Operator radiation exposure in cardiac catheterization

Abstract

Introduksjon Røntgenveiledete hjerteprosedyrer utsetter både pasient og operatør for ioniserende stråling. Selv om operatørdosen er en brøkdel av pasientdosen, kan en operatør utføre tusenvis av prosedyrer i løpet av en yrkeskarriere. Strålevern er viktig og obligatorisk. Utfordringen med strålevern ved hjertekateterisering er at operatøren må stå tett inntil pasienten og ha steril vaskulær tilgang for å manipulere utstyr inni blodbanen under røntgengjennomlysning. I tillegg er både C-buen og pasientbordet bevegelig. Bedre bruk og oppgradering til moderne røntgenutstyr kan redusere gitt dose til pasient, noe som også vil redusere operatørdose. Skjerming reduserer operatørdosen ytterligere, men konvensjonelle bord- og takmontert beskyttelse etterlater uskjermede områder som har tendens til å øke i størrelse underveis i prosedyren. Det er derfor et behov for nye skjermingsløsninger som er bedre tilpasset arbeidssituasjonen til invasive kardiologer.

Materiale og metode For å se på pasient- og operatørdoser og evaluere effekten av oppgraderinger i røntgenutstyr og skjerming, analyserte vi 21499 koronare angiografier og perkutan koronar intervensjon (PCI) utført ved Haukeland Universitetssykehus mellom 2013 og juni 2019. Prosedyredata ble hentet fra Norsk register for invasiv kardiologi (NORIC), og operatørdoser ble innhentet fra Direktoratet for strålevern og atomsikkerhet. Vi utviklet deretter et nytt fleksibelt multikonfigurasjons røntgenskjold (FMX) og testet skjermingseffekt i et eksperimentelt oppsett som speiler hverdagspraksis. Ettersom røntgenprojeksjoner i stor grad påvirker dose til operatør, analyserte vi data fra 7681 prosedyrer for å kartlegge hvilke projeksjoner blir brukt og i hvilken proporsjon. FMX ble så utprøvd i en randomisert klinisk studie med 103 hjertekateteriseringer der halvparten av prosedyrene ble utført med rutinemessig skjerming med bord- og takmontert røntgenbeskyttelse, og halvparten med rutinemessig skjerming + FMX.

Resultater Mellom 2013 og 2019 sank gjennomsnittlig pasientdose per prosedyre med 37 % ved koronar angiografi (fra 2981 til 1891 μGy·m2, p < 0,001) og 39 % ved PCI (fra 8358 til 5055 μGy·m2, p<0,001). I samme periode gikk operatørdosen ned 70%. Den mest markante nedgang i operatørdose ble observert i 2018 noe som sammenfaller med innføringen av forbedrede stråleverntiltak. I et eksperimentelt oppsett reduserte FMX relativ operatørdose med 94.9% sammenlignet med et standard skjermingsoppsett bestående av et bord- og takmontert beskyttelse. FMX var spesielt effektiv i venstre kranial og venstre skrå projeksjoner. I en klinisk randomisert studie reduserte FMX median relativ operatørdose med 84.4% (fra 3,63 til 0,57 μSv/μGy·m2·10–3) og mottok svært positive tilbakemeldinger fra brukerne vedrørende funksjonalitet og brukervennlighet.

Konklusjoner Registerstudien viser en tydelig reduksjon i stråledoser til pasient og operatør ved Haukeland Universitetssykehus mellom 2013-2019. Oppgradert røntgenutstyr, forbedret skjerming og økt operatørbevissthet er sannsynlige bidragsytere til denne utviklingen. I en benkmodell er FMX et enkelt skjermingstiltak som kompletterer eksisterende røntgenbeskyttelse og fører til markant reduksjon i relativ operatørdose. Klinisk testing bekrefter at FMX er effektiv, brukervennlig og attraktiv, og kan enkelt implementeres i eksisterende arbeidsflyt.

