Reference levels for patient radiation doses in interventional radiology: proposed initial values for U.S. practice

Three-dimensional C-arm CT-guided transjugular intrahepatic portosystemic shunt placement: Feasibility, technical success and procedural time

OBJECTIVES

Establishment of transjugular intrahepatic portosystemic shunts (TIPS) constitutes a standard procedure in patients suffering from portal hypertension. The most difficult step in TIPS placement is blind puncture of the portal vein. This study aimed to evaluate three-dimensional mapping of portal vein branches and targeted puncture of the portal vein.

METHODS

Twelve consecutive patients suffering from refractory ascites by liver cirrhosis were included in this retrospective study to evaluate feasibility, technical success and procedural time of C-arm CT-targeted puncture of the portal vein. As a control, 22 patients receiving TIPS placement with fluoroscopy-guided blind puncture were included to compare procedural time.

RESULTS

Technical success could be obtained in 100 % of the study group (targeted puncture) and in 95.5 % of the control group (blind puncture). Appropriate, three-dimensional C-arm CT-guided mapping of the portal vein branches could be achieved in all patients. The median number of punctures in the C-arm CT-guided study group was 2 ± 1.3 punctures. Procedural time was significantly lower in the study group (14.8 ± 8.2 min) compared to the control group (32.6 ± 22.7 min) (p = 0.02).

CONCLUSIONS

C-arm CT-guided portal vein mapping is technically feasible and a promising tool for TIPS placement resulting in a significant reduction of procedural time.

KEY POINTS

• C-arm CT-mapping of the portal vein for 3D TIPS guidance is feasible. • Targeted punctures of the portal vein by C-arm CT reduce procedural time. • A decreased number of punctures could improve patient safety.

Radiation Doses in Patient Eye Lenses during Interventional Neuroradiology Procedures

BACKGROUND AND PURPOSE

Eye lenses are among the most sensitive organs to x-ray radiation and may be considered at risk during neurointerventional radiology procedures. The threshold dose to produce eye lens opacities has been recently reduced to 500 mGy by the International Commission on Radiologic Protection. In this article, the authors investigated the radiation doses delivered to patients' eyes during interventional neuroradiology procedures at a university hospital.

MATERIALS AND METHODS

Small optically stimulated luminescence dosimeters were located over patients' eyes during 5 diagnostic and 31 therapeutic procedures performed in a biplane x-ray system. Phantom measurements were also made to determine the level of radiation to the eye during imaging runs with conebeam CT.

RESULTS

The left eye (located toward the lateral C-arm x-ray source) received a 4.5 times greater dose than the right one. The average dose during embolization in the left eye was 300 mGy, with a maximum of 2000 mGy in a single procedure. The patient who received this maximum eye dose needed 6 embolization procedures to treat his high-volume AVM. If one took into account those 6 embolizations, the eye dose could be 2-fold. Sixteen percent of the embolizations resulted in eye doses of >500 mGy.

CONCLUSIONS

A relevant fraction of patients received eye doses exceeding the threshold of 500 mGy. A careful optimization of the procedures and follow-up of these patients to evaluate potential lens opacities should be considered.

Novel X-Ray Imaging Technology Allows Substantial Patient Radiation Reduction without Image Quality Impairment in Repetitive Transarterial Chemoembolization for Hepatocellular Carcinoma

RATIONALE AND OBJECTIVES

To assess patient radiation dose reduction and the image quality of a new X-ray imaging technology during repetitive transarterial chemoembolization (TACE) for hepatocellular carcinoma (HCC).

METHODS

Fifty HCC patients (36 men; 57 ± 11 years) undergoing repetitive TACE were first randomly assigned to receive a TACE treatment on a reference X-ray system or a low-dose system with advanced real-time image processing. The alternate system was used for a repeated TACE (treatment interval, 0.5-6 months). Fluoroscopy time, number of digital subtraction angiography (DSA), air kerma (AK), and dose area product (DAP) were compared between the two systems and between the two repetitive TACE. Three interventional radiologists independently rated the image quality in blinded offline readings.

RESULTS

Fluoroscopy time (8.7 ± 5.9 minutes vs. 8.7 ± 7.9 minutes, P = .981), numbers of DSA runs (6 ± 4 vs. 6 ± 4, P = .735), and exposure images (173 ± 86 vs. 168 ± 91, P = .916) were equivalent between the two systems. No statistical difference in X-ray usage was found between repeated treatments. Compared to the reference system, the technology significantly reduced AK and DAP by 48.6% (0.17 ± 0.13 Gy vs. 0.41 ± 0.36 Gy, P < .0001) and 50.3% (77.3 ± 55.2 Gy cm(2) vs. 195.0 ± 155.5 Gy cm(2), P < .0001), respectively. Image quality was rated comparable between the new system and the reference, with average scores of 3.9 ± 0.3 versus 4.4 ± 0.3 in fluoroscopy and 4.5 ± 0.2 versus 4.3 ± 0.3 in DSA.

CONCLUSIONS

Patient radiation exposure can be substantially reduced by a factor of approximately two with the novel X-ray imaging technology while maintaining image quality.

Radiation dose and mortality risk to children undergoing therapeutic interventional cardiology

BACKGROUND

Children undergoing interventional cardiology procedures deserve special concern due to the greater radiation sensitivity of their tissues and more remaining years of life during which a radiation-induced cancer may develop.

PURPOSE

To determine the patient radiation dose for pediatric therapeutic interventional cardiology and to estimate the patient effective dose and lifetime mortality risk to children associated with five common procedures.

MATERIAL AND METHODS

Ninety children with congenital heart defects undergoing interventional therapy were enrolled in this study. Data regarding fluoroscopy and radiography time, dose-area product (DAP) and peak skin dose (PSD) for each case were measured. Patients were divided into five groups. The patient effective dose (E) was calculated using a multiplicative model of ICRP 60. The overall lifetime mortality risk was evaluated using appropriate risk coefficients.

