Modes Of Radiation Decay
Radiation Decay is the process in which all unstable radioactive atoms give off energy, in the form of radiation, in order to become stable (non-radioactive). 4 of the modes of radiation decay are discussed below
ALPHA
Compositiion: Mass & Energy
Utility: Therapeutic
Energy: 5-30 MeV (HIGH)
Range: <1mm (SHORT)
DNA Damage: Double Stranded Breaks
Number of Hits to Kill Cell: 2-10
Examples: Ac225, Pb212, Th227, At211, Ra223
BETA
Compositiion: Mass & Energy
Utility: Therapeutic
Energy: 0.1-0.5 MeV (MEDIUM)
Range: 1-10mm (MEDIUM)
DNA Damage: Single Strand Breaks
Number of Hits to Kill Cell: ~2,000
Examples: Lu177, Cu67, Tb167, I131
GAMMA
Compositiion: Photons: Energy ONLY, No Mass
Utility: SPECT Imaging
Energy: 70-700 keV (HIGH)
Range: 2-3 feet
DNA Damage: N/A
Number of Hits to Kill Cell: N/A
Examples: Tc99m, In111
POSITRON
Compositiion: Mass & Energy
Utility: PET Imaging
Energy: ~1.0 MeV
Range: 1-3mm
DNA Damage: N/A
Number of Hits to Kill Cell: N/A
Examples: C11, Cu64, F18, Ga68, Zr89
Isotopes
Radioisotopes are the unstable (radioactive) atoms that are linked to a ligand (delivery system) that are then used to either image a cancer or treat a cancer depending on the properties of each radioisotope as discussed below
ACTINIUM-225
Radioisotope: Ac-225
Theranostic Role: Therapeutic Agent & SPECT Imaging
T1/2 (Half-Life): 9.9 Days
Decay Mode: ALPHA, GAMMA
Energy: 5.8-8.4 MeV
Range: 47-85 micrometers
Decay Daughters: Ra225, Fr221, At217, Bi213, 209, Po213, 209, TL209, 205
Status: Clinical Trials Only
ASTATINE-211
Radioisotope: At-211
Theranostic Role: Therapeutic Agent
T1/2 (Half-Life): 7.2 hours
Decay Mode: ALPHA, ELECTRON CAPTURE
Energy: 2 Alpha particles 5.87 & 7.45 MeV
Range: 50-100 micrometers
Decay Daughters: Bi207, Po211
Status: Clinical Trials Only
CARBON-11
Radioisotope: C-11
Theranostic Role: PET Imaging, SPECT Imaging
T1/2 (Half-Life): 20.4 Min
Decay Mode: POSITRON β+ (99.8%), ELECTRON CAPTURE (0.2%), GAMMA
Energy: max 0.96 MeV, mean 386 keV, Gamma 511 keV
Range: N/A
Decay Daughters: B11 (Stable)
Status: FDA Approval: Carbon 11 Choline (2012)
COPPER-64
Radioisotope: Cu-64
Theranostic Role: PET Imaging
T1/2 (Half-Life): 12.7 Hours
Decay Mode: POSITRON β+, BETA, Electron Capture, GAMMA
Energy: 0.65 MeV, Gamma 511 keV
Range: max 2.5mm, mean 0.7mm
Decay Daughters: Ni64 (Stable), Zn64 (Stable)
Status: FDA Approval: DETECTNET®
COPPER-67
Radioisotope: Cu-67
Theranostic Role: Therapeutic Agent & SPECT Imaging
T1/2 (Half-Life): 62 Hours
Decay Mode: BETA, GAMMA
Energy: Beta: max 575 keV, mean 154 keV, Gamma: 184 keV (44%). 91/93 keV (21%)
Range: In Tissue: 0.6-2.2 mm
Decay Daughters: Zn67 (Stable)
Status: Clinical Trials Only
FLUORINE-18
Radioisotope: F-18
