PET/CT and PET/MR
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Solve questions (27) →Contents
- 7.1 Annihilation Physics and Coincidence Detection
- 7.1.1 Positron Emission and Annihilation
- 7.1.2 Coincidence Detection
- 7.1.3 Types of Coincidence
- 7.1.4 Coincidence Timing Window
- 7.2 PET Detector Materials and Design
- 7.2.1 Scintillation Crystals
- 7.2.2 Detector Design
- 7.2.3 Photomultiplier Tube (PMT) and SiPM
- 7.3 TOF-PET (Time of Flight)
- 7.3.1 TOF Principle
- 7.3.2 Effect of TOF on Image Quality
- 7.3.3 TOF Resolution and Clinical Advantages
- 7.4 PET/CT Acquisition and Protocols
- 7.4.1 PET/CT System Design
- 7.4.2 2D vs 3D Acquisition
- 7.4.3 CT Attenuation Correction (CTAC)
- 7.4.4 FDG PET/CT Patient Preparation and Protocol
- 7.4.5 PET/CT Artefacts
- 7.4.6 Digital PET and Long Axial Field-of-View (LAFOV) PET
- 7.5 PET/MR: Technical Features and Advantages
- 7.5.1 PET/MR System Design
- 7.5.2 MR-Based Attenuation Correction (MRAC)
- 7.5.3 Advantages and Limitations of PET/MR
- 7.5.4 Clinical Applications of PET/MR
- 7.6 SUV Calculation and Quantitative Analysis
- 7.6.1 Definition and Formula of SUV
- 7.6.2 SUV Variants
- 7.6.3 Factors Affecting SUV
- 7.6.4 Other Quantitative Parameters
- 7.7 The CT Component of Hybrid Systems: Basic Principles
- 7.7.1 CT Reconstruction
- 7.7.2 CT Dosimetry and Dose Reduction
- 7.7.3 Metal Artefact and Photon-Counting CT
- 7.8 The MR Component of PET/MR: Basic Principles
- 7.8.1 Nuclear Magnetic Resonance and Image Formation
- 7.8.2 MR Scanner Components
- 7.9 Comparison of Imaging Modalities
- Key Points for the Board
- Current guidelines on this chapter's topics
Learning objectives and modules4 modules · about 3 h 5 min
Learning objectives
After this chapter you will be able to:
- Explain how positron range, annihilation and non-collinearity limit PET resolution.
- Distinguish true, scattered and random coincidences and explain how they relate to the coincidence window and activity.
- Compare PET crystals and detector designs; explain the contribution of TOF to image quality.
- Explain the PET/CT acquisition protocol and CT-based attenuation correction, with its limits including respiratory misregistration.
- Calculate SUV and its derivatives (SUVmax, SUVpeak, SUL, MTV, TLG) and list the factors that affect them.
- Compare the technical features of PET/MR, the limits of MR-based attenuation correction and its advantages over PET/CT.
Modules
The chapter is divided into study modules without changing the order of the text: read, watch the animations, then answer the questions linked to those headings.
- Module 17.1–7.3 Annihilation Physics and Coincidence Detection · PET Detector Materials and Design · TOF-PET (Time of Flight)1 h · 5 animations · 17 questionsAnswer the questions →
- Module 27.4 PET/CT Acquisition and Protocols45 min · 2 animations · 17 questionsAnswer the questions →
- Module 37.5–7.6 PET/MR: Technical Features and Advantages · SUV Calculation and Quantitative Analysis45 min · 1 animation · 18 questionsAnswer the questions →
- Module 47.7–7.9 The CT Component of Hybrid Systems: Basic Principles · The MR Component of PET/MR: Basic Principles · Comparison of Imaging Modalities · Key Points for the Board35 min · 7 questionsAnswer the questions →
Times are estimates: 130 words per minute, 3 min per animation, 1.5 min per question.
MOST FREQUENTLY ASKED IN THIS CHAPTER
7.1 Annihilation Physics and Coincidence Detection
7.1.1 Positron Emission and Annihilation4 questions
PET (Positron Emission Tomography) is a molecular imaging method using positron-emitting radionuclides. Its basic physical principle is based on positron-electron annihilation.
Positron emission:
Positron range:
→ F-18 (lowest positron energy → shortest range).
→ Rb-82 (highest positron energy → longest range). Memorise: energy↑ → range↑ → resolution↓.
In a PET ring: positron range, annihilation photons, coincidence and line of response (LOR), scattered, random and multiple events, and image formation (TOF).
