CT Ventilation is software that shows us how well different areas of the lung are performing. This means we can make sure we protect the healthy areas during radiation therapy.
Cancer and lung function.
For people with lung cancer, there are numerous factors other than the cancer itself which can seriously impact on the health of their lungs. There can be existing problems such as chronic pulmonary obstructive disorder (CPOD), fibrosis and thickening of the lymphatics in the lung, emphysema, asbestosis and partial lung collapse. As well as this, side effects from cancer treatment can include fluid on the lungs, inflammation and pneumonitis, or even partial lung removal. With so many factors contributing to lung function, it is important to save as much healthy lung tissue as possible during lung cancer treatment, to give patients the best possible chance of survival and quality of life.
Lung cancer is one of the most commonly diagnosed cancers, and one of the most difficult to treat. With 3 out of 4 lung cancer patients being able to benefit from radiation therapy, innovation in this field has the potential to improve the outcomes for tens of thousands of patients in Australia alone. Unfortunately, 30% of patients experience pneumonitis and painful inflammation from the treatment, and for 2% of patients these side effects prove fatal.
Studies indicate that side effects from radiotherapy could be reduced by avoiding irradiation of healthy (functional) lung tissue. Irradiation of healthy lung tissue happens for a variety of reasons: tumour motion during breathing, the limitations of cancer imaging and treatment accuracy, and treatment planning – designing the strength and location of the radiation beam.
A World-first Solution: CT Ventilation Imaging
Researchers at our institute have developed ‘CT Ventilation’ – a novel software-based solution that can map out the healthy areas of the lung simultaneously while routine pre-treatment scans are carried out. This means that we could improve treatment plans and therefore reduce side effects for cancer patients without conducting any extra scans.
How does CT Ventilation Work?
- Aquire CT-images of the lung at exhale and inhale states, using breath-hold CT, or 4D-CT (CT imaging which is in 3D and captures the image over time, to show movement).
- Deformable image registration (DIR) software is used to determine a spatial mapping (“deformation map”) between the exhale and inhale CT images.
- Application of a ventilation metric involves quantitative analysis based on the information from the DIR software.
The resulting ventilation image can be superimposed directly onto the anatomic image, providing an added dimension of functional information which is easy to understand and can be of direct benefit in planning a radiotherapy treatment.
Validating CT-ventilation imaging
We have conducted a clinical study at Royal North Shore Hospital testing the physiological accuracy of CT ventilation imaging for use in lung cancer radiotherapy. The physiological accuracy of CT ventilation imaging was assessed via a correlation study against the current gold standard for ventilation imaging, nuclear medicine imaging.
We also quantified the dosimetric impact of CT ventilation imaging for Functional Avoidance Lung Radiotherapy. Functional avoidance is a method of treatment planning which tries to avoid irradiation of high-functioning (well-ventilated) lung regions.
The results of this study were published in the European Journal of Cardio-Thoracic Surgery, with our method attaining similar results to the gold standard for ventilation imaging.
“VESPIR” (VEntilation via Scripted Pulmonary Image Registration) has now been developed.
For more information about VESPIR, you may like to view the following presentation (video link) from the 2015 Cancer Institute NSW Innovations Conference. Note that the code mentioned in the presentation is no longer publicly available
-25 publications in high impact journals (Medical Physics, IJROBP and Radiother. Oncol.)
-International research consortium formed – clinical trials occurring across three cancer centres.
-Cancer Institute NSW funding $550k
US Patent – PCT #7668357 Method and system for using computed tomography to test pulmonary function – granted 23 February 2010
Three US clinical trials underway:
- NCT02528942: 4DCT Ventilation Imaging in Radiation Treatment Planning in Patients with Lung Cancer, University of Colorado Cancer Center – Anschutz Cancer Pavilion
- The proposed study is in the field of thoracic radiation oncology where radiation therapy is used to treat lung cancer. The primary objective of the early phase clinical trial will be to evaluate the safety of performing functional avoidance radiation therapy for lung cancer patients using 4D computed tomography (4DCT) ventilation imaging.
