Accurate Delineation of Mucosal Lesions in Treatment-Planning Computed Tomography Using Iodine Paste Markers for Oral Mucosal Melanoma

Hiroaki Ikawa,Masashi Koto,Tapesh Bhattacharyya,Takashi Kaneko,Hirotoshi Takiyama,Makoto Shinoto,Akihiro Nomoto,Shigeru Yamada,Hiroshi Tsuji

doi:10.1016/j.prro.2022.01.009

Abstract

This technical report introduces the utility of iodine paste markers using endodontic materials for the accurate contouring of mucosal lesions of oral mucosal melanoma, which are difficult to delineate on imaging during the planning of carbon-ion radiation therapy (CIRT). The patient had a primary oral mucosal melanoma located in the palatal mucosa without palatal or maxillary bone invasion. A dental root canal filling material, which is a calcium hydroxide/iodoform nonhardenable paste, was used as a marker. We first performed treatment-planning computed tomography (CT) without an iodine paste marker for mucosal lesions. Subsequently, we placed an iodine paste marker on the palatal mucosal lesion to accurately delineate the mucosal lesions of the palate. Finally, we obtained a reference CT image with an iodine paste marker. Computed tomography without the marker was fused to the reference CT with markers during treatment planning, and the gross tumor volume was contoured. Thereafter, CIRT was delivered without markers. During CIRT, expected acute mucositis was observed in the area of the planning target volume, including melanosis, in accordance with the dose distribution. The use of iodine paste markers for localized mucosal lesions, which are difficult to delineate on CT and magnetic resonance imaging, may be useful for accurately contouring gross tumor volumes on treatment-planning CT.

Highlights

We previously demonstrated the efficacy and utility of carbon-ion radiation therapy (CIRT) with acceptable toxicity and preserved oral function in treating oral mucosal melanoma (OMM).[1, 2] CIRT provides an excellent conformal physical dose distribution because of its Bragg peak property and sharper lateral penumbra.[3]
With T3 diseases, the lesion was localized to the mucosa and was difficult to detect by treatment planning computed tomography (CT)
Owing to the uncertainty in gross tumor volume (GTV) delineation, a robust CTV was considered as the CTV margin expanded

Summary

Introduction

We previously demonstrated the efficacy and utility of carbon-ion radiation therapy (CIRT) with acceptable toxicity and preserved oral function in treating oral mucosal melanoma (OMM).[1, 2] CIRT provides an excellent conformal physical dose distribution because of its Bragg peak property and sharper lateral penumbra.[3] the delineation of gross tumor volume (GTV) must be sufficiently accurate to obtain optimal local control with minimal side effects in high-precision RT. Intraoral endoscopic findings are helpful, it is difficult to accurately identify and contour the exact tumor site on treatment planning CT. The accurate delineation of mucosal lesions in treatment planning CT is of utmost importance for the accurate delivery of RT. No method has been reported to accurately delineate mucosal lesions in treatment planning CT

Methods

Results

Conclusion