Neurointerventions in children: radiation exposure and its import

Diagnostic reference levels in interventional neuroradiology procedures - a systematic review

INTRODUCTION

The establishment of diagnostic reference levels (DRLs) is challenge for interventional neuroradiology (INR) due to the complexity and variability of its procedures.

OBJECTIVE

The main objective of this systematic review is to analyse and compare DRLs in fluoroscopy-guided procedures in INR.

METHODS

An observational study reporting DRLs in INR procedures, specifically cerebral arteriography, cerebral aneurysm embolisation, cerebral thrombectomy, embolisation of arteriovenous malformations (AVM), arteriovenous fistulas (AVF), retinoblastoma embolisation, and spinal cord arteriography. Comprehensive literature searches for relevant studies published between 2017 and 2023 were conducted using the Scopus, PubMed, and Web of Science databases.

RESULTS

A total of 303 articles were identified through an extensive literature search, with 159 removed due to duplication. The title and abstract of 144 studies were assessed and excluded if they did not meet the inclusion criteria. Thirty-one out of the 144 articles were selected for a thorough full-text screening. Twenty-one articles were included in the review after the complete text screening.

CONCLUSION

The different conditions of patients undergoing INR procedures pose a barrier to the standardization of DRLs; nevertheless, they are extremely important for monitoring and optimising radiological practices.

Management of Pediatric Intracranial Arteriovenous Malformations

Pediatric intracranial arteriovenous malformations (AVMs) are challenging lesions managed by pediatric neurosurgeons. The high risk of hemorrhage and neurologic injury is compounded by the unique anatomy of each malformation that requires individualizing treatment options. This article reviews the current status of pediatric AVM epidemiology, pathophysiology and clinical care, with a specific focus on the rationale and methodology of surgical resection.

Optimization of Radiation Protection in Pediatric Interventional Radiology in Latin America and the Caribbean: Development, Advancements, Challenges and Achievements of the OPRIPALC Program

This article presents the development, advancements, challenges and achievements of the "Optimization of Protection in Pediatric Interventional Radiology in Latin America and the Caribbean" (OPRIPALC) program. This international initiative is led by the World Health Organization, the Pan American Health Organization and the International Atomic Energy Agency. The main objectives of OPRIPALC are to foster a culture of radiological protection in pediatric interventions, enhance these procedures' quality, and define optimization strategies such as the use of diagnostic reference levels (DRLs). Currently, 33 centers from 12 countries participate actively in the program. Significant progress has been made towards the proposed objectives, overcoming the challenges posed by the COVID-19 pandemic. Through many virtual meetings for coordination, planning, training and follow-up, a comprehensive set of DRLs for both diagnostic and therapeutic procedures, categorized by weight and age, have been established and are in use. A consensus document on good practices is in the final stage of development. The program's continuation into at least a second phase is essential to address pending issues, including the integration of automatic dose management systems, the levels of occupational radiation doses, their correlation with pediatric patient doses, and strategies to reduce them.

Magnetic Resonance Imaging/Angiography Versus Catheter Angiography for Annual Follow-up of Pediatric Moyamoya Patients: A Cost Outcomes Analysis

BACKGROUND

Digital subtraction angiography (DSA) assesses revascularization in pediatric moyamoya patients after surgery, but MRI and angiography (MRI/A) may provide comparable data.

OBJECTIVE

To evaluate DSA and MRI/A with respect to clinical utility in postoperative follow-up, complication profile, and relative cost at 1 year.

METHODS

All pediatric moyamoya patients who received bilateral indirect revascularization between 2011 and 2020 were retrospectively reviewed at 1 institution. Patients who underwent MRI/A-only, DSA-only, or both after 1 year were compared.

RESULTS

Eighty-two patients were included. At 1 year, patients who underwent either MRI/A (n = 29) or DSA (n = 40) had no significant differences in detection rate of new at-risk hypovascular territories (6.9% vs 2.5%, P = .568) or need for subsequent revascularization beyond the mean 40 ± 24-month follow-up period (3.4% vs 5.0%, P > .9). Among patients who underwent both MRI/A and DSA (n = 13), both studies identified the same at-risk territories. No patients experienced MRI/A-related complications, compared with 3 minor DSA-related complications. The use of MRI/A yielded a 6.5-fold reduction in cost per study vs DSA at 1 year.

CONCLUSION

Using DSA to follow moyamoya patients after indirect revascularization is generally safe but associated with a low rate of minor complications and a 6.5-fold greater financial cost relative to MRI/A. These data support changing practice to eliminate the use of DSA when following routine bilateral moyamoya cases in the absence of clinical symptoms or specific concerns. Using MRI/A as the primary postoperative follow-up modality in this select population provides noninferior care and greater patient access, while reducing cost and potentially decreasing risk.

Neuromonitoring in Children with Cerebrovascular Disorders

BACKGROUND

Cerebrovascular disorders are an important cause of morbidity and mortality in children. The acute care of a child with an ischemic or hemorrhagic stroke or cerebral sinus venous thrombosis focuses on stabilizing the patient, determining the cause of the insult, and preventing secondary injury. Here, we review the use of both invasive and noninvasive neuromonitoring modalities in the care of pediatric patients with arterial ischemic stroke, nontraumatic intracranial hemorrhage, and cerebral sinus venous thrombosis.

METHODS

Narrative review of the literature on neuromonitoring in children with cerebrovascular disorders.

RESULTS

Neuroimaging, near-infrared spectroscopy, transcranial Doppler ultrasonography, continuous and quantitative electroencephalography, invasive intracranial pressure monitoring, and multimodal neuromonitoring may augment the acute care of children with cerebrovascular disorders. Neuromonitoring can play an essential role in the early identification of evolving injury in the aftermath of arterial ischemic stroke, intracranial hemorrhage, or sinus venous thrombosis, including recurrent infarction or infarct expansion, new or recurrent hemorrhage, vasospasm and delayed cerebral ischemia, status epilepticus, and intracranial hypertension, among others, and this, is turn, can facilitate real-time adjustments to treatment plans.

CONCLUSIONS

Our understanding of pediatric cerebrovascular disorders has increased dramatically over the past several years, in part due to advances in the neuromonitoring modalities that allow us to better understand these conditions. We are now poised, as a field, to take advantage of advances in neuromonitoring capabilities to determine how best to manage and treat acute cerebrovascular disorders in children.

