Dosimetric comparison of the Leksell Gamma Knife Perfexion and 4C

Object The recently introduced Leksell Gamma Knife (LGK) Perfexion is an entirely new system with a different beam geometry compared with the LGK 4C. The new Perfexion system has 192 cobalt-60 sources that are fixed on 8 sectors (each sector has 24 sources). Each sector can be moved independently of the others and can be set to 1 of 5 different positions: 3 positions defining collimator sizes of 4, 8, and 16 mm; an off position (sources are blocked); and a home position. The purpose of this study is to compare the dosimetric characteristics of the GK 4C and the Perfexion models. This comparison is important especially for the treatment of functional disorders when only a single shot with the 4- or 8-mm collimator is used. Methods A 160-mm-diameter spherical polystyrene phantom was used for all measurements and calculations. The irradiation geometry consisted of the placement of a single shot at the center of this phantom. Comparisons were made among different dosimetric parameters obtained from calculations performed using Leksell GammaPlan v. 8.0 and measurements performed using film dosimetry. The dosimetric parameters investigated were dose profiles for all collimators in all 3 stereotactic planes (x, y, and z) including the full width at half maximum and the penumbra for each profile, cumulative dose–volume histograms, the volume encompassed by the 50% isodose surface, the mean doses delivered to a defined matrix volume, and relative output factors for all collimator sizes. Results There was excellent agreement between the dosimetric parameters of GK 4C and Perfexion for the 4- and 8-mm collimators. Conclusions The results of this study suggest that consistent treatments of functional disorders will be delivered using either GK 4C or Perfexion.

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Method of predicting the mean lung dose based on a patient׳s anatomy and dose-volume histograms

Medical Dosimetry ◽

10.1016/j.meddos.2016.12.001 ◽

2017 ◽

Vol 42 (1) ◽

pp. 57-62 ◽

Cited By ~ 5

Author(s):

Anna Zawadzka ◽

Marta Nesteruk ◽

Beata Brzozowska ◽

Paweł F. Kukołowicz

Keyword(s):

Lung Dose ◽

Dose Volume Histograms ◽

Dose Volume ◽

The Mean ◽

Mean Lung Dose

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The mean absolute dose deviation–A common metric for the evaluation of dose-volume histograms in radiation therapy

Medical Dosimetry ◽

10.1016/j.meddos.2019.10.004 ◽

2020 ◽

Vol 45 (2) ◽

pp. 186-189 ◽

Cited By ~ 3

Author(s):

Vincent Vinh-Hung ◽

Nicolas Leduc ◽

Dirk Verellen ◽

Claire Verschraegen ◽

Giovanna Dipasquale ◽

...

Keyword(s):

Radiation Therapy ◽

Dose Volume Histograms ◽

Dose Volume ◽

The Mean

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An Effective Method of Simulation for the Leksell Gamma Knife Perfexion by Rotating Particles in the Phase Space File

Medical Radiology and radiation safety ◽

10.12737/1024-6177-2020-65-1-54-58 ◽

2020 ◽

Vol 65 (1) ◽

pp. 54-58

Author(s):

T. Medjadj ◽

A. Ksenofontov ◽

A. Dalechina

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

Phase Space ◽

Gamma Knife ◽

Homogeneous Medium ◽

Planning System ◽

Monte Carlo Code ◽

Output Factors ◽

Gamma Knife Perfexion ◽

Conical Form

Purpose: To develop an effective method of Monte Carlo simulation of the GammaKnife Perfexion system by rotating particles in the phase space file (PSF). This method does not require simulating of all 192 sources that are distributed in the conical form of the Perfexion collimator. The simulation was performed only for 5 out of 192 sources for each collimator size. Material and methods: Monte Carlo simulation of dose distribution for previous models of GammaKnife system requires phase space file for only one source, since this phase space is identical for all the 201 sources. The Perfexion model is more complex due to the non-coaxial positions of the sources and the complexity of the collimator system itself. In this work, we present an effective method to simulate the Perfexion model using a phase space file. Penelope Monte Carlo code was used to perform this simulation. In this method, the PSF was obtained for one source in each ring, resulting in five files for each collimator size. PSF for other sources were created by azimuthal redistribution of particles, in the obtained PSF, by rotation around the Z-axis. The phase space files of the same ring were then stored together in a single file. Results: The paper presented MC simulation using the azimuthal redistribution of particles in the phase space file by rotation around the Z-axis. The simulation has been validated comparing the dose profiles and output factors with the data of the algorithm TMR10 planning system Leksell Gamma Plan (LGP) in a homogeneous environment. The acceptance criterion between TMR10 and Monte Carlo calculations for the profiles was based on the gamma index (GI). Index values more than one were not detected in all cases, which indicates a good agreement of results. The differences between the output factors obtained in this work and the TMR10 data for collimators 8 mm and 4 mm are 0.74 and 0.73 %, respectively. Conclusion: In this work successfully implemented an effective method of simulating the Leksell Gamma knife Perfexion system. The presented method does not require modeling for all 192 sources distributed in the conical form of the Perfexion collimator. The simulation was performed for only five sources for each collimator and their files PSF were obtained. These files were used to create the PSF files for other sources by azimuthal redistribution of particles, in these files, by rotation around the Z-axis providing correct calculations of dose distributions in a homogeneous medium for 16, 8 and 4 mm collimators.