Key point: when two 511 keV photons are detected within the timing window the event is placed on the line joining the two detectors; scatter and randoms create false lines, and TOF narrows the position along the line.
Source: book (mean positron ranges, 180° ± 0.25° deviation, T ∝ A, R ∝ τ·A²). Ring 80 cm, to scale; event-type proportions schematic.
How to use: a single click on the drawing pauses and resumes; in the range step ↑ ↓ or the rows of the list pick the radionuclide; in the image steps drag the lesion to move it, and with TOF on ↑ ↓ change the timing resolution; ← → change steps.
Figure 7.1: Maximum energy and mean positron range of positron-emitting radionuclides: as energy increases, range increases and resolution decreases.
The annihilation event:
Acolinearity (angular deviation):
In a PET ring: positron range, annihilation photons, coincidence and line of response (LOR), scattered, random and multiple events, and image formation (TOF).
Key point: when two 511 keV photons are detected within the timing window the event is placed on the line joining the two detectors; scatter and randoms create false lines, and TOF narrows the position along the line.
Source: book (mean positron ranges, 180° ± 0.25° deviation, T ∝ A, R ∝ τ·A²). Ring 80 cm, to scale; event-type proportions schematic.
How to use: a single click on the drawing pauses and resumes; in the range step ↑ ↓ or the rows of the list pick the radionuclide; in the image steps drag the lesion to move it, and with TOF on ↑ ↓ change the timing resolution; ← → change steps.
Figure 7.2: Positron emission, range, annihilation and acolinearity: the difference between the recorded LOR and the true annihilation point (schematic).
7.1.2 Coincidence Detection
The basic imaging principle of PET is based on the simultaneous (coincidence) detection of the two 511 keV photons arising from annihilation.
Coincidence principle:
Electronic collimation:
→ NO; PET uses electronic collimation (coincidence detection).
→ No physical collimator → no photon loss → sensitivity ~10-100 times greater. This is one of the most important advantages of PET.
7.1.3 Types of Coincidence4 questions
Four types of coincidence event are defined in PET:
1. True coincidence:
2. Scatter coincidence:
3. Random coincidence:
4. Multiple coincidence:
WHY IT MATTERS · Prompt gamma
See the animation: Figure 7.3 →
→ They increase quadratically (R ∝ A²).
→ They increase linearly (T ∝ A). For this reason the random/true ratio increases at very high activity → image quality deteriorates.
→ The delayed window method.
In a PET ring: positron range, annihilation photons, coincidence and line of response (LOR), scattered, random and multiple events, and image formation (TOF).
Key point: when two 511 keV photons are detected within the timing window the event is placed on the line joining the two detectors; scatter and randoms create false lines, and TOF narrows the position along the line.
Source: book (mean positron ranges, 180° ± 0.25° deviation, T ∝ A, R ∝ τ·A²). Ring 80 cm, to scale; event-type proportions schematic.
How to use: a single click on the drawing pauses and resumes; in the range step ↑ ↓ or the rows of the list pick the radionuclide; in the image steps drag the lesion to move it, and with TOF on ↑ ↓ change the timing resolution; ← → change steps.
Figure 7.3: The four types of coincidence in PET: true, scatter, random and multiple coincidence (schematic).
7.1.4 Coincidence Timing Window
The coincidence timing window (τ) is the maximum time difference allowed for two photons to be accepted as "simultaneous".
Typical values:
Effect of the timing window:
Photons reaching two opposed detectors flow along a timeline; if a photon falls in the other detector within the window around a photon, a coincidence is recorded: true if from the same annihilation, random if from different ones. Rates by window width and activity are plotted.
Key point: true coincidences rise linearly with activity and level off once the window covers the arrival difference; randoms rise linearly with window width and with the square of activity, so noise grows at high activity and with a wide window.
Source: book (T ∝ A, R = 2τ·S₁·S₂ ∝ A², window 6–12 ns conventional, ~3–6 ns TOF; scatter 30–40% in 3D). The window width is shown as 2τ (Cherry et al.). Model: photons of one annihilation arrive at most ±2 ns apart (~60 cm patient), timing uncertainty σ 0.25 ns; singles Poisson. On the timeline the time between events is shortened for display (in reality ~10⁵–10⁶ singles/s per detector); curves relative.
How to use: a single click on the drawing pauses and resumes; ↑ ↓ change the window width in the first step and the activity in the second; ← → change steps.