Evolving indications for pediatric neurointerventional radiology: A single institutional 25-year experience in infants less than one year of age and a brief historical review

BACKGROUND AND PURPOSE

Pediatric neurointerventional radiology is an evolving subspecialty with growing indications and technological advancement such as miniaturization of devices and decreased radiation dose. The ability to perform these procedures is continuously balanced with necessity given the inherently higher risks of radiation and cerebrovascular injury in infants. The purpose of this study is to review our institution's neurointerventional experience in infants less than one year of age to elucidate trends in this patient population.

METHODS

We retrospectively identified 132 patients from a neurointerventional database spanning 25 years (1997-2022) who underwent 226 procedures. Treatment type, indication, and location as well as patient demographics were extracted from the medical record.

RESULTS

Neurointerventional procedures were performed as early as day of life 0 in a patient with an arteriovenous shunting malformation. Average age of intervention in the first year of life is 5.9 months. Thirty-eight of 226 procedures were completed in neonates. Intra-arterial chemotherapy (IAC) for the treatment of retinoblastoma comprised 36% of neurointerventional procedures completed in infants less than one year of age followed by low flow vascular malformations (21.2%), vein of Galen malformations (11.5%), and dural arteriovenous fistulas (AVF) (9.3%). Less frequent indications include non-Galenic pial AVF (4.4%) and tumor embolization (3.0%). The total number of interventions has increased secondary to the onset of retinoblastoma treatment in 2010 at our institution.

CONCLUSION

The introduction of IAC for the treatment of retinoblastoma in the last decade is the primary driver for the increased trend in neurointerventional procedures completed in infants from 1997 to 2022.

Neuroimaging in Pediatric Stroke

Pediatric stroke is unfortunately not a rare condition. It is associated with severe disability and mortality because of the complexity of potential clinical manifestations, and the resulting delay in seeking care and in diagnosis. Neuroimaging plays an important role in the multidisciplinary response for pediatric stroke patients. The rapid development of adult endovascular thrombectomy has created a new momentum in health professionals caring for pediatric stroke patients. Neuroimaging is critical to make decisions of identifying appropriate candidates for thrombectomy. This review article will review current neuroimaging techniques, imaging work-up strategies and special considerations in pediatric stroke. For resources limited areas, recommendation of substitute imaging approaches will be provided. Finally, promising new techniques and hypothesis-driven research protocols will be discussed.

Application of reference air kerma alert levels for pediatric fluoroscopic examinations

The purpose of this study was to provide an empirical model to develop reference air kerma (RAK) alert levels as a function of patient thickness or age for pediatric fluoroscopy for any institution to use in a Quality Assurance program. RAK and patient thickness were collected for 10&663 general fluoroscopic examinations and 1500 fluoroscopically guided interventions (FGIs). RAK and patient age were collected for 6137 fluoroscopic examinations with mobile-C-arms (MC). Coefficients of linear regression fits of logarithmic RAK as a function of patient thickness or age were generated for each fluoroscopy group. Regression fits of RAK for 50%, 90%, and 98% upper prediction levels were used as inputs to derive an empirical formula to estimate alert levels as a function of patient thickness. A methodology is presented to scale results from this study for any patient thickness or age for any institution, for example, the patient thickness dependent RAK alert level at the top 1% of expected RAK can be set using the 98% upper prediction interval boundary given by:RAK 98 % = e m . x avg + s 98 . c ̂ ${\rm{RAK}}_{98\% } = {e}^{m.{x}_{{\rm{avg}}} + {s}_{98}.\hat{c}}\ $ , where xavg is the institute's average patient thickness or age, andc ̂ $\hat{c}$ is the intercept based on the average RAK of the patient population calculated asc ̂ = ln ( RAK avg ) - m . x avg . RA K avg $\hat{c} = \ln ( {{\rm{RAK}}_{{\rm{avg}}}} )\ - m.{x}_{{\rm{avg}}}{\rm{.RA}}{{\rm{K}}}_{{\rm{avg}}}$ is the institution's average RAK (mGy). m and s98 are constants presented for each type of fluoroscope and RAK group and represent slope of the fit and scale factor, respectively. An empirical equation, which estimates alert levels expressed as air Kerma without backscatter at the interventional reference point as a function of patient thickness or age is provided for each fluoroscopic examination type. The empirical equations allow any facility with limited data to scale the results of this study's single facility data to model their practice's unique RAK alert levels and patient population demographics to establish pediatric alert levels for fluoroscopic procedures.

Cerebral Digital Subtraction Angiography in Acute Intracranial Hemorrhage: Considerations in Critically Ill Children

Cerebrovascular disorders are an important cause of morbidity and mortality in children. Although minimally invasive, cerebral digital subtraction angiography (DSA) has been shown to be safe in children and is a valuable, and perhaps underutilized, technique for the diagnosis and management of pediatric cerebrovascular disorders in the critical care setting. Through a case-based approach, we explore the utility of DSA in critically ill children with acute intracranial hemorrhage (ICH). We discuss the use of DSA in the acute management of aneurysm and arteriovenous malformation rupture as well as cerebral vasospasm. Those caring for critically ill children with acute ICH should consider cerebral DSA as part of a comprehensive approach to the diagnosis and management of these conditions.

Soft robotic steerable microcatheter for the endovascular treatment of cerebral disorders

Catheters used for endovascular navigation in interventional procedures lack dexterity at the distal tip. Neurointerventionists, in particular, encounter challenges in up to 25% of aneurysm cases largely due to the inability to steer and navigate the tip of the microcatheters through tortuous vasculature to access aneurysms. We overcome this problem with submillimeter diameter, hydraulically actuated hyperelastic polymer devices at the distal tip of microcatheters to enable active steerability. Controlled by hand, the devices offer complete 3D orientation of the tip. Using saline as a working fluid, we demonstrate guidewire-free navigation, access, and coil deployment in vivo, offering safety, ease of use, and design flexibility absent in other approaches to endovascular intervention. We demonstrate the ability of our device to navigate through vessels and to deliver embolization coils to the cerebral vessels in a live porcine model. This indicates the potential for microhydraulic soft robotics to solve difficult access and treatment problems in endovascular intervention.

Trends in endovascular interventions for pediatric ischemic stroke at the national level: data from 2000 to 2009

PURPOSE

Present knowledge is limited with regard to endovascular and interventional management of pediatric acute ischemic stroke (AIS). The current practice of neurointerventions in this population was analyzed via a national database.

