1. Cumulative dose and skin damage
Colin Martin and David Sutton

2. Skin effects
Histologic view of the skin
Transient erythema: May occur 1 to 24 hours after irradiation > 3 Gy
Erythema: Occurs after 2-3 weeks for doses of 3-10 Gy
Alopecia(loss or absence of hair): 2-3 weeks, >3 Gy is reversible; 20 Gy is irreversible.
Dry or moist desquamation: after 3-5 weeks for doses 8-15 Gy.
DERMIS
EPIDERMIS
From “Atlas de Histologia...”. J. Boya
Basal stratum cells, highly mitotic, more susceptible to radiation damage

3. Back Scattered Radiation
The skin receives a higher dose as some radiation is scattered back from underlying tissues.
Entrance surface dose is 30% higher than the incident air kerma.
X-rays
Tissue
Backscatter

4. ICRP Report 85 (2001): Avoidance of Radiation Injuries from Interventional Procedures
ICRP recommend:
Warn patient of risk, if maximum skin dose exceeds 3 Gy
Identify patients who have repeated interventions where the dose exceeds 1 Gy and warn them of risk

5. Use of a single projection concentrates dose and increases skin damage
Complex procedures may lead to high skin doses.
Multiple coronary angiography and angioplasty procedures performed.
Evidence of injury weeks after procedures.
Skin injury 18 months after procedures
Images reproduced with permission from Wagner LK and Archer BR.
Minimizing Risks from Fluoroscopic Radiation, R. M. Partnership,
Houston, TX 2004, and T Shope from ICRP Publication 85 (2000).,

6. Distribution of Interventional skin exposure
Different shape and size of the fields, films show changes in collimation and beam angle during the procedure.

7. Lesions from overlapping fields
Examinations generally use beams from different directions.
There are risks of high doses from overlapping fields
Lesion required grafting

8. Erythema from Cardiology procedures
Skin erythema after fluoroscopy
Cumulative build-up of dose from steeply angled beams through large patient
Images reproduced with permission from Wagner LK and Archer BR.
Minimizing Risks from Fluoroscopic Radiation, R. M. Partnership,
Houston, TX 2004, and T Shope from ICRP Publication 85 (2000).,

9. Cumulative Dose Interventional Reference Point (IEC,60601-2-43, 2000)
15 cm in front of iso-centre
15 cm
Isocenter
IRP
Cumulative dose does not take account of movement of X-ray tube

10. Method for MESAK evaluation: radiochromic large area detector
Example: Radiochromic films type Gafchromic XR R 14”x17”
usefull dose range: Gy
minimal photon energy dependence ( keV)
acquisition with a flatbed scanner:b/w image, bit/pixel or, measure of OD measurement with a reflection densitometer

11. Relationship between Peak Skin Dose and Cumulative dose
Neuroradiology
Interventional Cardiology
Reasonable link between peak skin dose and cumulative dose

12. Proposed follow-up for of skin injury in other Interventional Radiology
Set “trigger values” for cumulative skin dose that roughly equates to peak skin dose of 3 Gy
2-3 Gy Neuroradiology
3-5 Gy Cardiology
Identify where procedures are repeated on the same patient giving a skin dose in this range.
Introduce a follow-up protocol for patients who could have received high skin doses

13. Cumulative dose distribution for Angiography and Stent procedures
A few percent of procedures have cumulative doses above 5 Gy

14. Doses to the skin depend on area irradiated and focus to skin distance

15. Patients follow up Clinics
The cumulative dose should be recorded in the patient’s notes, so that it can be referred to during follow-up clinic visits.
The clinicians conducting the follow-up should be aware if the patient’s dose has exceeded the threshold
Clinicians should be able to recognise radiation skin effects

16. Patient dosimetry in IR
Dosimetry for quality assurance
Air kerma area product (KAP, PKA)
Dosimetry for stochastic risk evaluation
dose equivalent to selected organs
effective dose
Dosimetry to prevent deterministic effects of radiation (maximum skin dose assessment)
Maximum skin dose (MSD or Dskin,max)