The Variable Ellipsoid Modeling Technique as a Verification Method for the Treatment Planning System of Gamma Knife Radiosurgery

OBJECTIVEThe role of tractography in Gamma Knife thalamotomy (GK-T) planning is still unclear. Pyramidal tractography might reduce the risk of radiation injury to the pyramidal tract and reduce motor complications.METHODSIn this study, the ventralis intermedius nucleus (VIM) targets of 20 patients were bilaterally defined using Iplannet Stereotaxy Software, according to the anterior commissure–posterior commissure (AC-PC) line and considering the localization of the pyramidal tract. The 40 targets and tractography were transferred as objects to the GammaPlan Treatment Planning System (GP-TPS). New targets were defined, according to the AC-PC line in the functional targets section of the GP-TPS. The target offsets required to maintain the internal capsule (IC) constraint of < 15 Gy were evaluated. In addition, the strategies available in GP-TPS to maintain the minimum conventional VIM target dose at > 100 Gy were determined.RESULTSA difference was observed between the positions of both targets and the doses to the IC. The lateral (x) and the vertical (z) coordinates were adjusted 1.9 mm medially and 1.3 mm cranially, respectively. The targets defined considering the position of the pyramidal tract were more medial and superior, based on the constraint of 15 Gy touching the object representing the IC in the GP-TPS. The best strategy to meet the set constraints was 90° Gamma angle (GA) with automatic shaping of dose distribution; this was followed by 110° GA. The worst GA was 70°. Treatment time was substantially increased by the shaping strategy, approximately doubling delivery time.CONCLUSIONSRoutine use of DTI pyramidal tractography might be important to fine-tune GK-T planning. DTI tractography, as well as anisotropy showing the VIM, promises to improve Gamma Knife functional procedures. They allow for a more objective definition of dose constraints to the IC and targeting. DTI pyramidal tractography introduced into the treatment planning may reduce the incidence of motor complications and improve efficacy. This needs to be validated in a large clinical series.

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A real-time optimal inverse planning for Gamma Knife radiosurgery by convex optimization: description of the system and first dosimetry data

Journal of Neurosurgery ◽

10.3171/2018.7.gks181572 ◽

2018 ◽

Vol 129 (Suppl1) ◽

pp. 111-117 ◽

Cited By ~ 4

Author(s):

Marc Levivier ◽

Rafael E. Carrillo ◽

Rémi Charrier ◽

André Martin ◽

Jean-Philippe Thiran

Keyword(s):

Convex Optimization ◽

Real Time ◽

Treatment Planning ◽

Gamma Knife ◽

Gamma Knife Radiosurgery ◽

Planning System ◽

Optimal Plan ◽

Inverse Planning ◽

Planning Approach ◽

Dosimetry Data

OBJECTIVEThe authors developed a new, real-time interactive inverse planning approach, based on a fully convex framework, to be used for Gamma Knife radiosurgery.METHODSThe convex framework is based on the precomputation of a dictionary composed of the individual dose distributions of all possible shots, considering all their possible locations, sizes, and shapes inside the target volume. The convex problem is solved to determine the plan, i.e., which shots and with which weights, that will actually be used, considering a sparsity constraint on the shots to fulfill the constraints while minimizing the beam-on time. The system is called IntuitivePlan and allows data to be transferred from generated dose plans into the Gamma Knife treatment planning software for further dosimetry evaluation.RESULTSThe system has been very efficiently implemented, and an optimal plan is usually obtained in less than 1 to 2 minutes, depending on the complexity of the problem, on a desktop computer or in only a few minutes on a high-end laptop. Dosimetry data from 5 cases, 2 meningiomas and 3 vestibular schwannomas, were generated with IntuitivePlan. Results of evaluation of the dosimetry characteristics are very satisfactory and adequate in terms of conformity, selectivity, gradient, protection of organs at risk, and treatment time.CONCLUSIONSThe possibility of using optimal, interactive real-time inverse planning in conjunction with the Leksell Gamma Knife opens new perspectives in radiosurgery, especially considering the potential use of the full capabilities of the latest generations of the Leksell Gamma Knife. This approach gives new users the possibility of using the system for easier and quicker access to good-quality plans with a shorter technical training period and opens avenues for new planning strategies for expert users. The use of a convex optimization approach allows an optimal plan to be provided in a very short processing time. This way, innovative graphical user interfaces can be developed, allowing the user to interact directly with the planning system to graphically define the desired dose map and to modify on-the-fly the dose map by moving, in a very user-friendly manner, the isodose surfaces of an initial plan. Further independent quantitative prospective evaluation comparing inverse planned and forward planned cases is warranted to validate this novel and promising treatment planning approach.