METHODS

The Kids' Inpatient Database for years 2000, 2003, 2006, and 2009 was examined for patients aged < 18 years discharged with a primary diagnosis of AIS and identified according to ICD-9 codes. Descriptive statistics were tabulated on each of the subcohorts.

RESULTS

There were 3467 patients identified; 920 (26.5%) underwent angiograms, 51 (1.5%) angiogram + thrombolysis, and 18 (0.5%) received angiogram + endovascular recanalization. The angiogram only subcohort was significantly younger compared with thrombolysis and endovascular procedure subcohorts (9.8 vs. 12.2 vs. 14.9 years, P < 0.001). Mortality was 4.3%, significantly lower for angiogram only than for thrombolysis (1.1% vs. 18.2%, P < 0.0001). Thrombolysis also had significantly higher hospital charges ($149,045 vs. $64,826, P < 0.0001). While not many differences in outcomes between angiogram only versus endovascular procedures, the latter had higher financial burden ($122,482 vs. $64,826, P < 0.0001).

CONCLUSIONS

This national study suggests that children receiving neurointerventions tend to be older (> 12 years) and heart and valvular defects are their most likely comorbidities. There was a lower mortality and fewer complications with endovascular procedures when compared with intravenous/intraarterial thrombolysis alone. Thrombolysis was also associated with more non-routine discharges and lengthier stay.

Estimation of radiation exposure of children undergoing superselective intra-arterial chemotherapy for retinoblastoma treatment: assessment of local diagnostic reference levels as a function of age, sex, and interventional success

PURPOSE

This study aims to determine local diagnostic reference levels (LDRLs) of intra-arterial chemotherapy (IAC) procedures of pediatric patients with retinoblastoma (RB) to provide data for establishing diagnostic reference levels (DRLs) in pediatric interventional radiology (IR).

METHODS

In a retrospective study design, LDRLs and achievable dose (AD) were assessed for children undergoing superselective IAC for RB treatment. All procedures were performed at the flat-panel angiography systems (I) ArtisQ biplane (Siemens Healthineers) and (II) Allura Xper (Philips Healthcare). Patients were differentiated according to age (A1: 1-3 months; A2: 4-12 months; A3: 13-72 months; A4: 73 months-10 years; A5: > 10 years), sex, conducted or not-conducted chemotherapy.

RESULTS

248 neurointerventional procedures of 130 pediatric patients (median age 14.5 months, range 5-127 months) with RB (68 unilateral, 62 bilateral) could be included between January 2010 and March 2020. The following diagnostic reference values, AD, and mean values could be determined: (A2) DRL 3.9 Gy cm², AD 2.9 Gy cm², mean 3.5 Gy cm²; (A3) DRL 7.0 Gy cm², AD 4.3 Gy cm², mean 6.0 Gy cm²; (A4) DRL 14.5 Gy cm², AD 10.7 Gy cm², mean 10.8 Gy cm²; (A5) AD 8.8 Gy cm², mean 8.8 Gy cm². Kruskal-Wallis-test confirmed a significant dose difference between the examined age groups (A2-A5) (p < 0.001). There was no statistical difference considering sex (p = 0.076) and conducted or not-conducted chemotherapy (p = 0.627). A successful procedure was achieved in 207/248 cases.

CONCLUSION

We report on radiation exposure during superselective IAC of a pediatric cohort at the German Retinoblastoma Referral Centre. Although an IAC formally represents a therapeutic procedure, our results confirm that radiation exposure lies within the exposure of a diagnostic interventional procedure. DRLs for superselective IAC are substantially lower compared with DRLs of more complex endovascular interventions.

Neuroimaging of Pediatric Intracerebral Hemorrhage

Hemorrhagic strokes account for half of all strokes seen in children, and the etiologies of these hemorrhagic strokes differ greatly from those seen in adult patients. This review gives an overview about incidence and etiologies as well as presentation of children with intracerebral hemorrhage and with differential diagnoses in the emergency department. Most importantly it describes how neuroimaging of children with intracerebral hemorrhage should be tailored to specific situations and clinical contexts and recommends specific imaging protocols for acute and repeat imaging. In this context it is important to keep in mind the high prevalence of underlying vascular lesions and adapt the imaging protocol accordingly, meaning that vascular imaging plays a key role regardless of modality. Magnetic resonance imaging (MRI), including advanced sequences, should be favored whenever possible at the acute phase.

Eye lens radiation exposure in paediatric interventional treatment of retinoblastoma

Retinoblastoma represents 3% of cancers in children under fifteen years of age. The standard paediatric treatment for saving the affected eye is supraselective intra-arterial chemotherapy performed in interventional rooms. In order to address the radiation toxicity due to the angiography, the aim of this study was to determine the typical dose value corresponding to the procedure, estimate the paediatric patients' eye lens dose and study the relationship between dose indicators and dose to the lens. An automatic dose management software was installed in two interventional rooms to obtain the distribution of the dose indicators kerma-area product and reference-point air kerma, getting a typical value 16 Gy·cm2 and 130 mGy, respectively (n = 35). The eye lens dose estimates were obtained with photoluminescent dosimeters placed on the patient's eyelids. In the left eye, the entrance surface air kerma was 44.23 ± 2.66 mGy, and 12.72 ± 0.89 mGy in the right eye (n = 10). There was a positive correlation between dose to the lens per procedure and dose indicators, with R2 > 0.65 for both eyes. Based on this information, the threshold for the onset of radiation-induce cataracts (500 mGy) will be exceeded if the treatment is performed for more than 8 sessions.

Quantitative color-coded digital subtraction neuroangiography for pediatric arteriovenous shunting lesions

BACKGROUND

Several complex pediatric neurovascular conditions are amenable to endovascular treatment. Given the unique anatomical and physiological challenges in children, there is an ongoing need for tools and techniques that provide accurate information for treatment planning, while minimizing exposure to ionizing radiation and contrast. This is more so for neonates and infants with high-flow arteriovenous (AV) shunts that are challenging to assess using conventional techniques.

OBJECTIVE

In this brief report, we describe, through representative cases, the potential role of quantitative color-coded digital subtraction angiography (qDSA) in neuroendovascular procedures in children with high-flow AV shunting lesions.

