Plan Quality and Treatment Efficiency for Radiosurgery to Multiple Brain Metastases: Non-Coplanar RapidArc vs. Gamma Knife.

OBJECTIVES: This study compares the dosimetry and efficiency of two modern radiosurgery [stereotactic radiosurgery (SRS)] modalities for multiple brain metastases [Gamma Knife (GK) and LINAC-based RapidArc/volumetric modulated arc therapy], with a special focus on the comparison of low-dose spread. METHODS: Six patients with three or four small brain metastases were used in this study. The size of targets varied from 0.1 to 10.5 cc. SRS doses were prescribed according to the size of lesions. SRS plans were made using both Gamma Knife(®) Perfexion and a single-isocenter, multiple non-coplanar RapidArc(®). Dosimetric parameters analyzed included RTOG conformity index (CI), gradient index (GI), 12 Gy isodose volume (V 12Gy) for each target, and the dose spread (Dspread) for each plan. Dspread reflects SRS plan\u27s capability of confining radiation to within the local vicinity of the lesion and to not spread out to the surrounding normal brain tissues. Each plan has a dose (Dspread), such that once dose decreases below Dspread (on total tissue dose-volume histogram), isodose volume starts increasing dramatically. Dspread is defined as that dose when volume increase first exceeds 20 cc/0.1 Gy dose decrease. RESULTS: RapidArc SRS has smaller CI (1.19 ± 0.14 vs. 1.50 ± 0.16, p \u3c 0.001) and larger GI (4.77 ± 1.49 vs. 3.65 ± 0.98, p \u3c 0.01). V 12Gy results were comparable (2.73 ± 1.38 vs. 3.06 ± 2.20 cc, p = 0.58). Moderate to lower dose spread, V6, V4.5, and V3, were also equivalent. GK plans achieved better very low-dose spread (≤3 Gy) and also had slightly smaller Dspread, 1.9 vs. 2.5 Gy. Total treatment time for GK is estimated between 60 and 100 min. GK treatments are between 3 and 5 times longer compared to RapidArc treatment techniques. CONCLUSION: Dosimetric parameters reflecting prescription dose conformality (CI), dose fall off (GI), radiation necrosis indicator (V 12Gy), and dose spread (Dspread) were compared between GK SRS and RapidArc SRS for multi-mets. RapidArc plans have smaller CI but larger GI. V 12Gy are comparable. GK appears better at reducing only very low-dose spread (\u3c3 \u3eGy). The treatment time of RapidArc SRS is significantly reduced compared to GK SRS

LINAC based stereotactic radiosurgery for multiple brain metastases: guidance for clinical implementation

Introduction: Stereotactic radiosurgery (SRS) is a promising treatment option for patients with multiple brain metastases (BM). Recent technical advances have made LINAC based SRS a patient friendly technique, allowing for accurate patient positioning and a short treatment time. Since SRS is increasingly being used for patients with multiple BM, it remains essential that SRS be performed with the highest achievable quality in order to prevent unnecessary complications such as radionecrosis. The purpo

Image-Guided Hypofractionated Radiosurgery of Large and Complex Brain Lesions

Hypofractionated radiosurgery either through frame or image guidance has emerged as the most important area of research and development for intracranial and extracranial radiosurgery. In this chapter, we focused on discussions of three state-of-the-art platforms: Frame- and Image-Guided Gamma Knife, Robotic X-Band Cykerknife, and Flattening-Filter-Free intensity-modulated S-band medical linear accelerators. Practical principles with detailed workflow and clinical implementations are presented in a systematic approach. With rapid evolvement of both hardware and software in the realm of delivering hypofractionated radiosurgery, this chapter aims to offer a reader physical clarity on judging and balancing of achieving high-precision and high-quality treatments with practical examples and guidelines on intracranial applications

ISRS Technical Guidelines for Stereotactic Radiosurgery: Treatment of Small Brain Metastases (≤1 cm in Diameter).

The objective of this literature review was to develop International Stereotactic Radiosurgery Society (ISRS) consensus technical guidelines for the treatment of small, ≤1 cm in maximal diameter, intracranial metastases with stereotactic radiosurgery. Although different stereotactic radiosurgery technologies are available, most of them have similar treatment workflows and common technical challenges that are described. A systematic review of the literature published between 2009 and 2020 was performed in Pubmed using the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) methodology. The search terms were limited to those related to radiosurgery of brain metastases and to publications in the English language. From 484 collected abstract 37 articles were included into the detailed review and bibliographic analysis. An additional 44 papers were identified as relevant from a search of the references. The 81 papers, including additional 7 international guidelines, were deemed relevant to at least one of five areas that were considered paramount for this report. These areas of technical focus have been employed to structure these guidelines: imaging specifications, target volume delineation and localization practices, use of margins, treatment planning techniques, and patient positioning. This systematic review has demonstrated that Stereotactic Radiosurgery (SRS) for small (1 cm) brain metastases can be safely performed on both Gamma Knife (GK) and CyberKnife (CK) as well as on modern LINACs, specifically tailored for radiosurgical procedures, However, considerable expertise and resources are required for a program based on the latest evidence for best practice