RESULTS

The mean, median, standard deviation, and range of time, PSD, DAP, and E were presented for the five study groups. When these metrics were considered, there were wide variations for different cases within the same group and statistically significant differences between the five groups. The PSD correlated significantly with DAP (Pearson r = 0.70; P < 0.01), but the correlation in individual cases was poor. For all cases, the range of E was found to be between 0.44 and 66.7 mSv. The corresponding risk of lifetime mortality was 1.16 per thousand.

CONCLUSION

The current study provides overall data on the time, PSD, E, and lifetime mortality risk for pediatric therapeutic interventional cardiology. Radio frequency ablation showed the highest radiation risk.

Radiation Exposure in Transjugular Intrahepatic Portosystemic Shunt Creation

PURPOSE

Transjugular intrahepatic portosystemic shunt (TIPS) creation is considered as being one of the most complex procedures in abdominal interventional radiology. Our aim was twofold: quantification of TIPS-related patient radiation exposure in our center and identification of factors leading to reduced radiation exposure.

MATERIALS AND METHODS

Three hundred and forty seven consecutive patients underwent TIPS in our center between 2007 and 2014. Three main procedure categories were identified: Group I (n = 88)-fluoroscopic-guided portal vein targeting, procedure done in an image intensifier-based angiographic system (IIDS); Group II (n = 48)--ultrasound-guided portal vein puncture, procedure done in an IIDS; and Group III (n = 211)--ultrasound-guided portal vein puncture, procedure done in a flat panel detector-based system (FPDS). Radiation exposure (dose-area product [DAP], in Gy cm(2) and fluoroscopy time [FT] in minutes) was retrospectively analyzed.

RESULTS

DAP was significantly higher in Group I (mean ± SD 360 ± 298; median 287; 75th percentile 389 Gy cm(2)) as compared to Group II (217 ± 130; 178; 276 Gy cm(2); p = 0.002) and Group III (129 ± 117; 70; 150 Gy cm(2) p < 0.001). The difference in DAP between Groups II and III was also significant (p < 0.001). Group I had significantly longer FT (25.78 ± 13.52 min) as compared to Group II (20.45 ± 10.87 min; p = 0.02) and Group III (19.76 ± 13.34; p < 0.001). FT was not significantly different between Groups II and III (p = 0.73).

CONCLUSIONS

Real-time ultrasound-guided targeting of the portal venous system during TIPS creation results in a significantly lower radiation exposure and reduced FT. Further reduction in radiation exposure can be achieved through the use of modern angiographic units with FPDS.

Measurement of maximum skin dose in interventional radiology and cardiology and challenges in the set-up of European alert thresholds

To help operators acknowledge patient dose during interventional procedures, EURADOS WG-12 focused on measuring patient skin dose using XR-RV3 gafchromic films, thermoluminescent detector (TLD) pellets or 2D TL foils and on investigating possible correlation to the on-line dose indicators such as fluoroscopy time, Kerma-area product (KAP) and cumulative air Kerma at reference point (CK). The study aims at defining non-centre-specific European alert thresholds for skin dose in three interventional procedures: chemoembolization of the liver (CE), neuroembolization (NE) and percutaneous coronary interventions (PCI). Skin dose values of >3 Gy (ICRP threshold for skin injuries) were indeed measured in these procedures confirming the need for dose indicators that correlate with maximum skin dose (MSD). However, although MSD showed fairly good correlation with KAP and CK, several limitations were identified challenging the set-up of non-centre-specific European alert thresholds. This paper presents preliminary results of this wide European measurement campaign and focuses on the main challenges in the definition of European alert thresholds.

Comparison of radiation exposure during fluoroscopy-guided transforaminal epidural steroid injections at different vertebral levels

Objective

To estimate and compare radiation exposure during transforaminal fluoroscopy-guided epidural steroid injection (TFESI) at different vertebral levels.

Materials and Methods

Fluoroscopy-guided TFESI was performed in 181 patients. The patients were categorized into three groups according to the injected lumbosacral nerve level of L2-4, L5, or S1. Fluoroscopy time (FT) and dose area product (DAP) were recorded for all patients; correlations between FT and DAP were determined at each level, and both FT and DAP were compared between the different vertebral levels.

Results

The numbers of patients who received ESI at L2-4, L5, and S1 were 29, 123, and 29. Mean FT was 44 seconds at L2-4, 33.5 seconds at L5, and 37.7 seconds at S1. Mean DAP was 138.6 µGy·m² at L2-4, 100.6 µGy·m² at L5, and 72.1 µGy·m² at S1. FT and DAP were positively correlated in each group (p values < 0.001). FT was significantly shorter at L5 than that at L2-4 (p = 0.004) but was not significantly different between S1 and L2-4 or L5 (p values = 0.286 and 0.532, respectively). DAP was significantly smaller at L5 and S1 than that at L2-4, but L5 and S1 were not significantly different. After correcting for FT, DAP was significantly smaller at S1 than that at either L2-4 or L5 (p values = 0.001 and 0.010).

Conclusion

The radiation dose was small during a single procedure of ESI and showed differences between different lumbosacral spine levels.

Clinical apparatus for the reduction of dose area product for patients undergoing x-ray catheterization

PURPOSE

The authors describe a design for prepatient region of interest attenuators (ROIAs) to reduce dose area product (DAP) for clinical use. The authors describe a model to predict DAP values from x-ray technique parameters recorded during a clinical procedure for image sequences obtained in the presence or absence of ROIAs. The model was developed primarily to determine what the DAP to a patient undergoing cardiac catheterization with a ROIA would have been if no ROIA had been used allowing a determination of DAP reduction.

METHODS

Copper ROIAs with thicknesses that vary gradually so as not to cause significant image artifacts were constructed. X-ray image sequences were acquired on a clinical catheterization system with and without ROIAs with varying x-ray technique parameters. DAP values were measured for all said exposures using an ionization chamber and compared to a model the authors developed.