METHODS

Images were obtained using an ArtisQ biplane system (Siemens Healthineers, Erlangen, Germany). Post-processing was performed at a dedicated workstation (Syngo, Siemens) using the iFlow module to generate color-coded maps of individual digital subtraction angiography runs.

CONCLUSION

Color-coded qDSA provides real-time quantitative information in high-flow AV shunting neurovascular lesions. This can potentially help direct treatment choices, optimize endovascular treatment protocols, monitor outcomes, and determine treatment end points.

The Risk of Developing Secondary Central Nervous System Tumors After Diagnostic Irradiation From Computed Tomography in Pediatrics: A Literature Review

BACKGROUND

Advanced diagnostic imaging has provided tremendous benefits; however, increased use of ionizing radiation modalities such as cranial computed tomography (CT) may be associated with an increased risk of developing central nervous system tumors.

METHODS

A literature review identified studies published for more than the last 50 years from 1968 to 2018 that explored the association between head CT scans and developing central nervous system tumors in pediatrics. We reviewed seven studies that described and analyzed the risk of brain tumors.

RESULTS

A positive correlation between exposure to CT scans and developing central nervous system tumors was evident in all cohorts. The strength of the association varied across the studies. Exclusion of patients with predisposing factors to central nervous system tumors was examined in four studies with a decreased risk to develop central nervous system tumors noted in three studies. Two studies reported nonsignificant reduction in the excess relative risk per milliGray of brain dose after adjusting for predisposing factors, whereas the reduction was significant in one study. The frequency of CT exposure was proportional to the risk of developing tumors in two studies although not significantly maintained in two other studies. Gender had no significant effect on the central nervous system tumor risk. The calendar year at the time of imaging showed decreasing risk in those exposed to CT in more recent years compared with prior decades.

CONCLUSIONS

Prospective epidemiologic studies are needed to examine the precise carcinogenic effect of exposure to ionizing radiation and help tailor further preventive measures.

What is the best therapeutic approach to a pediatric patient with a deep-seated brain AVM?

Although brain arteriovenous malformations (bAVMs) account for a very small proportion of cerebral pathologies in the pediatric population, they are the cause of roughly 50% of spontaneous intracranial hemorrhages. Pediatric bAVMs tend to rupture more frequently and seem to have higher recurrence rates than bAVMs in adults. Thus, the management of pediatric bAVMs is particularly challenging. In general, the treatment options are conservative treatment, microsurgery, endovascular therapy (EVT), gamma knife radiosurgery (GKRS), proton-beam stereotactic radiosurgery (PSRS), or a combination of the above. In order to identify the best approach to deep-seated pediatric bAVMs, we performed a systematic review, according to the PRISMA guidelines. None of the options seem to offer a clear advantage over the others when used alone. Microsurgery provides the highest obliteration rate, but has higher incidence of neurological complications. EVT may play a role when used as adjuvant therapy, but as a stand-alone therapy, the efficacy is low and the long-term side effects of radiation from the multiple sessions required in deep-seated pediatric bAVMs are still unknown. GKRS has a low risk of complication, but the obliteration rates still leave much to be desired. Finally, PSRS offers promising results with a more accurate radiation that avoids the surrounding tissue, but data is limited due to its recent introduction. Overall, a multi-modal approach, or even an active surveillance, might be the most suitable when facing deep-seated bAVM, considering the difficulty of their management and the high risk of complications in the pediatric population.

Risk of Radiation-Induced Cancer From Computed Tomography Angiography Use in Imaging Surveillance for Unruptured Cerebral Aneurysms

Background and Purpose- Although computed tomography angiography (CTA) is an excellent, noninvasive imaging modality for surveillance of intracranial aneurysms, radiation concerns have been cited to restrict its use in surveillance imaging. The goal of this study was to estimate distributions of radiation-induced central nervous system cancer incidence from CTA surveillance for intracranial aneurysms, and the impact of frequency and duration of surveillance imaging using follow-up CTAs. Methods- Simulation-modeling approach was performed using data on CTA associated radiation risk. We used the Radiation Risk Assessment Tool, based on the data using the BEIR VII report (BEIR VII). Each CTA was assigned as a separate exposure event. Men and women, respectively, starting surveillance imaging at 30, 40, and 50 years and receiving annual CTAs were considered as separate subgroups. As a comparison, we also calculated the radiation-induced cancer risk in the same groups of patients but receiving CTAs every 2 and 5 years, respectively. Results- CTA-associated excess cancer risk per exposure increases relatively more rapidly with the first 10 exposures and plateaus after the 44th exposure. On average, per CTA incurs ≈0.0026% in excess lifetime cancer risk. Receiving CTA follow-up at a younger age, more frequent follow-up, longer surveillance period, and men are the major factors contributing to an elevated excess lifetime risk. In the highest risk group, male patient receiving annual CTA follow-ups from the age of 30 years, the excess lifetime risk is 0.115% at the age of 81 years. Conclusions- Radiation-induced brain cancer incidence associated with unruptured intracranial aneurysm surveillance strategies using CTA is low relative to the risk for aneurysmal rupture. Further cost-effectiveness/utility analyses might help assess this risk in the context of aneurysmal ruptures prevented by surveillance imaging.

Impact of low dose settings on radiation exposure during pediatric fluoroscopic guided interventions

PURPOSE

To evaluate the effects of lowering the detector entrance exposure in children undergoing interventional radiology procedures.

MATERIALS AND METHODS

The study retrospectively investigated radiation dose levels in pediatric patients aged 0-18 years before (n = 39) and after (n = 26) lowering detector entrance dose, undergoing embolization of peripheral Arteriovenous malformations, Portal Vein Interventions or Percutaneous Transhepatic Cholangio Drainage (PTCD) between 2014 and 2017. Patient characteristics, fluoroscopy time, protocols used as well as resulting Skin Dose and Dose Area Product (DAP) were compared in each cohort. Image quality was assessed by two independent readers.

RESULTS

The two patient cohorts did not differ in terms of patient demographics. Similarly, fluoroscopy time did not differ before and after implementation of the low dose settings. An overall reduction of skin dose of 75.1% for AVM embolizations, 80.5% for Portal Vein Interventions and 85.3% for PTCD placement was observed. The DAP decrease was 82.5% for AVM embolizations, 72.2% for Portal Vein Interventions and 79.8% for PTCD placement. Image quality was generally considered to be good with an insignificant difference between pre and post implementation of the low dose approach and good agreement between the two readers. Manual inroom-switching to higher dose levels was possible, however this was not performed more frequently after implementation of the low dose settings.

