Intracranial Radiation Research Articles

Accuracy of Hypofractionated Intracranial Stereotactic Radiation Therapy Under Cone Beam Computed Tomography Image Guidance With a 6 Degrees of Freedom Robotic Couch and Mask System

Accuracy of Hypofractionated Intracranial Stereotactic Radiation Therapy Under Cone Beam Computed Tomography Image Guidance With a 6 Degrees of Freedom Robotic Couch and Mask System

SU-E-J-258: Inter- and Intra-Fraction Setup Stability and Couch Change Tolerance for Image Guided Radiation Therapy

Purpose: Immobilization devices combine rigid patient fixation as well as comfort and play a key role providing the stability required for accurate radiation delivery. In the setup step, couch re-positioning needed to align the patient is derived via registration of acquired versus reference image. For subsequent fractions, replicating the initial setup should yield identical alignment errors when compared to the reference. This is not always the case and further couch re-positioning can be needed. An important quality assurance measure is to set couch tolerances beyond which additional investigations are needed. The purpose of this work was to study the inter-fraction couch changes needed to re-align the patient and the intra-fraction stability of the alignment as a guide to establish the couch tolerances. Methods: Data from twelve patients treated on the Accuray CyberKnife (CK) system for fractionated intracranial radiotherapy and immobilized with Aquaplast RT, U-frame, F-Head-Support (Qfix, PA, USA) was used. Each fraction involved image acquisitions and registration with the reference to re-align the patient. The absolute couch position corresponding to the approved setup alignment was recorded per fraction. Intra-fraction set-up corrections were recorded throughout the treatment. Results: The average approved setup alignment was 0.03±0.28mm, 0.15±0.22mm, 0.06±0.31mm in the L/R, A/P, S/I directions respectively and 0.00±0.35degrees, 0.03±0.32degrees, 0.08±0.45degrees for roll, pitch and yaw respectively. The inter-fraction reproducibility of the couch position was 6.65mm, 10.55mm, and 4.77mm in the L/R, A/P and S/I directions respectively and 0.82degrees, 0.71degrees for roll and pitch respectively. Intra-fraction monitoring showed small average errors of 0.21±0.21mm, 0.00±0.08mm, 0.23±0.22mm in the L/R, A/P, S/I directions respectively and 0.03±0.12degrees, 0.04±0.25degrees, and 0.13±0.15degrees in the roll, pitch and yaw respectively. Conclusion: The inter-fraction reproducibility should serve as a guide to couch tolerances, specific to a site and immobilization. More patients need to be included to make general conclusions.

Gamma Knife radiosurgery to four or more brain metastases in patients without prior intracranial radiation or surgery

Data on stereotactic radiosurgery (SRS) for four or more metastases are limited. Existing studies are confounded by significant proportions of patients receiving prior whole-brain radiation therapy (WBRT) or concurrent WBRT with SRS. Furthermore, published results disagree about the impact of tumor volume on overall survival. A retrospective review identified 38 patients without prior intracranial radiation or surgery who received Gamma Knife (GK) as sole treatment to ≥4 brain metastases in a single session. Twenty-eight cases with follow-up imaging were analyzed for intracranial progression. Prognostic factors were examined by univariate (log-rank test) and multivariate (Cox proportional hazards model) analyses. Common primary tumors were non-small cell lung (45%), melanoma (37%), and breast (8%). Cases were recursive partitioning analysis class II (94%) or III (6%). Patients harbored a median five tumors (range 4–12) with median total tumor volume of 1.2 cc. A median dose of 21 Gy was prescribed to the 50% isodose line. Patients survived a median 6.7 months from GK. Local treatment failure occurred in one case (4%) and distant failure in 22 (79%). On multivariate analysis, total tumor volume ≥3 cc was significantly associated with distant failure and worsened overall survival (P = 0.042 and 0.040). Fourteen patients (37%) underwent salvage WBRT at a median 10.3 months from GK and seven patients received repeat GK. GK as sole initial treatment for four or more simultaneous metastases spares some patients WBRT and delays it for others. Increased total tumor volume (≥3 cc) is significantly associated with worsened overall survival.

