Craniospinal irradiation using a forward planned segmented field technique

Abstract

Craniospinal irradiation is technically demanding due to the complex shape of the planning target volume (PTV). Radiotherapy treatment techniques have evolved over time as imaging and radiotherapy treatment technology have improved. However, most are variations on a class solution utilizing a prone patient position with two shaped lateral cranial portals and a matched posterior spinal portal with moving junctions. Major areas of difficulty remain with the accurate definition of the PTV and achieving a homogeneous dose within it, especially at the junctions. We describe a three-dimensionally (3D) planned craniospinal radiation technique that permits rapid image acquisition with reduced localization time, simplified spinal PTV definition and standardized cranial PTV definition. Improved dose homogeneity within the PTV is achieved by use of a segmented "field-in-field" technique (forward planned intensity-modulated radiotherapy (IMRT)) in place of customized compensators. This has negated the requirement for constructing physical compensators. Autosequencing for field delivery enables the junction to be "moved" during a single fraction and reduces the overall treatment time, an important consideration when treating very young patients.

High-precision radiotherapy for craniospinal irradiation: evaluation of three-dimensional conformal radiotherapy, intensity-modulated radiation therapy and helical TomoTherapy

“…Contemporary state-of-art technology available for radiotherapy planning and delivery has also been investigated for designing sophisticated and novel treatment strategies to reduce the dose to nontarget tissues. Forward planned segmented field IMRT and inverse planned IMRT have been proposed for the spinal component of CSI [22,23]. As these techniques were mainly aimed at improving the target coverage and dose homogeneity, the dose-volume relationship to the underlying normal tissues was not addressed.…”

Choice of appropriate beam model and gantry rotational angle for low-dose gradient-based craniospinal irradiation using volumetric-modulated arc therapy

“…14,[19][20][21][22][23][24][25] However, these IMRT techniques suffer from the demerits such as a 3DCRT like beam arrangement and restricted jaw movement. 14,[19][20][21][22][23][24][25] These techniques lead to compromised dose homogeneity in neuraxis as well as the requirement of junction shifts. In our study, we used a junction-free technique for VMAT planning, similar in some respects to that described by Fogliata et al 12 or Lee et al 13 .…”

“…Although several investigators have investigated the CSI using intensity-modulated technique, which is majorly concentrating of dose homogeneity and advantage of junction-free technique. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] The present dosimetric challenge is to further reduce the dose to the non-target volume areas. Recent breakthroughs in linear accelerator technology include flattening filter-free (3F) beam, finer width multileaf collimator (MLC) (0•5 cm) and advanced delivery technique like VMAT.…”

Leptomeningeal Metastasis

“…Given the technical complexity of treating the entire craniospinal axis, associated toxicities, and incurability of leptomeningeal metastases, craniospinal irradiation remains investigational. Perhaps advances in radiotherapy, such as with IMRT [135][136][137] or proton radiotherapy, 138,139 may improve the therapeutic ration and render craniospinal irradiation more clinically useful.…”