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Measurement of relative output factors for the 8 and 4 mm collimators of Leksell Gamma Knife Perfexion by film dosimetry

Medical Physics ◽

10.1118/1.3113904 ◽

2009 ◽

Vol 36 (5) ◽

pp. 1768-1774 ◽

Cited By ~ 27

Author(s):

Josef Novotny ◽

Jagdish P. Bhatnagar ◽

Mubina A. Quader ◽

Greg Bednarz ◽

L. Dade Lunsford ◽

...

Keyword(s):

Gamma Knife ◽

Film Dosimetry ◽

Output Factors ◽

Gamma Knife Perfexion

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Predictors of Hearing Loss After Gamma Knife Radiosurgery for Vestibular Schwannomas: Age, Cochlear Dose, and Tumor Coverage

Neurosurgery ◽

10.1227/neu.0b013e31821a42f3 ◽

2011 ◽

Vol 69 (3) ◽

pp. 605-614 ◽

Cited By ~ 28

Author(s):

Melandee Brown ◽

Michael Ruckenstein ◽

Douglas Bigelow ◽

Kevin Judy ◽

Vasthi Wilson ◽

...

Keyword(s):

Hearing Loss ◽

Gamma Knife ◽

Odds Ratio ◽

Pure Tone ◽

Tumor Volume ◽

Gamma Knife Radiosurgery ◽

Hearing Preservation ◽

Dose Volume Histograms ◽

Pure Tone Average ◽

Dose Volume

Abstract BACKGROUND: Deterioration in hearing after Gamma Knife radiosurgery of vestibular schwannomas is a well-documented risk. Recent studies suggest a correlation between cochlear radiation dose and hearing preservation. OBJECTIVE: This study identifies additional variables that predict hearing loss after radiosurgery. METHODS: Retrospective analysis of 53 patients with audiogram follow-up. Median marginal tumor dose was 12.5 Gy. Mean tumor volume was 1.11 cm3. Statistical analysis included multivariate stepwise backward linear regression and multivariate logistic regression. Variables included age, prescription dose, tumor volume, intracanalicular length, and maximum and mean cochlear dose. Dose volume histograms were generated. The percentage of the cochlear volume that received 3.6 Gy or greater, 4.7 Gy or greater, and 5.3 Gy or greater was calculated. Plan conformality indicators were calculated. RESULTS: Forty-two patients had a less than 20-dB change in their pure tone average, with a hearing preservation rate of 79%. Two statistically significant predictors of hearing loss were identified using multivariate analysis: tumor coverage (odds ratio: 1.38 × 1018) and age (odds ratio: 1.1 per year). Multivariate linear regression was used to predict change in pure tone average. Age and percentage of the cochlear volume receiving 5.3 Gy or greater were found to be statistically significant predictor variables. CONCLUSION: Older patients are more vulnerable to detrimental effects of Gamma Knife radiosurgery on hearing. We propose that cochlear dose volume histograms be created and used to reduce the percentage of the cochlear volume exposed to radiation doses greater than 5.3 Gy. This is the first report to suggest that the conformity index tumor coverage may be an important predictor of hearing outcomes.

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Gamma knife radiosurgery for trigeminal neuralgia: dose—volume histograms of the brainstem and trigeminal nerve

Journal of Neurosurgery ◽

10.3171/jns.2000.93.supplement_3.0155 ◽

2000 ◽

Vol 93 (supplement_3) ◽

pp. 155-158 ◽

Cited By ~ 55

Author(s):

Ronald Brisman ◽

R. Mooij

Keyword(s):