RESULTS

The model can predict DAP values within 3.5% on average with or without ROIAs when compared to ionization chamber measurements.

CONCLUSIONS

The proposed experimental design is adequate for measuring DAP reductions on the order of 1.5-3.5 that are expected when introducing a ROIA during patient catheterization imaging.

Patient skin dose measurements using a cable free system MOSFETs based in fluoroscopically guided percutaneous vertebroplasty, percutaneous disc decompression, radiofrequency medial branch neurolysis, and endovascular critical limb ischemia

The purpose of this work has been to dosimetrically investigate four fluoroscopically guided interventions: the percutaneous vertebroplasty (PVP), the percutaneous disc decompression (PDD), the radiofrequency medial branch neurolysis (RF) (hereafter named spine procedures), and the endovascular treatment for the critical limb ischemia (CLI). The X-ray equipment used was a Philips Integris Allura Xper FD20 imaging system provided with a dose-area product (DAP) meter. The parameters investigated were: maximum skin dose (MSD), air kerma (Ka,r), DAP, and fluoroscopy time (FT). In order to measure the maximum skin dose, we employed a system based on MOSFET detectors. Before using the system on patients, a calibration factor Fc and correction factors for energy (CkV) and field size (CFD) dependence were determined. Ka,r, DAP, and FT were extrapolated from the X-ray equipment. The analysis was carried out on 40 patients, 10 for each procedure. The average fluoroscopy time and DAP values were compared with the reference levels (RLs) proposed in literature. Finally, the correlations between MSD, FT, Ka,r, and DAP values, as well as between DAP and FT values, were studied in terms of Pearson's product-moment coefficients for spine procedures only. An Fc value of 0.20 and a very low dependence of CFD on field size were found. A third-order polynomial function was chosen for CkV. The mean values of MSD ranged from 2.3 to 10.8cGy for CLI and PVP, respectively. For these procedures, the DAP and FT values were within the proposed RL values. The statistical analysis showed little correlation between the investigated parameters. The interventional procedures investigated were found to be both safe with regard to deterministic effects and optimized for stochastic ones. In the spine procedures, the observed correlations indicated that the estimation of MSD from Ka,r or DAP was not accurate and a direct measure of MSD is therefore recommended.

Impact of Anatomical, Procedural, and Operator Skill Factors on the Success and Duration of Fluoroscopy-Guided Transjugular Intrahepatic Portosystemic Shunt

PURPOSE

To assess the impact of anatomical, procedural, and operator skill factors on the success and duration of fluoroscopy-guided transjugular intrahepatic portoystemic shunt following standard operating procedure (SOP).

MATERIAL AND METHODS

During a 32-month period, 102 patients underwent transjugular intrahepatic portosystemic shunt creation (TIPS) by two interventional radiologists (IR) following our institutional SOP based on fluoroscopy guidance. Both demographic and procedural data were assessed. The duration of the intervention (D(Int)) and of the portal vein puncture (D(Punct)) was analyzed depending on the skill level of the IR as well as the anatomic or procedural factors.

RESULTS

In 99 of the 102 patients, successful TIPS without peri-procedural complications was performed. The mean D(Int) (IR1: 77 min; IR2: 51 min, P < 0.005) and the mean D(Punct) (IR1: 19 min; IR2: 13 min, P < 0.005) were significantly higher in TIPS performed by IR1 (with 2 years of clinical experience performing TIPS, n = 38) than by IR2 (>10 years of clinical experience performing TIPS, n = 61), (P < 0.005 both, Mann-Whitney U test). D Int showed a higher correlation with D(Punct) for IR2 (R(2) = 0.63) than for IR1 (R(2) = 0.13). There was no significant difference in the D(Punct )for both IRs with regard to the success of the wedged portography (P = 0.90), diameter of the portal vein (P = 0.60), central right portal vein length (P = 0.49), or liver function (MELD-Score before the TIPS procedure; P = 0.14).

CONCLUSION

TIPS following SOP is safe, fast, and reliable. The only significant factor for shorter D(Punct) and D(Int) was the clinical experience of the IR. Anatomic variability, successful portography, or liver function did not alter the duration or technical success of TIPS.

[Construction and usefulness of the dose management system using DICOM radiation dose structured report (Dose SR) in angiography]

The International Commission on Radiological Protection recommends diagnostic reference levels (DRL) in each radiological examination for justification and optimization of patients' dose in medicine. The aim of our study was to propose the dose management system by utilizing dose information in diagnostic X-ray radiation dose structured report (Dose SR) in The Digital Imaging and Communications in Medicine to optimize radiation dose in institutions. Our dose management system is able to organize dose information obtained from various angiography systems and CTs. It is possible to provide this information to operators for justification and optimization of patient dose. Our system would be useful for the estimation of organ dose and could be used for the determination of local DRL (LDRL) for each radiological practice. In addition, the optimization became possible to compare LDRL with national DRL.

Radiation exposure for fluoroscopy-guided lumbosacral epidural steroid injections: comparison of the transforaminal and caudal approaches

STUDY DESIGN

A retrospective investigation.

OBJECTIVE

We evaluated and compared the radiation exposure caused by using the fluoroscopy-guided transforaminal and caudal approaches of lumbosacral epidural steroid injection (ESI).

SUMMARY OF BACKGROUND DATA

Only a few studies focused on the radiation exposure to patients who underwent lumbosacral ESI for pain management.

MATERIALS AND METHODS

A total of 228 patients (83 males, 145 females; mean age, 63.3 y) who received lumbosacral ESI were included. Transforaminal ESI was performed in 181 patients (67 males, 114 females; mean age, 61.3 y) and caudal ESI was used in 47 patients (16 males, 31 females; mean age, 69.7 y). All ESIs were performed under a single-plane fluoroscopic guidance by 1 musculoskeletal radiologist. The kerma-area product (KAP) and fluoroscopy time were recorded in all patients. Both measurements were correlated and compared for each approach.

