National Diagnostic Reference Levels (NDRLs) from 13 October 2022
Updated 24 November 2022
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1. Introduction
The following tables list the National Diagnostic Reference Levels (NDRLs) for the UK. National Dose Reference Levels for radiotherapy planning CT scans are also listed.
The NDRL values should be considered by employers when setting their local DRLs as required by the Ionising Radiation (Medical Exposure) Regulations 2017 and the Ionising Radiation (Medical Exposure) Regulations (Northern Ireland) 2018 (as amended).
The UK National DRLs are based on body region examined and, where appropriate, the clinical requirement for the examination.
The NDRLs for general radiography and simple fluoroscopy are primarily based on National Reference Doses (NRDs) previously published by Public Health England – now the UK Health Security Agency (UKHSA). For details of how these values were obtained, please refer to the reports referenced below.
These reports also contain dose information which may be of use for setting local DRLs for radiographic procedures where there was insufficient data to formally recommend an NDRL.
The values for CT examinations are mainly taken from UKHSA-RCE-1: Doses from computed tomography (CT) examinations in the UK (2019 review). Coronary CT angiography values are additional. Paediatric examinations have also been updated and additional values added. The sources for these additional values are referenced below.
The values for radiography and fluoroscopy are taken from HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic x-ray imaging procedures in the UK (2010 review).
The values for dental radiography are taken from PHE-CRCE-51: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 review.
Additional NDRLs are based on data from national dose surveys undertaken by radiology professionals in conjunction with, or in close liaison with, UKHSA. The proposed NDRLs have then been approved by the UKHSA working party on national dose surveys and DRLs. This working party has representation from UKHSA, radiology professional bodies and the Department of Health and Social Care.
The additional or updated NDRLs (and Dose Reference Levels) are for paediatric CT, coronary CT angiography, CT in hybrid imaging (PET-CT, SPECT-CT), screening mammography, and radiotherapy planning CT.
These are sourced from:
- Worrall, M. and others. Analysis and results from a UK national dose audit of paediatric CT examinations. British Journal of Radiology. 2021;95(1129)
- Castellano, I.A. and others. A prospective national survey of coronary CT angiography radiation doses in the United Kingdom. Journal of Cardiovascular Computed Tomography. 2017;11:268 to 273
- Iball, G.R. and others. A national survey of computed tomography doses in hybrid PET-CT and SPECT-CT examinations in the UK. Nuclear Medicine Communications. 2017;38(6):459 to 470
- Loveland J., Young K.C., Oduko J.M. and Mackenzie A. Radiation doses in the United Kingdom breast screening programmes 2016–2019. British Journal of Radiology 2022;95:1135
- Wood T.J. and others. IPEM topical report: the first UK survey of dose indices from radiotherapy treatment planning computed tomography scans for adult patients. Physics in Medicine and Biology 2018;63:185008
Enquiries for NDRLs and for diagnostic radiology should be sent to the UKHSA Medical Dosimetry Group medicalradiationdoses@ukhsa.gov.uk
For nuclear medicine studies, the ARSAC Notes for Guidance provide diagnostic reference levels for the most common examinations.
Further information can be found on the ARSAC website.
2. National DRLs for computed tomography
2a. Adult CT examinations
| Examination | Clinical Indication | Scan region / technique | CTDI vol per sequence (mGy) | DLP per complete examination (mGy cm) | Year NDRL adopted |
|---|---|---|---|---|---|
| Head[footnote 1] | Acute stroke | All sequences | 47 | 790 | 2022 |
| Paranasal sinuses[footnote 1] | Sinus disease | All sequences | 12 | 160 | 2022 |
| Cervical spine[footnote 1] | Fracture | All sequences | 16 | 400 | 2022 |
| Neck, chest, abdomen and pelvis[footnote 1] | Cancer | All sequences | 850 | 2022 | |
| Chest[footnote 1] | Lung cancer | All sequences | 8.5 | 290 | 2022 |
| Chest and Abdomen[footnote 1] | Lung cancer | All sequences | 470 | 2022 | |
| Chest – high resolution[footnote 1] | Interstitial lung disease | Helical | 8 | 300 | 2022 |
| Chest-abdomen-pelvis[footnote 1] | Cancer | All sequences | 660 | 2022 | |
| CT Pulmonary Angiography (CTPA)[footnote 1] | Pulmonary embolism | All sequences | 9.1 | 310 | 2022 |
| Abdomen and pelvis[footnote 1] | Abscess | All sequences | 10 | 530 | 2022 |
| Virtual colonoscopy[footnote 1] | Polyps/Tumour | All sequences | 690 | 2022 | |
| Kidneys-ureters-bladder[footnote 1] | Stones/Colic | All sequences | 6.3 | 290 | 2022 |
| Urogram[footnote 1] | Tumour/Stones/Colic | All sequences | 890 | 2022 | |
| Coronary CT angiography (CTA)[footnote 2] | Prospective, no padding | 170 | 2018 | ||
| Prospective, with padding | 280 | 2018 | |||
| Retrospective, with gating | 380 | 2018 |
Doses for the head and paranasal sinus examinations refer to measurements in the 16cm standard CT dosimetry phantom. All other doses refer to measurements in the 32cm standard CT dosimetry phantom.
