# 9702 P4 PET scanning Topic Questions

> CIE IAL 9702 P4: every PET scanning topic question from 3 papers (2025), grouped by syllabus point. 16 questions, 27 marks, with direct links into the papers.

- Canonical HTML: https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/
- Markdown mirror: https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/index.md

---

CIE IAL · Physics · 9702 P4 · A Level

Every 9702 P4 PET scanning topic question from the 2025–2027 syllabus, drawn from 3 papers (2025) and grouped by syllabus point. Each row opens a page listing the exact question numbers, marks and a direct link into the paper. These are questions by topic, not full papers, so you can revise one topic at a time.

- 9702 P4
- 6 subtopics
- 16 topic questions
- 3 papers
- 27 tagged marks
- [Back to PET scanning](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/)
- [All paper codes](https://www.examsci.com/topics/)

Core finding

**3 understand that annihilation occurs when a particle interacts with… is the most frequently assessed subtopic in PET scanning, with 9 topic questions and 14 marks across 3 papers.** 4 explain that, in PET scanning, positrons emitted by the… follows with 5 topic questions and 7 marks. The topic contains 6 subtopics, 16 topic questions and 27 marks in total. Rows count only the parts tagged to that subtopic, keep the same colour in both charts and repeat paper count, tagged marks and year range in the native table.

## Topic question count and mark distribution

Subtopics are on the vertical axis and sorted from highest to lowest. Only the parts whose knowledge graph matches a subtopic are counted for it, and percentages are each row's share of the tagged total in that chart. A part tagged to several subtopics is counted in each bar, so the bars are not a partition of the topic total.

### Questions by subtopic

question items

- [3 understand that annihilation occurs when a particle interacts with its antiparticle and that mass–energy and momentum are conserved in the process](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/3-understand-that-annihilation-occurs-when-a-particle-interacts-with-its-antiparticle/) (3 papers) — 9 · 42.9%
- [4 explain that, in PET scanning, positrons emitted by the decay of the tracer annihilate when they interact with electrons in the tissue, producing a pair of gamma-ray photons travelling in opposite directions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/4-explain-that-in-pet-scanning-positrons-emitted-by-the-decay-of-the-tracer/) (3 papers) — 5 · 23.8%
- [5 calculate the energy of the gamma-ray photons emitted during the annihilation of an electron-positron pair](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/5-calculate-the-energy-of-the-gamma-ray-photons-emitted-during-the-annihilation-of-an/) (2 papers) — 3 · 14.3%
- [2 recall that a tracer that decays by $\beta^+$ decay is used in positron emission tomography (PET scanning)](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/2-recall-that-a-tracer-that-decays-by-beta-decay-is-used-in-positron-emission/) (1 papers) — 2 · 9.5%
- [1 understand that a tracer is a substance containing radioactive nuclei that can be introduced into the body and is then absorbed by the tissue being studied](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/1-understand-that-a-tracer-is-a-substance-containing-radioactive-nuclei-that-can-be/) (1 papers) — 1 · 4.8%
- [6 understand that the gamma-ray photons from an annihilation event travel outside the body and can be detected, and an image of the tracer concentration in the tissue can be created by processing the arrival times of the gamma-ray photons](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/6-understand-that-the-gamma-ray-photons-from-an-annihilation-event-travel-outside-the/) (1 papers) — 1 · 4.8%

### Marks by subtopic

marks

- [3 understand that annihilation occurs when a particle interacts with its antiparticle and that mass–energy and momentum are conserved in the process](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/3-understand-that-annihilation-occurs-when-a-particle-interacts-with-its-antiparticle/) (3 papers) — 14 · 41.2%
- [4 explain that, in PET scanning, positrons emitted by the decay of the tracer annihilate when they interact with electrons in the tissue, producing a pair of gamma-ray photons travelling in opposite directions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/4-explain-that-in-pet-scanning-positrons-emitted-by-the-decay-of-the-tracer/) (3 papers) — 7 · 20.6%
- [5 calculate the energy of the gamma-ray photons emitted during the annihilation of an electron-positron pair](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/5-calculate-the-energy-of-the-gamma-ray-photons-emitted-during-the-annihilation-of-an/) (2 papers) — 7 · 20.6%
- [2 recall that a tracer that decays by $\beta^+$ decay is used in positron emission tomography (PET scanning)](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/2-recall-that-a-tracer-that-decays-by-beta-decay-is-used-in-positron-emission/) (1 papers) — 3 · 8.8%
- [1 understand that a tracer is a substance containing radioactive nuclei that can be introduced into the body and is then absorbed by the tissue being studied](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/1-understand-that-a-tracer-is-a-substance-containing-radioactive-nuclei-that-can-be/) (1 papers) — 2 · 5.9%
- [6 understand that the gamma-ray photons from an annihilation event travel outside the body and can be detected, and an image of the tracer concentration in the tissue can be created by processing the arrival times of the gamma-ray photons](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/6-understand-that-the-gamma-ray-photons-from-an-annihilation-event-travel-outside-the/) (1 papers) — 1 · 2.9%

## Subtopic comparison matrix

Curriculum order is by syllabus number, then alphabetically. Every row links to the matching past-paper question list.