Results of a questionnaire regarding practice patterns for the diagnosis and treatment of intracranial radiation necrosis after SRS

Although stereotactic radiosurgery (SRS) is an effective treatment option for patients with brain tumors, its increased use has raised concern for increased incidence of radiation necrosis (RN). No established standard or guidelines exists regarding non-invasive techniques to diagnose or treat RN. This study was conducted to assess current patterns of evaluation and treatment of RN among physicians who treat intracranial malignancies. A questionnaire consisting of 20 questions was sent to 3,041 members of the American Society for Radiation Oncology (ASTRO) and the Society for Neurologic Oncology (SNO). Questions addressed demographics, utilization of SRS, perceptions regarding RN diagnosis treatment, approach to steroid-refractory RN, and management of two clinical scenarios using Kwiksurvey© software. The survey response rate was 8.74 % (266/3,041). Most respondents practice in an academic and/or university setting (62 %) at a facility that performs SRS (94 %) with a variety of systems. The number of annual cases performed at the participant's institution varied from <50 to >400, with a wide degree of variability. Most respondents practice at an institution that performs 50-100 cases/year (28 %). The most common range of symptomatic RN seen in clinical practice was 1-5 % (61 %). Most respondents reported that asymptomatic RN occurs in 6-10 % (33 %). Favored non-invasive diagnostic mechanisms were clinical evaluation (37 %) and MRI (19 %). In response to a clinical scenario depicting an asymptomatic patient post-SRS for brain metastasis with an enlarging lesion and edema at the treatment site, most respondents felt the image represented RN or a combination of RN and tumor progression. Most (58 %) favored short-term follow-up with repeat MRI. Ninety-three percent of the respondents initiated steroids as a first-line approach if patient was to develop symptoms. Steroids were the preferred first therapy in symptomatic patients on initial follow-up (81 %). In steroid-refractory patients, most recommend surgical intervention (63 %). Most physicians who responded to this questionnaire believe that post-SRS RN is uncommon (≤10 % of cases). The approach to establish the diagnosis of RN is variable. Steroids are the most commonly utilized first-line treatment for suspected RN. Considerable variation exists in the management of steroid-refractory RN. Additional studies are required to establish guidelines for evaluation and treatment of RN.

A case report of stereotactic radiosurgery in a patient with Ehlers–Danlos syndrome

In this report, we outline the case of a patient who has Ehlers–Danlos Syndrome (EDS) who received two courses of CyberKnife stereotactic radiosurgery (SRS) for metastatic non-small cell lung cancer. Patients with EDS have increased blood vessel fragility, and therefore are subject to increased risk of bleeding. There are no published data regarding the risks of hemorrhage associated with SRS for intracranial metastases in this patient population. The patient described in this case report had two courses of SRS for two sites of brain metastases. She tolerated treatment well, with no acute toxicity and good local control to date. We have also included a discussion of published literature regarding toxicity of intracranial radiation in patients with EDS.

SU-E-T-360: Development of a Detection System for Intra-Fractional Motion in Intracranial Treatment Using Patient Surface Pressure

Purpose: To develop a dedicated real-time monitoring system to detect intra-fractional motion in intracranial radiotherapy using patient surface pressure. Methods: The motion for two volunteers was analyzed by a new type of immobilization system that detect load given to a patient head. The immobilization system consists of sensors with a thickness of 0.55 mm and a radius of 9.1 mm, a thermoplastic mask, a vacuum bag, and an acrylic baseplate. The four pieces of sensors were positioned at left-right sides, superior-inferior sides on the vacuum bag, respectively. The other four pieces of sensors were positioned at up-down sides, left-right sides of chin just under the thermoplastic mask, respectively. The load given to the volunteer was detected by the immobilization system that the eight sensors were attached. The pressures for sensors were calculated using a measuring resistor in a voltage divider configuration. The three pieces of light-emitting diodes (LEDs) were located on the thermoplastic mask at the chin and the pair of cheeks to detect the volunteer motion. The three-dimensional positions of LEDs were continuously detected using the Cyberknife Synchrony system. The sensor's pressures were compared with the root mean square (RMS) of LEDs displacement during the 30 min interval. Results: The RMS values of LEDs displacement within 1 mm or less were almost related to the pressures of sensors at left and superior sides on the vacuum bag. The pressures of other sensors were not detected or no relationship with the RMS values of LEDs displacement in two volunteers. Conclusion: The dedicated real-time monitoring system using patient surface pressure can detect intra-fractional motion in intracranial treatment with high precision of 1 mm or less.