CONCLUSION

Lowering the detector entrance dose in pediatric interventional radiology procedures results in a significant decrease of the radiation dose burden.

Radiation Dosimetry of 3D Rotational Neuroangiography and 2D-DSA in Children

BACKGROUND AND PURPOSE

The benefit-risk assessment concerning radiation use in pediatric neuroangiography requires an extensive understanding of the doses delivered. This work evaluated the effective dose of 3D rotational angiography in a cohort of pediatric patients with complex neurovascular lesions and directly compared it with conventional 2D-biplane DSA.

MATERIALS AND METHODS

Thirty-three 3D rotational angiography acquisitions were acquired in 24 pediatric patients (mean age, 10.4 years). When clinically indicated, following 2D-biplane DSA, 3D rotational angiography was performed with 1 of 3 technical protocols (2 subtracted, 1 unsubtracted). The protocols consisted of 1 factory and 2 customized techniques, with images subsequently reconstructed into CT volumes for clinical management. Raw projections and quantitative dose metrics were evaluated, and the effective dose was calculated.

RESULTS

All 3D rotational angiography acquisitions were of diagnostic quality and assisted in patient management. The mean effective doses were 0.5, 0.12, and 0.06 mSv for the factory-subtracted, customized-subtracted, and customized-unsubtracted protocols, respectively. The mean effective dose for 2D-biplane DSA was 0.9 mSv. A direct intraprocedural comparison between 3D and 2D acquisitions indicated that customized 3D rotational angiography protocols delivered mean relative doses of 9% and 15% in unsubtracted and subtracted acquisitions, respectively, compared with biplane DSA, whereas the factory subtracted protocol delivered 68%.

CONCLUSIONS

In pediatric neuroangiography, the effective dose for 3D rotational angiography can be significantly lower than for 2D-biplane DSA and can be an essential adjunct in the evaluation of neurovascular lesions. Additionally, available 3D rotational angiography protocols have significant room to be tailored for effectiveness and dose optimization, depending on the clinical question.

The Patient Size Setting: A Novel Dose Reduction Strategy in Cerebral Endovascular Neurosurgery Using Biplane Fluoroscopy

BACKGROUND

In some fluoroscopy machines, the dose-rate output of the fluoroscope is tied to a selectable patient size. Although patient size may play a significant role in visceral or cardiac procedures, head morphology is less variable, and high dose outputs may not be necessary even in very obese patients. We hypothesized that very small patient size setting can be used to reduce dose for cerebral angiography without compromising image quality.

METHODS

Patients who underwent endovascular neurosurgical procedures during the 2015-2016 academic year were identified, and estimated procedural air kerma (AK) was tabulated retrospectively. Technologists were instructed to begin using the very small patient size setting for all procedures performed using our Philips Allura Xper FD20 biplane fluoroscopy system beginning in March 2016. No changes were made in a second procedure room using a Toshiba Infinix system. Student t tests and logistic regression models were used to compare radiation exposure before and after March 1, 2016, for both machines.

RESULTS

For diagnostic cerebral angiograms performed on the Philips system (n = 302), AK was reduced by approximately 17% (1277 vs. 1061 mGy; P = 0.0006.) Changes in table height, total fluoroscopy time, patient weight, and body mass index did not contribute to this difference. No significant change was seen in total AK using the Toshiba system (n = 237). Blinded review by a neuroradiologist did not demonstrate any change in image quality.

CONCLUSIONS

Using the very small patient size reduces fluoroscopy dose by 17% for cerebral angiography without impacting image quality.

The technique of superselective ophthalmic artery chemotherapy for retinoblastoma: The Garrahan Hospital experience

Background Superselective ophthalmic artery chemotherapy (SOAC) is a proven therapy for the treatment of retinoblastomas. We describe the technique, results and complications of SOAC performed in our hospital. Objective The aim of this article is to demonstrate that a seemingly complex technique can be carried out with a low morbidity rate. Methods A retrospective analysis of patients receiving SOAC in our department from November 2014 to April 2017 was performed. Data collected were age, gender, number of procedures, arteries approached, bilaterality of treatment, and complications. The procedure was performed using a 3F sheath and a flow-dependent 1.5F microcatheter that was navigated from the femoral artery to the ostium of the ophthalmic artery (OA). When the OA was too small or a stable position could not be achieved, the microcatheter was navigated in the external carotid artery to reach an anastomotic ramus (AR) of the middle meningeal artery (MMA) to the OA. The drugs were then injected through the microcatheter in a pulsatile way. Results Forty-one patients underwent SOAC. A total of 248 procedures were performed in 45 eyes, and 248 arteries were approached (205 OAs and 43 MMAs). Four patients underwent tandem therapy (both eyes treated in the same procedure). Complications were: hypotension and bradycardia during the procedure (five cases), transient thrombosis of the femoral artery (two cases), retinal hemorrhage (one case), alopecia (one case), and anaphylactic shock to carboplatin (one case). No patient showed adverse effects of radiation or ischemic stroke. Conclusion SOAC is a safe technique with a very low complication rate.

Radiation reduction of minimally invasive transforaminal lumbar interbody fusion with localisation system in overweight patients: practical technique

AIMS

Minimally invasive transforaminal lumbar interbody fusion (MITLIF) has been well validated in overweight and obese patients who are consequently subject to a higher radiation exposure. This prospective multicentre study aimed to investigate the efficacy of a novel lumbar localisation system for MITLIF in overweight patients.

PATIENTS AND METHODS

The initial study group consisted of 175 patients. After excluding 49 patients for various reasons, 126 patients were divided into two groups. Those in Group A were treated using the localisation system while those in Group B were treated by conventional means. The primary outcomes were the effective radiation dosage to the surgeon and the exposure time.

RESULTS

There were 62 patients in Group A and 64 in Group B. The mean effective dosage was 0.0217 mSv (standard deviation (sd) 0.0079) in Group A and 0.0383 mSv (sd 0.0104) in Group B (p < 0.001). The mean fluoroscopy exposure time was 26.42 seconds (sd 5.91) in Group A and 40.67 seconds (sd 8.18) in Group B (p < 0.001). The operating time was 175.56 minutes (sd 32.23) and 206.08 minutes (sd 30.15) (p < 0.001), respectively. The mean pre-operative localisation time was 4.73 minutes (sd 0.84) in Group A and 7.03 minutes (sd 1.51) in Group B (p < 0.001). The mean screw placement time was 47.37 minutes (sd 10.43) in Group A and 67.86 minutes (sd 14.15) in Group B (p < 0.001). The pedicle screw violation rate was 0.35% (one out of 283) in Group A and 2.79% (eight out of 287) in Group B (p = 0.020).

