Clinical application of breathing-adapted 4D CT: image quality comparison to conventional 4D CT

Abstract

Purpose: 4D CT imaging is an integral part of 4D radiotherapy workflows. However, 4D CT data often contain motion artifacts that mitigate treatment planning. Recently, breathing-adapted 4D CT (i4DCT) was introduced into clinical practice, promising artifact reduction in in-silico and phantom studies. Here, we present an image quality comparison study, pooling clinical patient data from two centers: a new i4DCT and a conventional spiral 4D CT patient cohort.Methods: The i4DCT cohort comprises 129 and the conventional spiral 4D CT cohort 417 4D CT data sets of lung and liver tumor patients. All data were acquired for treatment planning. The study consists of three parts: illustration of image quality in selected patients of the two cohorts with similar breathing patterns; an image quality expert rater study; and automated analysis of the artifact frequency.Results: Image data of the patients with similar breathing patterns underline artifact reduction by i4DCT compared to conventional spiral 4D CT. Based on a subgroup of 50 patients with irregular breathing patterns, the rater study reveals a fraction of almost artifact-free scans of 89% for i4DCT and only 25% for conventional 4D CT; the quantitative analysis indicated a reduction of artifact frequency by 31% for i4DCT.Conclusion: The results demonstrate 4D CT image quality improvement for patients with irregular breathing patterns by breathing-adapted 4D CT in this first corresponding clinical data image quality comparison study.

Optimized raw data selection for artifact reduction of breathing controlled four-dimensional sequence scanning

“…In the present study, an algorithm for optimized raw data selection in the presence of strong breathing irregularities aiming to improve image quality as well as geometric accuracy was evaluated. It seamlessly followed previous in-silico , phantom-based and clinical studies, which demonstrated a significant improvement in image quality with i4DCT compared to conventional algorithms [13] , [14] , [15] , [16] , [25] . Although 74% of the phantom [16] and 89% of the patient scans [25] were described as (nearly) artifacts-free with i4DCT compared to 13% and 25% with conventional algorithms, respectively, image artifacts still occurred in some cases, especially for single significant longer breathing cycles or breathing amplitudes < 50% of the reference cycle.…”

“…It seamlessly followed previous in-silico , phantom-based and clinical studies, which demonstrated a significant improvement in image quality with i4DCT compared to conventional algorithms [13] , [14] , [15] , [16] , [25] . Although 74% of the phantom [16] and 89% of the patient scans [25] were described as (nearly) artifacts-free with i4DCT compared to 13% and 25% with conventional algorithms, respectively, image artifacts still occurred in some cases, especially for single significant longer breathing cycles or breathing amplitudes < 50% of the reference cycle. For radiation protection reasons, a scan is currently stopped at a distinct z -position when reaching a maximum scan time t max , resulting in insufficient information for image reconstruction.…”

First implementation of an innovative infra‐red camera system integrated into a mobile CBCT scanner for applicator tracking in brachytherapy—Initial performance characterization

“…An alternative is optical or IR tracking applied many times in radiotherapy, e.g. for patient positioning at the linear accelerator [40][41][42] or four-dimensional CT. 43,44 For interventions and surgery, such tracking was also already used for (pre-)clinical investigations. [45][46][47] However, corresponding approaches are mainly based on external tracking cameras that would again require a tracking of both CBCT scanner and actual marker tool to establish a position transfer, concomitant with increased inaccuracies of up to >2 mm reported.…”

“…An alternative is optical or IR tracking applied many times in radiotherapy, e.g. for patient positioning at the linear accelerator 40–42 or four‐dimensional CT 43,44 . For interventions and surgery, such tracking was also already used for (pre‐)clinical investigations 45–47 .…”