Gamma-knife Radiosurgery to 4 or More Brain Metastases in Patients Without Prior Intracranial Radiation or Surgery

Gamma-knife Radiosurgery to 4 or More Brain Metastases in Patients Without Prior Intracranial Radiation or Surgery

SU-E-J-38: Rotational Setup Errors in Pediatric Patients Receiving Radiation Therapy for Intracranial Tumors.

We have clinically observed that larger rotational setup errors are more prominent in pediatric patients who received radiation therapy for brain tumors. In this work, we quantitatively evaluated the daily setup corrections in pitch, roll, and yaw axes for children who received intracranial radiation therapy under x-ray image guidance. Daily localization data of 43 patients between the ages of 10 months and 21.9 years were analyzed in this study. Patients were immobilized with thermoplastic mask during treatments, and 2D orthogonal x-ray images wereacquired for setup corrections before each treatment. Rotational setup corrections in pitch, roll, and yaw axes were extracted from 873 treatment fractions, and were analyzed for the whole group of patients and for two age groups: < 5 and = 5 years old. The mean values for the pitch corrections were 1.91° and 1.65° (p:0.02), roll corrections were 1.37° and 1° (p<0.001), and yaw corrections were 1.93° and 1.47° (p<0.001), respectively. For patients < 5 years, 21.7% of treatments had pitch corrections more than 3°, versus 15.6% of treatments required pitch corrections more than 3° for patients >= 5 years. Similarly, 10.6% of roll corrections and 20.9% of yaw corrections were more than 3° for patients < 5 years. On the other hand, 2.1% of roll and 13.8% of yaw corrections were more than 3° for patients = 5 years old. Data indicate that children less than 5 years old are more prone to rotational setup errors during intracranial radiation therapy. This can be attributed to reduced efficacy of immobilization devices due to smaller and rounder anatomicalfeatures of pediatric patients, and challenges in setup while the patient is under anesthesia. The role of daily image guidance and rotational setup corrections becomes important to ensure target coverage, especially for children < 5 years old.

SU-E-J-78: Enhance Patient Positioning Accuracy with Optically Guided Frameless Target Localization Technique for Intracranial Radiation Therapy.

To make use of the optical guided frameless stereotactic target localization technique to detect the interfraction and intrafraction patient positioning errors and correct the patient position for fractional intracranial therapy, therefore, to enhance the patient positioning accuracy. Four patients who underwent fractionated intracranial intensity modulated radiation therapy (IMRT) were studied. For each patient, in addition to the thermoplastic head mask, frameless array and bite-block were used for patient positioning. Optical guided frameless planning was utilized to define the coordinates of the isocenter during the treatment planning procedure. In each treatment fraction, the patient was first set up by matching the room lasers to the BB markers attached on the mask. The optical guided frameless system then captured the patient position and reported displacements of the current patient position to the planned patient position. These displacements were called interfraction errors. The treatment plan was designed to have up to 8 non-coplanar fields. Dose delivery of the non-coplanar fields required couch rotation which introduced isocenter displacements called intrafraction errors. Population statistics of interfraction and intrafraction errors (4 patient, 110 fractions) were calculated. The optical guided frameless system monitored the patient positioning errors and provided guidance for correction prior to the dose delivery. Among all patients and radiation treatment fractions, the overall detected interfraction error was 3.6±1.3 mm (mean ±SD) and the intrafraction error was 1.4±0.8 mm. Both types of errors were online corrected with the guidance of optical guided frameless system. Conventional laser guided thermoplastic mask patient position for intracranial therapy has interfraction and intrafraction errors. The optical guided frameless target localization technique allows clinicians to dectect and correct these errors online, therefore, to enhance the patient positioning accuracy for intracranial radiation therapy.

