Physician self-regard benefits patients’ radiation exposure: real-time monitoring of patient and occupational dose

There has been increasing emphasis on quality improvement throughout radiology departments. Radiation exposure to both the patient and the operator is one important aspect of this. This prospective study evaluated the effects of dose to patients and operators when employing real time dose monitoring of both patients and operators during fluoroscopic procedures.

Two experienced operators were enrolled in this study. These operators performed 730 procedures during the study (720 included for analysis) which was subdivided into two discreet periods. In the first period, real time monitoring of patient dose was performed using the DoseWatch (GE Healthcare Systems, Buc, France) program. In the second period, both the patient dose and operator dose were recorded in real time. Operator dose was recorded via four individual wireless devices (Ray-Safe i2; Unfors RaySafe, Inc, Billdal, Sweden). During both periods operator dose was recorded with a thermoluminescent dosimeter. Data was available real time, for the patient dose in the control room with alarms for certain thresholds, and for the operator dose on a touch screen in the procedure room with color coded dose rates and cumulative doses. Comparison of kerma area product (KAP) for each procedure type was then made between the two study periods. Mean KAP was significantly lower in period 2 (37 mGy · cm²) compared to period 1 (47 mGy · cm²), and this held true for 15/19 of the procedure types performed. In addition, a direct correlation was observed between patient dose and occupational dose (r = 0.88). From period 2, it was observed that the mean dose per procedure was 4.6 µSv, with a dose rate of 0.24 mSv/hr.

Commentary:

This study demonstrates real time monitoring of patient and occupational dose results in decreased KAP when compared to monitoring patient dose alone. This study’s most noticeable confounding variable is its susceptibility to the Hawthorne effect, as both operators were aware of the two ongoing study periods. In addition, while there was a direct correlation between KAP and accumulated operator dose, no direct measure of operator dose per procedure was performed during the first study period. Lastly, KAP had a poor correlation with operator dose at low exposure levels. However, given the significant differences observed between the two study periods, the results are noteworthy. It would be interesting to see this tool implemented in our residency and fellowship programs to more effectively teach our trainees the benefits of radiation safety.





Figure 2. Correlation between KAP (Gy ∙ cm2) and dose to operator. Overall, there was a strong correlation of KAP, measured with the patient dose monitoring system, and accumulated equivalent dose per intervention (μSv), registered with the real-time occupational dose monitoring system. However, correlation in low-dose areas (KAP < 10 Gy ∙ cm2) was poor.

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Heilmaier, C. et al. Combined use of a patient dose monitoring system and a real-time occupational dose monitoring system for fluoroscopically guided interventions. J Vasc Interv Radiol 2016; 10.1016/j.jvir.2015.11.033.

Post Author:
Daniel Sheeran, MD
VIR Pathway Resident at University of Virginia

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Risk factors for thromboembolic occlusions and efficacy of aspiration thrombectomy

A recent study from researchers at Shanghai Jiao Tong University has evaluated the predictive factors behind thromboembolic occlusions occurring during endovascular revascularization (EVR) and the success rate of percutaneous aspiration thrombectomy. A total of 260 patients underwent EVR. EVR was done using intraluminal and/or subintimal recanalization with 4000U heparin given prior to angioplasty. Uncovered self-expandable stents were placed in patients with flow-limiting dissections or residual stenosis. Of the 260 patients, 237 patients had restoration of flow without thromboembolic occlusion. 23 patients had EVR with subsequent thromboembolic occlusion. In patients with thromboembolic occlusion, a 5F or 6F guiding catheter was introduced and passed though the thromboembolic segment. A 20- or 50-mL syringe was connected to the guiding catheter after removal of the guide wire. After confirming adequate clot removal, 250,000–500,000 U urokinase was diluted in 50 mL saline solution and gradually infused into the treated artery to dissolve any remaining clots in all cases, even though no clots were present angiographically. Technical success was defined as <30% residual stenosis. Investigators report a technical success rate of 95.7% in the aspiration thrombectomy group. Interestingly, there were no significant differences in the clinical outcomes of the two groups including ABI, maximum walking distance, ulcer healing, restenosis/occlusion, and limb salvage rates. Further, there were few factors that could be cited as significant risk factors for thromboembolic occlusion during EVR including stenosis >90% and intraluminal angioplasty. The authors concluded that aspiration thrombectomy is an effective therapy for acute thromboembolic occlusion and may be considered primary treatment when this event occurs during infrainguinal arterial EVR.

Commentary:

This manuscript is interesting and noteworthy for the simple methods used to both perform revascularization and to treat a thromboembolic complication. While this study is limited due to the small sample size of thromboembolic occlusions (n=23), the small number of variables strengthen the results. All patients were treated initially with either PTA or self-expanding stent. If there was an occlusion, it was treated with aspiration thrombectomy using a 5F or 6F catheter and a syringe. The low thromboembolic occlusion rate (6.6%) and high likelihood of success after aspiration thrombectomy argue against the added cost and complexity of a distal embolic protection device. However, more research is needed to determine the risk in interventions with limited runoff vessels and more complex revascularization techniques.

Figure 3. Arterial thrombosis in the left SFA in a 78-year-old man with severe claudication for 3 weeks. (a,b) Long-segment occlusion is detected in the left SFA on contrast-enhanced MR angiography and DSA (arrows, aand b), and severe arterial thrombosis after stent placement is observed in the SFA (arrows, c). PAT was performed and arterial thrombotic material was aspirated out (d). (e) Final angiogram shows good SFA patency. 

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Wei L, Zhu Y, Liu F, et al. Infrainguinal endovascular recanalization: risk factors for arterial thromboembolic occlusions and efficacy of percutaneous aspiration thrombectomy. J Vasc Interv Radiol 2016; 10.1016/j.jvir.2015.11.025

Post Author:
Luke R. Wilkins, MD