Image-guided Radiosurgery Research Articles

FreeArcs Knife: a Novel Stereotactic Radiosurgery System

This paper describes the design of an innovative linear accelerator image-guided radiosurgery (IGRS) device, which is based on a composite twofold rotary gantry structure. The paper discusses five aspects of the innovative device: its overall composition, the safety net space created by the accelerator radiation head as it rotates around the patient's longitudinal axis, the non-coplanar spherical coverage in the direction of the incidence angle for quasi-4π delivery, the structural features of the composite twofold rotary gantry, and the processes of treatment planning and implementation. It elaborates on the device's manufacturing feasibility, safety, effectiveness, accuracy, and efficiency. The conclusion is that this innovative device design holds significant development value and market promotion potential.

Frameless image-guided linear accelerator (LINAC) stereotactic radiosurgery for medically refractory trigeminal neuralgia: Clinical outcomes in 116 patients.

Frameless image-guided radiosurgery (IGRS) is an effective and non-invasive method of treating patients who are unresponsive to medical management for trigeminal neuralgia (TN). This study evaluated the use of frameless IGRS to treat patients with medically refractory TN. We performed a retrospective review of records of 116 patients diagnosed with TN who underwent frameless IGRS using a linear accelerator (LINAC) over 10 years (March 2012-February 2023). All patients had failed medical management for TN. Facial pain was graded using the Barrow Neurological Institute (BNI) scoring system. Each patient received a BNI score before frameless IGRS and following treatment. Failure was defined as a BNI score IV-V at the last follow-up and/or undergoing a salvage procedure following IGRS. All patients had a BNI score of either IV or V before the frameless IGRS. The mean follow-up duration for all 116 patients following IGRS was 44.1 months. Most patients (81 [69.8%]) had not undergone surgery (microvascular decompression [MVD] or rhizotomy) or stereotactic radiosurgery (SRS) for TN before frameless IGRS. A total of 41 (35.3%) patients underwent a salvage procedure (MVD, rhizotomy, or an additional IGRS) following frameless IGRS. The mean duration between the initial frameless IGRS and salvage procedure was 20.1 months. At the last follow-up, a total of 110 (94.8%) patients had a BNI score of I-III. No complications were reported after the frameless IGRS. The BNI score at the last follow-up was lower compared to the initial BNI for patients regardless of prior intervention (P < 0.001). Patients who failed IGRS had a higher BNI score at the last follow-up compared to those who did not fail IGRS (2.8 vs. 2.5, P = 0.05). Patients with pain relief had a shorter follow-up compared to those with pain refractory to SRS (38.0 vs. 55.1, P = 0.005). In this large cohort of patients with medically refractory TN, frameless IGRS resulted in durable pain control in the majority of patients without any toxicity.

Neurological Manifestations of Paragangliomas of the Head and Neck.

This paper will outline the clinical neurologic presentation and diagnostic evaluation of patients with paragangliomas of the head and neck. Contemporary management options will be outlined for these rare and complex tumors. The majority of recent publications and research on these tumors are dedicated to traditional and robotic image-guided radiosurgery in the treatment of head and neck paragangliomas. Paragangliomas are rare, slow-growing tumors of the head and neck which usually cause silent cranial nerve deficits or compensated mild speech or swallowing symptoms. While radiologic surveillance is often the best treatment option, subtotal resection with case-specific radiosurgery is commonly used in patients with large tumors.

Image-Guided Stereotactic Radiosurgery for the Treatment of Spasticity and Pain: A Preliminary Experience.

