Gamma Knife Radiosurgery Clinical Trial
Official title:
Evaluation of Dosimetric Differences Between the TMR 10 and Convolution Algorithm for Gamma Knife Radiosurgery Planning
Gamma Knife Radiosurgery (GKR) is a well established treatment modality for brain tumors and
functional disorders of the brain. It relies on mathematical algorithms to predict dose
distribution and to calculate the dose at arbitrary points in the head. For the last 25
years, doses applied using Gamma Knife Radiosurgery have been calculated using a simple
algorithm, called the Tissue Maximum Ratio algorithm (TMR). Dose planning using this
algorithm, relies on a number of approximations to enable fast isodose computation during
treatment planning. One of the most significant of these is the approximation of the head to
water-equivalent density. The increased electron density of brain and bone (relative to
water) and the near-zero density of air cavities in the skull may make significant
perturbations to isodose and beam-on time calculations.
With the advent of faster workstations, the effect of tissue in-homogeneities can finally be
calculated in reasonable time during the treatment planning process; a newer, more modern
algorithm known as convolution algorithm is now commercially available. It uses the values
of density indicated in the CT scan to predict the dose distribution and is expected to more
accurately calculate radiation dose, although it needs further investigation before clinical
implementation. Inter- and intra-indication differences between the old and new algorithms
need to be understood before this method can be confidently employed in a clinical setting.
It is the aim of this study to understand the dosimetric differences between these dose
calculation algorithms and to evaluate the implications of using the convolution algorithm
for GKR. A large number of treatments will be re-planned using the convolution algorithm and
compared to the TMR plans used to treat the patients. Beam-on-time, which is proportional to
dose and a number of commonly used metrics for the targets such as coverage, selectivity,
gradient index, and mean and maximum dose, will be estimated with both algorithms. Subgroup
analysis will be done to assess whether any factor such as diagnosis, size of the head or
location of the target could impact on the relative difference between the methods. The
treatment plans will be compared and the potential implications on treatment planning will
be elucidated.
| Status | Recruiting |
| Enrollment | 100 |
| Est. completion date | October 2016 |
| Est. primary completion date | October 2015 |
| Accepts healthy volunteers | No |
| Gender | Both |
| Age group | 18 Years and older |
| Eligibility |
Inclusion Criteria: - Adult patients receiving Gamma Knife treatment for any diagnosis in the Gamma Knife centre at QSRC. - The subject consents to participate in the study and consent to have a stereotactic non contrast CT scan of the brain after GKR has finished. Exclusion Criteria: - Inability to consent - Younger than 18 years of age: Children are not eligible to give consent by themselves and at the moment only adults are being treated at the QSRC. - Patient is not suitable for CT scan: There are no absolute clinical contraindications for CT scan. However, for the purpose of the study, pregnancy is considered an absolute contraindication. Claustrophobia or anxiety disorders are considered a relative contraindication; however, this is more likely to affect the subject ability to tolerate Gamma Knife treatment and MRI scanning, which would make the patient not eligible or the study. - Co-morbidity or previous treatment in the patient is not to be considered as exclusion criteria. |
Time Perspective: Prospective
| Country | Name | City | State |
|---|---|---|---|
| United Kingdom | The Gamma Knife Centre at Queen Square | London | London,City of |
| Lead Sponsor | Collaborator |
|---|---|
| University College, London | University College London Hospitals |
United Kingdom,
| Type | Measure | Description | Time frame | Safety issue |
|---|---|---|---|---|
| Primary | Beam-on time (difference in the Beam-on-time of the treatment plans obtained using TMR 10 and convolution algorithm for each lesion treated) | The difference in the Beam-on-time of the treatment plans obtained using TMR 10 and convolution algorithm for each lesion treated will be the primary outcome of the study | Beam-on time obtained with the TMR 10 algorithm at the time of treatment (baseline) vs Beam-on time observed when the treatment is re-planned with the convolution algorithm, that being a few hours after the actual treatment is delivered (maximum 1 day) | No |