Radiothérapie stéréotaxique intracrânienne : prescription de la dose

The aim of this article was the study of the successive steps permitting the prescription of dose in stereotactic intracranial radiotherapy, which includes radiosurgery and fractionated stereotactic radiotherapy. The successive steps studied are: the choice of stereotactic intracranial radiotherapy among the therapeutic options, based on curative or palliative treatment intent, then the selection of lesions according to size/volume, pathological type and their number permitting the choice between radiosurgery or fractionated stereotactic radiotherapy, which have the same methodological basis. Clinical experience has determined the level of dose to treat the lesions and limit the irradiation of healthy adjacent tissues and organs at risk structures. The last step is the optimization of the different parameters to obtain a safe compromise between the lesion dose and healthy adjacent structures. Study of dose–volume histograms, coverage indices and 3D imaging permit the optimization of irradiation. For lesions close to or included in a critical area, the prescribed dose is planned using the inverse planification method. Implementation of the successively described steps is mandatory to insure the prescription of an optimized dose. The whole procedure is based on the delineation of the lesion and adjacent healthy tissues. There are sometimes difficulties to assess the delineation and the volume of the target, however improvement of local control rates and reduction of secondary effects are the proof that the totality of the successive procedures are progressively improved. In practice, stereotactic intracranial radiotherapy is a continually improved treatment method, which constantly benefits from improvements in the choice of indications, imaging, techniques of irradiation, planification/optimization methodology and irradiation technique and from data collected from prolonged follow-up.

Outcomes after Whole Brain Reirradiation in Patients with Brain Metastases

Patients with brain metastases are often treated with whole brain radiation therapy (WBRT). Management of those who experience subsequent intracranial disease progression can include a second course of WBRT, although there is controversy surrounding its safety and efficacy. This study examines outcomes of patients at Massachusetts General Hospital who underwent whole brain reirradiation. We examined the medical records of 16 patients from MGH with brain metastases who were treated with WBRT between 2003 and 2009 and were subsequently retreated with a second course of WBRT in that time period. The median age at initial diagnosis was 57 (range: 42-76). Primary sites were lung (12 patients), breast (3), and colon (1). Median dose for the first course of WBRT was 35 Gy (range: 28-40 Gy). Median dose for the second course was 21.3 Gy (range: 14-30 Gy). Average KPS before initial WBRT was 88. Five patients received their initial course of therapy prophylactically. The second course of WBRT was administered upon radiographic disease progression, and 13 patients suffered from symptoms. Average KPS prior to reirradiation was 82. Four patients had also received additional intracranial radiation therapy after initial WBRT. Seven patients experienced complete or partial symptom resolution, while 2 did not show clinical improvement. At 3-month follow-up, 8 patients had died, 3 had a worsened performance status, and 5 had stable KPS. Average KPS in those still living was 85. Time to radiographic progression was 5.5 months in 10 patients who were scanned before death. Six patients received additional SRS after retreatment. Median overall survival was 30 months. Median survival time after initiation of the second course of WBRT was 4 months (mean: 8.4, range: 1-27). In 5 patients with stable extracranial disease, median survival time after retreatment was 20 months (mean: 16, range: 3-27), with 1 patient still living (27 months post-RT), while those with systemic disease progression had a median survival of 3 months (mean: 5, range: 1-26). Adverse reactions that may be attributable to WBRT occurred in 3 patients and included short-term memory difficulty, cognitive impairment, weakness, and fatigue. One patient suffered from side effects secondary to additional SRS treatment. In select patients and especially those with stable extracranial disease, a second course of WBRT may be an appropriate and effective intervention to provide symptomatic relief and slow intracranial disease progression. Side effects were minimal and did not cause substantial changes in quality of life.