BackgroundSpasticity is a major health problem worldwide. Response to current medical and rehabilitation treatments is often poor. Surgical treatment is available only for a very limited number of patients.AimWe recently reported the application of stereotactic radiosurgery as a treatment option for spasticity and related pain. This paper describes a larger experience using image-guided stereotactic radiosurgery targeting the cervical or lumbar spinal roots to relieve spasticity and pain in four patients.MethodsAll the patients had refractory spasticity and related pain, one patient had additional paroxystic neuralgic pain. The cause of spasticity and pain was a traumatic brain and/or spinal cord injury, brain and/or spinal cord surgery, and stroke. Symptoms affected the right superior limb in one patient, and the inferior limbs in three patients (unilaterally in two, bilaterally in one). According to the symptoms, one patient was treated at the cervical level (C7 right sensory root) and three patients at lumbar level (right L4, left S1, and L2 roots bilaterally). The target was selected on constructive interference in steady-state (CISS) MR, focusing the irradiation on the postganglionic sensory segment of the cervical root or the intra-foraminal dorsolateral sensory portion of the lumbar roots. Appropriate spasticity and pain scales were used to assess the patient’s status after the treatment.ResultsThe treatments were tolerated well. Marked symptomatic relief was found in all the treated patients. Improvements in spasticity and pain scales were observed up to the latest follow-up. After 2 years, the mean reduction of the visual analog scale (VAS) and Modified Ashworth Scale (MAS) was 64.3% and 43.7%, respectively, while the median reduction of MAS score was 50%.ConclusionsExcept for a previous case report, this is the first study describing a novel noninvasive technique based on image-guided radiosurgery to treat severe spasticity and pain due to brain and spinal cord injury. This novel technique appears to be safe and effective and deserves to be studied further.

Image-Guided Robotic Radiosurgery for the Treatment of Same Site Spinal Metastasis Recurrences.

BackgroundDue to recent medical advancements, patients suffering from metastatic spinal disease have a prolonged life expectancy than several decades ago, and some will eventually experience relapses. Data for the retreatment of spinal metastasis recurrences occurring at the very same macroscopic spot as the initially treated lesion are limited. Previous studies mainly included recurrences in the boundary areas as well as other macroscopic parts of the initially affected vertebrae. This study exclusively analyzes the efficacy and safety of spinal reirradiation for recurrences on the same site utilizing single-session robotic radiosurgery.Materials and MethodsPatients between 2005 and 2020 who received radiotherapy for a spinal metastasis suffering from a local recurrence were eligible for analysis. Only patients undergoing a single-session reirradiation were included. All recurrences must have been occurred in the same location as the initial lesion. This was defined as a macroscopic recurrence on computed tomography occurring at the same site as the initial spinal metastasis. All other lesions, including those in the boundary areas or other parts of the initially affected vertebrae, were excluded.ResultsFifty-three patients with fifty-three lesions were retreated for spinal metastases. The median dose and number of fractions for the initial radiotherapy were 36 Gy and 15, respectively. Eleven patients were initially treated with stereotactic body radiotherapy. Retreatment was performed with a median dose of 18 Gy prescribed to a median isodose of 70%. The local control was 77% after a median follow-up of 22.2 months. Patients experiencing a second recurrence received a lower dose (p = 0.04), mostly below 18 Gy, and had a worse coverage (p = 0.01) than those showing local tumor control. 51% of patients experienced an improvement in pain control after treatment delivery. Besides, four vertebral compression fractures (7% of patients) but no other adverse events higher than grade 2 were observed.ConclusionSingle-session robotic radiosurgery appears to be a safe, time-saving, and effective treatment modality for spinal metastasis recurrences occurring in the same initial location if a considerable dose and coverage can be applied. Treatment results are comparable to reirradiated metastases in the boundary areas.

Radiosurgery for Multiple Brain Metastases using Volumetric Modulated Arc Therapy: Clinical Outcomes and Toxicity from a Single-Institutional Series

To analyze clinical outcomes and toxicities in patients with multiple brain metastases undergoing SRS using VMAT technique. Retrospective analyzes of SRS for brain metastasis using VMAT in a single institution from 2012 to 2019. GTV was defined on enhanced lesion at Magnetic Resonance Image overlapped to planning CT, expanded for PTV from 1 to 2mm. All the patients used thermoplastic mask for frameless image-guided radiosurgery, using cone beam CT with 6D positioning and surface-guided set-up were applied in some cases. The collected data were demographic and histopathologic features, local control, brain and systemic control from patient charts. Local control (LC) was analyzed from SRS treatment to local progression (any failure inside the brain). Other treatments, and toxicities (acute and late) were also evaluated. There were 75 patients with totalizing 418 lesions. The average number of treated lesions was 5.6 (range 2 – 19). Patients with 2 lesions were the most prevalent (18.6%). The primary sites were lung (45%), breast (29.3%), melanoma (8%), colon (8%), and others (8.7%). Most patients already had received systemic therapy before SRS (chemotherapy in 52, targeted therapy or immunotherapy in 36). Only 3 patients underwent hypofractionated treatments (2 in 3 fractions and 1 in 5 fractions). The median single-shot dose was 18 (12 – 24) Gy. The median follow-up was 7.3 months (1 – 40). The 1-, and 2-year local recurrence free survival were respectively 65% and 47.3%. The mean time to local recurrence was 7.1 months. The 1-year brain recurrence free survival and overall survival were respectively 28% and 36%. There were 11 local recurrences and 30 non-local tumors, having 7 of them leptomeningeal spread. Grade 1 or 2 acute toxicities were present in 7.1% (headache, seizures, perilesional edema), whereas late toxicities including radionecrosis and neurocognitive impairment were seen respectively in 3.38%, and in 3.44%. The use of VMAT – SRS for multiple brain metastases was feasible, effective, and with low treatment-related toxicity rates. We might infer that the simultaneous treatment provided by VMAT is an advantageous way to yield local control without compromise toxicity.