CONCLUSION

The study shows that the localisation system can effectively reduce radiation exposure, exposure time, operating time, pre-operative localisation time, and screw placement time in overweight patients undergoing MITLIF. Cite this article: Bone Joint J 2017;99-B:944-50.

Radiation Dose Reduction without Compromise to Image Quality by Alterations of Filtration and Focal Spot Size in Cerebral Angiography

Objective

Different angiographic protocols may influence the radiation dose and image quality. In this study, we aimed to investigate the effects of filtration and focal spot size on radiation dose and image quality for diagnostic cerebral angiography using an in-vitro model and in-vivo patient groups.

Materials and Methods

Radiation dose and image quality were analyzed by varying the filtration and focal spot size on digital subtraction angiography exposure protocols (1, inherent filtration + large focus; 2, inherent + small; 3, copper + large; 4, copper + small). For the in-vitro analysis, a phantom was used for comparison of radiation dose. For the in-vivo analysis, bilateral paired injections, and patient cohort groups were compared for radiation dose and image quality. Image quality analysis was performed in terms of contrast, sharpness, noise, and overall quality.

Results

In the in-vitro analysis, the mean air kerma (AK) and dose area product (DAP)/frame were significantly lower with added copper filtration (protocols 3 and 4). In the in-vivo bilateral paired injections, AK and DAP/frame were significantly lower with filtration, without significant difference in image quality. The patient cohort groups with added filtration (protocols 3 and 4) showed significant reduction of total AK and DAP/patient without compromise to the image quality. Variations in focal spot size showed no significant differences in radiation dose and image quality.

Conclusion

Addition of filtration for angiographic exposure studies can result in significant total radiation dose reduction without loss of image quality. Focal spot size does not influence radiation dose and image quality. The routine angiographic protocol should be judiciously investigated and implemented.

Ionizing Radiation-Induced Immune and Inflammatory Reactions in the Brain

Radiation-induced late brain injury consisting of vascular abnormalities, demyelination, white matter necrosis, and cognitive impairment has been described in patients subjected to cranial radiotherapy for brain tumors. Accumulating evidence suggests that various degrees of cognitive deficit can develop after much lower doses of ionizing radiation, as well. The pathophysiological mechanisms underlying these alterations are not elucidated so far. A permanent deficit in neurogenesis, chronic microvascular alterations, and blood–brain barrier dysfunctionality are considered among the main causative factors. Chronic neuroinflammation and altered immune reactions in the brain, which are inherent complications of brain irradiation, have also been directly implicated in the development of cognitive decline after radiation. This review aims to give a comprehensive overview on radiation-induced immune alterations and inflammatory reactions in the brain and summarizes how these processes can influence cognitive performance. The available data on the risk of low-dose radiation exposure in the development of cognitive impairment and the underlying mechanisms are also discussed.

Radiation dose associated with CT-guided drain placement for pediatric patients

BACKGROUND

To date, there are limited radiation dose data on CT-guided procedures in pediatric patients.

OBJECTIVE

Our goal was to quantify the radiation dose associated with pediatric CT-guided drain placement and follow-up drain evaluations in order to estimate effective dose.

MATERIALS AND METHODS

We searched the electronic medical record and picture archiving and communication system (PACS) to identify all pediatric (<18 years old) CT-guided drain placements performed between January 2008 and December 2013 at our institution. We compiled patient data and radiation dose information from CT-guided drain placements as well as pre-procedural diagnostic CTs and post-procedural follow-up fluoroscopic abscess catheter injections (sinograms). Then we converted dose-length product, fluoroscopy time and number of acquisitions to effective doses using Monte Carlo simulations and age-appropriate conversion factors based on annual quality-control testing.

RESULTS

Fifty-two drainages were identified with mean patient age of 11.0 years (5 weeks to 17 years). Most children had diagnoses of appendicitis (n=23) or inflammatory bowel disease (n=11). Forty-seven patients had diagnostic CTs, with a mean effective dose of 7.3 mSv (range 1.1-25.5 mSv). Drains remained in place for an average of 16.9 days (range 0-75 days), with an average of 0.9 (0-5) sinograms per patient in follow-up. The mean effective dose for all drainages and follow-up exams was 5.3 mSv (0.7-17.1) and 62% (32/52) of the children had effective doses less than 5 mSv.

CONCLUSION

The majority of pediatric patients who have undergone CT-guided drain placements at our institution have received total radiation doses on par with diagnostic ranges. This information could be useful when describing the dose of radiation to parents and providers when CT-guided drain placement is necessary.

The Efficacy of Shielding Systems for Reducing Operator Exposure during Neurointerventional Procedures: A Real-World Prospective Study

BACKGROUND AND PURPOSE

Neurointerventional surgery may expose patients and physician operators to substantial amounts of ionizing radiation. Although strategies for reducing patient exposure have been explored in the medical literature, there has been relatively little published in regards to decreasing operator exposure. The purpose of this study was to evaluate the efficacy of shielding systems in reducing physician exposure in a modern neurointerventional practice.

MATERIALS AND METHODS

Informed consent was obtained from operators for this Health Insurance Portability and Accountability Act-compliant, institutional review board-approved study. Operator radiation exposure was prospectively measured during 60 consecutive neurointerventional procedures from October to November 2013 using a 3-part lead shielding system. Exposure was then evaluated without lead shielding in a second 60-procedure block from April to May 2014. A radiation protection drape was randomly selected for use in half of the cases in each block. Two-way analysis of covariance was performed to test the effect of shielding systems on operator exposure while controlling for other covariates, including procedure dose-area product.

RESULTS

Mean operator procedure dose was 20.6 μSv for the entire cohort and 17.7 μSv when using some type of shielding. Operator exposure significantly correlated with procedure dose-area product, but not with other covariates. After we adjusted for procedure dose-area product, the use of lead shielding or a radiation protection drape significantly reduced operator exposure by 45% (F = 12.54, P < .0001) and 29% (F = 7.02, P = .009), respectively. The difference in protection afforded by these systems was not statistically significant (P = .46), and their adjunctive use did not provide additional protection.

