Deep inspiration breath-hold radiotherapy for lung cancer: impact on image quality and registration uncertainty in cone beam CT image guidance

Abstract

Objective: We investigated the impact of deep inspiration breath-hold (DIBH) and tumour baseline shifts on image quality and registration uncertainty in imageguided DIBH radiotherapy (RT) for locally advanced lung cancer. Methods: Patients treated with daily cone beam CT (CBCT)-guided free-breathing (FB) RT had an additional CBCT in DIBH at three fractions. These CBCT scans were offline rigidly registered (on tumour) to FB and DIBH CT scans acquired at planning. All registrations were repeated to evaluate the intraobserver uncertainty. CBCT scans were scored on degree of streak artefacts and visualization of tumour and anatomical structures. We examined the impact of tumour baseline shift between consecutive DIBHs on CBCT image quality. Results: CBCT scans from 15 patients were analysed. Intraobserver image registration uncertainty was approximately 2 mm in both FB and DIBH, except for the craniocaudal direction in FB, where it was .3 mm. On the 31st fraction, the intraobserver uncertainty increased compared with the second fraction. This increase was more pronounced in FB. Image quality scores improved in DIBH compared with FB for all parameters in all patients. Simulated tumour baseline shifts #2 mm did not affect the CBCT image quality considerably. Conclusion: DIBH CBCT improved image quality and reduced registration uncertainty in the craniocaudal direction in image-guided RT of locally advanced lung cancer. Baseline shifts #2 mm in DIBH during CBCT acquisition did not affect image quality. Advances in knowledge: DIBH RT has dosimetric advantages over FB; this work demonstrates an additional benefit of DIBH in terms of registration accuracy because of improved image quality.

Feasibility of Optical Surface-Guidance for Position Verification and Monitoring of Stereotactic Body Radiotherapy in Deep-Inspiration Breath-Hold

“…Moreover, SGRT reliably detects intrafractional shifts during treatment delivery when deviations extend 2 mm, as confirmed by CBCT (24). In addition, DIBH improves image quality and reduces craniocaudal registration uncertainties compared to free-breathing in lung cancer radiotherapy (25). Furthermore, using breath-hold for SBRT delivery reduces motion artifacts that is especially important for small lung tumors that are poorly visualized on imaging even with modern linear accelerators (26).…”

Acuros® dose verification of ultrasmall lung lesions with EBT‐XD film in a homogeneous and heterogeneous anthropomorphic phantom setup

“…46,47 Motion mitigation, especially for small tumors also increases tumor visibility on CBCT and fluoroscopic images, as image blurring is substantially reduced. 48 New techniques with fast gantry rotation and ultrafast single breath-hold CBCT acquisition might further improve SBRT lung treatments and create opportunities to treat also very small tumors with high spatial accuracy. 49 Nevertheless, the accuracy of dose calculation algorithms needs to improve as well for small fields, which was the main focus in this work.…”

“…The inclusion of tumor motion and its effect on dosimetry may be investigated in future work although arguments exist to mitigate motion as much as possible for SBRT lung treatments 46,47 . Motion mitigation, especially for small tumors also increases tumor visibility on CBCT and fluoroscopic images, as image blurring is substantially reduced 48 . New techniques with fast gantry rotation and ultrafast single breath‐hold CBCT acquisition might further improve SBRT lung treatments and create opportunities to treat also very small tumors with high spatial accuracy 49 .…”

Deep inspiration breath hold in locally advanced lung cancer radiotherapy: validation of intrafractional geometric uncertainties in the INHALE trial

“…We anticipated daily image guidance with cone beam CT (CBCT) registered on the target. 20 Additional uncertainties, included in the margin calculation, were interfractional differential motion between T and N, 16 lack of 6D corrections, 21 image registration uncertainty 22 and penumbra width. All systematic and random errors were added in quadrature.…”