Monitoring and Follow-Up of High Radiation Dose Cases in Interventional Radiology

Establishment of Diagnostic Reference Levels in Portuguese Interventional Radiology departments

PURPOSE

To establish Portuguese Diagnostic Reference Levels (DRLs), for six body fluoroscopy guided interventional procedures (FGIP).

METHOD

A retrospective study was conducted in five interventional departments most representative of Interventional Radiology (IR) practice. Dose values, in terms of air kerma area product (PKA in Gy.cm2), air kerma at the patient entrance reference point (Ka,r in mGy), and exposure parameters (fluoroscopy time (FT) and number of cine runs) were collected. Examinations were selected per procedure (at least 20), according to the antero-posterior and lateral diameter mean value (±5 cm), measured on previous Computed Tomography (CT) examinations.

RESULTS

Data of 489 body FGIP show a large variation on dose values per procedure and per department. National DRLs in terms of PKA were 20.2 Gy.cm2 for Percutaneous transhepatic biliary drainage (PTBD), 98.2 Gy.cm2 for Bronchial artery embolisation (BAE), 247.7 Gy.cm2 for Transarterial chemoembolisation (TACE), 331.6 Gy.cm2 for Inferior epigastric arteries embolisation (IEAE), 312.0 Gy.cm2 for Transjugular intrahepatic portosystemic shunt (TIPS) and 19.3 Gy.cm2 for Endovascular treatment of femoral popliteal arteries (ETFPA).

CONCLUSIONS

This is the first study reporting Interventional Radiology DRLs in Portugal and we propose preliminary national estimates for the six more common body FGIP. The results of this study will be presented and discussed with all Portuguese IR departments, to promote procedures optimisation.

Neurointerventions on two generations of angiography systems: Recent systems reduce radiation exposure by half

PURPOSE

Fluoroscopically-guided neurointervention may be associated with prolonged procedure time and substantial radiation exposure to the patient and staff. This study sought to examine technological features affecting the potential radiation exposure reduction of new angiography systems, compared to older systems, for neurointerventional procedures.

METHODS

Consecutive neurointerventional patients (2020-2022) were retrospectively analyzed. The air kerma at the reference point (Ka,r) and kerma-area product (KAP) were compared between Artis icono and Artis zee (Siemens) using statistical analyses (two-tailed t tests), where P < 0.05 is considered significant. X-ray tube potential and copper filtration were examined. Tests with an anthropomorphic phantom (Sun Nuclear) on Artis icono were conducted and entrance skin exposure and x-ray spectral half value layer were measured. Effective spectral filtration was characterized by x-ray spectral modeling.

RESULTS

The number of procedures was 1158 [median (range) age, 59 (7-95) years] on Artis zee and 1087 [60 (1-95) years] on Artis icono, without significant difference in age (p = 0.059) between cohorts. Ka,r was 925.4 (890.6-960.1) mGy [mean (95 % CI)] and KAP was 119.8 (115-124.5) Gy∙cm2 on Artis zee. The measures were 48-50 % lower on Artis icono, 440.5 (411.7-469.4) mGy (Ka,r) and 59.5 (55.4-63.6) Gy∙cm2 (KAP); while the difference in fluoroscopic time between the two generations of angiography systems was insignificant (p = 0.55).

CONCLUSIONS

The newer angiography system, with updated hardware and software, was found to result in half the radiation exposure compared to older technology of the same manufacturer, even though fluoroscopic time was similar.

Patient follow-up for possible radiation injury from fluoroscopically-guided interventions: Need to consider high cumulative exposure from multiple procedures

PURPOSE

Patient skin dose from interventional fluoroscopy procedures may exceed the threshold of tissue injuries and established guidelines recommend patient follow-up for air kerma at reference point (K_a,r) ≥ 5 Gy for individual procedures. Patients may undergo multiple procedures and skin injuries may be possible by cumulative exposure, even when individually insufficient to cause injury. This study sought to quantify the frequency of patients whose individual procedure doses are below 5 Gy but whose cumulative K_a,r is ≥ 5 Gy.

