Initial Experience with the eXtend System: A Relocatable Frame System for Multiple-Session Gamma Knife Radiosurgery

Sayer, Faisal T.; Sherman, Jonathan H.; Yen, Chun-Po; Schlesinger, David; Kersh, Ronald; Sheehan, Jason P.

doi:10.1016/j.wneu.2010.12.051

Cited by 43 publications

(43 citation statements)

References 27 publications

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“…In the second step of our registration we used a constrained optimization. In practice, a noninvasive frame 27,34 may be used during the CT imaging and treatment to provide a rough initial alignment of the two data sets prior to optimizing the registration and would allow the use of a constrained solver.…”

Section: Discussionmentioning

confidence: 99%

Registration of human skull computed tomography data to an ultrasound treatment space using a sparse high frequency ultrasound hemispherical array

et al. 2016

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Purpose: Transcranial focused ultrasound (FUS) shows great promise for a range of therapeutic applications in the brain. Current clinical investigations rely on the use of magnetic resonance imaging (MRI) to monitor treatments and for the registration of preoperative computed tomography (CT)-data to the MR images at the time of treatment to correct the sound aberrations caused by the skull. For some applications, MRI is not an appropriate choice for therapy monitoring and its cost may limit the accessibility of these treatments. An alternative approach, using high frequency ultrasound measurements to localize the skull surface and register CT data to the ultrasound treatment space, for the purposes of skull-related phase aberration correction and treatment targeting, has been developed. Methods: A prototype high frequency, hemispherical sparse array was fabricated. Pulse-echo measurements of the surface of five ex vivo human skulls were made, and the CT datasets of each skull were obtained. The acoustic data were used to rigidly register the CT-derived skull surface to the treatment space. The ultrasound-based registrations of the CT datasets were compared to the gold-standard landmark-based registrations. Results: The results show on an average sub-millimeter (0.9 ± 0.2 mm) displacement and subdegree (0.8• ± 0.4 • ) rotation registration errors. Numerical simulations predict that registration errors on this scale will result in a mean targeting error of 1.0 ± 0.2 mm and reduction in focal pressure of 1.0% ± 0.6% when targeting a midbrain structure (e.g., hippocampus) using a commercially available low-frequency brain prototype device (InSightec, 230 kHz brain system). Conclusions: If combined with ultrasound-based treatment monitoring techniques, this registration method could allow for the development of a low-cost transcranial FUS treatment platform to make this technology more widely available. C

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Section: Discussionmentioning

confidence: 99%

Registration of human skull computed tomography data to an ultrasound treatment space using a sparse high frequency ultrasound hemispherical array

et al. 2016

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“…Studies using either continuous radiation exposures, with different dose-rates, or studies involving two or more doses per day with variable incomplete repair intervals between them have been used to obtain information related to the kinetics of repair of sub lethal radiation damage [9], albeit for larger irradiated volumes. These studies have clearly identified a fast component of repair of sublethal radiation injury with a half time of approximately 0.2 h, which infers that repair of sublethal radiation injury is an important factor in RS treatments [15]. Moreover, in a previously unpublished study, that involved the uniform irradiation of a 10 cm length of the spinal cord of pigs (Hopewell et al, previously unpublished data), a marked difference in response was seen when doses were delivered at two different dose-rates and therefore different overall irradiation times.…”

Section: Discussionmentioning

confidence: 85%

“…Such values are calculated using the basic BED equation [4], which assumes that doses are delivered in a short time relative to the fast half-time for repair and thus that repair of sublethal radiation damage is not a factor in treatments. Such an assumption is clearly inappropriate for either single or multi-session RS treatments [15]. Thus the basic BED equation should not be used for estimating the equivalent dose when converting from experience gained from treatment with single treatment sessions into multiple treatment sessions using BED equivalence.…”