CONCLUSIONS

Extensive lead shielding should be used as much as possible in neurointerventional surgery to reduce operator radiation exposure to acceptable levels. A radiation protection drape is a reasonable alternative when standard lead shielding is unavailable or impractical to use without neglecting strategies to minimize the dose.

Patient radiation doses and reference levels in pediatric interventional radiology

OBJECTIVES

To describe, in a multicentric paediatric population, reference levels (RLs) for three interventional radiological procedures.

METHODS

From January 2012 to March 2015, children scheduled for an interventional radiological procedure in two French tertiary centres were retrospectively included and divided into four groups according to age: children younger than 2 years (A1), aged 2-7 years (A5), 8-12 years (A10) and 13-18 years (A15). Three procedures were identified: cerebral digital subtraction angiography (DSA), brain arteriovenous malformation (bAVM) embolization, and head and neck superficial vascular malformation (SVM) percutaneous sclerotherapy. Demographic and dosimetric data, including dose area product (DAP), were collected.

RESULTS

550 procedures were included. For DSA (162 procedures), the proposed RL values in DAP were 4, 18, 12 and 32 Gy∙cm² in groups A1, A5, A10 and A15, respectively. For bAVM embolization (258 procedures), values were 33, 70, 105 and 88 Gy∙cm² in groups A1, A5, A10 and A15, respectively. For SVM sclerotherapy (130 procedures), values were 350, 790, 490 and 248 mGy∙cm² in groups A1, A5, A10 and A15, respectively.

CONCLUSION

Consecutive data were available to permit a proposal of reference levels for three major paediatric interventional radiology procedures.

KEY POINTS

• We determined reference levels (RLs) for bAVM embolization, DSA and SVM sclerotherapy. • The proposed RLs will permit benchmarking practice with an external standard. • The proposed RLs by age may help to develop paediatric dose guidelines.

Blunt cerebrovascular injury in children

Blunt cerebrovascular injury in children is an uncommon occurrence that if missed and left untreated can result in devastating long-term neurologic consequences. Diagnosis can be readily obtained by a computed tomographic angiogram of the head and neck. If confirmed, treatment with antithrombotic therapy dramatically reduces the risk of a cerebrovascular accident. The difficulty lies in determining which child should be screened for such an injury. Several institutions have come up with criteria for screening. In this article, we review the nuances of the cerebrovascular system and its resulting injury. We present recent literature on the subject in an attempt to add clarity to this challenging situation.

Selective ophthalmic artery chemosurgery (SOAC) for retinoblastoma: fluoroscopic time and radiation dose parameters. A baseline study

OBJECTIVE

To evaluate fluoroscopic time and radiation dose parameters, and factors affecting these parameters, during selective ophthalmic artery chemosurgery (SOAC) for retinoblastoma.

MATERIALS AND METHODS

Retrospective review from the prospective database of all patients with retinoblastoma treated with SOAC over a 5-year period (September 2009-January 2015) at a single institution after receiving institutional review board approval. Patient demographics, arterial approach, access device, side of treatment, number of SOAC cycles/patient, number of drugs/SOAC, and radiation parameters (outcome variables), including the fluoroscopic time, dose-area product (DAP), and total radiation dose, were obtained from the database. Generalized linear regression was used for univariate and multivariate analysis of the outcome variables.

RESULTS

In 218 patients (M:F=94:124), 272 eyes were treated by 833 SOAC infusions during 792 procedures. Mean age, weight, SOAC cycle/patient, and drugs/cycle were 19±19.5 months, 11.4±6.4 kg, 2.72±1.6, and 2.48±0.8, respectively. Mean fluoroscopic time, DAP, and doses were 10.2±8.4 min, 218.7±240.8 cGy.cm², and 42.3±41.4 mGy, respectively. Radiation parameters (fluoroscopic time, DAP, and dose) were significantly lower (p<0.001) for the ophthalmic artery (OA) approach (7.5±5.4; 147.7±138.4; 28.5±29.4) than with middle meningeal artery (13.4±5.6; 242±138; 51.4±27) and balloon-assisted infusion in the internal carotid artery (ICA; 17.8±11.5; 449.8±361; 81.8±63.3). Radiation parameters for microcatheter access (8.6±7.1; 193.4±181.3; 42.3±37) were significantly lower (p<0.001) than with the ICA (17.8±11.5; 449.8±361; 81.8±63.3). Radiation parameters for bilateral IA chemotherapy (IAC; 16.8±11.6; 320.7±268.7; 60.8±45.6) were significantly higher (p<0.001) than for unilateral IAC (8.9±6.6; 212.7±247; 42±41).

CONCLUSIONS

In SOAC for retinoblastoma, the OA approach, microcatheter access, and unilateral treatment were associated with significantly lower radiation parameters. We established benchmark radiation parameters for retinoblastoma SOAC in our patient cohort.

Pediatric neurointervention: collimation on radiation exposure-associated lifetime excess tumor risk

Background

Intracranial vascular malformations in children are being addressed through a variety of treatment modalities including open surgery, external beam radiation, and image-guided neuroendovascular procedures. These patients often receive multiple treatments and incur serial exposures to ionizing radiation which has been linked to tumor development in population-based data.

Objective

This study quantifies the effect of collimation on exposures from single procedures and over patient lifetimes to estimate excess risk of lifetime tumor development.

Methods

215 patients aged 0–21 years from a single center took part in the study. Radiation exposure from neuroendovascular procedures was tabulated and converted to brain doses using modeled data and extrapolated to risk ratios using results of population-based estimates found in the literature.

Results

Lifetime and per procedure risk was highest in patients with brain arteriovenous malformations, brain arteriovenous fistulas, and vein of Galen malformations, a reflection of our institutional referral patterns. Across all pathologies the per procedure excess relative risk decreased from 13.4 to 2.3 when full collimation was employed. Lifetime excess relative risk decreased from 49.0 to 7.7 for full collimation.

Conclusions

This is the first study to quantify the effect of collimation on lifetime and per procedure risk of tumor development in a pediatric population. In addition to collimation, technical and operator-based aspects of the neurointerventional suite are discussed to further reduce patient exposure without sacrificing image quality.