METHODS

This retrospective study analyzed 37,917 consecutive procedures in interventional radiology and vascular surgery at a tertiary-care hospital between January 2016 and June 2021. Radiation dosage was retrieved from the fluoroscopy acquisition systems. For a patient receiving multiple procedures, but each with K_a,r < 5 Gy, cumulative K_a,r within 2, 7, 14, 30, 183, and 365 days was assessed.

RESULTS

Nearly 1/3rd (37.4 %) patients underwent multiple procedures. With individual procedures of K_a,r < 5 Gy exclusively, 1.9, 4.4, and 5.6 in 1000 patients received cumulative K_a,r of 5-14.1 Gy from the procedures within 30, 183, and 365 days, respectively. From the procedures within 14 days, 1.3 in 1000 patients received cumulative K_a,r of 5-11.4 Gy; and from those within 7 days, 0.87 in 1000 patients received 5-9.1 Gy. In comparison, 4.3 in 1000 patients received K_a,r of 5-12 Gy from a single procedure.

CONCLUSIONS

In the absence of guidelines on patient follow-up for multiple procedures, our study may provide good material for setting up such guidelines.

Investigation of Radiation Dose Estimates and Image Quality Between Commercially Available Interventional Fluoroscopy Systems for Fluoroscopically Guided Interventional Procedures

RATIONALE AND OBJECTIVES

To investigate differences in radiation dose and image quality for single-plane flat-panel-detector based interventional fluoroscopy systems from two vendors using phantom study and clinical procedures.

MATERIALS AND METHODS

AlluraClarityIQ (Philips) and Artis Q (Siemens-Healthineers) interventional fluoroscopy systems were evaluated. Phantom study included comparison of system-reported air-kerma rates (AKR) for clinical protocols with simulated patient thicknesses (20-40 cm). Differences in system-reported radiation dose estimates, cumulative-air-kerma (CAK) and kerma-area-product (KAP), for different clinical procedures were investigated. Subset analysis investigated differences in CAK, KAP and other factors affecting radiation dose when the same patients underwent repeat embolization procedures performed by the same physician on the two different fluoroscopy systems. Two blinded interventional radiologists reviewed image-quality for these procedures using a five-point scale (1-5; 5-best) for five parameters.

RESULTS

Phantom study revealed that air-kerma rates was significantly higher for Artis Q system for 30-40cm of simulated patient thicknesses (p < 0.05). Overall data analysis from 4381 clinical cases revealed significant differences in CAK and KAP for certain procedures (p < 0.05); with significantly lower values for AlluraClarityIQ systems (median CAK lower by: 29%-58%). Subset analysis with 40 patients undergoing repeat embolization procedures on both systems revealed that median CAK and KAP were significantly lower for AlluraClarityIQ systems (p < 0.02) by 45% and 31%, respectively. Image quality scores for AlluraClarityIQ systems were significantly greater (mean difference range for five parameters: 1.3-1.6; p < 0.005).

CONCLUSION

Radiation dose and image quality differences were observed between AlluraClarityIQ and Artis Q systems. AlluraClarityIQ systems showed lower radiation utilization and an increase in subjective perception of image quality.

The impact of x-ray incident angle on indirect fluoroscopy skin dose estimation

Indirect dosimetry to calculate peak skin dose (PSD) is generally based on reference air kerma or kerma-area-product, with effects of table attenuation, inverse square law and backscatter factor applied. When the incident x-ray beam angle changes, these factors would change as well. The purpose of this study is to identify the impact of incident x-ray beam angle on the accuracy of indirect PSD calculation and develop a correction method. Monte Carlo simulation was conducted to assist analytical equation derivation and to validate the developed analytical method. Direct PSD measurements were performed a Siemens Artis Zee biplane fluoroscopy and a GE OEC C-Arm at different angles to validate the proposed correction method and its independence of fluoroscopy systems. Compared with MC simulated PSD, the derived analytical equation successfully predicts these PSD changes for incident angles of 0, 15, 30 and 40 degrees, with the residual error magnitude of 0.3%–3.1% corresponding to different SSDs. The agreement between calculated PSD also agrees well with direct measurement.

