth.
Method & assumptions. 1-D homogeneous-slab diffusion model. Time-averaged surface irradiance I₀ = P·duty / treatment-area (scanning distributes energy over the whole area; movement speed cancels for average dose but governs peak dwell & coverage). Beam-on time = treatment time × duty. Penetration ordering 810 > 1064 > 635 > 980 > 525 nm; 980 nm dips due to the water absorption peak.
Off skin (in): models beam divergence (assumed ~7° half-angle) — the spot enlarges across the air gap, so in-zone surface irradiance drops by the inverse-area of spot growth. Contact (0 in) = no loss. Pressure applied: tissue compression blanches superficial blood and displaces interstitial water (lowering μa), induces optical clearing (lowering μs′), and physically thins the path — net effect is deeper penetration (mechanical optical clearing has shown up to ~5× depth enhancement). Compression factors here are representative estimates — tune per device/tissue. Near-surface build-up (2–5×) and thermal/burn risk are NOT modeled — use a Pennes bioheat model for Class IV thermal safety.