Evaluation of deformable image registration methods for dose monitoring in head and neck radiotherapy.

Bastien Rigaud,Joël Castelli,Pascal Haigron,Antoine Simon,Juan-David Ospina Arango,Guillaume Cazoulat,Maxime Gobeli,Olivier Henry,Renaud De Crevoisier

doi:10.1155/2015/726268

Bastien Rigaud, Joël Castelli + Show 7 more

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https://doi.org/10.1155/2015/726268

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Abstract

In the context of head and neck cancer (HNC) adaptive radiation therapy (ART), the two purposes of the study were to compare the performance of multiple deformable image registration (DIR) methods and to quantify their impact for dose accumulation, in healthy structures. Fifteen HNC patients had a planning computed tomography (CT0) and weekly CTs during the 7 weeks of intensity-modulated radiation therapy (IMRT). Ten DIR approaches using different registration methods (demons or B-spline free form deformation (FFD)), preprocessing, and similarity metrics were tested. Two observers identified 14 landmarks (LM) on each CT-scan to compute LM registration error. The cumulated doses estimated by each method were compared. The two most effective DIR methods were the demons and the FFD, with both the mutual information (MI) metric and the filtered CTs. The corresponding LM registration accuracy (precision) was 2.44 mm (1.30 mm) and 2.54 mm (1.33 mm), respectively. The corresponding LM estimated cumulated dose accuracy (dose precision) was 0.85 Gy (0.93 Gy) and 0.88 Gy (0.95 Gy), respectively. The mean uncertainty (difference between maximal and minimal dose considering all the 10 methods) to estimate the cumulated mean dose to the parotid gland (PG) was 4.03 Gy (SD = 2.27 Gy, range: 1.06–8.91 Gy).

Highlights

Large anatomical variations can be observed during the seven weeks of head and neck cancer (HNC) intensity-modulated radiation therapy (IMRT) treatment course, such as weight loss [1, 2], primary tumor shrinking [1], parotid gland (PG) volume reduction [3], and reduction of the neck diameter [4, 5]
(i) Considering all the anatomical structures, the three methods corresponding to the maximum Dice Similarity Coefficient (DSC) were the “demons with mean squared error (MSE) on delineation maps,” the “free form deformation (FFD) with mutual information (MI) on filtered computed tomography (CT)” and the “demons with MI on filtered CTs.”
The “FFD with MI on filtered CTs” DSC values were higher than the DSC values of all other methods (P ≤ 0.01), except the “demons with MSE on delineation maps” method

Summary

Introduction

Large anatomical variations can be observed during the seven weeks of head and neck cancer (HNC) intensity-modulated radiation therapy (IMRT) treatment course, such as weight loss [1, 2], primary tumor shrinking [1], parotid gland (PG) volume reduction [3], and reduction of the neck diameter [4, 5]. Volume and shape variations can be compensated by replanning, implying to perform new computed tomography (CT) scans during the course of treatment, since the CBCT cannot be yet straightly used for replanning. This recent adaptive radiotherapy (ART) strategy appears complex, in particular to decide when and how many times to replan during the treatment course [11, 12]. A key step is the capability to monitor the cumulated dose received by the deformed OARs, fraction after fraction, to compare this dose with the planned dose, and to decide whether or not to replan within a dose-guided adaptive radiotherapy strategy [13, 14]

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