RESULTS

KAP was 3.02-1048.2 μGy m (mean, 101.7 μGy m; median, 67.8 μGy m) for transforaminal ESI and 16.0-604.5 μGy m (mean, 101.8 μGy m; median, 54.6 μGy m) for caudal ESI. The fluoroscopy time was 11-161 seconds for transforaminal ESI (mean, 36.0 s; median, 29 s) and 4-78 seconds (mean, 18.2 s; median, 13 s) for caudal ESI. KAP and fluoroscopy time were positively correlated for each approach (P<0.001). Fluoroscopy time was significantly longer for transforaminal ESI (correlation coefficient=-0.77, P=0.000). After correction for the fluoroscopy time, KAP was less in transforaminal ESI than in caudal ESI (correlation coefficient=0.74, P=0.000).

CONCLUSIONS

The longer the fluoroscopy time, the greater the KAP in both transforaminal and caudal ESIs. The fluoroscopy time for transforaminal ESI was longer than that for caudal ESI. However, KAP of transforaminal ESI was less than that of the caudal ESI, after being corrected for the length of fluoroscopy time.

Patient radiation doses in uterine artery embolisation using Monte Carlo simulation

This study aims at quantification of ovarian dose in uterine artery embolisation to study the level of optimisation of this dose. Individual anatomical data and all relevant exposure parameters of individual beam projections were recorded in 52 patients who underwent uterine artery embolisation in two angiography units. The recorded information was used to calculate the individual ovarian doses by Monte Carlo simulation. The mean dose-area product was 196 Gy cm(2). The corresponding mean ovarian dose was 149 mGy. The performance of the two angiography units was analysed starting from these data. Dose-area product and ovarian doses obtained in this study were compared with data from other uterine artery embolisation patient dose studies. It was concluded that although the mean dose-area product and ovarian dose are acceptable, it is possible to optimise the procedure by improving the performance of the units.

A radiation exposure index for CT

The purpose of this study is to define an Exposure Index for CT (EI(CT)) and to estimate the magnitude of the EI(CT) for common clinical CT examinations. For a single-axial rotation of a CT X-ray tube that includes only rays that pass through the patient, the CT Exposure Index (EI(CT)) is defined as the average Air Kerma that would be incident on an extended 360° detector array completely surrounding the patient. For an axial scan of a uniform cylindrical phantom, EI(CT) can be approximated as T × [(CTDI(air))/4] × [β°/360°] where T is the fractional transmission through the cylinder, CTDI(air) is the CT Dosimetry Index-determined 'free in air' at isocentre, and β/2 is the fan beam angle that will completely irradiate a cylindrical phantom at isocentre. The value of CTDI(air) can be estimated from the weighted CTDI (CTDI(w)) for a given CT examination, and the angle β depends on the irradiation geometry that can be obtained from the cylinder diameter (r) and the focus to isocentre distance (R). At a voltage of 120 kV, transmission through an adult head was ∼2.6%, through an adult abdomen∼0.4% and through a 5-y-old paediatric abdomen ∼3%. Average ratios of CTDI(air)/CTDI(w) were 1.42 ± 0.12 in 16-cm dosimetry phantom and 2.82 ± 0.37 in 32-cm phantom. Values of β ranged from 30.1° (R = 61 cm and r=8 cm) to 85.3° (R = 55 cm and r=20 cm). For an adult head CT examination, EI(CT) was estimated to be∼70 µGy at a CTDI(vol) of 75 mGy (16 cm), and for an adult abdominal CT examination, EI(CT) was estimated to be∼11 µGy at a CTDI(vol) of 25 mGy (32 cm). For an abdomen CT examination in a 5-y-old child, EI(CT) was estimated to be ∼21 µGy at a CTDI(vol) of 20 mGy (16 cm). The EI(CT) is introduced that provides a quantitative measure of the amount of the radiation used to generate images in any CT examination and is analogous to the average image receptor Exposure Index recently proposed for use in projection imaging. The EI(CT) metric provides operators with an objective index of the amount of the radiation used to create CT images and can be used to control quantum mottle in CT.

Overall measurements of dose to patients in common interventional cardiology procedures

This study was designed to measure peak skin dose (PSD), dose-area product (DAP), cumulative dose (CD) and fluoroscopy time (FT) for interventional cardiology procedures and to evaluate whether patient doses were higher than that in other published data. Three cardiac procedure types, including coronary angiography (CAG), percutaneous transluminal coronary angioplasty (PTCA) and radio frequency (RF) ablation, were entered into the study. Data of four special metrics (PSD, DAP, CD and FT) for these procedures were collected and measured. A total of 238 patients who underwent interventional radiology procedures participated in this study. For every procedure, data about PSD were resulted from six TLD arrays and DAP, CD and FT were collected from the displayed monitor. The mean, standard deviation (SD), range and third quartile of the distribution of PSD, DAP, CD and FT recorded and measured on spot were calculated for all procedures. High-dose cases were specifically recorded. There was wide variation in the doses observed for different instances of the same procedure. PSD for PTCA and RF ablation ranged from 0.1 Gy to more than 3 Gy. Of 238 instances, there were 22 (9.2 %) with PSDs greater than 2 Gy and 4 (1.7 %) than 3 Gy. The third quartile of the distribution for PTCA had exceeded the DIMOND preliminary reference levels by 41.1 % in DAP and 25.0 % in FT. Mean DAP was in the range of reported values for CAG procedure, but higher than all data obtained in literatures for PTCA. Data from this study are in the range of most reported values for CAG and RF ablation procedure, while higher than that obtained in some literatures for PTCA. In case of a constant delivering of high doses to patient and physician himself, thorough training of interventionalists and staff is necessary, and the legislation has to be revised and set dose constrains especially for the interventional high-dose procedures.