Theranostic Role: PET Imaging
T1/2 (Half-Life): 1.8 Hours
Decay Mode: POSITRON β+ (96.7%), ELECTRON CAPTURE (3.3%), GAMMA 511 keV
Energy: Eβ+ 635 keV
Range: N/A
Decay Daughters: O18 (Stable)
Status: FDA Approvals: FDG (Cancer 2005): GLUDEF®, METATRACE® AXUMIN® (2016), PYLARIFY® (2023), POSLUMA® (2024)
GALLIUM-68
Radioisotope: Ga-68
Theranostic Role: PET Imaging
T1/2 (Half-Life): 68 minutes
Decay Mode: POSITRON β+ (88.9%), GAMMA, ELECTRON CAPTURE (8.7%)
Energy: Beta: max 1.9 MeV Gamma 1.1 MeV, 511 keV
Range: N/A
Decay Daughters: Zn68 (Stable)
Status: FDA Approvals: NETSPOT® (2016), LOCAMETZ® (2022), ILLUCIX® (2021)
INDIUM-111
Radioisotope: In-111
Theranostic Role: SPECT Imaging
T1/2 (Half-Life): 2.8 Days
Decay Mode: ELECTRON CAPTURE, GAMMA
Energy: 173 keV, 247 keV
Range: N/A
Decay Daughters: Cd111 (Stable)
Status: FDA Approvals: ONCOSCINT® (1992), OCTREOSCAN® (1994)
IODINE-123
Radioisotope: I-123
Theranostic Role: SPECT Imaging
T1/2 (Half-Life): 13.2 Hours
Decay Mode: BETA, GAMMA
Energy: Beta: 127 keV (14%), 154 keV (2%) Gamma: 539 keV (1%), 159 keV (83%), 27 keV (71%)
Range: N/A
Decay Daughters: Te123 (Stable)
Status: FDA Approvals: DATSCAN®(2011), ADREVIEW® (2008)
IODINE-131
Radioisotope: I-131
Theranostic Role: Therapeutic Agent & SPECT Imaging
T1/2 (Half-Life): 8 Days
Decay Mode: BETA, GAMMA
Energy: βeta max 0.6 MeV Gamma 364 keV
Range: In Tissue: 0.8 -2.1 mm
Decay Daughters: Xe131
Status: FDA Approval: 1951-First FDA Approved Radiopharmaceutical), AZEDRA® (2018)
LEAD-203
Radioisotope: Pb-203
Theranostic Role: SPECT Imaging
T1/2 (Half-Life): 52 Hours
Decay Mode: ELECTRON CAPTURE, GAMMA
Energy: Gamma 279keV (81%)
Range: N/A
Decay Daughters: Tl203 (Stable)
Status: Clinical Trials Only
LEAD-212
Radioisotope: Pb-212
Theranostic Role: Therapeutic Agent
T1/2 (Half-Life): 10.6 Hours
Decay Mode: ALPHA, BETA, GAMMA
Energy: Alpha 6 MeV (25%), 6 MeV (10%), 8.7 MeV (71%) Beta 1.5 MeV (18%), 1.8 MeV (20%), 2.2 MeV (53%) Gamma 583 keV (30%), 2.6 MeV (36%)
Range: 50-100 micrometers
Decay Daughters: Bi212, Tl208, Po212, Pb208
Status: Clinical Trials Only, 2024 FDA Breakthrough Therapy Designation for ALPHAMEDIX™ GEP-NET Tumors
LUTETIUM-177
Radioisotope: Lu-177
Theranostic Role: Therapeutic Agent & SPECT Imaging
T1/2 (Half-Life): 6.7 Days
Decay Mode: BETA, GAMMA
Energy: Eβeta max 497 keV, Gamma 113-208 keV
Range: In Tissue: 0.25-2mm
Decay Daughters: Hf177
Status: FDA Approvals: PLUVICTO® (2022), LUTATHERA® (2017)
PHOSPHORUS-32
Radioisotope: P-32
Theranostic Role: Therapeutic Agent, SPECT Imaging
T1/2 (Half-Life): 14.3 Days
Decay Mode: BETA
Energy: Max: 1.71 MeV, Avg: 694 keV
Range: Air: 20 feet, Water/Tissue: 8.7mm
Decay Daughters: S32 (Stable)
Status: Clinical Trials Only
RADIUM-223
Radioisotope: Ra-223