Trauma, Tumors, Spine, Functional Neurosurgery

This book is written for graduate students, researchers, and practitioners who are interested in learning how the knowledge from research can be implemented in clinical competences. The first section is dedicated to deep brain stimulation, a surgical procedure which is the paramount example of how clinical practice can take advantage from fundamental research. The second section gathers four chapters on four different topics and illustrates how significant is the challenge to translate scientific advances into clinical practice because the route from evidence to action is not always obvious. It is hoped that this book will stimulate the interest in the process of translating research into practice for a broader range of neurosurgical topics than the one covered by this book, which could result in a forthcoming more comprehensive publication

Intensity modulated radiation therapy and arc therapy: validation and evolution as applied to tumours of the head and neck, abdominal and pelvic regions

Intensiteitsgemoduleerde radiotherapie (IMRT) laat een betere controle over de dosisdistributie (DD) toe dan meer conventionele bestralingstechnieken. Zo is het met IMRT mogelijk om concave DDs te bereiken en om de risico-organen conformeel uit te sparen. IMRT werd in het UZG klinisch toegepast voor een hele waaier van tumorlocalisaties. De toepassing van IMRT voor de bestraling van hoofd- en halstumoren (HHT) vormt het onderwerp van het eerste deel van deze thesis. De planningsstrategie voor herbestralingen en bestraling van HHT, uitgaande van de keel en de mondholte wordt beschreven, evenals de eerste klinische resultaten hiervan. IMRT voor tumoren van de neus(bij)holten leidt tot minstens even goede lokale controle (LC) en overleving als conventionele bestralingstechnieken, en dit zonder stralingsgeïnduceerde blindheid. IMRT leidt dus tot een gunstiger toxiciteitprofiel maar heeft nog geen bewijs kunnen leveren van een gunstig effect op LC of overleving. De meeste hervallen van HHT worden gezien in het gebied dat tot een hoge dosis bestraald werd, wat erop wijst dat deze “hoge dosis” niet volstaat om alle clonogene tumorcellen uit te schakelen. We startten een studie op, om de mogelijkheid van dosisescalatie op geleide van biologische beeldvorming uit te testen. Naast de toepassing en klinische validatie van IMRT bestond het werk in het kader van deze thesis ook uit de ontwikkeling en het klinisch opstarten van intensiteitgemoduleerde arc therapie (IMAT). IMAT is een rotationele vorm van IMRT (d.w.z. de gantry draait rond tijdens de bestraling), waarbij de modulatie van de intensiteit bereikt wordt door overlappende arcs. IMAT heeft enkele duidelijke voordelen ten opzichte van IMRT in bepaalde situaties. Als het doelvolume concaaf rond een risico-orgaan ligt met een grote diameter, biedt IMAT eigenlijk een oneindig aantal bundelrichtingen aan. Een planningsstrategie voor IMAT werd ontwikkeld, en type-oplossingen voor totaal abdominale bestraling en rectumbestraling werden onderzocht en klinisch toegepast

Cerebral arteriovenous malformations : molecular biology and enhancement of radiosurgical treatment

Object Rupture of intracranial arteriovenous malformations is a leading cause of stroke in children and young adults. Treatment options include surgery and highly focused radiation (stereotactic radiosurgery). For large and deep seated lesions, the risks of surgery may be prohibitively high, while radiosurgery has a disappointingly low efficacy and long latency. Radiosurgery carries the most promise for significant advances, however the process by which radiosurgery achieves obliteration is incompletely understood. Inflammation and thrombosis are likely to be important in the radiation response and may be amenable to pharmacological manipulation to improve radiosurgical efficacy. Materials and methods Immunohistochemistry and electron microscopy were used to study normal cerebral vessels, cavernous malformations and AVMs, some of which had previously been irradiated. An attempt was made to culture AVM endothelial cells to study the immediate response of AVM endothelium to radiosurgery. The effects of radiosurgery in a rat model of AVM were studied using immunohistochemistry and the results used to determine the choice of a pharmacological strategy to enhance the thrombotic effects of radiosurgery. Results Vascular malformations have a different endothelial inflammatory phenotype than normal cerebral vessels. Radiosurgery may cause long term changes in inflammatory molecule expression and leads to endothelial loss with exposure of pro-thrombotic molecules. Ultrastructural effects of irradiation include widespread cell loss, smooth muscle cell (SMC) proliferation and thrombosis. Endothelial culture from AVMs proved difficult due to SMC predominance in initial cultures. Radiosurgery upregulated several endothelial inflammatory molecules in the animal model and may induce pro-thrombotic cell membrane alterations. The administration of lipopolysaccharide and soluble tissue factor to rats following radiosurgery led to selective thrombosis of irradiated vessels. Conclusions Inflammation and thrombosis are important in the radiosurgical response of AVMs. Lumen obliteration appears to be mediated by proliferation of cells within the vessel wall and thrombosis. Upregulation of inflammatory molecules and perhaps disruption of the normal phospholipid asymmetry of the endothelial and SMC membranes are some of the earliest responses to radiosurgery. The alterations induced by radiation may be harnessed to selectively initiate thrombus formation. Stimulation of thrombosis may improve the efficacy of radiosurgery, increasing treatable lesion size and reducing latency