[Diagnostic reference levels in interventional radiology]

This article discusses the diagnostic reference levels for radiation exposure proposed by the International Commission on Radiological Protection (ICRP) to facilitate the application of the optimization criteria in diagnostic imaging and interventional procedures. These levels are normally established as the third quartile of the dose distributions to patients in an ample sample of centers and are supposed to be representative of good practice regarding patient exposure. In determining these levels, it is important to evaluate image quality as well to ensure that it is sufficient for diagnostic purposes. When the values for the dose received by patients are systematically higher or much lower than the reference levels, an investigation should determine whether corrective measures need to be applied. The European and Spanish regulations require the use of these reference values in quality assurance programs. For interventional procedures, the dose area product (or kerma area product) values are usually used as reference values together with the time under fluoroscopy and the total number of images acquired. The most modern imaging devices allow the value of the accumulated dose at the entrance to the patient to be calculated to optimize the distribution of the dose on the skin. The ICRP recommends that the complexity of interventional procedures be taken into account when establishing reference levels. In the future, diagnostic imaging departments will have automatic systems to manage patient dosimetric data; these systems will enable continuous dosage auditing and alerts about individual procedures that might involve doses several times above the reference values. This article also discusses aspects that need to be clarified to take better advantage of the reference levels in interventional procedures.

Radiological protection of the patient: an integral part of quality of care

Modern medicine now demands rapid diagnosis and treatment often centered on multiple investigations using ionizing radiation, particularly computed tomography (CT). Technological development continues at a rapid pace, and there is also an inexorable rise in minimally invasive therapy using fluoroscopically guided techniques. This has offered great benefit to many patients, who otherwise may not be fit enough for more invasive surgery. However, there are now many younger patients being treated using such techniques, where the risks of radiation in the longer term become more of an issue.

Efforts to optimize radiation protection in interventional fluoroscopy

While it has been known for more than a century that radiation presents risks to both the physician and the patient, skin injuries from fluoroscopy became increasingly rare after the 1930s, and radiation risk from fluoroscopy appeared to be adequately controlled. However, beginning in approximately 1975, new technologies and materials for interventional devices were developed. These enabled new procedures, and as these were instituted, skin injuries again occurred in patients. Four central issues were identified: equipment, quality management, operator training, and occupational radiation protection. Recognition that these were areas for improvement provoked changes in technology and practice that continue today.

Radiation exposure in CT-guided interventions

PURPOSE

To investigate radiation exposure in computed tomography (CT)-guided interventions, to establish reference levels for exposure, and to discuss strategies for dose reduction.

MATERIALS AND METHODS

We analyzed 1576 consecutive CT-guided procedures in 1284 patients performed over 4.5 years, including drainage placements; biopsies of different organs; radiofrequency and microwave ablations (RFA/MWA) of liver, bone, and lung tumors; pain blockages, and vertebroplasties. Data were analyzed with respect to scanner settings, overall radiation doses, and individual doses of planning CT series, CT intervention, and control CT series.

RESULTS

Eighty-five percent of the total radiation dose was applied during the pre- and post-interventional CT series, leaving only 15% applied by the CT-guided intervention itself. Single slice acquisition was associated with lower doses than continuous CT-fluoroscopy (37 mGy cm vs. 153 mGy cm, p<0.001). The third quartile of radiation doses varied considerably for different interventions. The highest doses were observed in complex interventions like RFA/MWA of the liver, followed by vertebroplasty and RFA/MWA of the lung.

CONCLUSIONS

This paper suggests preliminary reference levels for various intervention types and discusses strategies for dose reduction. A multicenter registry of radiation exposure including a broader spectrum of scanners and intervention types is needed to develop definitive reference levels.

Effects of low-dose protocols in endovascular treatment of intracranial aneurysms: development of workflow task analysis during cerebral endovascular procedures

OBJECTIVE

Reducing radiation exposure through the use of low-dose protocols during cerebral endovascular procedures is recommended, but evaluation of the impact on the procedure itself is difficult and subjective. A workflow task analysis could provide an objective comparison of two different radiation exposure protocols.

SUBJECTS AND METHODS

Twenty endovascular aneurysm treatments were analyzed using a low-dose protocol (reducing radiation exposure by 20%) in 10 cases and a normal-dose protocol in the other 10 cases. The procedure was subdivided into five phases, each comprising a sequence of tasks. Each task was defined as a triplet, associating an action, an instrument, and an anatomic structure. A workflow editor was used to record tasks and phases with a tablet PC. The total duration of the entire procedure, the duration of each task, and the number of task repetitions were isolated and used as the metric. Moreover, the tasks involving x-ray use, essential for navigation and treatment phases, were separated and analyzed.

RESULTS

For the microcatheter navigation and treatment phases, no statistically significant difference was found between the two radiation exposure protocols. For guide catheter navigation in cervical vessels, the total phase duration and total and mean time of tasks specifically involving x-ray use increased with age, but there was no difference between the two radiation protocols.

CONCLUSION

Workflow task analysis of endovascular aneurysm treatment shows no difference between low-dose and normal-dose protocols in the guide catheter navigation, microcatheter navigation, or treatment phases.

Impact of the X-ray system setting on patient dose and image quality; a case study with two interventional cardiology systems

This study investigates the influence of the initial X-ray system setting on patient doses and image quality in interventional cardiology procedures. Two dedicated interventional cardiology systems were studied: a system with image intensifier (II) and a flat detector (FD) system. Entrance surface air kerma (ESAK) rates in fluoroscopy and ESAK per frame in the acquisition mode were measured on the surface of a PMMA phantom for the field of views (FOV) of 23 and 17 cm (II system) and 25 and 20 cm (FD system). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were estimated using DICOM images obtained during the measurements. System performances were compared using a figure of merit combining SNR and ESAK. The influence of system setting on patient doses was investigated analysing the information for air kerma area product (KAP) and cumulative dose (CD) at the patient entrance reference point, for a sample of coronary angiography examinations. ESAK rates in fluoroscopy modes were a factor of 2 higher in the FD system for the similar FOVs, resulting in a factor of 1.9 higher median values of KAP and CD for patients with FD system than for the II system. SNR and CNR for the FD system were better than the equivalent FOVs with II. The resulting FOM was better for the FD system in both FOVs. Potential for optimisation was suggested by adjusting system settings.