Stereotactic Dorsolateral Irradiation of Spinal Nerve Roots: A Novel Technique for the Treatment of Spasticity and Pain

Selective dorsal rhizotomy is an established surgical treatment to improve the neurological and functional status of children with spastic cerebral palsy and adults with spasticity and pain caused by a variety of brain and spinal injuries. This procedure requires a dorsolumbar laminectomy to expose the appropriate dorsal rootlets, which are sectioned according to the presence of sustained electromiographic discharges.Image-guided robotic radiosurgery targeting the intracisternal sensory root of the trigeminal nerve has been described as a safe and effective non-invasive treatment for trigeminal neuralgia, a paroxystic pain disorder which often responds poorly to medical therapy. Image-guided radiosurgery requires no frame placement and can treat brain or spinal targets with submillimetric precision. This technique can be used to treat cervical or lumbar dorsal roots.A 44-year-old patient with von Hippel-Lindau disease developed severe spastic tetraparesis following multiple brain and spinal procedures. Spasticity and related pain mostly affected the right leg, with sustained electromiographic discharges originating from the right L4 nerve root. Response to medical therapy with baclofen and cannabinoids was poor. Due to geographical and logistical issues, the patient declined the placement of an intrathecal baclofen pump.Considering the poor general condition of the patient and his decision to avoid invasive procedures, a novel treatment option was offered to provide relief from spasticity and pain: stereotactic image-guided irradiation delivered to the sensory root. The patient underwent a right intraforaminal dorsolateral L4 root stereotactic irradiation with a delivered dose of 45 Gy prescribed to the 82% isodose.The treatment was well tolerated, without side effects. Resolution of spasticity and related pain in the right leg was found six months after the procedure. A marked reduction of spasticity and pain was also evident in the contralateral leg. These improvements have been stable over the last 18 months.So far, two additional patients underwent stereotactic dorsolateral spinal root irradiation (one delivered to a cervical, the other to a lumbar), with similar positive outcomes. These preliminary results suggest that spinal root stereotactic image-guided irradiation, a novel treatment option in the neurosurgical armamentarium, is a safe and effective procedure and deserves further investigation.

Factors affecting outcome in frameless non-isocentric stereotactic radiosurgery for trigeminal neuralgia: a multicentric cohort study

BackgroundStereotactic radiosurgery (SRS) is an effective treatment for trigeminal neuralgia (TN). Nevertheless, a proportion of patients will experience recurrence and treatment-related sensory disturbances. In order to evaluate the predictors of efficacy and safety of image-guided non-isocentric radiosurgery, we analyzed the impact of trigeminal nerve volume and the nerve dose/volume relationship, together with relevant clinical characteristics.MethodsTwo-hundred and ninety-six procedures were performed on 262 patients at three centers. In 17 patients the TN was secondary to multiple sclerosis (MS). Trigeminal pain and sensory disturbances were classified according to the Barrow Neurological Institute (BNI) scale. Pain-free-intervals were investigated using Kaplan Meier analyses. Univariate and multivariate Cox regression analyses were performed to identify predictors.ResultsThe median follow-up period was 38 months, median maximal dose 72.4 Gy, median target nerve volume 25 mm3, and median prescription dose 60 Gy. Pain control rate (BNI I-III) at 6, 12, 24, 36, 48, and 60 months were 96.8, 90.9, 84.2, 81.4, 74.2, and 71.2%, respectively. Overall, 18% of patients developed sensory disturbances. Patients with volume ≥ 30 mm3 were more likely to maintain pain relief (p = 0.031), and low integral dose (< 1.4 mJ) tended to be associated with more pain recurrence than intermediate (1.4–2.7 mJ) or high integral dose (> 2.7 mJ; low vs. intermediate: log-rank test, χ2 = 5.02, p = 0.019; low vs. high: log-rank test, χ2 = 6.026, p = 0.014). MS, integral dose, and mean dose were the factors associated with pain recurrence, while re-irradiation and MS were predictors for sensory disturbance in the multivariate analysis.ConclusionsThe dose to nerve volume ratio is predictive of pain recurrence in TN, and re-irradiation has a major impact on the development of sensory disturbances after non-isocentric SRS. Interestingly, the integral dose may differ significantly in treatments using apparently similar dose and volume constraints.

