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

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