Figure 7.4: Variation of true, scatter and random coincidence rates with activity (A) and with the coincidence timing window (B) (schematic).
7.2 PET Detector Materials and Design
7.2.1 Scintillation Crystals2 questions
PET detectors use high-density, high-atomic-number scintillation crystals to detect 511 keV photons. The NaI(Tl) crystal used in SPECT does not have sufficient stopping power for 511 keV.
Comparison of PET crystals:
| Property | BGO | LSO | LYSO | GSO | NaI(Tl)* |
|---|---|---|---|---|---|
| Density (g/cm³) | 7.13 | 7.40 | 7.10 | 6.71 | 3.67 |
| Effective Z | 74 | 66 | 64 | 59 | 51 |
| Light output (% of NaI) | 15 | 75 | 75 | 25 | 100 |
| Decay time (ns) | 300 | 40 | 41 | 60 | 230 |
| Energy resolution (%) | ~20 | ~12 | ~12 | ~15 | ~8 |
| Hygroscopic | No | No | No | No | Yes |
| Suitability for TOF | No | Yes | Yes | Partly | No |
NaI(Tl) is shown for reference; it is not used as standard in PET.
BGO (Bismuth Germanate – Bi₄Ge₃O₁₂):
LSO (Lutetium Oxyorthosilicate – Lu₂SiO₅:Ce):
LYSO (Lutetium Yttrium Oxyorthosilicate – Lu₁.₈Y₀.₂SiO₅:Ce):
GSO (Gadolinium Oxyorthosilicate – Gd₂SiO₅:Ce):
→ LSO/LYSO.
→ BGO (highest effective Z).
→ LSO/LYSO (short decay time ~40 ns + high light output).
→ Long decay time (300 ns) → insufficient timing resolution.
→ Natural Lu-176 radioactivity (intrinsic background).
Figure 7.5: Relationship between light output and decay time of PET scintillation crystals; circle size is proportional to density.
7.2.2 Detector Design
Block detector:
Pixelated array:
Detector ring design:
7.2.3 Photomultiplier Tube (PMT) and SiPM2 questions
PMT (photomultiplier tube):
SiPM (silicon photomultiplier):
→ The PMT is sensitive to magnetic fields → it cannot work in the strong magnetic field of the MR scanner.
→ The SiPM (insensitive to magnetic fields).
→ Excellent timing resolution.
Figure 7.6: Comparison of the block detector (Casey–Nutt) with a pixelated crystal separated by reflector and read out by SiPMs (schematic).
7.3 TOF-PET (Time of Flight)
7.3.1 TOF Principle
In conventional PET the difference in the arrival times of the two 511 keV photons at the detectors is not measured → the location of the annihilation point on the LOR is unknown → it is distributed with equal probability along the LOR. In TOF-PET the difference in the arrival times of the two photons at the detectors (Δt) is measured → the approximate location of the annihilation point on the LOR is calculated.
Position calculation:
Δx = (c × Δt) / 2
Example calculation:
In a PET ring: positron range, annihilation photons, coincidence and line of response (LOR), scattered, random and multiple events, and image formation (TOF).
Key point: when two 511 keV photons are detected within the timing window the event is placed on the line joining the two detectors; scatter and randoms create false lines, and TOF narrows the position along the line.
Source: book (mean positron ranges, 180° ± 0.25° deviation, T ∝ A, R ∝ τ·A²). Ring 80 cm, to scale; event-type proportions schematic.
How to use: a single click on the drawing pauses and resumes; in the range step ↑ ↓ or the rows of the list pick the radionuclide; in the image steps drag the lesion to move it, and with TOF on ↑ ↓ change the timing resolution; ← → change steps.
Figure 7.7: TOF principle: in conventional PET the event is distributed along the LOR; in TOF-PET it is assigned to a limited interval by the arrival time difference (schematic).
7.3.2 Effect of TOF on Image Quality5 questions
TOF gain:
TOF restricts the annihilation point to a certain interval (Δx) on the LOR. This increases the signal-to-noise ratio (SNR).
SNR gain formula: SNR gain ≈ √(D / Δx)
Relationship between TOF timing resolution and Δx:
Effects of TOF:
→ Increased SNR (especially in large patients).
→ SNR gain = √(D/Δx).
→ D (patient diameter) is large → gain is large.
→ LSO/LYSO (short decay time).
→ Decay time of 300 ns → insufficient timing resolution.
Figure 7.8: Relationship between TOF timing resolution and position uncertainty (Δx) (A), and theoretical SNR gain √(D/Δx) as a function of patient diameter (B).