A Daily QA Phantom for Linear Accelerator with Image-Guided Radiosurgery Capability

Image guided radiosurgery and stereotactic body radiotherapy (IG-SRS/SBRT) have been widely adopted on linear accelerators. Ideally, a daily quality assurance program on such machines should provide the targeting accuracy from image guidance quantitatively and efficiently. A suitable phantom for such test requires sufficient landmarks for robust online image registration and a high contrast ball bearing (BB) to provide clear images for Winston Lutz (WL) test. Such phantoms, however, are not widely available. In this study, we investigated a prototype daily QA phantom that allows all major components of the IG-SRS/SBRT process to be tested. The phantom is a 12 cm cube with 3 pairs of AL rods at 3 corners, and 4 embedded AL ceramic BBs. The BB in the center of phantom is 5/16 inch in diameter, while the others are ¼ inch in size. On the treatment table, the phantom sits atop a holder with build-in pitch, roll, and pitch. The holder can be index to the couch at a preset starting position. A high resolution planning CT was acquired of the phantom on a level surface. A plan was then generated with isocenter placed precisely in the central BB of the phantom. The plan was delivered on a medical linear accelerator and a radiosurgery system, using cone beam CT (CBCT) and stereoscopic x-ray system for image guidance, respectively. Both imaging systems provide 6DoF deviations that were subsequently applied to the treatment couch. Afterwards, verification imaging was acquired with an on-board imaging (OBI) KV/MV pair on a medical linear accelerator and a 2nd pair of stereotactic x-ray images on a radiosurgery system, and WL tests were performed to measure the agreement between central BB and machine isocenter. The plan was delivered 12 times each on the two machines. The initial correction, deviation from verification imaging, and WL test results (μ ± σ) are provided in the table below, where R represents 3D vector length.The verification imaging indicated that all 6DoF corrections were applied correctly, and WL test showed that both systems are able to localize well within 1 mm accuracy on a phantom. The phantom incorporates necessary features to enable daily QA with the goal of simulating IG-SRS/SBRT workflow and quantitatively evaluating localization accuracy. Accuracy determined from this daily QA procedure should represent the upper limit of targeting accuracy for ideal conditions.Abstract 3613; Table 1Medical Linear Accelerator (n=12)Radiosurgery System (n=12)CorrectionVerificationWL testCorrectionVerificationWL testVRT (mm)-8.0±0.10.0±0.10.02±0.04-8.6±0.30.0±0.10.30±0.15LNG (mm)6.8±0.10.2±0.20.25±0.087.0±0.40.0±0.10.18±0.10LAT (mm)6.3±0.2-0.1±0.2-0.20±0.146.0±0.40.1±0.10.20±0.13R (mm)12.2±0.20.4±0.10.34±0.0912.6±0.40.2±0.10.45±0.11Yaw (o)1.4±0.1-0.2±0.1-1.4±0.20.1±0.1-Pitch (o)-1.8±0.10.1±0.1--1.7±0.10.0±0.1-Roll (o)-1.0±0.10.1±0.1--0.9±0.10.0±0.1- Open table in a new tab

Frameless Image-Guided Radiosurgery for Multiple Brain Metastasis Using VMAT: A Review and an Institutional Experience.

