Acquisition Parameters: SPECT & Planar
Representative adult activity, collimator, energy window, matrix, and timing by study
Quick Answer
This is a representative adult acquisition reference for common SPECT/planar studies — radiopharmaceutical, typical activity, collimator, energy window, matrix/acquisition, and timing. Values are representative and institution/guideline-dependent (SNMMI/EANM procedure standards); pediatric activity is weight-based (EANM Dosage Card / North American consensus). The three levers that most often decide image quality are the collimator (matched to isotope energy), the energy window (centered on the photopeak), and adequate counts/time.
⚠️ Representative parameters for orientation and study — verify against current society guidelines and your local protocol before clinical use. Activities in mCi (MBq in parentheses where helpful).
Collimator Selection (the First Decision)
| Isotope (photopeak) | Collimator |
|---|---|
| Tc-99m (140 keV), Tl-201 (~70 keV), I-123 (159 keV) | Low-energy (LEHR / LEAP) |
| In-111 (173/247), Ga-67 (93/185/300) | Medium-energy |
| I-131 (364 keV) | High-energy |
A low-energy collimator with a high-energy isotope → septal-penetration (star) artifact. Pinhole collimation is used for thyroid/parathyroid and small-organ high-resolution imaging.
Renal, Genitourinary
| Study | Agent | Activity | Collimator / window | Acquisition | Timing / notes |
|---|---|---|---|---|---|
| Dynamic renography | Tc-99m-MAG3 | ~5–10 mCi | LEHR / 140 keV | Dynamic 64×64: flow 1–3 s frames, then 15–20 s ×20–30 min; supine, posterior | Diuretic F+20/F−15/F0; hydrate, empty bladder |
| GFR | Tc-99m-DTPA | ~3–5 mCi | LEHR / 140 | Gates camera method or plasma sampling | Filtered marker |
| Cortical / DMSA | Tc-99m-DMSA | ~2–5 mCi | LEHR or pinhole / 140 | Static high-count (~300–500k) planar (post + obliques); or pinhole | Image ~2–4 h; scarring at ~6 mo |
| Cystography (direct) | Tc-99m-pertechnetate/SC | per protocol (intravesical) | LEHR / 140 | Continuous dynamic through fill/void | Low gonadal dose |
Skeletal
| Study | Agent | Activity | Collimator / window | Acquisition | Timing |
|---|---|---|---|---|---|
| Bone scan (WB) | Tc-99m-MDP/HDP | ~20–30 mCi (740–1110 MBq) | LEHR / 140 | WB planar 256×1024 (~10–15 cm/min) ± SPECT 128×128, 60–120 views, 20–40 s/view | Delayed 2–4 h; hydrate/void |
| Three-phase | Tc-99m-MDP | as above | LEHR / 140 | Flow (1–3 s), blood pool (~5 min), delayed | Infection/CRPS/viability |
Cardiac
| Study | Agent | Activity | Collimator / window | Acquisition | Notes |
|---|---|---|---|---|---|
| MPI (Tc-99m) | sestamibi/tetrofosmin | stress/rest ~10–30 mCi (1- or 2-day) | LEHR / 140 | Gated SPECT 64×64, 180° (RAO→LPO), ~60–64 views, 20–25 s/view, 8–16 gates | Image 15–60 min post; prone/upright, AC |
| MPI (Tl-201) | thallous chloride | ~3–4 mCi | LEHR / 70 keV (+167) | Stress–redistribution ± reinjection | Redistribution = viability |
| MUGA | Tc-99m-RBC | ~20–25 mCi | LEHR / 140 | Gated planar LAO best-septal, 16–24 frames/cycle, high counts | In-vitro labeling; stable rhythm |
| PYP (ATTR) | Tc-99m-PYP | ~15–20 mCi | LEHR / 140 | Planar + SPECT at 1 h (± 3 h) | Monoclonal screen; SPECT mandatory |
Pulmonary
| Study | Agent | Activity | Collimator / window | Acquisition | Notes |
|---|---|---|---|---|---|
| Perfusion (Q) | Tc-99m-MAA | ~3–5 mCi (200k–500k particles) | LEHR / 140 | 8 planar views ± SPECT; supine injection | Reduce particles if R-to-L shunt |
| Ventilation | Technegas / DTPA aerosol / Xe-133 | per agent | LEHR | Wash-in/out (Xe) or single-breath/equilibrium | Central deposition in COPD (aerosol) |
Hepatobiliary & GI
| Study | Agent | Activity | Collimator / window | Acquisition | Notes |
|---|---|---|---|---|---|
| HIDA | Tc-99m-mebrofenin | ~3–8 mCi (↑ if high bilirubin) | LEHR / 140 | Dynamic 60 min (1 min/frame), anterior; delayed 3–4 h/24 h | Fast 4 h (not >24); morphine/CCK; phenobarbital (neonate) |
| Gastric emptying | Tc-99m-SC (egg meal) | ~0.5–1 mCi | LEHR / 140 | Anterior+posterior at 0,1,2,4 h; geometric mean | Standard meal; image to 4 h |
