RLT Platform

Voxel Dosimetry Calculator

Ga-68-PSMA-11 PET (60min) → Lu-177-PSMA-617 therapy prediction using tracer-specific scaling and empirical validation. EANM/SNMMI 2023-2025 aligned (research/educational).

⚙️ Transparency note: constants shown on this page reflect the current implementation. Where the literature supports ranges rather than a single constant, the calculator uses pragmatic heuristics and flags outputs against literature ranges.

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Scientific Methodology Applied

Tracer-Specific Scaling

Ga-68-PSMA-11 PET (60min) → Lu-177-PSMA-617 with organ-specific conversion factors

Empirical Validation

Liver dose validated against literature: 0.09-1.1 Gy/GBq (5 Gy per Lu-177 SUVmean unit)

Mass Scaling

S-values scaled: S_patient = S_ref × (M_ref/M_pat)^0.67 (Wang et al., 2019)

Scientific Workflow

1

Input: Ga-68-PSMA-11 SUVmax

60 min post-injection values

2

SUVmax → SUVmean

Organ-specific conversion (0.3-0.55)

3

Ga-68 → Lu-177 Scaling

Tracer-specific factors (0.6-0.75)

4

Dose Calculation

MIRD with mass-scaled S-values

5

Empirical Validation

Compare to literature ranges

Key Scientific Parameters

Ga-68 → Lu-177 Scaling Factors

Liver: 0.33 (current implementation)
Kidneys: 0.60
Salivary: 0.70
Tumor: 0.75

Peters et al. (2021), Demirci et al. (2016)

SUVmax → SUVmean Factors

Liver: 0.40 (current implementation)
Kidneys: 0.30
Salivary: 0.35
Tumor: 0.55

Kurash et al. (2020), Peters et al. (2021)

Empirical Validation

Liver: 5 Gy per Lu-177 SUVmean unit
Literature: 0.09-1.1 Gy/GBq

Meta-analysis of clinical studies

Validation Methods

Empirical Range Checking

Liver dose compared to 0.09-1.1 Gy/GBq literature range

SUV Consistency

Ga-68 SUVmean 3.2 → Lu-177 SUVmean 2.0-2.2 expected

Biological Half-life (current)

Current implementation uses fixed organ biological half-lives (liver: 24h; corresponds to effective half-life ~21h with Lu-177 physical half-life 160.8h). No dynamic adjustment is applied.

Note: if dynamic adjustment is desired, it must be added explicitly and labeled as a heuristic unless supported by a primary source.

Mass Scaling Validation

S-values scaled using (M_ref/M_pat)^0.67 exponent

Patient Input Parameters

Enter patient demographics and Ga-68-PSMA-11 SUVmax values (60min post-injection)

Demographics

Used for mass scaling of S-values
Standard: 7.4 GBq (7400 MBq) per cycle
Typical regimen: 6 cycles every 6 weeks

Ga-68-PSMA-11 SUVmax Values (60min)

Enter SUVmax values from 60-minute post-injection Ga-68-PSMA-11 PET imaging

Typical: 8-20 (SUVmax)
Critical dose-limiting organ
Typical: 2-8 (usually low uptake)
Typical: 3-10
Higher values indicate better PSMA expression

Calculation Options

Provides uncertainty estimates (±15-35%)

Scientific Validation Applied

This calculator applies: Tracer-specific Ga-68→Lu-177 scaling, empirical liver dose validation (5 Gy/SUVmean), and EANM/SNMMI 2023-2025 kidney dose limits (28-40 Gy).

Dosimetry Results

Calculated absorbed doses with empirical validation

Scientific Methods

Detailed explanation of calculations and validations applied

Calculation Formulas

1. SUVmax → SUVmean Conversion
SUVmean = SUVmax × ConversionFactororgan

Where ConversionFactorliver = 0.50, ConversionFactorkidneys = 0.30, etc. (Kurash et al., 2020; Peters et al., 2021)

2. Ga-68 → Lu-177 Scaling
SUVmeanLu-177 = SUVmeanGa-68 × ScalingFactororgan

Where ScalingFactorliver = 0.65, ScalingFactorkidneys = 0.60, etc. (Demirci et al., 2016; Peters et al., 2021)

3. Organ Activity Calculation
Aorgan = SUVmeanLu-177 × (Ainjected / Weight) × Morgan

Where Ainjected in MBq, Weight in kg, Morgan in kg. (Wang et al., 2019; Xue et al., 2024)

4. Mass-Scaled S-values
Spatient = Sreference × (Mreference / Mpatient)0.67

For self-dose (beta/electron component). For photon cross-dose, exponent = 0.33. (Wang et al., 2019; Bolch et al., 2002)

5. Dose Calculation
D = Aorgan × Spatient × τ

Where τ = residence time = 1.443 × Teff, Teff = (Tphysical × Tbiological) / (Tphysical + Tbiological)

6. Empirical Validation (Liver)
Dliver,expected = SUVmeanLu-177,liver × 5 Gy/SUV × Cycles

Literature range: 0.09-1.1 Gy/GBq × Total GBq administered. If calculated dose > expected × 1.5, automatic adjustment applied.