We undertook a structured review of stereotactic radiosurgery (SRS) using linear particle accelerator (linac) equipment, focusing on volumetric modulated arc therapy (VMAT) technology, and frameless image-guided radiotherapy (IGRT), for the treatment of brain metastases. We analyzed the role of linac SRS and its clinical applications, exploring stereotactic localization. Historically, there was a shift from fixed frames to frameless approaches, moving toward less invasive treatments. Thus, we reviewed the concepts of VMAT for multiple-target applications, comparing its dosimetric and technical features to those of other available techniques. We evaluated relevant technical issues and discussed the planning parameters that have gained worldwide acceptance to date. Thus, we reviewed the current literature on the clinical aspects of SRS, especially its main indications and how the advantages of VMAT may achieve clinical benefits in such scenarios. Finally, we reported our institutional results on IGRT-VMAT for SRS treatments for patients with multiple brain metastases.

Benefits of image-guided stereotactic hypofractionated radiation therapy as adjuvant treatment of craniopharyngiomas. A review.

Craniopharyngiomas account for 5.6-13% of intracranial tumors in children. Despite being histologically benign, these tumors remain a major neurosurgical challenge because of the typical tight adherence to adjacent critical structures. The optimal therapeutic approach for this disease is controversial. Large cystic size and adherence to neurovascular, neuroendocrine, and optic structures without a clear line of cleavage make complete resection problematic and often hazardous. For these reasons, partial resection and adjuvant treatment play an important role. Post-operative radiation therapy (RT) following either complete or incomplete tumor removal is associated with significantly decreased recurrence rates. The aim of this review is to analyze the potential advantage of the most modern technical advancements for RT of craniopharyngiomas. This narrative review on the topic of craniopharyngiomas was based on published data available on PUBMED/Medline. All data concerning adjuvant or upfront radiation therapy treatment of craniopharyngioma were reviewed and summarized. A more detailed analysis of fractionated frameless steretactic radiosurgery of these tumors is provided as well. We reviewed the possible improvement provided by intensity modulated beams, arc therapy, image guidance, proton radiation, and fractionated stereotactic radiosurgery. Many published findings on outcome and toxicity after RT involve the use of relatively outdated RT techniques. Technologic improvements in imaging, radiation planning, and delivery have improved the distribution of radiation doses to desired target volumes and reduced the dose to nearby critical normal tissues. Currently available techniques, providing image guidance and improved radiation doses distribution profile, have shown to maintain the efficacy of conventional techniques while significantly reducing the toxicity. Image-guided radiosurgery holds the dose distributions and precision of frame-based techniques with the remarkable advantage of multiple-session treatments that are better tolerated by sensitive peritumoral structures, such as the optic pathway and hypothalamus. This, together with the comfort of a frameless technique, candidates frameless image-guided radiosurgery to be the first option for the adjuvant post-operative treatment of craniopharyngiomas in children and young adults when total resection cannot be achieved, in particular those with hypothalamic involvement, and when the residual tumor is mostly solid.

Image-guided positioning in intracranial non-invasive stereotactic radiosurgery for the treatment of brain metastasis.

The aim of the study was to examine the feasibility of non-invasive image-guided radiosurgery to improve patient comfort and quality of life in stereotactic radiosurgery planning and treatment of patients with brain metastasis. Precise immobilization is a rule of thumb for stereotactic radiosurgery. Non-invasive immobilization techniques have the potential of improved quality of life compared with invasive procedures. A total of 92 lesions from 42 patients with brain metastasis were included in the study. After immobilization with a thermoplastic mask and a bite-block unlike the invasive frame-based procedure, planning computed tomography images were acquired and fused with magnetic resonance images. After contouring, intensity-modulated stereotactic radiosurgery (IM-SRS) planning was done, and the patients were re-immobilized on the treatment couch for the therapy procedures. While patients were on the treatment couch, kilovoltage-cone beam computed tomography images were acquired to determine setup errors and achieve on-line correction and then repeated after on-line correction to confirm precise tumor localization. The patients then underwent single-fraction definitive treatment. For the 92 lesions treated, mean ± SD values of translational setup corrections in X (lateral), Y (longitudinal), and Z (vertical) dimensions were 0.7 ± 0.7 mm, 0.8 ± 0.7 mm, and 0.6 ± 0.5 mm, and rotational set-up corrections were 0.5 ± 1.1°, 0.06 ± 1.1°, and -0.1 ± 1.1° in X (pitch), Y (roll), and Z (yaw), respectively. The mean three-dimensional correction vector was 1.2 ± 1.1 mm. Non-invasive image-guided radiosurgery for brain metastasis is feasible, and the non-invasive treatment approach can be routinely used in clinical practice to improve patients' quality of life.