| GI bleed | Tc-99m-RBC | ~20–25 mCi | LEHR / 140 | Dynamic 60–90 min (1 min/frame) + delayed | In-vitro label; appears-and-moves |
| Meckel | Tc-99m-pertechnetate | ~5–10 mCi (peds weight-based) | LEHR / 140 | Dynamic + statics 30–60 min, anterior | Cimetidine pretreat |
Endocrine
| Study | Agent | Activity | Collimator / window | Acquisition | Notes |
|---|---|---|---|---|---|
| Thyroid uptake/scan | I-123 (or Tc-99m-pertechnetate) | I-123 ~100–400 µCi; Tc ~2–10 mCi | Pinhole / 159 (I-123) or 140 (Tc) | Planar pinhole; uptake at 4–6 & 24 h (I-123) | Trapping (Tc) vs organification (I) |
| Parathyroid | Tc-99m-sestamibi | ~20–25 mCi | LEHR/pinhole / 140 | Dual-phase (10–15 min & 1.5–2.5 h) + SPECT/CT | ± ¹⁸F-fluorocholine PET |
| MIBG (I-123) | I-123-MIBG | ~10 mCi | LEHR / 159 | Planar + SPECT at 24 h | Thyroid block; hold interfering drugs |
| SSTR (legacy) | In-111-pentetreotide | ~6 mCi | Medium-energy / 173+247 | Planar + SPECT at 4 & 24 h (±48) | Superseded by DOTATATE PET |
Infection / Lymphatic / CNS
| Study | Agent | Activity | Collimator / window | Acquisition | Notes |
|---|---|---|---|---|---|
| Labeled WBC | Tc-99m-HMPAO WBC | ~7–10 mCi | LEHR / 140 | Planar ± SPECT/CT at 1–4 h | Pair with sulfur-colloid marrow |
| " | In-111-oxine WBC | ~0.5 mCi | Medium-energy / 173+247 | Imaging at 24 h | Cleaner abdomen; delayed imaging |
| Sentinel node | Tc-99m-SC (filtered)/tilmanocept | ~0.5–2 mCi | LEHR / 140 | Dynamic + static ± SPECT/CT | Filter colloid; intraop probe |
| DaTscan | I-123-ioflupane | ~3–5 mCi | LEHR/fanbeam / 159 | SPECT at 3–6 h | Thyroid block; review meds |
| Cisternography | In-111-DTPA (intrathecal) | ~0.5 mCi | Medium-energy / 173+247 | Sequential 1,3,6,24,48,72 h | NPH pattern; pledgets for leak |
| Brain perfusion | Tc-99m-HMPAO/ECD | ~20 mCi | LEHR / 140 | SPECT; inject at seizure onset (ictal) | Fixed-at-injection snapshot |
Board-Level Synthesis
Three levers decide a SPECT/planar study: the collimator (energy-matched — LEHR for Tc-99m/Tl-201/I-123, medium-energy for In-111/Ga-67, high-energy for I-131), the energy window (centered on the photopeak), and adequate counts/time. A low-energy collimator with I-131 produces a septal-penetration star artifact.
Timing is part of the protocol: bone delayed 2–4 h, HIDA 60 min (delayed to 4/24 h), gastric emptying to 4 h, DMSA scarring re-imaged at ~6 months, In-111 studies at 24 h (± 48). Cardiac and PYP require SPECT (gating for MPI; myocardial confirmation for PYP).
Activities are representative and guideline/institution-dependent; pediatric activity is weight-based with a minimum diagnostic floor (EANM Dosage Card / North American consensus). Special techniques recur: pinhole for thyroid/parathyroid, filtered colloid for sentinel node, in-vitro RBC labeling for bleed/MUGA, and diuretic/hydration/bladder control for renography.
Related Pages
- Reference: Acquisition parameters — PET, therapy administration protocols, quantitative thresholds & decision cutoffs.
- Physics: Radiation detection & instrumentation (collimators), quality control procedures.
Figure / Diagram Suggestions
- A collimator-by-isotope selection chart with the star-artifact warning.
- A one-page protocol card grid (agent / activity / collimator / window / timing).
Self-Check
Q1. Which collimator is required for I-131 imaging, and what happens if a low-energy one is used?
Answer: A high-energy collimator (I-131 photopeak 364 keV); a low-energy collimator causes septal-penetration (star) artifacts.
Q2. Why is In-111 imaged with a medium-energy collimator and at ~24 hours?
Answer: In-111's photopeaks are 173/247 keV (medium-energy), and its 2.8-day half-life supports delayed (24 h) imaging (e.g. WBC, OctreoScan, cisternography).
Q3. What acquisition and timing features are mandatory for a PYP cardiac amyloid study?
Answer: SPECT (to confirm myocardial vs blood-pool/rib uptake) at 1 h (± 3 h), alongside a monoclonal-protein screen.
Q4. How is pediatric administered activity determined?
Answer: Weight-based with a minimum diagnostic activity, per the EANM Dosage Card / North American consensus — not adult activity scaled arbitrarily.
Evidence & sources
https://nuc.med/acquisition-parameters-spect/ Report an issue