- NCT02308709: 4D CT Ventilation Image-Guided Personalized Radiation Therapy in Treating Patients with Lung Cancer or Lung Metastasis, University of California Davis Comprehensive Cancer Center
- The primary objective of this study is to assess the safety and feasibility of personalized radiotherapy with four-dimensional (4D) computed tomography (CT)-based pulmonary ventilation imaging, which selectively avoids irradiating highly-functional lung regions.
- NCT02843568: Improving Pulmonary Function Following Radiation Therapy, University of Wisconsin, Madison
- The purpose of this study is to develop radiation plans that will help preserve lung function in healthy tissue surrounding the tumor. We believe that 4DCT scans can be useful in designing radiation treatment plans that help us avoid healthy normal functioning lung tissue close to lung tumors. Currently 4DCT scans are used to help us determine exactly where the tumor is and how it moves when you breathe. In this study we will also use the 4DCT scans to try to identify high functioning normal lung tissue.
Our goal is to forge a partnership to enable the broad dissemination of this technology.
Potential to reduce the risk of severe pneumonitis by 5-8% for US population (as high as 52% for individual patients), approx. 5,200-8,300 patients per year.
Faught et al., Int J Radiat Oncol Biol Phys (2017)
Collaborating hospitals and organisations:
- University of California Davis Comprehensive Cancer Center
- Anschutz Cancer Pavillion
- The University of Wisconsin
- Royal North Shore Hospital
For more information on this project, contact Professor Paul Keall
- Eslick, E., Kipritidis, J., Gradinscak, D., Stevens, M., Bailey, D., Harris, B., Booth, J., Keall, P. (2018). CT ventilation imaging derived from breath hold CT exhibits good regional accuracy with Galligas PET. Radiotherapy and Oncology, 127(2), 267-273.
- Hegi-Johnson, F., Keall, P., Barber, J., Bui, C., Kipritidis, J. (2017). Evaluating the accuracy of 4D-CT ventilation imaging: First comparison with Technegas SPECT ventilation. Medical Physics, 44(8), 4045-4055.
a href=”http://dx.doi.org/10.1002/mp.12317″>[More Information]
- Woodruff, H., Shieh, C., Hegi-Johnson, F., Keall, P., Kipritidis, J. (2017). Quantifying the reproducibility of lung ventilation images between 4-Dimensional Cone Beam CT and 4- Dimensional CT. Medical Physics, 44(5), 1771-1781.
- Kipritidis, J., Hofman, M., Siva, S., Callahan, J., Le Roux, P., Woodruff, H., Counter, W., Keall, P. (2016). Estimating lung ventilation directly from 4D CT Hounsfield unit values. Medical Physics, 43(1), 33-43.
- Eslick, E., Bailey, D., Harris, B., Kipritidis, J., Stevens, M., Li, B., Bailey, E., Gradinscak, D., Pollock, S., Htun, C., Keall, P., et al (2016). Measurement of preoperative lobar lung function with computed tomography ventilation imaging: progress towards rapid stratification of lung cancer lobectomy patients with abnormal lung function. European Journal Of CardioThoracic Surgery, 49(4), 1075-1082.
- Kipritidis, J., Woodruff, H., Eslick, E., Hegi-Johnson, F., Keall, P. (2016). New pathways for end-to-end validation of CT ventilation imaging (CTVI) using deformable image registration. 2016 IEEE 13th International Symposium on Biomedical Imaging (ISBI): From Nano to Macro, Piscataway: Institute of Electrical and Electronics Engineers (IEEE).
- Kipritidis, J., Hugo, G., Weiss, E., Williamson, J., Keall, P. (2015). Measuring interfraction and intrafraction lung function changes during radiation therapy using four-dimensional cone beam CT ventilation imaging. Medical Physics, 42(3), 1255- 1267.
- Cooper, B., O’Brien, R., Kipritidis, J., Shieh, C., Keall, P. (2015). Quantifying the image quality and dose reduction of respiratory triggered 4D cone-beam computed tomography with patient-measured breathing. Physics in Medicine and Biology, 60(24), 9493-9513.
- Kipritidis, J., Siva, S., Hofman, M., Callahan, J., Hicks, R., Keall, P. (2014). Validating and improving CT ventilation imaging by correlating with ventilation 4D-PET/CT using 68Galabeled nanoparticles. Medical Physics, 41(1), 011910-1- 011910-12.