A Study of Six-Dimensional Intrafractional Shifts During Frameless Image-Guided Radiosurgery and Pain Outcome for Trigeminal Neuralgia

Precision targeting is essential to successful stereotactic radiosurgery (SRS) for trigeminal neuralgia (TGN). We investigate the impact of intra-fractional 6-dimensional shifts during frameless image-guided stereotactic radiosurgery (IGRS) on pain relief outcome for TGN patients. A total of 41 sets of intra-fractional shifts from 35 patients with idiopathic TGN treated by a dedicated Linac-based radiosurgery unit from 2009 to 2013 were retrospectively studied. All patients were immobilized by facemask and received 90 Gy point dose via a 4 mm cone from an average of 6 non-coplanar arcs to the affected trigeminal nerve. The in-room kV X-ray imaging system with 6-degree of freedom robotic couch was utilized for image-guided positioning corrections. During each frameless IGRS, translational shifts in lateral, longitudinal and vertical directions, as well as rotational shifts in pitch, roll and yaw were conducted at each couch angle. These 6-dimentional shifts and the average calculated distance derived from translational shifts were analyzed and correlated with clinical pain outcome. Clinical pain outcome was assessed by patient interviews according the 5-point Barrow Neurological Institute (BNI) pain scale. Student’s t test was used to detect significance between values. The absolute mean lateral, longitudinal and vertical translational were 0.46 ± 0.15, 0.36 ± 0.16 and 0.21 ± 0.08 mm, respectively. The absolute mean pitch, roll and yaw rotational shifts were 0.33 ± 0.24, 0.18 ± 0.09 and 0.27 ± 0.15 degrees, respectively. For patients with less than 2 points of pain relief, the absolute mean lateral, longitudinal and vertical translational shifts were 0.09 ± 0.01, 0.14 ± 0.01 and 0.09 ± 0.01 mm, respectively. The average calculated distance shift for patients with less than 2 points of pain relief was 0.23 ± 0.01 mm. The average absolute pitch, roll and yaw rotational shifts for these patients were 0.15 ± 0.01, 0.10 ± 0.00 and 0.09 ± 0.01 degrees, respectively. For patients with at least 2 points of pain relief, the average absolute lateral, longitudinal and vertical translational shifts were 0.12 ± 0.00, 0.16 ± 0.01 and 0.09 ± 0.00 mm, respectively. The average calculated distance shift for these patients was 0.26 ± 0.01 mm. The average absolute pitch, roll and yaw rotational shifts for these patients were 0.14 ± 0.01, 0.10 ± 0.00 and 0.13 ± 0.00 degrees, respectively. The two patient groups demonstrate no statistically significant difference in the translational or rotational intra-fractional shifts. Our analysis revealed no correlation between pain relief outcome and the amount of intra-fractional shift in all six dimensions during frameless IGRS. Our results indicate the less than 0.5 mm nominal mechanical deviation during frameless IGRS does not impact on TGN pain outcome.

EP-1636: Evaluation of the accuracy in frame-less image-guided radiotherapy and radiosurgery

EP-1636: Evaluation of the accuracy in frame-less image-guided radiotherapy and radiosurgery

Simultaneous deblurring and iterative reconstruction of CBCT for image guided brain radiosurgery