Radiation exposure in biliary procedures performed to manage anastomotic strictures in pediatric liver transplant recipients: comparison between radiation exposure levels using an image intensifier and a flat-panel detector-based system

PURPOSE

The aim of this study was to estimate radiation exposure in pediatric liver transplants recipients who underwent biliary interventional procedures and to compare radiation exposure levels between biliary interventional procedures performed using an image intensifier-based angiographic system (IIDS) and a flat panel detector-based interventional system (FPDS).

MATERIALS AND METHODS

We enrolled 34 consecutive pediatric liver transplant recipients with biliary strictures between January 2008 and March 2013 with a total of 170 image-guided procedures. The dose-area product (DAP) and fluoroscopy time was recorded for each procedure. The mean age was 61 months (range 4-192), and mean weight was 17 kg (range 4-41). The procedures were classified into three categories: percutaneous transhepatic cholangiography and biliary catheter placement (n = 40); cholangiography and balloon dilatation (n = 55); and cholangiography and biliary catheter change or removal (n = 75). Ninety-two procedures were performed using an IIDS. Seventy-eight procedures performed after July 2010 were performed using an FPDS. The difference in DAP between the two angiographic systems was compared using Wilcoxon rank-sum test and a multiple linear regression model.

RESULTS

Mean DAP in the three categories was significantly greater in the group of procedures performed using the IIDS compared with those performed using the FPDS. Statistical analysis showed a p value = 0.001 for the PTBD group, p = 0.0002 for the cholangiogram and balloon dilatation group, and p = 0.00001 for the group with cholangiogram and biliary catheter change or removal.

CONCLUSION

In our selected cohort of patients, the use of an FPDS decreases radiation exposure.

Assessments of medical exposures during interventional radiology procedures

This study aims to contribute to the construction of a scenario regarding patient radiation exposure in Brazilian interventional radiology, aiming to provide data for the future drafting of specific legislation on interventional radiology because there is currently a lack of safety regulations for haemodynamics services in this country. Fourteen haemodynamics services in the states of Santa Catarina and Bahia were evaluated. The radiological devices were characterised through measurements of air kerma-area product, entrance surface air kerma (Ke), exposure time, spatial resolution (SR), low-contrast resolution and half-value layer. During the evaluation of instrument parameters, several non-conformities were found according to current Brazilian regulations, with SR presenting the most critical situation. The results of the present study indicate the need for the optimisation of clinical practices in complex radiological procedures, although the overall results for the dose scenario in the present study revealed values similar to those reported in international publications.

Evaluation of fluoroscopic cases qualifying as potential fluoroscopic sentinel events

RATIONALE AND OBJECTIVES

To address the risk of radiation injury during interventional procedures, the Joint Commission has defined prolonged fluoroscopy resulting in a cumulative skin dose of 15 Gy or more to a single field as a reviewable sentinel event. The goal of this work is to present a system for identifying potential fluoroscopic sentinel events (FSE) and describing common case characteristics.

MATERIALS AND METHODS

Criteria based on fluoroscopic time (FT) > 150 minutes and reference air kerma (RAK) > 6 Gy were used to identify potential sentinel events. Case information including procedure type, number of procedures, and radiation dose parameters was recorded. Peak skin dose (PSD) was calculated by a medical physicist. Values were compared between procedure types and the relationship between FT, RAK, and PSD was evaluated.

RESULTS

Between 2008 and 2011, 183 events exceeding the investigation criteria were identified in three interventional categories: cardiology (54%), neuroradiology (31%), and vascular (16%). The average number of procedures/patient was 1.7 ± 0.1, with the majority (59.6%) having undergone only one procedure. Most cases could be identified using the RAK criterion alone (96.7%). Based on the PSD/RAK ratio, a threshold RAK of 7.5 Gy would effectively identify all cases that would exceed 15 Gy in PSD.

CONCLUSION

Radiation delivered during interventional cases can place patients at risk of cutaneous radiation injury and potential sentinel events. Using appropriate thresholds to determine which cases require detailed investigation allows efficient utilization of department resources for identifying sentinel events.

Patient radiation doses in interventional cardiology in the U.S.: advisory data sets and possible initial values for U.S. reference levels

PURPOSE

To determine patient radiation doses from interventional cardiology procedures in the U.S and to suggest possible initial values for U.S. benchmarks for patient radiation dose from selected interventional cardiology procedures [fluoroscopically guided diagnostic cardiac catheterization and percutaneous coronary intervention (PCI)].

METHODS

Patient radiation dose metrics were derived from analysis of data from the 2008 to 2009 Nationwide Evaluation of X-ray Trends (NEXT) survey of cardiac catheterization. This analysis used identified data and did not require review by an IRB. Data from 171 facilities in 30 states were analyzed. The distributions (percentiles) of radiation dose metrics were determined for diagnostic cardiac catheterizations, PCI, and combined diagnostic and PCI procedures. Confidence intervals for these dose distributions were determined using bootstrap resampling.

RESULTS

Percentile distributions (advisory data sets) and possible preliminary U.S. reference levels (based on the 75th percentile of the dose distributions) are provided for cumulative air kerma at the reference point (K(a,r)), cumulative air kerma-area product (P(KA)), fluoroscopy time, and number of cine runs. Dose distributions are sufficiently detailed to permit dose audits as described in National Council on Radiation Protection and Measurements Report No. 168. Fluoroscopy times are consistent with those observed in European studies, but P(KA) is higher in the U.S.

