Quantification of regional ventilation from treatment planning CT

Ventilation distribution calculation using 4D CT has shown promising potential in several clinical applications. This study evaluated the direct geometric ventilation calculation method, namely the ΔV method, with xenon‐enhanced CT (XeCT) ventilation data from four sheep, and compared it with two other published methods, the Jacobian and the Hounsfield unit (HU) methods. Spearman correlation coefficient (SCC) and Dice similarity coefficient (DSC) were used for the evaluation and comparison. The average SCC with one standard deviation was 0.44±0.13 with a range between 0.29 and 0.61 between the XeCT and DLV ventilation distributions. The average DSC value for lower 30% ventilation volumes between the XeCT and ΔV ventilation distributions was 0.55±0.07 with a range between 0.48 and 0.63. Ventilation difference introduced by deformable image registration errors improved with smoothing. In conclusion, ventilation distributions generated using ΔV‐4D CT and deformable image registration are in reasonably agreement with the in vivo XeCT measured ventilation distribution.PACS number(s): 87.57.N‐, 87.57.nj, 87.57.Q‐, 87.85.Pq

Section: Discussionsupporting

confidence: 79%

“…The change in density for each voxel is calculated by direct comparison of HUs 11 , 12 . The fraction of air in a CT lung volume may be estimated as,

F_{a i r} = - \frac{H U}{1000}

where HU represents the average Hounsfield unit value within the volume.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation of the ΔV 4D CT ventilation calculation method usingin vivoxenon CT ventilation data and comparison to other methods

Zhang

Latifi

et al. 2016

“…A form of functional imaging has been developed that uses 4‐dimensional computed tomography (4DCT) data along with image processing techniques to calculate 4DCT‐based lung ventilation maps 1, 2, 3. 4DCT‐ventilation has been gaining momentum in radiation oncology because 4DCT simulations are frequently acquired as part of the standard treatment planning process; which enables the calculation of 4DCT‐ventilation‐based lung function without burdening the patient with an extra imaging procedure.…”

Section: Introductionmentioning

confidence: 99%

Using 4DCT‐ventilation to characterize lung function changes for pediatric patients getting thoracic radiotherapy

Vinogradskiy

Faught

Castillo

et al. 2018

Self Cite

PurposeA form of lung functional imaging has been developed that uses 4DCT data to calculate ventilation (4DCT‐ventilation). Because 4DCTs are acquired as standard‐of‐care to manage breathing motion during radiotherapy, 4DCT‐ventilation provides functional information at no extra dosimetric or monetary cost. 4DCT‐ventilation has yet to be described in children. 4DCT‐ventilation can be used as a tool to help assess post‐treatment lung function and predict for future clinical thoracic toxicities for pediatric patients receiving radiotherapy to the chest. The purpose of this work was to perform a preliminary evaluation of 4DCT‐ventilation‐based lung function changes for pediatric patients receiving radiotherapy to the lungs.MethodsThe study used four patients with pre and postradiotherapy 4DCTs. The 4DCTs, deformable image registration, and a density‐change‐based algorithm were used to compute pre and post‐treatment 4DCT‐ventilation images. The post‐treatment 4DCT‐ventilation images were compared to the pretreatment 4DCT‐ventilation images for a global lung response and for an intrapatient dose–response (providing an assessment for dose‐dependent regional dose–response).ResultsFor three of the four patients, a global ventilation decline of 7–37% was observed, while one patient did not demonstrate a global functional decline. Dose–response analysis did not reveal an intrapatient dose–response from 0 to 20 Gy for three patients while one patient demonstrated increased 4DCT‐ventilation decline as a function of increasing lung doses up to 50 Gy.ConclusionsCompared to adults, pediatric patients have unique lung function, dosimetric, and toxicity profiles. The presented work is the first to evaluate spatial lung function changes in pediatric patients using 4DCT‐ventilation and showed lung function changes for three of the four patients. The early changes demonstrated with lung function imaging warrant further longitudinal work to determine whether the imaging‐based early changes can be predicted for long‐term clinical toxicity.

Functional avoidance‐based intensity modulated proton therapy with 4DCT derived ventilation imaging for lung cancer

Dougherty

Castillo

et al. 2021

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The primary objective is to evaluate the potential dosimetric gains of performing functional avoidance-based proton treatment planning using 4DCT derived ventilation imaging. 4DCT data of 31 patients from a prospective functional avoidance clinical trial were evaluated with intensity modulated proton therapy (IMPT) plans and compared with clinical volumetric modulated arc therapy (VMAT) plans. Dosimetric parameters were compared between standard and functional plans with IMPT and VMAT with one-way analysis of variance and post hoc paired student ttest. Normal Tissue Complication Probability (NTCP) models were employed to estimate the risk of two toxicity endpoints for healthy lung tissues. Dose degradation due to proton motion interplay effect was evaluated. Functional IMPT plans led to significant dose reduction to functional lung structures when compared with functional VMAT without significant dose increase to Organ at Risk (OAR) structures.When interplay effect is considered, no significant dose degradation was observed for the OARs or the clinical target volume (CTV) volumes for functional IMPT. Using fV20 as the dose metric and Grade 2+ pneumonitis as toxicity endpoint, there is a mean 5.7% reduction in Grade 2+ RP with the functional IMPT and as high as 26% in reduction for individual patient when compared to the standard IMPT planning.Functional IMPT was able to spare healthy lung tissue to avoid excess dose to normal structures while maintaining satisfying target coverage. NTCP calculation also shows that the risk of pulmonary complications can be further reduced with functional based IMPT.