Feasibility of dosimetric measurements using Al2O3:C OSL dosimeter during fluoroscopy-guided procedures

This study investigated the feasibility of dosimetric measurements using Al2O3:C optically stimulated luminescence (OSL) dosimeters during fluoroscopy-guided procedures. The linearity and energy dependence of Al2O3:C OSL dosimeters were evaluated, and the air kerma rate at the operator's position was measured. The response of Al2O3:C OSL dosimeters to short, repetitive irradiations was compared to that of long uninterrupted irradiation. The change in response of the Al2O3:C OSL dosimeter under automatic exposure rate control (AERC) was evaluated with the use of various thicknesses of polymethyl-methacrylate (PMMA) plates (15-30 cm). The Al2O3:C OSL dosimeters could detect 5µGy and showed good linearity in doses of ≥10µGy (R²: 0.997-0.999,p< 0.001). The relative response of the Al2O3:C OSL dosimeter normalised to that of 36.8 keV was 0.828-1.101 at the energies investigated (30.6-46.0 keV). The air kerma rate at the operator's position was estimated to be 2.61-7.17µGy min^-1depending on the heights representing different body parts. Repetitive short irradiations had no significant impact on the relative response of the Al2O3:C OSL dosimeters (p> 0.05). Despite a high energy dependence on the low energy beam used in fluoroscopy, the change in relative response of the Al2O3:C OSL dosimeter under AERC was within 5.7% depending on the thickness of the PMMA plates. Dosimetric measurement using Al2O3:C OSL dosimeters for patients and operators is feasible. However, one should be cautious about high standard deviations when measuring small doses of ≤20µGy using Al2O3:C OSL dosimeters. It is essential to perform intensive bleaching before measuring very small doses to minimise pre-irradiation counts.

Fluoroscopically-guided interventions with radiation doses exceeding 5000 mGy reference point air kerma: a dosimetric analysis of 89,549 interventional radiology, neurointerventional radiology, vascular surgery, and neurosurgery encounters

PURPOSE

To quantify and categorize fluoroscopically-guided procedures with radiation doses exceeding 5000 mGy reference point air kerma (Ka,r). Ka,r > 5000 mGy has been defined as a "significant radiation dose" by the Society of Interventional Radiology. Identification and analysis of interventions with high radiation doses has the potential to reduce radiation-induced injuries.

MATERIALS AND METHODS

Radiation dose data from a dose monitoring system for 19 interventional suites and 89,549 consecutive patient encounters from January 1, 2013 to August 1, 2019 at a single academic institution were reviewed. All patient encounters with Ka,r > 5000 mGy were included. All other encounters were excluded (n = 89,289). Patient demographics, medical specialty, intervention type, fluoroscopy time (minutes), dose area product (mGy·cm2), and Ka,r (mGy) were evaluated.

RESULTS

There were 260 (0.3%) fluoroscopically-guided procedures with Ka,r > 5000 mGy. Of the 260 procedures which exceeded 5000 mGy, neurosurgery performed 81 (30.5%) procedures, followed by interventional radiology (n = 75; 28.2%), neurointerventional radiology (n = 55; 20.7%), and vascular surgery (n = 49; 18.4%). The procedures associated with the highest Ka,r were venous stent reconstruction performed by interventional radiology, arteriovenous malformation embolization performed by neurointerventional radiology, spinal hardware fixation by neurosurgery, and arterial interventions performed by vascular surgery. Neurointerventional radiology had the highest mean Ka,r (7,799 mGy), followed by neurosurgery (7452 mGy), vascular surgery (6849 mGy), and interventional radiology (6109 mGy). The mean Ka,r for interventional radiology performed procedures exceeding 5000 mGy was significantly lower than that for neurointerventional radiology, neurosurgery, and vascular surgery.

CONCLUSIONS

Fluoroscopically-guided procedures with radiation dose exceeding 5000 mGy reference point air kerma are uncommon. The results of this study demonstrate that a large proportion of cases exceeding 5000 mGy were performed by non-radiologists, who likely do not receive the same training in radiation physics, radiation biology, and dose reduction techniques as radiologists.