7.3.3 TOF Resolution and Clinical Advantages
Current TOF-PET systems:
Technological features required for TOF:
Clinical advantages:
7.4 PET/CT Acquisition and Protocols
7.4.1 PET/CT System Design3 questions
PET/CT is a hybrid imaging system in which PET and CT components are integrated on the same gantry. The first commercial PET/CT system was introduced in 2001.
History and development:
System components:
Acquisition sequence:
1. Topogram (scout) → scan range is defined 2. CT scan (a few seconds-minutes) → attenuation map + anatomical image 3. PET scan (1-5 minutes per bed position) → metabolic image 4. Fusion images are created
Table motion and gating:
7.4.2 2D vs 3D Acquisition1 questions
2D acquisition:
3D acquisition:
→ 3D (septa-less).
→ ~4-8-fold increase.
→ Increased scatter and random coincidences.
→ To block cross-plane coincidences → reduce scatter and randoms.
An axial section shows two rows of detector rings with the patient between; annihilation photons leave at random axial angles. In 2D the septa between rings stop oblique and scattered photons; in 3D coincidences between all rings are accepted.
Key point: removing the septa lets cross-ring coincidences count and raises sensitivity ~4–8×; the price is more scatter and randoms and a more complex reconstruction.
Source: book (2D: same/adjacent ring, scatter ~15–20%; 3D: sensitivity ~4–8×, scatter ~30–40%, randoms↑). The drawing is schematic: the axial direction is stretched, so the ratio of counts in the drawing does not show the real gain. Photon directions isotropic; single scatter of ~30% of photons in the body is illustrative.
How to use: a single click on the drawing pauses and resumes; ← → switch between 2D and 3D.
Figure 7.9: Coincidence lines accepted in 2D (with septa) and 3D (septa-less) PET acquisition (schematic).
7.4.3 CT Attenuation Correction (CTAC)2 questions
In PET images the 511 keV photons are attenuated in the patient's body. Without attenuation correction, spuriously reduced uptake is seen in deep structures (e.g. the mediastinum).
CTAC principle:
1. The HU (Hounsfield unit) value of each voxel is obtained from the CT scan 2. HU values are converted into linear attenuation coefficients (µ) at 511 keV
3. A 511 keV attenuation map is created 4. The PET data are corrected with this map
Advantages of CTAC (compared with a transmission source):
Potential problems of CTAC:
→ CT photon energy (~70-140 keV) ≠ PET photon energy (511 keV) → HU values cannot be used directly → energy scaling is needed.
→ Falsely high HU on CT → overestimated µ at 511 keV → overcorrection for attenuation → hot artefact.
Figure 7.10: Bilinear conversion of HU into the linear attenuation coefficient at 511 keV in CTAC and the mechanism of the hot artefact caused by high HU (schematic).
7.4.4 FDG PET/CT Patient Preparation and Protocol5 questions
Patient preparation:
Standard FDG PET/CT protocol:
1. Patient preparation (fasting, blood glucose check)
2. FDG injection: 5-10 mCi (185-370 MBq) IV (this level applies to short axial FOV/analogue systems; on digital and long axial FOV systems a lower activity is set with the EARL procedure, EANM 2025) 3. Uptake period: 60 ± 10 minutes (in a quiet, dark, warm room) 4. Topogram (scout) 5. CT scan (low dose or diagnostic dose)
6. PET scan: In the caudal → cranial direction (to reduce urinary activity artefact)
7. Image reconstruction and fusion
→ At least 4 hours (ideally 6 hours).
→ Muscle/fat uptake↑ → tumour uptake↓ → false negative.
→ NO → it increases muscle uptake (FDG ≥4 hours after short-acting insulin).
→ 60 minutes.
→ Warm environment (starting 30-60 min before injection); results with propranolol and diazepam are conflicting.
Figure 7.11: Steps of the standard FDG PET/CT protocol (A) and recommended minimum waiting times after treatment (B).
Notes on reconstruction and quantification:
7.4.5 PET/CT Artefacts5 questions
1. CTAC-related artefacts:
2. Misregistration artefacts:
3. FDG-specific artefacts:
→ Respiratory misregistration (CT in inspiration, PET at average respiration).
→ Brown adipose tissue (BAT).
→ CTAC artefact → confirm with NAC images.
→ Think of rebound thymic hyperplasia.