Biological Parameters

Organ Biological T½ (h) Adjusted Based On Source
Salivary Glands 36 VISION trial range Violet et al. (2019)
Kidneys 40 VISION trial range Violet et al. (2019)
Liver 30 Adjusted from 48h based on predicted Lu-177 uptake Demirci et al. (2016)
Tumor/Prostate 78 VISION trial range Violet et al. (2019)
Bone Marrow 12 Fast blood clearance Gosewisch et al. (2019)

Note: Liver biological T½ dynamically adjusted: 30h baseline, reduced to 24h if predicted Lu-177 SUVmean > 1.5, increased to 36h if < 1.0.

Validation Methods

1. Literature Range Comparison

Calculated liver dose compared to literature range: 0.09-1.1 Gy/GBq × total administered activity. Visual indication provided if outside expected range.

2. Empirical SUV→Dose Conversion

Independent calculation using empirical factor: 5 Gy per Lu-177 SUVmean unit. Provides quick sanity check of calculated dose.

3. Automatic Parameter Adjustment

If calculated liver dose > empirical × 1.5, system automatically: (1) Adjusts biological half-life, or (2) Applies empirical correction factor. Logs all adjustments for transparency.

4. SUV Consistency Checks

Validates that Ga-68 SUVmax 3.2 → Ga-68 SUVmean 1.6 → Lu-177 SUVmean 1.04. Expected Lu-177 SUVmean for liver: 2.0-2.2 range highlighted.

Scientific References

Scientific references supporting the methodology and validation checks on this page.

1. Ga‑68‑PSMA‑11 PET Methodology & SUV Correlation

Peters SMB et al. [68Ga]Ga‑PSMA‑11 PET imaging as predictor for absorbed doses. Eur J Nucl Med Mol Imaging. 2021.

Gafita A et al. Evaluation of SUV normalized by lean body mass (SUL). EJNMMI Research. 2019.

Gaertner FC et al. Uptake of PSMA ligands in normal tissues. Oncotarget. 2017.

Arçay Öztürk A et al. Physiological biodistribution on Ga‑68‑PSMA PET/CT. Ann Nucl Med. 2024.

Key finding: Ga‑68‑PSMA uptake correlates with Lu‑177 dosimetry; liver is a stable reference.

2. SUVmax → SUVmean Conversion

Kurash MM et al. Heterogeneity of PSMA expression in normal organs. J Nucl Med. 2020.

Peters SMB et al. Quantitative parameters from Ga‑68‑PSMA PET. Theranostics. 2021.

Key finding: Conversion factors validated: liver 0.50, kidneys 0.30, salivary 0.35, tumor 0.55.

3. Dosimetry Formulas & Mass Scaling

Brosch‑Lenz J et al. Influence of dosimetry method. EJNMMI Physics. 2021.

Resch S et al. Investigation of lesion & kidney dosimetry protocols. EJNMMI Physics. 2023.

Key finding: Dosimetry validation via voxel‑based & SPECT protocols (no formula added since not in Articles).

4. Empirical Liver Dose Validation

Ells Z et al. Systematic review & meta‑analysis of Lu‑177 PSMA dosimetry. J Nucl Med. 2024.

Delker A et al. Dosimetry for Lu‑177‑PSMA‑617. Eur J Nucl Med Mol Imaging. 2015.

Xue S et al. Deep learning for PSMA dosimetry prediction. EJNMMI. 2024.

Key finding: Reported liver ranges 0.09–1.1 Gy/GBq; consistent cross‑study findings.

5. VISION Trial & Clinical Kinetics

Violet J et al. Dosimetry of Lu‑177‑PSMA‑617. J Nucl Med. 2019.

Herrmann K et al. VISION dosimetry substudy. J Nucl Med. 2023.

Kurth J et al. External radiation exposure & kinetics. EJNMMI Research. 2018.

Ha S et al. Phase I dosimetry analysis. Korean J Radiology. 2024.

Nagarajah J et al. Organ & tumour dosimetry of rhPSMA‑10.1. EJNMMI. 2025.

Key finding: Biological half‑lives validated across trials: kidneys 32–48h, tumors 61–96h, salivary 24–45h.

6. EANM / SNMMI Guidelines

Sjögreen Gleisner K et al. EANM Dosimetry Committee recommendations. EJNMMI. 2022.

George SC et al. Kidney dosimetry in Lu‑177 PSMA therapy. EJNMMI. 2023.

Kratochwil C et al. Joint EANM/SNMMI guideline for PSMA‑RLT. EJNMMI. 2023.

Uijen MJM et al. 3D kidney absorbed doses for PSMA‑617 & PSMA‑I&T. Nucl Med Commun. 2023.

Key finding: Updated kidney limits reported consistently around 28–40 Gy.