Long PCI: Patient Skin Dose and a Trainee's Collar Badge
A 58-year-old man (BMI 34) undergoes PCI of the right coronary artery. Total fluoroscopy time is 48 minutes, DAP is 320 Gy·cm², and the air kerma at the interventional reference point (Ka,r) is 4.6 Gy. The procedure included several long DSA runs in steep LAO/cranial projections. Before leaving the lab he complains of burning pain between the shoulder blades. Separately, the monthly dosimetry report arrives: a first-year trainee's collar badge, worn outside the lead apron at the neck, reads 9.6 mSv, while the waist badge worn under a 0.5 mm Pb apron reads 0.6 mSv. Your facility's dose investigation level is 0.5 mSv per month for Hp(10), and the trainee has never previously exceeded 1 mSv.
1. For the patient: interpret the three dose metrics, assess the deterministic risk, and state what you would do before he leaves the department.
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Interpretation: fluoroscopy time says nothing about dose on its own - 48 minutes at low pulse rate can be less than 10 minutes of continuous acquisition. DAP (320 Gy·cm²) reflects the total energy imparted and drives the stochastic estimate; Ka,r (4.6 Gy) is the best available surrogate for peak skin dose at the reference point, and the true peak may be higher where the beam entered through the back in steep LAO/cranial projections for prolonged periods.
Risk: 4.6 Gy is above the ~2 Gy threshold for transient erythema and is approaching the range (around 5 Gy) at which more significant skin injury becomes possible. The burning interscapular pain is consistent with an early skin reaction and must not be dismissed as muscular.
Actions:
- Record Ka,r, DAP and fluoroscopy time in the procedure note and on the patient's record.
- Notify the interventionalist and the RPA the same day; if your policy trigger is Ka,r > 5 Gy or DAP > 500 Gy·cm², he is just below it, but the symptom converts this into a clinical event.
- Give him written advice to inspect the skin and report redness, blistering or pain, and arrange dermatology/radiology review at 2–4 weeks.
- Flag 'no repeat intervention at the same site without review' and avoid overlapping projections if a further procedure is required.
2. For the staff member: is a collar reading of 9.6 mSv plausible alongside an under-apron reading of 0.6 mSv? What does it tell you, and what actions follow?
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Plausibility: yes. The collar badge sits outside the apron near the thyroid and lens, so it measures essentially unshielded neck/upper-torso dose. A ratio of roughly 16:1 between collar and under-apron readings is not unusual in a trainee who stands close and slightly obliquely during acquisitions, and it is far more likely than a badge fault - but a badge fault must still be excluded.
Interpretation: the effective dose is much lower than 9.6 mSv when the apron is worn correctly, but the collar figure is nearly 20 times your monthly investigation level and cannot be dismissed as artefact. It points to a behavioural and possibly equipment problem: proximity during DSA runs, no thyroid shield, or a defective apron.
Actions:
- Check the apron by visual and fluoroscopic inspection for cracks and overlaps; replace if defective.
- Issue and enforce a thyroid collar; confirm the trainee's standing position - step back during acquisition, never hold the patient or the catheter.
- Review technique: collimation, table height, detector as close to the patient as possible, pulsed/low-dose fluoroscopy, last-image-hold instead of live screening.
- Consider double dosimetry formally (collar + under-apron) and calculate effective dose using your facility's algorithm rather than reading the collar value as whole-body dose.
- Re-badge next month; if the reading does not fall, escalate to the RPA and occupational health, and record the investigation.
3. How would you decide whether this is a reportable event, and what would you put in writing?
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The decision rests on which limit or trigger is engaged, not on how the number feels.
- Patient: there is no dose limit for a justified medical exposure, so nothing here is an 'overexposure' in the regulatory sense. The reporting question is a local clinical one: was a substantial-dose notification threshold crossed, and was the procedure justified and optimised? The written record should state technique factors, Ka,r, DAP, fluoroscopy time, the projection distribution, the symptom, the advice given, and the follow-up appointment.
- Staff: the collar value is a personal monitoring result, and 9.6 mSv in a month triggers a formal investigation against your investigation level. Create a written investigation record identifying likely cause, corrective actions, responsible person and review date, and retain the previous 12 months of dose records to show whether there is a trend.
- Reporting: both cases may be notifiable internally (radiation safety committee, RPA, quality/risk) even when no statutory limit is breached; a genuine statutory notification is triggered only by exceeding a dose limit, a suspected overexposure, or a faulty dosimeter - none of which is yet established here.
Good practice is to write the record as if it will be read by someone reconstructing the case a year later with no memory of the shift.