Semi-robotic 6 degree of freedom positioning for intracranial high precision radiotherapy; first phantom and clinical results

BackgroundTo introduce a novel method of patient positioning for high precision intracranial radiotherapy.MethodsAn infrared(IR)-array, reproducibly attached to the patient via a vacuum-mouthpiece(vMP) and connected to the table via a 6 degree-of-freedom(DoF) mechanical arm serves as positioning and fixation system. After IR-based manual prepositioning to rough treatment position and fixation of the mechanical arm, a cone-beam CT(CBCT) is performed. A robotic 6 DoF treatment couch (HexaPOD™) then automatically corrects all remaining translations and rotations. This absolute position of infrared markers at the first fraction acts as reference for the following fractions where patients are manually prepositioned to within ± 2 mm and ± 2° of this IR reference position prior to final HexaPOD-based correction; consequently CBCT imaging is only required once at the first treatment fraction.The preclinical feasibility and attainable repositioning accuracy of this method was evaluated on a phantom and human volunteers as was the clinical efficacy on 7 pilot study patients.ResultsPhantom and volunteer manual IR-based prepositioning to within ± 2 mm and ± 2° in 6DoF was possible within a mean(± SD) of 90 ± 31 and 56 ± 22 seconds respectively. Mean phantom translational and rotational precision after 6 DoF corrections by the HexaPOD was 0.2 ± 0.2 mm and 0.7 ± 0.8° respectively. For the actual patient collective, the mean 3D vector for inter-treatment repositioning accuracy (n = 102) was 1.6 ± 0.8 mm while intra-fraction movement (n = 110) was 0.6 ± 0.4 mm.ConclusionsThis novel semi-automatic 6DoF IR-based system has been shown to compare favourably with existing non-invasive intracranial repeat fixation systems with respect to handling, reproducibility and, more importantly, intra-fraction rigidity. Some advantages are full cranial positioning flexibility for single and fractionated IGRT treatments and possibly increased patient comfort.

Intracranial plasmacytoma with apoplectic presentation and spontaneous intracerebral hemorrhage: Case report and review of the literature

Involvement of the nervous system is not uncommon in patients with multiple myeloma, with polyneuropathy and myelopathy predominating. Intracranial involvement producing neurological symptoms, however, is distinctly uncommon. Massive intraparenchymal hemorrhage from a previously unrecognized intracranial plasmacytoma is exceedingly rare. The authors report the case of a 57-year-old male who presented with sudden onset of severe headache, rapid onset of right-sided weakness and deterioration in level of consciousness while at work. Two years earlier the patient had completed treatment for multiple myeloma and was considered to be in remission, with a recent bone marrow biopsy that was negative, and complete normalization of serum protein electrophoresis. Imaging studies revealed a massive intracerebral hemorrhage with the possibility of an underlying lesion, and the patient was taken for emergent hematoma evacuation and tumor resection. The patient made an excellent recovery and was treated with intracranial radiation. Even in patients with multiple myeloma without evidence of systemic disease following successful treatment, the possibility of unrecognized lesions lingers. The onset of new symptoms referable to potential intracranial pathology in this setting should prompt consideration of intracranial plasmacytoma in the differential diagnosis.

Radiation-induced gliomas

Radiation-induced gliomas represent a relatively rare but an extensively published entity in the neuro–oncologic literature. Extensive retrospective cohort data in pediatric populations after therapeutic intracranial radiation show an increased risk in glioma incidence that is both patient age- and radiation dose/volume-dependent. Data in adults are more limited but show heightened risk in certain groups exposed to radiation. In both populations, there is no statistically increased risk associated with routine exposure to diagnostic radiation. At the molecular level, there are conflicting data concerning whether distinct genetic differences between radiation-induced gliomas and their spontaneously occurring counterparts exist. Clinically, there is understandable reluctance on the part of clinicians to re-treat patients owing to concern for cumulative neurotoxicity. However, available data suggest that aggressive intervention can lead to improved outcomes in patients with radiation-induced gliomas.

Brainstem cavernous malformations: a review with two case reports

Central nervous system (CNS) cavernous malformations (CMs) are developmental malformations of the vascular bed with a highly variable clinical course due to their dynamic nature. We present one case of 'de novo' brainstem cavernous malformation after radiation therapy adding to the increasing number of reported cases in the medical literature, and the case of a pregnant patient with symptomatic intracranial hemorrhage related to brainstem CMs to illustrate the complex nature in management of these patients, followed by a review of clinical and radiographic characteristics. CMs account for 8-15% of all intracranial and intraspinal vascular malformations. Although traditionally thought to be congenital in origin, CMs may present as acquired lesions particularly after intracranial radiation therapy. Clinical manifestations are protean and surgical treatment should be considered for patients with progressive neurologic deficits.