Introduction During X-ray guided cardiac catheterization, both the patient and operator are exposed to ionizing radiation. Whereas the patient is exposed to the primary beam, the main source of operator exposure is scatter radiation from the patient. Operator dose is only a small fraction of patient dose, but an operator may perform thousands of procedures during a career spanning multiple decades. Radiation protection is mandatory and important to reduce the occupational health risk of working in the cardiac catheterization laboratory. Although lead and lead-equivalent devices are effective at stopping radiation in the energetic spectrum encountered in the cath lab, there are important challenges and constraints to the seemingly simple task of improving operator shielding. During cardiac catheterization, the operator needs to be close to the patient and have sterile access to vascular puncture sites to steer the catheters, wires, balloons, and stents under fluoroscopic guidance. The C-arm must be able to move freely, and table height and position will often change throughout the procedure. A routine setup with table- and ceiling-mounted shield leaves unshielded areas which tend to increase during the procedure due to progressively suboptimal positioning of shielding devices related to table- and C-arm movement. As a first step, registry analysis was done to evaluate temporal trends in patient and operator X-ray exposure between 2013 and mid 2019 at Haukeland University Hospital and the impact of upgrades in X-ray equipment and shielding, as well as operator awareness measures. We then developed a novel Flexible Multi-configuration X-ray shield (FMX) to address shortcomings of existing shielding devices. The shielding effect was evaluated in an experimental setup mirroring everyday practice. Finally, a fully functional prototype of the FMX was tested in a clinical trial to evaluate efficacy and user feedback during routine cardiac catheterization.

Materials and methods Data on 21499 coronary angiographies and percutaneous coronary angiographies performed at our institution between the start of 2013 and June 2019 was extracted from the Norwegian Registry for Invasive Cardiology (NORIC). Personal operator dosimetry records for the same period were provided by the Norwegian Radiation and Nuclear Safety Authority. Patient and operator X-ray exposure was analyzed in relation to patient and procedural characteristics, upgraded X-ray equipment, improved shielding, and enhanced operator awareness. To create an experimental setup mirroring everyday practice, Radiation Dose Structured Report (RDSR) data from 7681 routine procedures was used to establish a reference for a typical cardiac catheterization procedure and which C-arm angulations are used. Using this data, we assessed the shielding potential of the FMX. To evaluate effect in clinical practice, relative operator dose (operator dose indexed for patient dose) was measured during 103 consecutive cardiac catheterizations randomized in a 1:1 proportion to current routine shielding or FMX + routine shielding. User feedback was collected on perceived function, relevance, and likelihood of adoption into clinical practice.

Results Registry analysis showed that, between 2013 and 2019, mean patient dose per procedure (assessed by Dose Area Product) decreased by 37% in coronary angiography (from 2981 μGy·m2 in 2013 to 1891 μGy·m2 in 201, p < 0.001) and 39% in percutaneous coronary intervention (from 8358 to 5055 μGy·m2, p<0.001). During the same period annual operator dose decreased 70% with a marked drop in 2018 which coincided with the implementation of improved radiation protection measures. In a bench testing setup mirroring everyday practice, adding an FMX to a standard shielding setup comprising a table- and ceiling-mounted shield resulted in a 94.9% reduction in estimated operator dose. With a standard shielding setup, the operator receives most of the X-ray exposure (86%) when imaging in cranial and left anterior oblique projections where the ceiling-mounted shield offers less protection. The FMX was particularly effective in these projections. In the clinical trial, adding the FMX to routine shielding setup resulted in an 84.4% reduction in median relative operator dose (from 3.63 to 0.57 μSv/µGy·m2·10–3). The FMX received highly positive user feedback regarding size, functionality, ease of use, likely to use, critical issues, shielding, draping, procedure time, vascular access, patient discomfort, and risk.

Conclusions Registry analysis showed a temporal trend towards considerable reduction in X-ray doses received by the patient and operator during cardiac catheterization. Upgraded X-ray equipment, improved shielding, and enhanced operator awareness are likely contributors to this development. In a bench model, the FMX is a simple shielding measure that has the potential to reduce operator dose. In clinical use, FMX reduces operator radiation exposure considerably. The FMX represents an effective and attractive device for radiation protection that can easily be implemented in existing workflow. FMX has potential for general use with maintained visualization, vascular access, and shielding in routine cardiac catheterization.