Values taken from references that are detailed by the footnotes to this table. Please scroll to the bottom of the page to view full information.
Caution is required when comparing your local dose values with the NDRL for the chest exam. There are separate NDRLs for ‘chest’ and ‘chest and abdomen’, covering the appropriate body regions. However, the descriptor for the ‘chest’ exam for the previous NDRL (based on the 2011 survey) extended to the liver region, and therefore may not be directly comparable.
2b. Paediatric CT examinations
| Examination | Clinical indication | Scan region / technique | CTDIvol per sequence (mGy) | DLP per complete examination (mGy cm) | Year NDRL adopted |
|---|---|---|---|---|---|
| Paediatric head: 0 to <1 y |
Trauma | All sequences | 19 | 290 | 2022 |
| Paediatric head: 1 to <5 y |
Trauma | All sequences | 24 | 420 | 2022 |
| Paediatric head: 5 to <10y |
Trauma | All sequences | 36 | 570 | 2022 |
| Paediatric head: 10 to <15y |
Trauma | All sequences | 46 | 690 | 2022 |
| Paediatric head: 15 to <18y (adult head CT values applied) |
Acute Stroke | All sequences | 47 | 790 | 2022 |
| Paediatric chest: 0 to <5kg |
Query cancer | All sequences | 0.44 | 8 | 2022 |
| Paediatric chest: 5 to <15kg |
Query cancer | All sequences | 0.86 | 18 | 2022 |
| Paediatric chest: 15 to <30kg |
Query cancer | All sequences | 2.0 | 40 | 2022 |
| Paediatric chest: 30 to <50kg |
Query cancer | All sequences | 2.6 | 62 | 2022 |
| Paediatric chest: 50 to <80kg |
Query cancer | All sequences | 3.8 | 110 | 2022 |
Doses for the head examination refer to measurements in the 16 cm standard CT dosimetry phantom. Doses for chest examinations refer to measurements in the 32 cm standard CT dosimetry phantom.
Values taken from Worrall, M. and others. Analysis and results from a UK national dose audit of paediatric CT examinations. British Journal of Radiology. 2021;95(1129).
For paediatric head (15 to less than 18 years) adult head values are applied.
For the paediatric chest 0 to less than 5kg and 50 to less than 80kg categories, the values are based on sample sizes smaller than commonly used to set NDRLs. The application of these NDRLs should therefore be carefully considered by the Medical Physics Expert (MPE).
2c. Adult CT examinations as part of PET-CT and SPECT-CT examinations
| Examination | Clinical indication | Scan region / technique | CTDIvol per sequence (mGy) | DLP per complete examination (mGy cm) | Year NDRL adopted |
|---|---|---|---|---|---|
| PET half body | attenuation correction and localisation of the nuclear medicine signal | All sequences | 4.3 | 400 | 2018 |
| SPECT bone scan | attenuation correction and localisation of the nuclear medicine signal | All sequences | 4.9 | 150 | 2018 |
| SPECT parathyroid | attenuation correction and localisation of the nuclear medicine signal | All sequences | 5.6 | 170 | 2018 |
| SPECT post-thyroid ablation | attenuation correction and localisation of the nuclear medicine signal | All sequences | 5.9 | 210 | 2018 |
| SPECT mIBG/octreotide | attenuation correction and localisation of the nuclear medicine signal | All sequences | 5.5 | 240 | 2018 |
| SPECT cardiac | attenuation correction | All sequences | 2.1 | 36 | 2018 |
Doses refer to measurements in the 32cm standard CT dosimetry phantom.