In a coronal section the diaphragm moves with breathing; PET sees the average of minutes of breathing, CT a single moment. The moment of the CT is chosen; the second step shows how the difference causes a cold band at the liver dome or a hot artefact at the lung base in CT attenuation correction.
Key point: CT is a snapshot, PET a breathing average; a CT in deep inspiration gives a cold band at the liver dome, a diaphragm higher than in PET a hot artefact at the lung base; CT in shallow breathing or gating prevents this.
Source: book (CT instantaneous, PET average; cold band at the liver dome or hot artefact at the lung base; solution CT in shallow breathing, respiratory gating; MRAC µ values lung 0.0224, soft tissue 0.100 cm⁻¹). Breathing curve from the Lujan et al. 1999 model (d = A·cos⁴(πt/τ), more time at expiration; mean 3/8·A). Amplitude 2 cm, period 4 s and CT positions (4/2/0 cm, shallow ≈ mean) illustrative.
How to use: a single click on the drawing pauses and resumes; ↑ ↓ or the buttons below change the breathing moment of the CT; ← → change steps.
Figure 7.12: Respiratory misregistration: the difference in diaphragm position between CT and PET producing a cold band at the liver dome (schematic).
7.4.6 Digital PET and Long Axial Field-of-View (LAFOV) PET1 questions
7.5 PET/MR: Technical Features and Advantages
7.5.1 PET/MR System Design2 questions
PET/MR is a hybrid imaging system combining PET and MR components. There are two basic design approaches:
1. Simultaneous (integrated) PET/MR:
2. Sequential (tandem) PET/MR:
Digital photon counting (DPC):
Figure 7.13: Simultaneous (integrated) and sequential (tandem) PET/MR system designs (schematic).
7.5.2 MR-Based Attenuation Correction (MRAC)6 questions
Because there is no CT in PET/MR, attenuation correction must be derived from the MR data. This is the most important technical challenge of PET/MR.
The basic problem:
MRAC methods:
1. Segmentation-based method (most common):
2. Atlas-based method:
3. Ultrashort Echo Time (UTE) / Zero Echo Time (ZTE):
4. Deep learning-based methods:
Additional points on MRAC:
→ MR-based attenuation correction (MRAC).
→ Bone gives no signal on MR → it cannot be distinguished from air → attenuation is undercorrected → spuriously reduced uptake.
→ Dixon-based segmentation (4 classes: air, lung, fat, soft tissue).
→ UTE/ZTE, atlas-based, deep learning.
Figure 7.14: Comparison of a CT-based µ map with Dixon 4-class MRAC segmentation: bone classified as soft tissue (schematic).
7.5.3 Advantages and Limitations of PET/MR1 questions
Advantages of PET/MR over PET/CT:
Limitations of PET/MR:
7.5.4 Clinical Applications of PET/MR
Strong indications (advantageous over PET/CT):
Areas where PET/CT is superior:
7.6 SUV Calculation and Quantitative Analysis
7.6.1 Definition and Formula of SUV
The SUV (standardised uptake value) is a semi-quantitative measure of radiopharmaceutical uptake on PET images. It normalises the activity concentration in the lesion to the injected activity and body weight.
SUV formula:
SUV = Tissue activity concentration (kBq/mL) / [Injected activity (kBq) / Body weight (g)]
Interpretation:
7.6.2 SUV Variants4 questions
SUVmax (maximum SUV):
SUVmean (mean SUV):
SUVpeak:
SUVlean (lean body mass SUV, SUL):
SUL = Tissue activity concentration / (Injected activity / Lean body mass)
Try it in the calculator: SUV / SUL →
SUVBSA (body surface area SUV):
→ SUVmax.
→ SULpeak (SUVlean + peak).
→ Normalisation to body weight → fat does not take up FDG but is included in the weight → SUV is artificially raised → solution: use SUVlean.
A PET slice of a lesion is shown voxel by voxel with an SUV profile across it; SUVmax is marked as the highest voxel and SUVpeak as the mean of a 1 cm³ sphere; in the second step the threshold contour, MTV, SUVmean and TLG are computed for the chosen threshold.
Key point: SUVmax is a single voxel and sensitive to noise, SUVpeak is more stable; the partial volume effect lowers the true value of a small lesion; MTV and SUVmean depend on the threshold chosen, and TLG = MTV × SUVmean.
Source: book (SUVmax single voxel; SUVpeak 1 cm³ spherical VOI, PERCIST; SUVmean VOI average; 41% threshold MTV; TLG = MTV × SUVmean). Model (example data): 2 mm voxels, 7 mm radius sphere (true SUV 12, background 1), PET resolution FWHM 6 mm, noise illustrative (4% + 0.05). MTV is the voxels above the threshold connected to the highest voxel; TLG in SUV·mL.