CONCLUSIONS

Sufficient data exist to suggest possible initial benchmarks for patient radiation dose for certain interventional cardiology procedures in the U.S. Our data suggest that patient radiation dose in these procedures is not optimized in U.S. practice.

Avaliação de exposições médicas em procedimentos pediátricos de radiologia intervencionista

OBJETIVO: Avaliar as exposições pediátricas de radiologia intervencionista em dois hospitais do Estado da Bahia, visando contribuir para a construção de um cenário estadual e nacional, possibilitando o conhecimento das exposições e da necessidade de sua otimização, visto que as peculiaridades que envolvem a radiologia e a pediatria se potencializam quando se trata de procedimentos de radiologia intervencionista, em razão das doses elevadas de radiação. MATERIAIS E MÉTODOS: Foram avaliados 32 procedimentos em quatro salas nos dois principais hospitais que realizam procedimentos de radiologia intervencionista pediátrica na Bahia. Foram avaliados os valores de kerma no ar incidente e o produto kerma-área no ar de 27 procedimentos cardiológicos e 5 procedimentos cerebrais. RESULTADOS: Os valores máximos de produto kerma-área e kerma obtidos para procedimentos cardiológicos foram, respectivamente, 129,9 Gy.cm² e 947,0 mGy, e para procedimentos cerebrais, 83,3 Gy.cm² e 961,0 mGy. CONCLUSÃO: Os resultados deste estudo mostraram valores de exposições superiores em até 14 vezes os obtidos em estudos realizados em outros países, chegando próximos de resultados obtidos para procedimentos em adultos. Isto revela quão elevadas podem ser as exposições pediátricas, indicando a necessidade de constante otimização dos procedimentos e avaliação das exposições.

Radiation exposure in vascular angiographic procedures

PURPOSE

To evaluate dose reduction in vascular angiographic procedures by using fluoroscopy capture instead of digital subtraction angiography frames for documentation.

MATERIALS AND METHODS

A total of 764 consecutive vascular interventional procedures performed over a period of 1 year were retrospectively analyzed with respect to the fluoroscopy time and the resulting dose-area product (DAP), the DAP of the radiographic frames, and the overall DAP.

RESULTS

A total of 70% of the total DAP was a result of the acquisition of radiographic frames, leaving only 30% being applied by fluoroscopy.

CONCLUSIONS

Fluoroscopy capture should be used for documentation whenever possible. A registry of radiation exposure should not only comprise a sufficiently large number of interventions but also different intervention types to allow the development of interventional reference levels.

An audit of diagnostic reference levels in interventional cardiology and radiology: are there differences between academic and non-academic centres?

A wide variation in patient exposure has been observed in interventional radiology and cardiology. The purpose of this study was to investigate the patient dose from fluoroscopy-guided procedures performed in non-academic centres when compared with academic centres. Four procedures (coronary angiography, percutaneous coronary intervention, angiography of the lower limbs and percutaneous transluminal angioplasty of the lower limbs) were evaluated. Data on the dose-area product, fluoroscopy time and number of images for 1000 procedures were obtained from 23 non-academic centres and compared with data from 5 academic centres. No differences were found for cardiology procedures performed in non-academic centres versus academic ones. However, significantly lower doses were delivered to patients for procedures of the lower limbs when they were performed in non-academic centres. This may be due to more complex procedures performed in the academic centres. Comparison between the centres showed a great variation in the patient dose for these lower limb procedures.

Quality initiatives: Establishing an interventional radiology patient radiation safety program

The Interventional Radiology Patient Radiation Safety Program was created to better educate patients who are scheduled to undergo high-dose interventional radiologic procedures about the risks of radiation, better monitor the delivered doses, and reduce the risk for deterministic effects. The program combines preprocedure evaluation and counseling, intraprocedure monitoring, and postprocedure documentation and counseling with the guidelines of the National Cancer Institute and the Society of Interventional Radiology. Between July 2009, when the program was implemented, and September 2010, over 3500 interventional radiologic procedures were monitored and documented, and 63 procedures with an adjusted cumulative dose of more than 3 Gy were identified and further analyzed; four procedures were found to be outside the control limits. Additional review of these four procedures resulted in practice modifications. Anecdotal feedback from physician assistants and attending physicians indicated that the program had another positive effect: Patients who required postprocedure counseling about the potential for radiation-induced skin injuries were no longer surprised by this information. Implementation of this program is straightforward, requires little infrastructure and few resources, and may be applied in most interventional radiology practices. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.321115002/-/DC1.

Reference air kerma and kerma-area product as estimators of peak skin dose for fluoroscopically guided interventions

PURPOSE

To determine more accurate regression formulas for estimating peak skin dose (PSD) from reference air kerma (RAK) or kerma-area product (KAP).

METHODS

After grouping of the data from 21 procedures into 13 clinically similar groups, assessments were made of optimal clustering using the Bayesian information criterion to obtain the optimal linear regressions of (log-transformed) PSD vs RAK, PSD vs KAP, and PSD vs RAK and KAP.

RESULTS

Three clusters of clinical groups were optimal in regression of PSD vs RAK, seven clusters of clinical groups were optimal in regression of PSD vs KAP, and six clusters of clinical groups were optimal in regression of PSD vs RAK and K AP. Prediction of PSD using both RAK andKAP is significantly better than prediction of PSD with either RAK or KAP alone. The regression of PSD vs RAK provided better predictions of PSD than the regression of PSD vs KAP. The partial-pooling (clustered) method yields smaller mean squared errors compared with the complete-pooling method.

CONCLUSION

PSD distributions for interventional radiology procedures are log-normal. Estimates of PSD derived from RAK and KAP jointly are mos t accurate, followed closely byestimates derived from RAK alone. Estimates of PSD derived from KAP alone are the least accurate. Using a stochastic search approach, it is possible to cluster together certain dissimilar types of procedures to minimize the total error sum of squares.

