Researchers at Saint Louis University have conceived an approach to enable the adjustment of the patient head and cervical vertebrae positions simultaneously to match the reference image position. Such correction would precede the use of the conventional image-guided tools and would mitigate the repositioning errors of the cervical vertebrae thus enabling the accurate targeting of all PTVs and the accurate sparing of OARs.
Head and neck (H&N) cancer occurrences are common and radiation therapy is an essential treatment arm. The annual incidence of head and neck cancers worldwide is more than 550,000 cases with around 300,000 deaths each year. The dose regimen in H&N cancer is 70Gy delivered during the course of 35 daily fractions at 2Gy/fraction. Historically, H&N cancers were treated using 3D conformal radiation therapy (3DCRT), which utilizes conservatively large fields, defined clinically base on anatomical knowledge and are less susceptible to errors resulting from repositioning uncertainties and anatomical changes during the course of therapy. The downside of 3DCRT are toxicities of normal tissues surrounding the cancer. The primary organs at risk (OARs) in H&N cancers are the parotids. One of the most common and serious side effect of H&N cancer treated with 3DCRT is the loss of salivary function. Currently, intensity modulated radiation therapy (IMRT) is the standard treatment modality for H&N cancers. While IMRT can reduce side effects seen with 3DCRT, there are persisting challenges with this treatment technique. The primary disease area may be the nasopharynx, oropharynx, tonsil(s), larynx, tongue, sinus or other organs, but the treatment area may extend to the neck lymphatic chain all the way down to the supraclavicular level. Daily repositioning variations are observed consistently due to the flexible nature of the cervical vertebrae. Archived computed tomography (CBCT) images show clearly the variability in cervical spine position in every treatment session; in some patients more pronounced than others. Incorrect daily repositioning of the patient could result in marginal miss of the planning target volumes (PTVs) which may lead to a less than optimal therapy outcome.
The potential benefits of this technology include:
- Minimize repositioning errors of the cervical vertebrae during radiation therapy
- Minimize damage to organs at risk (OARs) during radiation therapy
- Minimize inaccuracies in clinical target volumes (CTVs) in radiation therapy
This technology has potential application for intensity modulated radiation therapy used to treat head and neck (H&N) cancers.
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