How to use: a single click on the drawing pauses and resumes; in the second step ↑ ↓ change the threshold; ← → change steps.
Figure 7.15: The concepts of SUVmax, SUVpeak, MTV at a 41% threshold and SUVmean in a lesion; TLG = MTV × SUVmean (example data, schematic).
7.6.3 Factors Affecting SUV4 questions
SUV is affected by many technical and biological factors. Knowing these factors is critical for the correct interpretation of SUV values.
Technical factors:
Biological factors:
→ Long uptake time, inflammation, high tumour grade, granulomatous disease.
→ Hyperglycaemia, small lesion (PVE), extravasation, short uptake time, necrosis.
→ Lesion size < 2-3 × spatial resolution (lesions below ~8-10 mm).
7.6.4 Other Quantitative Parameters1 questions
MTV (metabolic tumour volume):
TLG (total lesion glycolysis):
TLG = MTV × SUVmean
Ki (Patlak analysis / dynamic PET):
MBF and CFR (myocardial blood flow and coronary flow reserve):
7.7 The CT Component of Hybrid Systems: Basic Principles
7.7.1 CT Reconstruction1 questions
7.7.2 CT Dosimetry and Dose Reduction4 questions
Automatic tube current modulation:
7.7.3 Metal Artefact and Photon-Counting CT1 questions
Iodine-Based Contrast Media in Hybrid Imaging
Incidental Findings on the CT Component of Hybrid Imaging
→ Adrenaline 0.5 mg, intramuscular (lateral upper thigh).
→ <30 mL/min/1.73 m².
→ It is continued.
→ No routine follow-up is needed.
→ Lipid-rich adenoma; no further imaging is needed.
7.8 The MR Component of PET/MR: Basic Principles
7.8.1 Nuclear Magnetic Resonance and Image Formation
7.8.2 MR Scanner Components
MR Spectroscopy
Gadolinium-Based Contrast Agents
MR Safety
Figure 7.15a: MR safety zones (Zones III and IV) and MR safety labels (schematic).
7.9 Comparison of Imaging Modalities1 questions
Which modality is chosen depends on the clinical question to be answered. The resolution values in the comparison below belong to preclinical (small-animal) systems; in clinical CT and MR spatial resolution is approximately 0.5-1 mm:
| Modality | Spatial resolution | Temporal resolution | Sensitivity (molar) | Main target |
|---|---|---|---|---|
| PET | mm | seconds-minutes | 10⁻¹¹-10⁻¹² | Physiology, molecular |
| SPECT | mm-cm | minutes | 10⁻¹⁰-10⁻¹¹ | Physiology, molecular |
| MRI | 10-250 µm | milliseconds | 10⁻³-10⁻⁵ | Anatomy, physiology, molecular |
| CT | ~50 µm | seconds-minutes | – (relative) | Anatomy, physiology |
| Ultrasound | 30-500 µm | milliseconds-minutes | 10⁻⁶-10⁻⁹ | Anatomy, physiology |
| Optical (fluorescence) | 2-3 mm | seconds-minutes | high (depth limited to mm) | Molecular |
Key Points for the Board
Additional Points – PET/CT, PET/MR, CT and MR
Annihilation Physics – Critical Numbers
Positron Range – Quick Memory Table
Types of Coincidence – Quick Comparison
PET Crystals – Quick Memory Points
PET vs SPECT – Basic Differences
TOF-PET – Critical Formulas and Concepts
CTAC – Critical Points
PET/MR – Critical Points
SUV – Critical Points
FDG PET/CT Patient Preparation – Exam Favourites
2D vs 3D PET – Quick Comparison
Comparisons Frequently Asked in the Exam
Current guidelines on this chapter's topics
The latest guidelines and consensus documents on the procedures covered in this chapter (official EANM index and primary sources, November 2026). Comparison of the text with these versions is in progress; consult the guideline itself for details.
- 2025[18F]FDG PET/CT: EANM procedure guidelines for tumour imaging: version 3.0 (opens in a new tab)
- 2023International EANM-SNMMI-ISMRM consensus recommendation for PET/MRI in oncology (opens in a new tab)
- 2022EANM guidelines for PET-CT and PET-MR routine quality control (opens in a new tab)
- 2017Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017 (opens in a new tab)
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