Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 
Year : 2014  |  Volume : 10  |  Issue : 1  |  Page : 29-37

Critical neurological structure sparing radiosurgery of vestibular schwannoma: Dosimetric comparison of different techniques and dose prescription methods

1 Department of Radiation Oncology, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Andheri, Mumbai, India
2 Department of Neurosurgery, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Andheri, Mumbai, India

Correspondence Address:
Shamurailatpam Dayananda Sharma
Department of Radiation Oncology, Room No AS/55024, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Four Bungalows, Andheri (W), Mumbai - 400 053
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0973-1482.131353

Rights and Permissions

Aim: To investigate potential sparing of critical neurological structures (CNSs) during radiosurgery of vestibular schwannoma (VS) employing different techniques and dose prescription methods. Materials and Methods: Fused CT and MRI datasets of eight patients with unilateral VS representing a wide range of target volume (0.48 to 12.08 cc; mean = 3.56 cc), shape and proximity to CNSs such as cochlea, trigeminal nerve and brainstem were re-planned employing static conformal field (SCF), dynamic conformal arc (DCA) and intensity modulated radiosurgery (IMRS) techniques. For every patient, five plans were created for a fixed margin dose of 12 Gy prescribed at 80% in three plans (SCF_80%, DCA_80%, and IMRS_80%) and 50% in another two plans (SCF_50% and DCA_50%). All plans were compared using standard dosimetric indices. Results: Primary goal of every plan to cover ≥99% of target volume with 12 Gy was fulfilled for all patients with minimum significant dose to target (D 99 ) ≥11.99 Gy. Best conformity index (CI Paddick = 0.62 ± 0.12) was observed in SCF_80% and DCA_80% plans whereas; sharpest dose gradient index of 3.40 ± 0.40 was resulted from DCA_50%. All five plans resulted similar maximum dose to brainstem (11.04 ± 2.23 to 11.53 ± 1.10 Gy), cochlea (9.02 ± 1.79 to 10.15 ± 1.26 Gy) and trigeminal nerve (11.55 ± 1.38 to 12.19 ± 2.12 Gy). Among 80% prescription plans, IMRS_80% reduces mean and D 5 (P < 0.05) to all CNSs. Prescription of dose at 50% isodose sharpened the dose gradient and significantly (P < 0.05) reduced mean dose and D 5 to all CNSs at the cost of target conformity (P = 0.01). Mean dose to cochlea and trigeminal nerve were least at 4.53 ± 0.86 and 6.95 ± 2.02 Gy from SCF_50% and highest at 6.65 ± 0.70 and 8.40 ± 2.11 Gy from DCA_80% plans respectively. Conclusion: This dosimetric data provides a guideline for choosing optimum treatment option and scope of inter institutional dosimetric comparison for further improvement in radiosurgery of Vestibular Schwannoma (VS).

Abstract in Chinese

前庭神经鞘瘤放射治疗中关键神经结构的保护:不同技术和处方剂量的剂量测定对照 目的:通过不同技术和处方剂量的方法评估前庭神经鞘瘤(VS)放疗过程中关健神经结构(CNSs)的潜在保护。 材料和方法:将8例单侧前庭神经鞘瘤病人CT和MRI融合资料,发现他们靶区容量差别较大(0.48cc到12.08cc;平均3.56cc),靠近关键神经结构如耳蜗、三叉神经和脑干处的靶区予重新计划,分别通过普通放疗(SCF),适形放疗(DCA),以及调强放疗(IMRS)技术。对每例病人,5次计划分别给予12Gy的固定剂量范围,三次给予80%等剂量线(SCF_80%, DCA_80%, IMRS_80%),另两次予以50%等剂量线(SCF_50%,DCA_50%)。所有计划用标准剂量指数来比较。 结果:每次计划的的主要目标,以12Gy剂量覆盖≥99%的靶区容量(D99),使所有病人病灶的最小有效剂量≥11.99Gy。最佳符合指数在SCF_80%和DCA_80%计划中可以得到(CIPaddick= 0.62 ± 0.12),而在DCA_50%计划中得出最锐利的剂量梯度曲线:3.40± 0.40。5次计划得出相似的最大剂量:脑干(11.04± 2.23 到11.53± 1.10Gy),耳蜗(9.02± 1.79到10.15 ± 1.26 Gy),三叉神经(11.55± 1.38 到12.19± 2.12Gy)。80%等剂量线处方计划中,调强80%减少了关键神经结构的平均剂量和D5(P<0.05)。50%处方等剂量线明显改变剂量梯度(P<0.05),减少关键神经结构的平均剂量和D5,但是改变了靶区一致性(P=0.01)。耳蜗和三叉神经的平均剂量至少为SCF_50%的4.53± 0.86和 6.95± 2.02Gy,最高达DCA_80%的6.65± 0.70和 8.40± 2.11Gy 。 结论:本次剂量测定的数据提供了最佳治疗选择方案的指导方针,以及机构间进一步改进治疗前庭神经鞘瘤剂量的范围。 关键词:耳蜗,放射量测定,调强放疗,放疗外科学,三叉神经,前庭神经鞘瘤

Print this article     Email this article
 Next article
 Previous article
 Table of Contents

 Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
 Citation Manager
 Access Statistics
 Reader Comments
 Email Alert *
 Add to My List *
 * Requires registration (Free)

 Article Access Statistics
    PDF Downloaded135    
    Comments [Add]    

Recommend this journal