Postoperative imaging for detection of recurrent arteriovenous malformations in children

OBJECT The optimal method for detecting recurrent arteriovenous malformations (AVMs) in children is unknown. An inherent preference exists for MR angiography (MRA) surveillance rather than arteriography. The validity of this strategy is uncertain. METHODS A retrospective chart review was performed on pediatric patients treated for cerebral AVMs at a single institution from 1998 to 2012. Patients with complete obliteration of the AVM nidus after treatment and more than 12 months of follow-up were included in the analysis. Data collection focused on recurrence rates, associated risk factors, and surveillance methods. RESULTS A total of 45 patients with a mean age of 11.7 years (range 0.5-18 years) were treated for AVMs via surgical, endovascular, radiosurgical, or combined approaches. Total AVM obliteration on posttreatment digital subtraction angiography (DSA) was confirmed in 27 patients, of whom the 20 with more than 12 months of follow-up were included in subsequent analysis. The mean follow-up duration in this cohort was 5.75 years (median 5.53 years, range 1.11-10.64 years). Recurrence occurred in 3 of 20 patients (15%). Two recurrences were detected by surveillance DSA and 1 at the time of rehemorrhage. No recurrences were detected by MRA. Median time to recurrence was 33.6 months (range 19-71 months). Two patients (10%) underwent follow-up DSA, 5 (25%) had DSA and MRI/MRA, 9 (45%) had MRI/MRA only, 1 (5%) had CT angiography only, and 3 (15%) had no imaging within the first 3 years of follow-up. After 5 years posttreatment, 2 patients (10%) were followed with MRI/MRA only, 2 (10%) with DSA only, and 10 (50%) with continued DSA and MRI/MRA. CONCLUSIONS AVM recurrence in children occurred at a median of 33.6 months, when MRA was more commonly used for surveillance, but failed to detect any recurrences. A recurrence rate of 15% may be an underestimate given the reliance on surveillance MRA over angiography. A new surveillance strategy is proposed, taking into account exposure to diagnostic radiation and the potential for catastrophic rehemorrhage.

Interventional neuroradiology in children: diagnostics and therapeutics

PURPOSE OF REVIEW

To highlight the spectrum of pediatric neurovascular conditions typically referred for diagnostic or interventional neuroangiography, the range of techniques available in contemporary pediatric neurointerventional practice, and the specific considerations relating to radiation and contrast dosing applicable to pediatric neurointerventional procedures.

RECENT FINDINGS

Neurointerventional procedures are increasingly utilized in children for a variety of indications, with continuous emphasis on improving safety and treatment effectiveness. Numerous steps can be taken to mitigate the potential risks of pediatric neurointerventional procedures, with recent data from high-volume centers suggesting similar, if not lower, complication rates in children compared with adults. Judicious patient selection and clarity of goals are critically important, however, because children undergoing complex and lengthy neurointerventional procedures are particularly vulnerable to the effects of ionizing radiation, vessel injury, and contrast overload.

SUMMARY

With continued advances in endovascular technology, neurointerventionalists stand to play an important and expanding role in the multidisciplinary management of pediatric neurovascular disease.

Safety of neuroangiography and embolization in children: complication analysis of 697 consecutive procedures in 394 patients

OBJECT

The safe treatment of children using catheter-based angiography and embolization poses unique challenges because of the technical factors regarding the size and fragility of access and target vessels, as well as unique pediatric cerebrovascular pathologies. The complication rates for neurointerventional procedures in children have not been established.

METHODS

The records of a consecutive cohort of pediatric patients who underwent neuroangiography and/or embolization between 2007 and 2013 were reviewed retrospectively to identify both intraprocedural and postprocedural complications. Demographic and clinical risk factors were analyzed with a multivariate logistic regression model.

RESULTS

The 697 consecutive procedures consisted of 429 diagnostic angiograms and 268 embolizations (mean age of patients 11.1 years; range 4 days to 18 years; 217 females). There were 130 intracranial, 122 extracranial, and 16 spinal embolizations. Pathologies included 28 intracranial arteriovenous malformations (AVMs), 12 spinal AVMs, 19 aneurysms, 29 vein of Galen malformations, 29 dural arteriovenous fistulas, 96 extracranial AVMs, 39 tumors, 3 strokes, and 13 others. Overall, 2 intraprocedural and 1 postprocedural complication (0.7%) occurred in the diagnostic group, all of which were nonneurological events. In the embolization group, 7 intraprocedural and 11 postprocedural complications (6.7%) were observed. Of these complications, 15 were nonneurological events (5.6%), 1 was a short-term neurological event (0.4%), and 2 were long-term neurological events (0.7%).

CONCLUSIONS

Neither the technical challenges posed by children's access and target vessels nor the unique neuro-vascular pathologies seen in children need result in an elevated morbidity rate related to neuroangiography and embolization. At a dedicated high-volume center, the complication rates may be lower than those for comparable procedures performed in adults.

Estimates of diagnostic reference levels for pediatric peripheral and abdominal fluoroscopically guided procedures

OBJECTIVE

The objective of our study was to survey radiation dose indexes of pediatric peripheral and abdominal fluoroscopically guided procedures from which estimates of diagnostic reference levels (DRLs) can be proposed for both a standard fluoroscope and a novel fluoroscope with advanced image processing and lower radiation dose rates.

MATERIALS AND METHODS

Radiation dose structured reports were retrospectively collected for 408 clinical pediatric cases: Half of the procedures were performed with a standard imaging technology and half with a novel x-ray technology. Dose-area product (DAP), air Kerma (AK), fluoroscopy time, number of digital subtraction angiography images, and patient mass were collected to calculate and normalize radiation dose indexes for procedures completed with the standard and novel fluoroscopes.

RESULTS

The study population was composed of 180 and 175 patients who underwent procedures with the standard and novel technology, respectively. The 21 different types of pediatric peripheral and abdominal interventional procedures produced 408 total studies. Median ages, mass and body mass index, fluoroscopy time per procedure, and total number of recorded images for the standard and novel technologies were not statistically different. The area of the x-ray beams was square at the level of the patient with a dimension of 10-13 cm. The dose reduction achieved with the novel fluoroscope ranged from 18% to 51% of the dose required with the standard fluoroscope. The median DAP and AK patient dose indexes were 0.38 Gy · cm(2) and 4.00 mGy, respectively, for the novel fluoroscope.

CONCLUSION

Estimates of dose indexes of pediatric peripheral and abdominal fluoroscopically guided, clinical procedures should assist in the development of DRLs to foster management of radiation doses of pediatric patients.