Comprehensive Evaluation of Carbon-Fiber-Reinforced Polyetheretherketone (CFR-PEEK) Spinal Hardware for Proton and Photon Planning

Role of radiotherapy in the management of spine metastases

Spine metastases are a common cause of pain in the oncologic patient which can generate functional limitation, in addition to complications derived from spinal cord compression, radicular compression and fractures. A complex approach to these metastases is required due to the risk of permanent sequelae. With the increase in survival rates due to new emerging treatments, the possibilities of presenting vertebral metastases are increasing, therefore, the management of these lesions should be aimed at pain relief and maintenance of ambulation. Radiotherapy has a fundamental role in the management of these lesions, and technological advances in recent years have made it possible to improve the quality and intentionality of the treatments, going from having a palliative intent to proposing treatments that improve local control. In this article we describe how the stereotactic body radiotherapy (SBRT) technique, in selected patients, can improve local control and its value in oligometastatic patients and after surgery.

[Translated article] Role of radiotherapy in the management of spine metastases

Spine metastases are a common cause of pain in the oncologic patient which can generate functional limitation, in addition to complications derived from spinal cord compression, radicular compression and fractures. A complex approach to these metastases is required due to the risk of permanent sequelae. With the increase in survival rates due to new emerging treatments, the possibilities of presenting vertebral metastases are increasing, therefore, the management of these lesions should be aimed at pain relief and maintenance of ambulation. Radiotherapy has a fundamental role in the management of these lesions, and technological advances in recent years have made it possible to improve the quality and intentionality of the treatments, going from having a palliative intent to proposing treatments that improve local control. In this article, we describe how the stereotactic body radiotherapy (SBRT) technique, in selected patients, can improve local control and its value in oligometastatic patients and after surgery.

Primary Osseous Malignancies of the Spine

Malignant primary vertebral tumours comprise an uncommon group of primary bone malignancies that can pose a diagnostic and therapeutic challenge. The most frequently encountered malignant primary vertebral tumours include chordoma, chondrosarcoma, Ewing sarcoma and osteosarcoma. These tumours often present with nonspecific symptoms, such as back pain, neurologic deficits and spinal instability, which can be confused for the more commonly encountered mechanical back pain and may delay their diagnosis and treatment. Imaging, including radiography, computed tomography (CT) and magnetic resonance imaging (MRI) is crucial for diagnosis, staging, treatment planning and follow-up. Surgical resection remains the mainstay of treatment for malignant primary vertebral tumours, but adjuvant radiotherapy and chemotherapy may be necessary for achieving complete tumour control depending on the type of tumour. In recent years, advances in imaging techniques and surgical approaches, such as en-bloc resection and spinal reconstruction, have improved the outcomes for patients with malignant primary vertebral tumours. However, the management can be complex due to the anatomy involved and the high morbidity and mortality associated with surgery. The different types of malignant primary vertebral lesions will be discussed in this article with an emphasis on the imaging features.

Evaluation of Carbon Fiber and Titanium Surgical Implants for Proton and Photon Therapy

PURPOSE

Impending and actual pathologic fractures secondary to metastatic bone disease, lymphoma, or multiple myeloma often require intramedullary fixation followed by radiation therapy. Because of carbon's low atomic number, there are reduced computed tomography (CT) imaging artifacts and dose perturbation when planning postoperative radiation for carbon fiber (CF) rods. Herein, we characterize the dosimetric properties of CF implants compared with titanium alloy (TA) for proton and photon.

METHODS AND MATERIALS

TA and CF samples were acquired from an implant manufacturer. Material characteristics were evaluated by CT scans with and without metal artifact reduction (MAR). Relative stopping power (RSP) was determined from the range pull-back of each sample in a 20-cm range proton beam. Photon transmission measurements were made in a solid water phantom and compared with the modeled dosimetry from the RayStation planning system.

RESULTS

CF caused no visible CT artifacts, and MAR was not necessary for Hounsfield unit (HU) determination (median, 364 HU) or contouring, whereas TA (median, 3071 HU) caused substantial artifacts, which were improved, but not eliminated by MAR. The proton RSP was measured as 3.204 for TA and 1.414 for CF. For 6 MV photons, the measured transmission was 89.3% for TA and 98% for CF. CF RSP calculation and transmission from CT HU showed a physical density overestimate compared with measurements, which would cause a slight, but acceptable, dose uncertainty (<10% proton range or 1% photon transmission).

CONCLUSIONS

With a density similar to bone, CF implants did not cause imaging artifacts and minimal dose perturbation compared with TA. Although the CF proton RSP is underestimated and the photon attenuation is overestimated by the HU, both effects are relatively small and may be most easily accounted for by planning with a 2-mm expansion around organs at risk beyond or in close proximity to the implant.