Theranostic Role: Therapeutic Agent
T1/2 (Half-Life): 11.4 Days
Decay Mode: ALPHA, BETA, GAMMA
Energy: Alpha (95%) 5-7.5 MeV Beta (3.6%) 445-492 keV Gamma (1%) 82-402 keV
Range: In Tissue <100 micrometers
Decay Daughters: 4 alpha daughters: Rn219, Po211,215, Bi211
Status: FDA Approval: XOFIGO® (2013)
RHENIUM-186
Radioisotope: Re-186
Theranostic Role: Therapeutic Agent and SPECT Imaging
T1/2 (Half-Life): 3.7 Days
Decay Mode: ELECTRON CAPTURE (7.5%), BETA (92.5%), GAMMA
Energy: EC 0.58 MeV; Beta mean 346 keV, Gamma 137 keV
Range: In Tissue: 4.5mm
Decay Daughters: Os186 (Stable), W186 (Stable)
Status: Clinical Trials Only, 2023 FDA Orphan Drug Status for Breast Cancer with Leptomeningeal Metastases
RHENIUM-188
Radioisotope: Re-188
Theranostic Role: Therapeutic Agent & SPECT Imaging
T1/2 (Half-Life): 17 Hours
Decay Mode: BETA, GAMMA
Energy: Max 2.1 MeV, Avg 784 keV Gamma: 155 keV (15%)
Range: In Tissue: 11mm
Decay Daughters: Os188 (Stable)
Status: ONCOBETA® (German) Rhenium-SCT® for non-melanoma skin cancer treatment
SAMARIUM-153
Radioisotope: Sm153
Theranostic Role: Therapeutic
T1/2 (Half-Life): 1.9 Days
Decay Mode: BETA, GAMMA
Energy: Beta: Max 808 keV Gamma: 103 keV (28%)
Range: 0.6 mm
Decay Daughters: Eu153 (Stable)
Status: FDA Approval: QUADRAMET® (1997)
TECHNETIUM-99m
Radioisotope: Tc-99m
Theranostic Role: SPECT Imaging
T1/2 (Half-Life): 6 Hours
Decay Mode: GAMMA
Energy: 140 keV (89.1%)
Range: N/A
Decay Daughters: Tc99
Status: FDA Approval: First in 1980’s
TERBIUM-161
Radioisotope: Tb-161
Theranostic Role: Therapeutic Agent & SPECT Imaging
T1/2 (Half-Life): 6.9 Days
Decay Mode: BETA, GAMMA
Energy: Beta: Avg 154 keV Gamma: 49 keV (17%), 75 keV (10%)
Range: 0.5-30 micrometers
Decay Daughters: Dy161 (Stable)
Status: Clinical Trials Only
THORIUM-227
Radioisotope: Th-227
Theranostic Role: Therapeutic Agent
T1/2 (Half-Life): 19 Days
Decay Mode: ALPHA, BETA
Energy: Alpha 5.9 MeV (Ra223), 5.7 MeV ( Rn219), Total 5 Alpha particles (Total 34MeV)
Range: <0.1 mm
Decay Daughters: Ra223, Rn219, Po215, Pb211, Bi211, Tl207 Pb207 (Stable)
Status: Clinical Trials Only
YTTRIUM-90
Radioisotope: Y-90
Theranostic Role: Therapeutic Agent, SPECT Imaging & PET Imaging
T1/2 (Half-Life): 2.7 Days
Decay Mode: BETA
Energy: max 2.2 MeV
Range: In Tissue: Avg 2.5 mm, Max 11 mm; In Air: 35 feet
Decay Daughters: Zr90 (Stable)
Status: FDA Approvals: SIR-SPHERES® (2000), THERASPHERES® (2021)
ZIRCONIUM-89
Radioisotope: Zr89
Theranostic Role: PET Imaging
T1/2 (Half-Life): 78 Hours
Decay Mode: POSITRON β+ (22%), ELECTRON CAPTURE (76%), GAMMA
Energy: max 0.9 MeV, E mean 397 keV, Gamma 511 keV
Range: N/A
Decay Daughters: Y89 (Stable)
Status: Clinical Trials Only
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