One of the limiting factors in cone-beam CT (CBCT) image quality is system blur, caused by detector response, x-ray source focal spot size, azimuthal blurring, and reconstruction algorithm. In this work, we develop a novel iterative reconstruction algorithm that improves spatial resolution by explicitly accounting for image unsharpness caused by different factors in the reconstruction formulation. While the model-based iterative reconstruction techniques use prior information about the detector response and x-ray source, our proposed technique uses a simple measurable blurring model. In our reconstruction algorithm, denoted as simultaneous deblurring and iterative reconstruction (SDIR), the blur kernel can be estimated using the modulation transfer function (MTF) slice of the CatPhan phantom or any other MTF phantom, such as wire phantoms. The proposed image reconstruction formulation includes two regularization terms: (1) total variation (TV) and (2) nonlocal regularization, solved with a split Bregman augmented Lagrangian iterative method. The SDIR formulation preserves edges, eases the parameter adjustments to achieve both high spatial resolution and low noise variances, and reduces the staircase effect caused by regular TV-penalized iterative algorithms. The proposed algorithm is optimized for a point-of-care head CBCT unit for image-guided radiosurgery and is tested with CatPhan phantom, an anthropomorphic head phantom, and 6 clinical brain stereotactic radiosurgery cases. Our experiments indicate that SDIR outperforms the conventional filtered back projection and TV penalized simultaneous algebraic reconstruction technique methods (represented by adaptive steepest-descent POCS algorithm, ASD-POCS) in terms of MTF and line pair resolution, and retains the favorable properties of the standard TV-based iterative reconstruction algorithms in improving the contrast and reducing the reconstruction artifacts. It improves the visibility of the high contrast details in bony areas and the brain soft-tissue. For example, the results show the ventricles and some brain folds become visible in SDIR reconstructed images and the contrast of the visible lesions is effectively improved. The line-pair resolution was improved from 12 line-pair/cm in FBP to 14 line-pair/cm in SDIR. Adjusting the parameters of the ASD-POCS to achieve 14 line-pair/cm caused the noise variance to be higher than the SDIR. Using these parameters for ASD-POCS, the MTF of FBP and ASD-POCS were very close and equal to 0.7 mm−1 which was increased to 1.2 mm−1 by SDIR, at half maximum.

Image-guided stereotactic radiosurgery for treatment of spinal hemangioblastoma.

OBJECTIVE Stereotactic radiosurgery (SRS) has been an attractive treatment option for hemangioblastomas, especially for lesions that are surgically inaccessible and in patients with von Hippel-Lindau (VHL) disease and multiple lesions. Although there has been a multitude of studies examining the utility of SRS in intracranial hemangioblastomas, SRS has only recently been used for spinal hemangioblastomas due to technical limitations. The purpose of this study is to provide a long-term evaluation of the effectiveness of image-guided radiosurgery in halting tumor progression and providing symptomatic relief for spinal hemangioblastomas. METHODS Between 2001 and 2011, 46 spinal hemangioblastomas in 28 patients were treated using the CyberKnife image-guided radiosurgery system at the authors' institution. Fourteen of these patients also had VHL disease. The median age at treatment was 43.5 years (range 19-85 years). The mean prescription radiation dose to the tumor periphery was 21.6 Gy (range 15-35 Gy). The median tumor volume was 0.264 cm3 (range 0.025-70.9 cm3). Tumor response was evaluated on serial, contrast-enhanced CT and MR images. Clinical response was evaluated by clinical and imaging evaluation. RESULTS The mean follow-up for the cohort was 54.3 months. Radiographic follow-up was available for 19 patients with 34 tumors; 32 (94.1%) tumors were radiographically stable or displayed signs of regression. Actuarial control rates at 1, 3, and 5 years were 96.1%, 92.3%, and 92.3%, respectively. Clinical evaluation on follow-up was available for 13 patients with 16 tumors; 13 (81.2%) tumors in 10 patients had symptomatic improvement. No patient developed any complications related to radiosurgery. CONCLUSIONS Image-guided SRS is safe and effective for the primary treatment of spinal hemangioblastomas and is an attractive alternative to resection, especially for those with VHL disease.

Frameless image-guided radiosurgery for trigeminal neuralgia.

Background:Frameless image-guided radiosurgery (IGRS) is a safe and effective noninvasive treatment for trigeminal neuralgia (TN). This study evaluates the use of frameless IGRS to treat patients with refractory TN.Methods:We reviewed the records of 20 patients diagnosed with TN who underwent frameless IGRS treatments between March 2012 and December 2013. Facial pain was graded using the Barrow Neurological Institute (BNI) scoring system. The initial setup uncertainty from simulation to treatment and the patient intrafraction uncertainty were measured. The median follow-up was 32 months.Results:All patients’ pain was BNI Grade IV or V before the frameless IGRS treatment. The mean intrafraction shift was 0.43 mm (0.28–0.76 mm), and the maximum intrafraction shift was 0.95 mm (0.53–1.99 mm). At last follow-up, 8 (40%) patients no longer required medications (BNI 1 or 2), 11 (55%) patients were pain free but required medication (BNI 3), and 1 (5%) patient had no pain relief (BNI 5). Patients who did not have prior surgery had a higher odds ratio for pain relief compared to patients who had prior surgery (14.9, P = 0.0408).Conclusions:Frameless IGRS provides comparable dosimetric and clinical outcomes to frame-based SRS in a noninvasive fashion for patients with medically refractory TN.