Values taken from Iball, G.R. and others. A national survey of computed tomography doses in hybrid PET-CT and SPECT-CT examinations in the UK. Nuclear Medicine Communications. 2017;38(6):459 to 470.
3. National DRLs for general radiography and fluoroscopy
3a. Individual radiographs on adult patients
| Radiograph | ESD per radiograph (mGy) | DAP per radiograph (Gy cm 2 ) | Year NDRL adopted |
|---|---|---|---|
| Abdomen AP | 4 | 2.5 | 2016 |
| Chest AP | 0.2 | 0.15 | 2016 |
| Chest LAT | 0.5 | 2016 | |
| Chest PA | 0.15 | 0.1 | 2016 |
| Cervical spine AP | 0.15 | 2016 | |
| Cervical spine LAT | 0.15 | 2016 | |
| Knee AP | 0.3 | 2016 | |
| Knee LAT | 0.3 | 2016 | |
| Lumbar spine AP | 5.7 | 1.5 | 2016 |
| Lumbar spine LAT | 10 | 2.5 | 2016 |
| Pelvis AP | 4 | 2.2 | 2016 |
| Shoulder AP | 0.5 | 2016 | |
| Skull AP/PA | 1.8 | 2016 | |
| Skull LAT | 1.1 | 2016 | |
| Thoracic spine AP | 3.5 | 1.0 | 2016 |
| Thoracic spine LAT | 7 | 1.5 | 2016 |
Values taken from HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review).
3b. Diagnostic radiography examinations on adult patients
| Examination | DAP per exam (Gy cm2) | Fluoroscopy time per exam (minutes) | Year NDRL adopted |
|---|---|---|---|
| Abdomen | 4.4 | 2016 | |
| Barium (or water soluble) enema | 21 | 2.6 | 2016 |
| Barium small bowel enema | 23 | 8.9 | 2016 |
| Barium follow through | 8.4 | 2.0 | 2016 |
| Barium meal | 12 | 2.6 | 2016 |
| Barium meal & swallow | 10 | 2.3 | 2016 |
| Barium (or water soluble) swallow | 7.5 | 2.1 | 2016 |
| Barium swallow (video) | 3.4 | 3.5 | 2016 |
| Chest | 0.3 | 2016 | |
| Coronary angiography[footnote 3] | 31 | 4.3 | 2016 |
| Coronary graft angiography[footnote 3] | 47 | 13 | 2016 |
| Femoral angiography | 56 | 5.9 | 2016 |
| Fistulography | 8 | 6.7 | 2016 |
| Hysterosalpingography | 2 | 0.7 | 2016 |
| Intravenous Urography (IVU) | 14 | 2016 | |
| Lumbar spine | 6 | 2016 | |
| Micturating Cystourethrography (MCU) | 7 | 1.6 | 2016 |
| Nephrostography | 9 | 3.9 | 2016 |
| Proctography | 14 | 1.3 | 2016 |
| Sialography | 2.8 | 1.5 | 2016 |
| Sinography | 7 | 1.7 | 2016 |
| T-tube cholangiography | 5 | 1.8 | 2016 |
Fluoroscopy time: time during a procedure that fluoroscopy is used, excluding cine acquisition imaging.
Values taken from HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review).
3c. Interventional procedures on adult patients
| Interventional procedure | DAP per exam (Gy cm2) | Fluoroscopy time per exam (minutes) | Year NDRL adopted |
|---|---|---|---|
| Biliary intervention | 43 | 14 | 2016 |
| Facet joint injection | 6 | 1.4 | 2016 |
| Hickman line insertion | 3 | 1.5 | 2016 |
| Nephrostomy | 13 | 6.7 | 2016 |
| Oesophageal stent | 13 | 5 | 2016 |
| Pacemaker (permanent) | 7 | 6 | 2016 |
| Percutaneous transluminal coronary angioplasty (PTCA) (single stent)[footnote 3] | 40 | 11.3 | 2016 |
Fluoroscopy time: time during a procedure that fluoroscopy is used, excluding cine acquisition imaging.
Values taken from HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review).