Pain Relief ◽

Trigeminal Neuralgia ◽

Gamma Knife ◽

Trigeminal Nerve ◽

Maximum Dose ◽

Gamma Knife Radiosurgery ◽

Content Type ◽

Dose Volume Histograms ◽

Dose Volume ◽

Fine Print

Object. The purpose of this study was to assess the relationship between the volume of brainstem that receives 20% or more of the maximum dose (VB20) and the volume of the trigeminal nerve that receives 50% or more of the maximum dose (VT50) on clinical outcome following gamma knife radiosurgery (GKS) for trigeminal neuralgia (TN). Methods. Patients with TN were treated with a single 4-mm isocenter with a maximum dose of 75 Gy directed at the trigeminal nerve close to where it leaves the brainstem. The VB20 and VT50, as determined on dose—volume histograms, were correlated with clinical outcomes at 6 and 12 months, laterality, presence of multiple sclerosis (MS), and each other. At 6 months excellent pain relief (no pain or required medicine) was achieved in 27 of 48 patients (p = 0.009) when VB20 was greater than or equal to 20 mm3 and in 25 of 78 when VB20 was less than 20 mm3, when all patients are considered. At 12 months excellent pain relief was achieved in 16 of 32 patients (p = 0.038) when VB20 was greater than or equal to 20 mm3 and in 14 of 52 when VB20 less than 20 mm3, when all patients are considered. When VB20 was less than 20 mm3 in MS patients, five of 21 had an excellent result at 6 months and two of 13 at 12 months. The VB20 was 20 mm3 or more in 38 of 64 on the right side and in eight of 41 on the left side (p < 0.001) in patients with TN and without MS. There is a difference between left and right dose—volume histograms even when the same isodose is placed on the surface of the brainstem. The VB20 was 20 mm3 or more in 45 of 105 patients with TN and without MS but in only three of 21 patients with TN and MS (p = 0.014). There was an inverse relationship between VB20 and VT50 (p = 0.01). Conclusions. Isocenter proximity to the brainstem, as reflected in a higher VB20, is associated with a greater chance of excellent outcome at 6 and 12 months. Worse results in patients with TN and MS may be partly explained by a lower VB20.

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Modeling fecal incontinence symptoms 6 years after high-dose radiation for prostate cancer: Clinical and dosimetric predictors.

Journal of Clinical Oncology ◽

10.1200/jco.2012.30.5_suppl.71 ◽

2012 ◽

Vol 30 (5_suppl) ◽

pp. 71-71

Author(s):

Giovanni Fellin ◽

Tiziana Rancati ◽

Claudio Fiorino ◽

Vittorio Vavassori ◽

Emanuela Cagna ◽

...

Keyword(s):

Prostate Cancer ◽

Fecal Incontinence ◽

Drug Prescription ◽

Surrogate Endpoint ◽

Continuous Variable ◽

High Dose ◽

Dose Volume Histograms ◽

Dose Volume ◽

The Mean ◽

Pre Treatment

71 Background: To evaluate the incidence of late fecal incontinence (linc) after high-dose radiotherapy (RT) in prostate cancer patients (pts) accrued in AIROPROS 0102 trial (RT doses: 70-80Gy, 1.8-2Gy/fr) and to model the relationship between linc and clinical/dosimetric factors. Methods: Self-reported questionnaires of 515 pts with a minimum follow up of 6 yrs were analyzed with respect to linc. G1 linc was scored if unintentional stool discharge was “sometimes” experienced, G2 linc if unintentional stool discharge was “often” experienced or if pts sporadically used sanitary pads; G3 if pts reported daily unintentional stool discharge or use of sanitary pad >2 times/week. Correlation between pre-treatment morbidities, hormonal therapy, drug prescription, presence of diabetes or hypertension, abdominal surgery prior to RT (SURG), presence of G2-G3 acute fecal incontinence (ACUINC), pelvic nodes and seminal vesicles irradiation, mean rectal dose, dose-volume histograms constraints (from V20Gy to V75Gy) and linc was investigated by uni- and multivariate (MVA) logistic analyses. 347/515 pts had at least 3 toxicity questionnaires in the first 36 mos after the end of RT. Correlation between the mean score of fecal incontinence in the first 36 mos and linc at 6 yrs was also investigated. Results: 50/515 G1, 3/515 G2 and 3/515 G3 linc were reported. In MVA, V40Gy (continuous variable, p=0.09, OR=1.015), use of antihypertensives (protective factors, p=0.005, OR=0.38), SURG (p=0.004, OR=4.7), presence of haemorrhoids (p=0.008, OR=2.6) and ACUINC (p=0.007, OR=4.4) resulted to be correlated to linc. Based on MVA results, a nomogram was developed. Linc at 6 yrs was also correlated to the mean incontinence scores in the first 36 mos (p<0.0001): pts without linc at 6 yrs had a mean score of 0.1 during the first 36 mos, while pts with G1 and with G2-G3 linc at 6 yrs had a mean score of 0.5 and 0.78 during the first 36 mos, respectively. Conclusions: Mean score for incontinence during the first 36 mos after RT can be used as a surrogate endpoint for late (>6yrs) fecal incontinence. Linc is correlated to clinical and dosimetric risk factors and individualised toxicity prediction can be performed through a nomogram.