An improved tracking framework for ultrasound probe localization in image-guided radiosurgery

Abstract Real-time target localization with ultrasound holds high potential for image guidance and motion compensation in radiosurgery due to its non-invasive image acquisition free from ionizing radiation. However, a two-step localization has to be performed when integrating ultrasound into the existing radiosurgery workflow. In addition to target localization inside the ultrasound volume, the probe itself has to be localized in order to transform the target position into treatment room coordinates. By adapting existing camera calibration tools, we have developed a method to extend the stereoscopic X-ray tracking system of a radiosurgery platform in order to locate objects such as marker geometries with six degrees of freedom. The calibration was performed with 0.1 mm reprojection error. By using the full area of the flat-panel detectors without pre-processing the extended software increased the tracking volume and resolution by up to 80%, substantially improving patient localization and marker detectability. Furthermore, marker-tracking showed sub-millimeter accuracy and rotational errors below 0.1°. This demonstrates that the developed extension framework can accurately localize marker geometries using an integrated X-ray system, establishing the link for the integration of real-time ultrasound image guidance into the existing system.

Analysis of translational errors in frame-based and frameless cranial radiosurgery using an anthropomorphic phantom.

ObjectiveTo evaluate three-dimensional translational setup errors and residual errors in image-guided radiosurgery, comparing frameless and frame-based techniques, using an anthropomorphic phantom.Materials and MethodsWe initially used specific phantoms for the calibration and quality control of the image-guided system. For the hidden target test, we used an Alderson Radiation Therapy (ART)-210 anthropomorphic head phantom, into which we inserted four 5mm metal balls to simulate target treatment volumes. Computed tomography images were the taken with the head phantom properly positioned for frameless and frame-based radiosurgery.ResultsFor the frameless technique, the mean error magnitude was 0.22 ± 0.04 mm for setup errors and 0.14 ± 0.02 mm for residual errors, the combined uncertainty being 0.28 mm and 0.16 mm, respectively. For the frame-based technique, the mean error magnitude was 0.73 ± 0.14 mm for setup errors and 0.31 ± 0.04 mm for residual errors, the combined uncertainty being 1.15 mm and 0.63 mm, respectively.ConclusionThe mean values, standard deviations, and combined uncertainties showed no evidence of a significant differences between the two techniques when the head phantom ART-210 was used.

Image-guided robotic radiosurgery as salvage therapy for locally recurrent prostate cancer after external beam irradiation: retrospective feasibility study on six cases

Technological advances in treatment planning and execution are providing new potential opportunities in the treatment of recurrent prostate cancer. This study was conducted to evaluate the feasibility and safety of reirradiation with image-guided radiosurgery using CyberKnife, a robotic arm-driven compact linear accelerator, for intraprostatic recurrence after external beam radiotherapy (EBRT). Between September 2007 and May 2008, 6 patients diagnosed with locally recurrent prostate cancer after EBRT were treated using the CyberKnife system. The total reirradiation dose was 30 Gy in five fractions. Prior to radiosurgery four patients were treated with androgen-deprivation therapy. Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria and the Houston-Phoenix definition (PSA nadir + 2 ng/mL) were used for toxicity and biochemical failure evaluation, respectively. After a median follow-up of 11.2 months (range, 9.6-18.6 months), all patients are alive with no evidence of severe urinary or rectal acute morbidity. Local control cannot be exactly determined due to the short follow-up and the bias of the use of androgen ablation. Four patients had biochemical failure, three of them with clinical failure evidence (lymph node, bone and lung metastasis, respectively): none of these patients had clinical evidence of tumor persistence in the prostate. Salvage radiosurgery with CyberKnife after irradiation is feasible with low urinary and rectal morbidity. A longer follow-up and a larger number of patients are necessary to evaluate its effectiveness and optimal patient selection criteria.