Tc-99m — routine SPECT (MDP, MIBI, ECD, MAG3, DMSA, sulphur colloid, pertechnetate)
Energy · 140 keV photopeak
Recommended tier · 6 mm Pb — standard SPECT tabletop
Rule · Routine cardiac, oncology, renal, hepato-biliary and lung SPECT lists. 18″×17″×26″ standard tabletop or 13″×13″×17″ Ultra compact.
Why · HVL ≈ 0.27 mm; 6 mm wall = ~ 22 HVL. Cumulative shift activity 10–20 GBq Tc-99m well inside operator-dose envelope.
Ga-67 — oncology / inflammation SPECT
Energy · 93, 184, 296, 388 keV mixed
Recommended tier · 6 mm Pb — standard SPECT tabletop
Rule · Diagnostic Ga-67 citrate scans. Standard 18″×17″×26″ tabletop with the same 6 mm tier as Tc-99m.
Why · Highest Ga-67 line at 388 keV; HVL ~ 3.2 mm; 6 mm wall = ~ 2 HVL on the hardest line. Typical diagnostic activity (~ 185 MBq) keeps the dose-rate inside envelope at this tier.
In-111 — DTPA, octreotide, prostatic-cancer ProstaScint
Energy · 171 / 245 keV doublet
Recommended tier · 6 mm Pb — standard SPECT tabletop
Rule · Same 6 mm SPECT tier as Tc-99m / Ga-67. Compact 13″×13″×17″ Ultra also valid for low-throughput In-111 work.
Why · HVL at 245 keV ~ 1.4 mm; 6 mm wall = ~ 4 HVL. Typical In-111 diagnostic activity (~ 185 MBq) sits comfortably inside the envelope.
I-131 — diagnostic uptake / scan + post-thyroidectomy ablation prep (low)
Energy · 364 keV gamma
Recommended tier · 12 mm Pb — I-131 routine tier
Rule · 12 mm tier for diagnostic uptake (1–5 mCi) and low-activity post-thyroidectomy ablation. Standard 18″×17″×26″ tabletop or 13″×13″×17″ Ultra.
Why · HVL at 364 keV ~ 3.0 mm; 12 mm wall = ~ 4 HVL (~ 94 % attenuation). Routine diagnostic and low-activity ablation per-shift cumulative dose sits inside envelope.
I-131 — high-activity thyroid-cancer ablation (75–250 mCi)
Energy · 364 keV gamma
Recommended tier · 25 mm Pb — I-131 boosted tier
Rule · 25 mm tier when per-shift cumulative ablation activity exceeds the 12 mm envelope. Larger 17″×18″×24″ footprint to handle the higher-activity capsule preparation workflow.
Why · 25 mm wall = ~ 8 HVL at 364 keV (~ 99.6 % attenuation). Required for therapy-prep workflows where the cumulative shift activity is several hundred mCi.
Y-90 — SIR-T microspheres + radiosynovectomy
Energy · Pure β (2.28 MeV endpoint)
Recommended tier · 6 mm Pb + 6 mm Perspex — β-γ hybrid build
Rule · SIR-T liver-tumour microsphere preparation, radiosynovectomy of inflamed joints. Standard 17″×18″×26″ tabletop with the Perspex inner layer.
Why · Perspex (low-Z) stops the beta before it reaches the lead inner surface; lead handles the residual bremsstrahlung X-rays. Without Perspex the lead generates substantial bremsstrahlung against the high-energy Y-90 beta.
P-32 — myeloproliferative disorders
Energy · Pure β (1.71 MeV endpoint)
Recommended tier · 6 mm Pb + 6 mm Perspex — β-γ hybrid build
Rule · P-32 phosphate dispensing for polycythaemia vera, essential thrombocythaemia. Same β-γ hybrid build as Y-90.
Why · Same bremsstrahlung physics as Y-90; the Perspex inner layer is the radiation-safety construction that handles pure-beta dispensing.
Sr-89 — bone-pain palliation
Energy · Pure β (1.49 MeV endpoint)
Recommended tier · 6 mm Pb + 6 mm Perspex — β-γ hybrid build
Rule · Sr-89 chloride dispensing for metastatic bone-pain palliation. β-γ hybrid build.
Why · Same physics as Y-90 / P-32 — the Perspex inner stops the beta, lead handles the residual bremsstrahlung.
