Dosimetric impact of tracheostomy devices in head and neck cancer patients

Anaesthesia for paediatric radiotherapy: A narrative review

INTRODUCTION

Radiotherapy is currently used in approximately one-third of children with cancer. Treatments are typically received as weekday outpatient appointments over 3-6 weeks. The treatment is painless but requires a still, co-operative patient who can lie alone in set positions, facilitated by the use of immobilisation devices, for up to 1 h.

METHODS

We conducted a literature search to identify relevant articles relating to radiotherapy treatment. Key search terms included: 'radiotherapy'; 'proton beam'; 'photon'; 'sedation'; 'anaesthesia'; and 'paediatric'. The abstracts of identified articles were assessed for relevance and their references reviewed for further relevant publications.

RESULTS

The requirement for anaesthesia is almost exclusively limited to younger children, who are committed to daily anaesthetics over the duration of their treatment course. Centres tend to adopt a primary anaesthetic technique of either general anaesthesia using a supraglottic airway device or deep sedation, with spontaneous ventilation maintained. A full variety of anaesthetic drugs has been used with insufficient evidence to support a standardised primary approach but an apparent global trend towards propofol by infusion for sedation. Children may become acutely unwell during their treatment course and systems for escalation of clinical care in this event are vital. Distance from the patient for staff radiation shielding, patient positioning for treatment delivery and the use of immobilisation devices may provide additional access challenges in the event of an emergency.

DISCUSSION

The requirement for anaesthesia for paediatric radiotherapy is typically confined to younger children. Patients may be unwell, with several specific considerations related to their cancer diagnosis and the impact of various treatments including surgery and chemotherapy, in addition to the radiotherapy. A multidisciplinary team approach to all aspects of care is imperative in this group of high-risk patients.

Dosimetric impact of hollow intraoral stents for head and neck cancer radiotherapy: A phantom study

PURPOSE

To investigate the dosimetric impact of the calculation boundaries and dose calculation algorithms of radiotherapy in head and neck cancer patients with an opened oral cavity connected to the exterior by a hollow intraoral positioning stent.

METHODS AND MATERIALS

A homemade silicone phantom with an opened oral cavity was placed in a CIRS head phantom to model head and neck cancer patients with a hollow intraoral positioning stent. 3D-CRT plans were designed on CT images of the phantom in Monaco and Pinnacle3 treatment planning systems (TPSs) with the same beam parameters. The default boundary and manually extrapolated boundary were both adopted in these two TPSs to explore the dosimetric impact on treatment plans. The nanoDot™ optically stimulated luminescence dosimeters (OSLDs) were chosen to measure the planned dose surrounding the oral cavity of the head phantom after calibration.

RESULT

The doses in the air cavity and two measuring points at the joint area were dramatically changed from 0.0, 92.4 and 148.8 cGy to 177.8, 244.2 and 244.1 cGy in Monaco after adopting the extrapolated boundary. While the calculated doses at the same place were changed from 61.2, 143.7 and 198.3 cGy to 175.4, 234.7 and 233.2 cGy in Pinnacle3 with a similar calculation boundary. For the Monaco TPS, the relative errors compared to the OSLD measured doses were 2.94 ± 1.93%, 0.53 ± 8.64%, 2.65 ± 1.87% and 3.93 ± 1.69% at 4 measuring positions. In contrast, the relative errors 4.03 ± 1.93%, 4.85 ± 8.64%, 7.61 ± 1.87% and 5.61 ± 1.69% were observed in Pinnacle3 .

CONCLUSION

The boundary setting of an opened oral cavity in TPSs has a significant dosimetric impact on head and neck cancer radiotherapy. An extrapolated boundary should be manually set up to include the whole oral cavity in the dose calculation domain to avoid major dose deviations.