3d. Diagnostic radiography examinations on paediatric patients
| Examination | Standard age (y) | DAP per examination (Gy cm2) | Year NDRL adopted |
|---|---|---|---|
| Micturating cystourethrography (MCU) | 0 | 0.1 | 2016 |
| 1 | 0.3 | 2016 | |
| 5 | 0.3 | 2016 | |
| 10 | 0.4 | 2016 | |
| 15 | 0.9 | 2016 | |
| Barium meal | 0 | 0.1 | 2016 |
| 1 | 0.2 | 2016 | |
| 5 | 0.2 | 2016 | |
| 10 | 0.7 | 2016 | |
| 15 | 2.0 | 2016 | |
| Barium swallow | 0 | 0.2 | 2016 |
| 1 | 0.4 | 2016 | |
| 5 | 0.5 | 2016 | |
| 10 | 1.8 | 2016 | |
| 15 | 3.0 | 2016 |
Values taken from HPA-CRCE-034: Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK (2010 review).
4. National DRLs for dental radiography
| Radiograph | Patient size | Patient entrance dose (PED) per radiograph (mGy) | Year NDRL adopted |
|---|---|---|---|
| Intra-oral mandibular molar | Adult | 1.2 | 2019 |
| Child | 0.7 | 2019 |
| Radiograph | Patient size (clinical indication) | DAP per radiograph (mGy cm2) | Year NDRL adopted |
|---|---|---|---|
| Panoramic (full jaw) | Adult | 81 | 2019 |
| Child | 60 | 2019 | |
| Lateral cephalometric | Adult | 35 | 2019 |
| Child | 24 | 2019 | |
| Dental CBCT | Adult (imaging prior to placement of a maxillary molar implant) | 265 | 2019 |
| Child (imaging of an impacted maxillary canine of a 12-year-old child) | 170 | 2019 |
Values taken from PHE-CRCE-51: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 review.
5. National DRLs for screening mammography
This value was proposed to the UKHSA NDRL working group by the Breast Screening Physics Clinical Professional Group (formerly National Breast Screening QA Co-ordinating Group for Physics), and the National Co-ordinating Centre for the Physics of Mammography (NCCPM).
| Radiograph | Mean glandular dose (MGD) (mGy) | Year NDRL adopted |
|---|---|---|
| Screening mammography | 2.5 | 2022 |
Average mean glandular dose (MGD) for mediolateral oblique breast exposures of a sample of 50mm to 60mm thick breasts using at least 10 patients, 2D full field digital mammography in screening using DR systems. Please note that only DR systems are used in the NHSBSP.
Value based on data in:
- Loveland J., Young K.C., Oduko J.M. and Mackenzie A. Radiation doses in the United Kingdom breast screening programmes 2016–2019. British Journal of Radiology 2022;95:1135
6. National Dose Reference Levels for Radiotherapy Planning CT Scans
Radiotherapy planning CT scans are not considered diagnostic scans, and therefore the use of the term Diagnostic Reference Levels is not appropriate. However, the use of dose reference levels is a useful method of demonstrating dose optimisation has taken place. The following table provides dose index values, which can be taken to be equivalent to formal NDRLs.
| Examination | CTDIvol per sequence (mGy) | DLP per complete examination (mGy cm) | Scan length (mm) | Year NDRL adopted |
|---|---|---|---|---|
| Breast | 10 | 390 | 360 | 2018 |
| Gynaecological | 16 | 610 | 400 | 2018 |
| Lung 3D | 14 | 550 | 390 | 2018 |
| Lung 4D | 63 | 1750 | 340 | 2018 |
| Prostate | 16 | 570 | 340 | 2018 |
| Brain | 50 | 1500 | 290 | 2018 |
| Head and Neck | 49 | 2150 | 420 | 2018 |
Doses for the brain and ‘head and neck’ examinations only refer to measurements in the 16cm standard CT dosimetry phantom. All other doses refer to measurements in the 32cm standard CT dosimetry phantom.
Values taken from Wood T.J. and others. IPEM topical report: the first UK survey of dose indices from radiotherapy treatment planning computed tomography scans for adult patients. Physics in Medicine and Biology 2018;63:185008.
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UKHSA-RCE-1 ‘Doses from computed tomography examinations in the UK (2019 review)’ ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13
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Castellano, I.A. and others. ‘A prospective national survey of coronary CT angiography radiation doses in the United Kingdom’ Journal of Cardiovascular Computed Tomography. 2017;11:268 to 273. ↩