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Linac-stereotactic radiosurgery (LSRS) in the management of trigeminal neuralgia

Journal of Clinical Oncology ◽

10.1200/jco.2006.24.18_suppl.18603 ◽

2006 ◽

Vol 24 (18_suppl) ◽

pp. 18603-18603

Author(s):

S. Gurley ◽

R. Mark ◽

P. J. Anderson ◽

T. Neumann ◽

M. Nair

Keyword(s):

Trigeminal Neuralgia ◽

Stereotactic Radiosurgery ◽

Treatment Planning ◽

Gamma Knife ◽

Root Zone ◽

Planning System ◽

Response To Treatment ◽

Treatment Planning System ◽

Facial Numbness ◽

Mri Scans

18603 Background: Stereotactic Radiosurgery (SRS) with the Gamma Knife (GK) has been used successfully in the treatment of Trigeminal Neuralgia (TN). Results have been comparable to open surgery. There have been few reports with the use of LSRS in the management of TN. We report our updated results with LSRS in the treatment of TN. Methods: Between 2000 and 2006, 37 patients with medically refractory TN were treated with LSRS. Prior neurosurgical intervention had been performed in 28 patients. Ten patients had one procedure, 10 patients two, and 3 patients three interventions. All patients had typical TN. LSRS was given to the cranial nerve V entry root zone into the brainstem. Targeting was defined by CT and MRI Scans, and CT Cisternogram, utilizing axial, coronal, and sagittal images. Treatment planning was accomplished thru the Radionics Treatment Planning System. The dose was 87 Gy to Dm, in one fraction using the 5 mm collimator and 6 arcs with the 20% Isodose line just touching the brainstem. This dosimetry is similar to Gamma Knife. The dose rate was 400 MU/min. Average Arc length was 130 degrees. Response to treatment was defined as excellent (no pain, off analgesics), good (no pain, with analgesics), and poor (continued pain despite analgesics). Results: With a median follow-up of 40 months (range 6–72 months), 73% (27/37) of patients have reported an excellent or good result after LSRS. One patient has sustained permanent ipsilateral facial numbness. Conclusions: LSRS offers comparable results to Gamma Knife SRS, with respect to both pain relief and complications, in the management of TN. No significant financial relationships to disclose.

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SU-FF-T-70: An Independent Verification of Dosimetry for the Leksell Gamma Knife® Treatment Planning System

Medical Physics ◽

10.1118/1.2760721 ◽

2007 ◽

Vol 34 (6Part8) ◽

pp. 2416-2417

Author(s):

M Weldon ◽

N Gupta ◽

C Kanellitsas

Keyword(s):

Treatment Planning ◽

Gamma Knife ◽

Planning System ◽

Treatment Planning System ◽

Independent Verification

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3-D treatment planning system—Leksell Gamma Knife treatment planning system

Medical Dosimetry ◽

10.1016/j.meddos.2018.03.001 ◽

2018 ◽

Vol 43 (2) ◽

pp. 177-183

Author(s):

Fanqing Guo

Keyword(s):

Treatment Planning ◽

Gamma Knife ◽

Planning System ◽

Treatment Planning System

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Three-dimensional assessment of the effects of high-density embolization material on the absorbed dose in the target for Gamma Knife radiosurgery of arteriovenous malformations

Journal of Neurosurgery ◽

10.3171/2016.7.gks161545 ◽

2016 ◽

Vol 125 (Supplement_1) ◽

pp. 123-128 ◽

Cited By ~ 2

Author(s):

Yoichi Watanabe ◽

Divyajot Sandhu ◽

Leighton Warmington ◽

Sean Moen ◽

Ramachandra Tummala

Keyword(s):