Section: Discussionmentioning

confidence: 99%

The role of the concept of biologically effective dose (BED) in treatment planning in radiosurgery

et al. 2015

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Radiosurgery (RS) treatment times vary, even for the same prescription dose, due to variations in the collimator size, the number of iso-centres/beams/arcs used and the time gap between each of these exposures. The biologically effective dose (BED) concept, incorporating fast and slow components of repair, was used to show the likely influence of these variables for Gamma Knife patients with Vestibular Schwannomas. Two patients plans were selected, treated with the Model B Gamma Knife, these representing the widest range of treatment variables; iso-centre numbers 3 and 13, overall treatment times 25.4 and 129.6 min, prescription dose 14 Gy. These were compared with 3 cases treated with the Perfexion(®) Gamma Knife. The iso-centre number varied between 11 and 18, treatment time 35.7 - 74.4 min, prescription dose 13 Gy. In the longer Model B Gamma Knife treatment plan the 14 Gy iso-dose was best matched by the 58 Gy2.47 iso-BED line, although higher and lower BED values were associated with regions on the prescription iso-dose. The equivalent value for the shorter treatment was 85 Gy2.47. BED volume histograms showed that a BED of 85 Gy2.47 only covered ∼65% of the target in the plan with the longer overall treatment time. The corresponding BED values for the 3 cases, treated with the Perfexion(®) Gamma Knife, were 59.5, 68.5 and 71.5 Gy2.47. In conclusion BED calculations, taking account of the repair of sublethal damage, may indicate the importance of reporting overall time to reflect the biological effectiveness of the total physical dose applied.

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“…Recently, the Extend system for the Gamma Knife Perfexion (Elekta Instruments, AB, Stockholm, Sweden) has been developed for hypofractionated GKRS procedures 3 , 4 , 5 . The Extend system consists with a vacuum‐assisted dental fixation device attached on a carbon‐fiber frame for noninvasive immobilization in Fig.…”

Section: Introductionmentioning

confidence: 99%

Inter‐ and intrafractional dose uncertainty in hypofractionated Gamma Knife radiosurgery

Kim

Sheehan

Schlesinger

2016

J Applied Clin Med Phys

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The purpose of this study is to evaluate inter‐ and intrafractional dose variations resulting from head position deviations for patients treated with the Extend relocatable frame system utilized in hypofractionated Gamma Knife radiosurgery (GKRS). While previous reports characterized the residual setup and intrafraction uncertainties of the system, the dosimetric consequences have not been investigated. A digital gauge was used to measure the head position of 16 consecutive Extend patients (62 fractions) at the time of simulation, before each fraction, and immediately following each fraction. Vector interfraction (difference between simulation and prefraction positions) and intrafraction (difference between postfraction and prefraction positions) shifts in patient position were calculated. Planned dose distributions were shifted by the offset to determine the time‐of‐treatment dose. Variations in mean and maximum target and organ at risk (OAR) doses as a function of positional shift were evaluated. The mean vector interfraction shift was 0.64 mm (Standard Deviation (SD): 0.25 mm, maximum: 1.17 mm). The mean intrafraction shift was 0.39 mm (SD: 0.25 mm, maximum: 1.44 mm). The mean variation in mean target dose was 0.66% (SD: 1.15%, maximum: 5.77%) for interfraction shifts and 0.26% (SD: 0.34%, maximum: 1.85%) for intrafraction shifts. The mean variation in maximum dose to OARs was 7.15% (SD: 5.73%, maximum: 30.59%) for interfraction shifts and 4.07% (SD: 4.22%, maximum: 17.04%) for intrafraction shifts. Linear fitting of the mean variation in maximum dose to OARs as a function of position yielded dose deviations of 10.58%/mm for interfractional shifts and 7.69%/mm for intrafractional shifts. Positional uncertainties when performing hypofractionated Gamma Knife radiosurgery with the Extend system are small and comparable to frame‐based uncertainties (<1 mm). However, the steep dose gradient characteristics of GKRS mean that the dosimetric consequences of positional uncertainties should be considered as part of treatment planning. These dose uncertainties should be evaluated in the context of tumor response and OAR tolerance for hypofractionated treatment scenarios where any increase in dose may be tempered by the increased protection hypofractionation provides to normal tissue.PACS number(s): 87.52.‐g

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Initial Experience with the eXtend System: A Relocatable Frame System for Multiple-Session Gamma Knife Radiosurgery

Cited by 43 publications

References 27 publications

Registration of human skull computed tomography data to an ultrasound treatment space using a sparse high frequency ultrasound hemispherical array

Registration of human skull computed tomography data to an ultrasound treatment space using a sparse high frequency ultrasound hemispherical array

The role of the concept of biologically effective dose (BED) in treatment planning in radiosurgery

Inter‐ and intrafractional dose uncertainty in hypofractionated Gamma Knife radiosurgery

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