Lu-177 (Lutetium-177) Decay Calculator

Decay-correct Lu-177 activity for PRRT & radioligand therapy — part of DecayCalculator.com

📐 ICRP 103 compliant 🔬 IAEA half-life data 🔒 Runs locally
← All DecayCalculator.com tools ❓ FAQ

☢ Lu-177 Decay Calculator

📊 Results
🔬 Enter parameters and click
Calculate Activity
📈 Time–Activity Curve
Calculate to generate chart

Lu-177 Half-Life, Decay Constant, and Clinical Use

Lutetium-177 (Lu-177) is a low-energy beta-emitting radioisotope with accompanying gamma emission (113 keV and 208 keV), widely used in radioligand therapy and peptide receptor radionuclide therapy (PRRT). Its most common clinical forms are 177Lu-DOTATATE (Lutathera) for somatostatin-receptor-positive neuroendocrine tumors, and 177Lu-PSMA-617 for metastatic castration-resistant prostate cancer. Because therapeutic doses are calibrated hours or days before administration, technicians and physicists need to decay-correct the reference activity to the actual infusion time.

Lu-177 has a physical half-life of 6.647 days (159.463 hours). Its decay constant is λ = ln(2) / T½ ≈ 0.004347 h⁻¹, meaning roughly 0.43% of the remaining activity is lost every hour, or about 50% every 6.6 days.

Worked example: a Lu-177 vial reads 7.4 GBq at calibration. What is the activity 3 days (72 hours) later? A(t) = A₀ × e−λt = 7.4 × e−0.004347 × 72 = 7.4 × e−0.313 ≈ 7.4 × 0.731 ≈ 5.41 GBq. Use the calculator below to run this — or any other — Lu-177 timing scenario automatically, with a time-activity chart.

📋 Lu-177 in Context: Other Common Isotopes

Isotope Full Name Half-Life Decay Constant λ (h⁻¹) Application

❓ Frequently Asked Questions — Lu-177

Lutetium-177 has a physical half-life of 6.647 days, equal to 159.463 hours. This is the time it takes for half of a given amount of Lu-177 activity to decay away.
Lu-177 is mainly used for radioligand and peptide receptor radionuclide therapy (PRRT). The two most common clinical forms are 177Lu-DOTATATE (brand name Lutathera) for somatostatin-receptor-positive neuroendocrine tumors, and 177Lu-PSMA-617 for metastatic castration-resistant prostate cancer.
The decay constant is λ = ln(2) / half-life. For Lu-177, λ = 0.6931 / 159.463 h ≈ 0.004347 h⁻¹. This means roughly 0.43% of the remaining Lu-177 activity decays away each hour.
Multiply the calibrated activity by the decay factor e−λt, where t is the elapsed time in hours between calibration and administration. The calculator above does this automatically: enter the reference activity, the calibration date/time, and the planned administration date/time to get the corrected activity and a time-activity chart.