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Pilot study: rectal contouring variability in patients treated with radical radiotherapy for prostate cancer: impact on rectum dose–volume histograms

Journal of Radiotherapy in Practice ◽

10.1017/s1460396908006419 ◽

2008 ◽

Vol 7 (3) ◽

pp. 173-184

Author(s):

Jacqueline E. Martin ◽

P. Kirkbride

Keyword(s):

Pilot Study ◽

Radiotherapy Planning ◽

Anterior Rectal Wall ◽

Observer Variability ◽

Prostate Radiotherapy ◽

Dose Volume Histograms ◽

Dose Volume ◽

Inter Observer Variability ◽

Rectal Volume ◽

The Mean

AbstractPurpose: The organ at risk in prostate radiotherapy is the anterior rectal wall . This pilot study was conducted to quantify the inter-observer variability of rectal contouring in conformal prostate radiotherapy planning using four contouring methods and to determine a standard rectal contouring definition.Methods and materials: Ten patients with T1/T2 disease and six clinical oncologists were recruited. Two cross-sectional and two length limits generated four rectal volumes. Each clinician contoured the four volumes for each patient and the dose–volume histograms (DVHs) were analysed. The percentage rectal volume receiving 20%, 50%, 80%, 90% and 95% of the total delivered dose and the mean and median rectal doses were calculated. Data were presented as mean ± 2 standard deviations.Results: The Sh Rec method (contouring the rectum including its contents extending from 2 cm above the upper limit of the prostate to 2 cm below the prostatic apex) was the least variable in the 80%, 90% and 95% percentage ranges. The mean difference in Sh Rec-contoured volume was 18.7 cm3 (± 22.3 cm3).Conclusions: The Sh Rec-contouring method showed the least inter-observer variability. The results are informative and will help define a standard rectal contouring method.

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Brachial plexopathy in breast cancer: is it radiation related? An analysis technique and dose volume parameters to brachial plexus in breast cancer radiotherapy

International Journal of Research in Medical Sciences ◽

10.18203/2320-6012.ijrms20170134 ◽

2017 ◽

Vol 5 (2) ◽

pp. 469

Author(s):

Beena Kunheri ◽

Anand Radhakrishnan ◽

Toyce Stephen ◽

Renil Mon ◽

Anjali Menon

Keyword(s):

Breast Cancer ◽

Brachial Plexus ◽

Maximum Dose ◽

Mean Value ◽

Brachial Plexopathy ◽

Dose Volume Histograms ◽

Dose Volume ◽

Supraclavicular Fossa ◽

Patient Reported ◽

The Mean

Background: Brachial plexus dysfunction is a rare but well-recognized complication of breast cancer surgery and radiotherapy. Most of the time it presents as paraesthesia of the arm. In an earlier publication Dan Lundstedt et al from Sweden, quantitatively assessed the radiation related brachial plexopathy (mainly paraesthesia) with the help of dose volume histograms and its co relation between patient reported paraesthesia. Paraesthesia was reported by 25% after radiation therapy to the supraclavicular fossa, with a V40 Gy 13.5 cm3 and maximum dose to brachial plexus (Dmax) was not found to correlate with paraesthesia. In order to predict the risk brachial plexopathy in our patients we decided to analyze the dose volume parameters for brachial plexus in carcinoma breast patients treated at our institution with modern radiotherapy techniques.Methods: Twenty five consecutive patients who received post mastectomy radiation during the period September 2015 to January 2016 with a dose of 50Gy in 25 fractions were included for this analysis. Brachial plexus contoured using RTOG guidelines, and dose volume parameters for brachial plexus were documented from the existing treatment plans.Results: The maximum dose to the brachial plexus ranged from 5045cGy to 5679cGy with a mean value of 5312.8cGy. The mean dose received by the brachial plexus ranged from 3093cGy to 4714cGy and the mean value was 4137.28cGy. Volume receiving 40Gy, that is V40, ranged from 2.0078cc to 11.56cc with a mean value of 7.57cc.Conclusions: Maximum dose and V40 Gy values were well below the tolerance limit of plexus, and hence post mastectomy irradiation with modern techniques is unlikely to produce significant brachial plexus neuropathy.

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