Patient radiation dose audits for fluoroscopically guided interventional procedures

PURPOSE

Quality management for any use of medical x-ray imaging should include monitoring of radiation dose. Fluoroscopically guided interventional (FGI) procedures are inherently clinically variable and have the potential for inducing deterministic injuries in patients. The use of a conventional diagnostic reference level is not appropriate for FGI procedures. A similar but more detailed quality process for management of radiation dose in FGI procedures is described.

METHODS

A method that takes into account both the inherent variability of FGI procedures and the risk of deterministic injuries from these procedures is suggested. The substantial radiation dose level (SRDL) is an absolute action level (with regard to patient follow-up) below which skin injury is highly unlikely and above which skin injury is possible. The quality process for FGI procedures collects data from all instances of a given procedure from a number of facilities into an advisory data set (ADS). An individual facility collects a facility data set (FDS) comprised of all instances of the same procedure at that facility. The individual FDS is then compared to the multifacility ADS with regard to the overall shape of the dose distributions and the percent of instances in both the ADS and the FDS that exceed the SRDL.

RESULTS

Samples of an ADS and FDS for percutaneous coronary intervention, using the dose metric of reference air kerma (K(a,r)) (i.e., the cumulative air kerma at the reference point), are used to illustrate the proposed quality process for FGI procedures. Investigation is warranted whenever the FDS is noticeably different from the ADS for the specific FGI procedure and particularly in two circumstances: (1) When the facility's local median K(a,r) exceeds the 75th percentile of the ADS and (2) when the percent of instances where K(a,r) exceeds the facility-selected SRDL is greater for the FDS than for the ADS.

CONCLUSIONS

Analysis of the two data sets (ADS and FDS) and of the percent of instances that exceed the SRDL provides a means for the facility to better manage radiation dose (and therefore both deterministic and stochastic radiation risk) to the patient during FGI procedures.

Clinical radiation management for fluoroscopically guided interventional procedures

The primary goal of radiation management in interventional radiology is to minimize the unnecessary use of radiation. Clinical radiation management minimizes radiation risk to the patient without increasing other risks, such as procedural risks. A number of factors are considered when estimating the likelihood and severity of patient radiation effects. These include demographic factors, medical history factors, and procedure factors. Important aspects of the patient's medical history include coexisting diseases and genetic factors, medication use, radiation history, and pregnancy. As appropriate, these are evaluated as part of the preprocedure patient evaluation; radiation risk to the patient is considered along with other procedural risks. Dose optimization is possible through appropriate use of the basic features of interventional fluoroscopic equipment and intelligent use of dose-reducing technology. For all fluoroscopically guided interventional procedures, it is good practice to monitor radiation dose throughout the procedure and record it in the patient's medical record. Patients who have received a clinically significant radiation dose should be followed up after the procedure for possible deterministic effects. The authors recommend including radiation management as part of the departmental quality assurance program.

Proposed local diagnostic reference levels in angiography and interventional neuroradiology and a preliminary analysis according to the complexity of the procedures

The aim of this study was to propose local diagnostic reference levels (DRL) for exposure to radiation during diagnostic procedures and neuroradiological interventions such as cerebral angiography and embolisation of cerebral aneurysms (intra-cranial aneurysms and arteriovenous malformations). Hospitals should adopt the national DRLs for use locally or establish their own DRLs based on local practice, if sufficient local data are available. For this purpose we studied a sample of 113 cerebral angiography procedures and 82 embolisations of cerebral aneurysms. The data recorded included the kerma-area product (KAP), the fluoroscopy time and the number of frames for each procedure: third quartiles from the total dosimetric databank were calculated and proposed as provisional local DRL. Since the complexity of a procedure must be taken into account when evaluating the radiation dose, in the case of embolisation of aneurysms (intra-cranial), in this initial phase we assessed whether the complexity of the embolisation procedure is related to the size of the aneurysm and/or its site. We, therefore, re-calculated the DRL for only intra-cranial aneurysms, leaving aside the arteriovenous malformations. Considering that the DRL calculated for all the therapeutic procedures are similar to those calculated considering only intra-cranial aneurysms, at the moment we propose, besides the DRL for cerebral angiography, a single DRL for all interventional procedures, even when the clinical pictures are very different. Local preliminary DRLs were proposed as follows: 180 Gy cm(2), 12 min and 317 frames for cerebral angiography and 487 Gy cm(2), 46 min and 717 frames for interventional procedures (intra-cranial aneurysms and arteriovenous malformations).

Can computer-assisted surgery reduce the effective dose for spinal fusion and sacroiliac screw insertion?

BACKGROUND

The increasing use of fluoroscopy-based surgical procedures and the associated exposure to radiation raise questions regarding potential risks for patients and operating room personnel. Computer-assisted technologies can help to reduce the emission of radiation; the effect on the patient's dose for the three-dimensional (3-D)-based technologies has not yet been evaluated.

QUESTIONS/PURPOSES

We determined the effective and organ dose in dorsal spinal fusion and percutaneous transsacral screw stabilization during conventional fluoroscopy-assisted and computer-navigated procedures.

PATIENTS AND METHODS

We recorded the dose and duration of radiation from fluoroscopy in 20 patients, with single vertebra fractures of the lumbar spine, who underwent posterior stabilization with and without the use of a navigation system and 20 patients with navigated percutaneous transsacral screw stabilization for sacroiliac joint injuries. For the conventional iliosacral joint operations, the duration of radiation was estimated retrospectively in two cases and further determined from the literature. Dose measurements were performed with a male phantom; the phantom was equipped with thermoluminescence dosimeters.

RESULTS

The effective dose in conventional spine surgery using 2-D fluoroscopy was more than 12-fold greater than in navigated operations. For the sacroiliac joint, the effective dose was nearly fivefold greater for nonnavigated operations.

CONCLUSION

Compared with conventional fluoroscopy, the patient's effective dose can be reduced by 3-D computer-assisted spinal and pelvic surgery.

LEVEL OF EVIDENCE

Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.