Lung stereotactic body radiation therapy (SBRT) often utilizes four-dimensional CT to quantify tumour motion. Respiratory gating delivers radiation only during a specific portion of the breathing cycle, potentially sparing healthy tissue. This study compares internal target volume/planning target volume (ITV/PTV) volumes and dosimetric outcomes between non-gated and gated (30–70% phase window) lung SBRT.

Twenty-five stage-1 NSCLC cases were analysed. Non-gated plans used ITVs delineated on MIP images from all respiratory phases while Gated plans utilized ITVs from the 30–70% phase window. A 5 mm PTV margin was applied to both. Dosimetric parameters for PTV and organ at risks were compared based on RTOG 0915/0813 protocols.

Gated plans showed a significant reduction in mean ITV (22·02 Vs 11·83 cc; p < 0·001) and PTV (48·87 Vs 31·25 cc; p < 0·001) volumes. While PTV dose parameters and homogeneity indices of the plans were found to have no significant difference, gradient measure, gradient index and R50% showed a significant difference between the plans (p-value: < 0·001). The mean lung dose (Dmean) has been reduced by 0·75 Gy with significant reductions in V20Gy, V10Gy and V5Gy (p < 0·001).

Utilizing a 30–70% gating window significantly reduces target volumes and dose to the lung, heart, ribs and oesophagus. Gating is a highly effective motion management strategy for lung SBRT when balancing volumetric reduction against delivery efficiency.

Imaging the Eustachian tube has proven difficult as it has an anatomical orientation that is not aligned with standard planes. In addition, the Eustachian tube is a dynamic structure, opening briefly during a variety of physiological manoeuvres.

A 54-year-old healthy and asymptomatic man underwent computed tomography utilising an area detector scanner. Multiplanar reconstruction was performed at 1 mm intervals. In addition, dynamic clips were constructed to demonstrate air and its movement in the field. Images and video were acquired whilst a Valsalva manoeuvre was being performed.

Although imaging techniques have been able to visualise the Eustachian tube well in the closed state, it may be more useful to have it imaged whilst open. Area detector computed tomography scanners can be used to acquire four-dimensional images. This allows dynamic imaging of the region, to assist in the diagnosis of various types of Eustachian tube dysfunction.