| Subtopic | Topic questions | Papers | Marks | Years | |
| --- | --- | --- | --- | --- | --- |
| **[1 understand that a tracer is a substance containing radioactive nuclei that can be introduced into the body and is then absorbed by the tissue being studied](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/1-understand-that-a-tracer-is-a-substance-containing-radioactive-nuclei-that-can-be/)** | 1 | 1 | 2 | 2025 | [Open topic questions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/1-understand-that-a-tracer-is-a-substance-containing-radioactive-nuclei-that-can-be/) |
| **[2 recall that a tracer that decays by $\beta^+$ decay is used in positron emission tomography (PET scanning)](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/2-recall-that-a-tracer-that-decays-by-beta-decay-is-used-in-positron-emission/)** | 2 | 1 | 3 | 2025 | [Open topic questions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/2-recall-that-a-tracer-that-decays-by-beta-decay-is-used-in-positron-emission/) |
| **[3 understand that annihilation occurs when a particle interacts with its antiparticle and that mass–energy and momentum are conserved in the process](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/3-understand-that-annihilation-occurs-when-a-particle-interacts-with-its-antiparticle/)** | 9 | 3 | 14 | 2025 | [Open topic questions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/3-understand-that-annihilation-occurs-when-a-particle-interacts-with-its-antiparticle/) |
| **[4 explain that, in PET scanning, positrons emitted by the decay of the tracer annihilate when they interact with electrons in the tissue, producing a pair of gamma-ray photons travelling in opposite directions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/4-explain-that-in-pet-scanning-positrons-emitted-by-the-decay-of-the-tracer/)** | 5 | 3 | 7 | 2025 | [Open topic questions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/4-explain-that-in-pet-scanning-positrons-emitted-by-the-decay-of-the-tracer/) |
| **[5 calculate the energy of the gamma-ray photons emitted during the annihilation of an electron-positron pair](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/5-calculate-the-energy-of-the-gamma-ray-photons-emitted-during-the-annihilation-of-an/)** | 3 | 2 | 7 | 2025 | [Open topic questions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/5-calculate-the-energy-of-the-gamma-ray-photons-emitted-during-the-annihilation-of-an/) |
| **[6 understand that the gamma-ray photons from an annihilation event travel outside the body and can be detected, and an image of the tracer concentration in the tissue can be created by processing the arrival times of the gamma-ray photons](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/6-understand-that-the-gamma-ray-photons-from-an-annihilation-event-travel-outside-the/)** | 1 | 1 | 1 | 2025 | [Open topic questions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/6-understand-that-the-gamma-ray-photons-from-an-annihilation-event-travel-outside-the/) |

## Browse every topic question

- [1 understand that a tracer is a substance containing radioactive nuclei that can be introduced into the body and is then absorbed by the tissue being studied](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/1-understand-that-a-tracer-is-a-substance-containing-radioactive-nuclei-that-can-be/) — 1 question items · 1 papers — 2 marks · 2025
- [2 recall that a tracer that decays by $\beta^+$ decay is used in positron emission tomography (PET scanning)](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/2-recall-that-a-tracer-that-decays-by-beta-decay-is-used-in-positron-emission/) — 2 question items · 1 papers — 3 marks · 2025
- [3 understand that annihilation occurs when a particle interacts with its antiparticle and that mass–energy and momentum are conserved in the process](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/3-understand-that-annihilation-occurs-when-a-particle-interacts-with-its-antiparticle/) — 9 question items · 3 papers — 14 marks · 2025
- [4 explain that, in PET scanning, positrons emitted by the decay of the tracer annihilate when they interact with electrons in the tissue, producing a pair of gamma-ray photons travelling in opposite directions](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/4-explain-that-in-pet-scanning-positrons-emitted-by-the-decay-of-the-tracer/) — 5 question items · 3 papers — 7 marks · 2025
- [5 calculate the energy of the gamma-ray photons emitted during the annihilation of an electron-positron pair](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/5-calculate-the-energy-of-the-gamma-ray-photons-emitted-during-the-annihilation-of-an/) — 3 question items · 2 papers — 7 marks · 2025
- [6 understand that the gamma-ray photons from an annihilation event travel outside the body and can be detected, and an image of the tracer concentration in the tissue can be created by processing the arrival times of the gamma-ray photons](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/6-understand-that-the-gamma-ray-photons-from-an-annihilation-event-travel-outside-the/) — 1 question items · 1 papers — 1 marks · 2025

## Other topics in 9702 P4

- [Capacitors and capacitance 17 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/capacitors-and-capacitance/)
- [Centripetal acceleration 25 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/centripetal-acceleration/)
- [Characteristics of alternating currents 21 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/characteristics-of-alternating-currents/)
- [Concept of a magnetic field 3 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/concept-of-a-magnetic-field/)
- [Damped and forced oscillations, resonance 7 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/damped-and-forced-oscillations-resonance/)
- [Discharging a capacitor 16 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/discharging-a-capacitor/)
- [Electric field of a point charge 8 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/electric-field-of-a-point-charge/)
- [Electric fields and field lines 7 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/electric-fields-and-field-lines/)
- [Electric force between point charges 12 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/electric-force-between-point-charges/)
- [Electric potential 26 question items](https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/electric-potential/)

## Topic question rules and edge cases

**How many subtopics does PET scanning contain?**

This page lists 6 subtopics tagged to the current syllabus. They are ordered by syllabus number, then alphabetically, and each row opens a page of matching past-paper questions.

**How are the subtopic question and mark totals calculated?**

A multiple-choice question contributes one item and its marks to every subtopic it is tagged with. A structured question contributes one item per tagged part, and that part’s marks; untagged parts of the same question are not counted here. A part tagged to several subtopics therefore appears under each of them.

**Why do some subtopics have no numbered prefix?**

Practical-skills statements and some syllabus bullets are unnumbered. Numbered statements come first; unnumbered statements and ties are sorted alphabetically.

**Is the LaTeX rendered without JavaScript?**

Yes. Subtopics that contain formulas are converted to static KaTeX HTML during the build, and the KaTeX stylesheet is served from the same site.

---

Full page with native tables, bar charts and Practice Hub links: https://www.examsci.com/topics/cie-ial/physics/9702-paper-4/pet-scanning/