TH-D-303A-09: Daily Image Guided Localization for Pediatric Brain Tumor Patients

Purpose: Establish the setup uncertainty (SU) for intracranial pediatric radiotherapy patients based on daily pre‐treatment CBCT and quantify the residual uncertainty (RU) based on post‐treatment CBCT. Also, quantify the inter‐observer uncertainty (OU) and mechanical uncertainty (MechU) of the CBCT system. Methods and Materials: 94 intracranial pediatric patients have completed therapy under an IRB approved localization protocol, and stratified based on treatment position (Supine/Prone) and the use of general anesthesia (GA). Patients received a localization CBCT prior to each fraction and at the end of every other fraction. The CBCT used was an investigational MV imaging beam line; the output was adjusted such that the patient isocenter dose was 1cGy per CBCT. The offset based on the registration of the pre‐fraction CBCT to the Sim‐CT, comprising the SU, were recorded in an electronic database and the patient moved into the correct position. The offset in the post‐fraction CBCT to the Sim‐CT comprised the RU. Nine individuals independently registered the first five CBCTs of the same five randomly chosen patients. The comparison established the inter‐observer uncertainty (OU). The mechanical uncertainty (MechU) was determined by acquiring a CBCT of a localization phantom monthly and recording the discrepancy between the known positions of landmarks within the phantom and the positions based on the CBCT.Results: The mean age of the 94 patients was 12.7±7.3 years. 69 were treated supine and 25 prone; 41 with GA and 53 without. The various uncertainties in mm were as follows: SU_Supine=3.5, SU_Prone=3.8, SU_GA=3.7, SU_noGA=3.6; RU_Supine=1.8, RU_Prone=2.4, RU_GA=1.5, RU_noGA=2.3. The OU was 0.9 and the MechU was 0.5 mm. Conclusion: The 1cGy CBCTs produced with the investigational imaging beam line can be used to confidently localize the patient before treatment and thereby reduce the setup uncertainty. Conflict of Interest: Supported in part by Siemens Medical USA.

SU-FF-T-532: Immobilization Accuracy of a Novel Re-Locatable Head Frame Investigated with a Real-Time Optical Tracking System

Purpose: To evaluate the immobilization accuracy of a novel vacuum bite block re‐locatable head frame (RHF) system in patients receiving intracranial stereotactic radiation therapy (SRT) by means of an infrared optical tracking system (OTS). Methods and Materials: The RHF was designed for multi‐session treatments on the Leksell GammaKnife Perfexion™. In the present REB approved study, the RHF was used for patients undergoing linac‐based SRT. A passive optical marker was placed on the bite block as a surrogate for patient motion. The OTS monitored patients continuously throughout each fraction. For each fraction, cone‐beam computed tomography(CBCT) was used to verify the patient position at three time points: after the initial setup, pre‐delivery following the automatic couch adjustments and post‐delivery. To investigate the reliability of the optical measurements, the OTS measurements were compared against the implemented couch shifts for patient setup. Intra‐fractional anatomical motion, as measured from the second and third CBCT scans, was compared with the difference in OTS marker positions. Real‐time OTS data throughout each fraction was assessed to determine if patients moved by more than 1 mm during treatments.Results: Currently, data from three patients have been analyzed. The couch motion measured from the OTS strongly correlated with the actual reported couch shift (Pearson correlation coefficient of 0.99). Mean differences between OTS and true couch motion were 0.01, 0.0, and 0.04 mm in the lateral, anterior‐posterior, and superior‐inferior directions, respectively. Mean differences between OTS and CBCT reported motion were 0.37, 0.07, and 0.01 mm respectively with a mean vector magnitude of 0.41 mm. The real‐time positional data indicated that there were few instances (3) of patient motion greater than 1mm. Conclusion: The OTS is a reliable tool for evaluation of intra‐fraction patient motion. The results of this study indicate that the RHF provides sufficient immobilization accuracy for SRT.