Treatment Planning ◽

Gamma Knife ◽

Gamma Knife Radiosurgery ◽

High Density ◽

Planning System ◽

Fixation Method ◽

Polymer Gel ◽

Dose Distributions ◽

Embolic Material ◽

Dose Difference

OBJECTIVEArteriovenous malformation (AVM) is an intracranial vascular disorder. Gamma Knife radiosurgery (GKRS) is used in conjunction with intraarterial embolization to eradicate the nidus of AVMs. Clinical results indicate that patients with prior embolization tend to gain less benefit from GKRS. The authors hypothesized that this was partly caused by dosimetric deficiency. The actual dose delivered to the target may be smaller than the intended dose because of increased photon attenuation by high-density embolic materials. The authors performed a phantom-based study to quantitatively evaluate the 3D dosimetric effect of embolic material on GKRS.METHODSA 16-cm-diameter and 12-cm-long cylindrical phantom with a 16-cm-diameter hemispherical dome was printed by a 3D printer. The phantom was filled with radiologically tissue-equivalent polymer gel. To simulate AVM treatment with embolization, phantoms contained Onyx 18. The material was injected into an AVM model, which was suspended in the polymer gel. The phantom was attached to a Leksell frame by standard GK fixation method, using aluminum screws, for imaging. The phantom was scanned by a Phillips CT scanner with the standard axial-scanning protocol (120 kV and 1.5-mm slice thickness). CT-based treatment planning was performed with the GammaPlan treatment planning system (version 10.1.1). The plan was created to cover a fictitious AVM target volume near the embolization areas with eleven 8-mm shots and a prescription dose of 20 Gy to 50% isodose level. Dose distributions were computed using both tissue maximum ratio (TMR) 10 and convolution dose-calculation algorithms. These two 3D dose distributions were compared using an in-house program. Additionally, the same analysis method was applied to evaluate the dosimetric effects for 2 patients previously treated by GKRS.RESULTSThe phantom-based analyses showed that the mean dose difference between TMR 10 and convolution doses of the AVM target was no larger than 6%. The difference for GKRS cases was 5%. There were small areas where a large dose difference was observed on the isodose line plots, and those differences were mostly at or in the vicinity of the embolization materials.CONCLUSIONSThe results of both the phantom and patient studies showed a dose reduction no larger than 5% due to the embolization material placed near the target. Although the comparison of 3D dose distributions indicated small local effects of the embolic material, the clinical impact on the obliteration rate is expected to be small.

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Dosimetric comparison of fractionated radiosurgery plans using frameless Gamma Knife ICON and CyberKnife systems with linear accelerator–based radiosurgery plans for multiple large brain metastases

Journal of Neurosurgery ◽

10.3171/2019.1.jns182769 ◽

2020 ◽

Vol 132 (5) ◽

pp. 1473-1479 ◽

Cited By ~ 5

Author(s):

Eun Young Han ◽

He Wang ◽

Dershan Luo ◽

Jing Li ◽

Xin Wang

Keyword(s):

Brain Metastases ◽

Gamma Knife ◽

Linear Accelerator ◽

Treatment Time ◽

Target Volume ◽

Planning System ◽

Treatment Planning System ◽

Normal Brain ◽

Large Brain ◽

The Mean

OBJECTIVEFor patients with multiple large brain metastases with at least 1 target volume larger than 10 cm3, multifractionated stereotactic radiosurgery (MF-SRS) has commonly been delivered with a linear accelerator (LINAC). Recent advances of Gamma Knife (GK) units with kilovolt cone-beam CT and CyberKnife (CK) units with multileaf collimators also make them attractive choices. The purpose of this study was to compare the dosimetry of MF-SRS plans deliverable on GK, CK, and LINAC and to discuss related clinical issues.METHODSTen patients with 2 or more large brain metastases who had been treated with MF-SRS on LINAC were identified. The median planning target volume was 18.31 cm3 (mean 21.31 cm3, range 3.42–49.97 cm3), and the median prescribed dose was 27.0 Gy (mean 26.7 Gy, range 21–30 Gy), administered in 3 to 5 fractions. Clinical LINAC treatment plans were generated using inverse planning with intensity modulation on a Pinnacle treatment planning system (version 9.10) for the Varian TrueBeam STx system. GK and CK planning were retrospectively performed using Leksell GammaPlan version 10.1 and Accuray Precision version 1.1.0.0 for the CK M6 system. Tumor coverage, Paddick conformity index (CI), gradient index (GI), and normal brain tissue receiving 4, 12, and 20 Gy were used to compare plan quality. Net beam-on time and approximate planning time were also collected for all cases.RESULTSPlans from all 3 modalities satisfied clinical requirements in target coverage and normal tissue sparing. The mean CI was comparable (0.79, 0.78, and 0.76) for the GK, CK, and LINAC plans. The mean GI was 3.1 for both the GK and the CK plans, whereas the mean GI of the LINAC plans was 4.1. The lower GI of the GK and CK plans would have resulted in significantly lower normal brain volumes receiving a medium or high dose. On average, GK and CK plans spared the normal brain volume receiving at least 12 Gy and 20 Gy by approximately 20% in comparison with the LINAC plans. However, the mean beam-on time of GK (∼ 64 minutes assuming a dose rate of 2.5 Gy/minute) plans was significantly longer than that of CK (∼ 31 minutes) or LINAC (∼ 4 minutes) plans.CONCLUSIONSAll 3 modalities are capable of treating multiple large brain lesions with MF-SRS. GK has the most flexible workflow and excellent dosimetry, but could be limited by the treatment time. CK has dosimetry comparable to that of GK with a consistent treatment time of approximately 30 minutes. LINAC has a much shorter treatment time, but residual rotational error could be a concern.

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