Strategy for surveying the proteome using affinity proteomics and mass spectrometry

Antibody-based microarrays is a rapidly evolving technology that has gone from the first proof-of-concept studies to more demanding proteome profiling applications, during the last years. Miniaturized microarrays can be printed with large number of antibodies harbouring predetermined specificities, capable of targeting high- as well as low-abundant analytes in complex, nonfractionated proteomes. Consequently, the resolution of such proteome profiling efforts correlate directly to the number of antibodies included, which today is a key limiting factor. To overcome this bottleneck and to be able to perform in-depth global proteome surveys, we propose to interface affinity proteomics with MS-based read-out, as outlined in this technical perspective. Briefly, we have defined a range of peptide motifs, each motif being present in 5-100 different proteins. In this manner, 100 antibodies, binding 100 different motifs commonly distributed among different proteins, would potentially target a protein cluster of 10(4) individual molecules, i.e. around 50% of the nonredundant human proteome. Notably, these motif-specific antibodies would be directly applicable to any proteome in a specie independent manner and not biased towards abundant proteins or certain protein classes. The biological sample is digested, exposed to these immobilized antibodies, whereby motif-containing peptides are specifically captured, enriched and subsequently detected and identified using MS.

RADIATION EXPOSURE DURING ENDOVASCULAR PROCEDURES

Abstract Objective: The duration of fluoroscopy exposure is routinely recorded as part of endovascular procedures. However, to better relate the duration of exposure to actual doses of surface and intracranial radiation, we compared surface doses during endovascular procedures with intracranial doses in a cadaver model exposed to lateral fluoroscopy. Methods: Optically stimulated luminescence dosimeter chips (Landauer, Glenwood, IL) were used to measure the cranial surface dose of three consecutive patients undergoing endovascular procedures. Bitemporal craniotomies were performed on a cadaver. Dosimeter chips were placed on both the ipsilateral and contralateral skin and meningeal surfaces, and the cadaver was exposed to lateral fluoroscopy. Finally, to assess mean fluoroscopy times in patients undergoing embolization procedures, the operative notes of 100 consecutive patients were reviewed. Results: Three patients undergoing endovascular treatment received peak doses of 0.24, 0.31, and 1.38 Gy, respectively. In the cadaver, the peak surface dose recorded after 120 minutes of exposure was 1.71 Gy. The cranium and scalp absorbed or reflected 29% of the surface dose. Time in minutes of fluoroscopy was found to correlate with surface dose (R2 = 0.925). Conclusion: Our data show that radiation exposure during endovascular treatment can reach clinically significant levels. The surface doses recorded during this study were comparable to the mean dose of 1.5 Gy estimated by others to increase the relative risk of inducing meningiomas, gliomas, and nerve sheath tumors. Pending long-term follow-up of patients exposed to endovascular procedures, consent for possible long-term sequelae of radiation may be warranted.

Radiation exposure during endovascular procedures.

The duration of fluoroscopy exposure is routinely recorded as part of endovascular procedures. However, to better relate the duration of exposure to actual doses of surface and intracranial radiation, we compared surface doses during endovascular procedures with intracranial doses in a cadaver model exposed to lateral fluoroscopy. Optically stimulated luminescence dosimeter chips (Landauer, Glenwood, IL) were used to measure the cranial surface dose of three consecutive patients undergoing endovascular procedures. Bitemporal craniotomies were performed on a cadaver. Dosimeter chips were placed on both the ipsilateral and contralateral skin and meningeal surfaces, and the cadaver was exposed to lateral fluoroscopy. Finally, to assess mean fluoroscopy times in patients undergoing embolization procedures, the operative notes of 100 consecutive patients were reviewed. Three patients undergoing endovascular treatment received peak doses of 0.24, 0.31, and 1.38 Gy, respectively. In the cadaver, the peak surface dose recorded after 120 minutes of exposure was 1.71 Gy. The cranium and scalp absorbed or reflected 29% of the surface dose. Time in minutes of fluoroscopy was found to correlate with surface dose (R2 = 0.925). Our data show that radiation exposure during endovascular treatment can reach clinically significant levels. The surface doses recorded during this study were comparable to the mean dose of 1.5 Gy estimated by others to increase the relative risk of inducing meningiomas, gliomas, and nerve sheath tumors. Pending long-term follow-up of patients exposed to endovascular procedures, consent for possible long-term sequelae of radiation may be warranted.