论文研究 - 4D计算机断层扫描（4DCT）和4D锥形束计算机断层扫描（4DCBCT）的精度比较

preview
试读
13页
4DCT
验证成像
需积分: 0 8 下载量 41 浏览量 更新于2020-06-02 1 收藏 1.62MB PDF 举报
呼吸相关的扇形束CT（4DCT）和呼吸相关的锥形束CT（4DCBCT）准确估计肿瘤体积的能力对于肺部立体定向放射治疗（SBRT）和其他运动管理疗法的准确剂量和治疗验证至关重要。 但是，已知4DCT和4DCBCT在图像获取和重建方面会有所不同，这可能会导致这两种模态之间出现差异。 为了评估呼吸运动下4DCT和4DCBCT成像之间的定量差异，我们在地面真实情况下进行了幻像研究。 使用可编程的呼吸运动体模来模拟已知大小病变的1D SI位置。 在4DCT和4DCBCT采集期间，应用了十个正弦曲线和二十个患者特定的呼吸波形来驱动病变运动。 对于正弦曲线和患者特定的呼吸运动，两种成像方式之间获得的病变体积差异分别高达34.4％和18.4％。 与真实体积相比，在大多数情况下，4DCT测量常常低估了病变的大小，而4DCBCT高估了病变的体积。 对于本研究中测试的大多数设置，与4DCT相比，4DCBCT可以更准确地恢复体积。 这些发现可能有助于改善内部目标的定义和计划目标体积裕度，并从机载治疗验证成像中提取定量信息。
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 2017, 6, 323-335
http://www.scirp.org/journal/ijmpcero
ISSN Online: 2168-5444
ISSN Print: 2168-5436
DOI: 10.4236/ijmpcero.2017.63029
August 30, 2017
Accuracy Comparison of 4D Computed
Tomography (4DCT) and 4D Cone Beam
Computed Tomography (4DCBCT)
Tzu-Cheng Lee
1
, Stephen R. Bowen
2,3
, Sara St. James
2*
, George A. Sandison
2,3
,
Paul E. Kinahan
1,2,3*
, Matthew J. Nyflot
2,3*
1
Department of Bioengineering, University of Washington, Seattle, WA, USA
2
Department of Radiation Oncology, University of Washington, Seattle, WA, USA
3
Department of Radiology, University of Washington, Seattle, WA, USA
Abstract
The ability of respiratory-correlated fan beam CT (4DCT) and respirat
o-
ry-
correlated cone beam CT (4DCBCT) to accurately estimate tumor volume
is critical to accurate dosimetry and treatment verification for lung stereota
c-
tic body radiation therapy (SBRT) and other motion-
managed therapies.
However, it is known that 4DCT and 4DCBCT differ in aspects of image a
c-
quisition and reconstruction that may lead to discrepancies
between the two
modalities. To evaluate quantitative differences between 4DCT and 4DCBCT
imaging under respiratory motion, we performed a phantom study in the
ground truth setting. A programmable respiratory motion phantom was used
to simulate the 1D S-I position of a known-
size lesion. Ten sinusoidal and
twenty patient-specific breathing waveforms were applied to drive lesion m
o-
tion during the 4DCT and 4DCBCT acquisitions. The difference in lesion v
o-
lume acquired between the two imaging modalities was as h
igh as 34.4% and
18.4% for sinusoidal and patient-
specific breathing motions, respectively.
When compared to the true volume, 4DCT measurement often underest
i-
mated the lesion size whereas 4DCBCT overestimated the lesion volume in
most of the cases. 4DCBCT
gave more accurate recovery of the volume than
4DCT for most settings tested in this study. These findings may be helpful for
improving the definition of internal target and planning target volume ma
r-
gins, and extracting quantitative information from on-board treatment verif
i-
cation imaging.
Keywords
4DCT, 4DCBCT, Verification Imaging, Respiratory Motion Phantom
How to cite this paper:
Lee, T.-C., Bowen,
S
.R., St. James, S., Sandison, G.
A., Kinahan,
P
.E. and Nyflot, M.J. (2017) Accuracy Com-
parison of 4D Computed Tomography
(4DCT) and 4D Cone Beam Computed
Tomography (4DCBCT)
.
International
Journal of
Medical Physics
,
Clinical
Engineering and Radiation Oncology
,
6,
323
-335.
https://doi.org/10.4236/ijmpcero.2017.63029
Received:
July 25, 2017
Accepted:
August 27, 2017
Published:
August 30, 2017
Copyright © 201
7 by authors and
Scientific
Research Publishing Inc.
This work is licensed under the Creative
Commons Attribution International
License (CC BY
4.0).
http://creativecommons.org/licenses/by/4.0/
Open Access
T.-C. Lee et al.
324
1. Introduction
Accurate computed tomography (CT) studies under the presence of respiratory
motion are necessary for treatment planning, treatment verification, and adap-
tive radiotherapy in many cancers, most commonly for cancers of the lung, liver,
and abdomen [1] [2] [3] [4] [5]. 4DCT imaging may be used for respiratory mo-
tion assessment and creating an external beam radiation treatment plan for a
free-breathing patient [6] [7]. Radiotherapy image-guided verification is com-
monly performed by comparing lesion position and motion estimated in the
treatment room with cone beam CT (CBCT), CT on rails, megavoltage CT
(MVCT) or other methods to the primary planning CT study acquired at the
time of treatment simulation. Beyond the critical role of verification imaging in
patient setup, changes in CT volumes have been used as indications for adaptive
re-planning and modeled to extract radiobiological parameters [8] [9].
It is known that respiratory motion leads to significant imaging artifacts
which may lead to incorrect treatment planning volumes, lesion localization, or
inference of change in tumor volume over time. Respiratory-correlated com-
puted tomography (4DCT) using external respiratory surrogates was first pro-
posed as solution for this problem [10] [11] [12] [13] and has rapidly become a
standard of care for radiotherapy simulation in the presence of respiratory mo-
tion [14] [15]. In the intervening years, cone beam computed tomography
(CBCT) technology has proliferated on linear accelerators to provide image
guidance for radiotherapy verification, and recently, respiratory-correlated cone
beam CT (4DCBCT) has become clinically available [16] [17] [18]. Sonke
et al.
investigated 4DCBCT versus 3DCBCT and fluoroscopy and found motion arti-
facts in 4D dataset were substantially reduced compared to a 3D scan [17].
Sweeney
et al.
investigated inter-observer variability of target localization for
4DCBCT and 3DCBCT imaging with patient data and found significantly re-
duced variability with 4DCBCT [19]. Lee
et al.
and Iramina
et al.
further ex-
amined the impact of scanning parameters and motion sorting methods related
to the accuracy of 4DCBCT images [20] [21].
However, clinical investigation of comparisons of 4DCBCT and 4DCT imag-
ing for tumor motion assessment has indicated significant differences in some
patients [22]. 4DCT and 4DCBCT imaging differs in numerous aspects in terms
of image acquisition, hardware geometry, and binning techniques [23] [24].
These differences include smaller x-ray beam volumetric coverage in CT versus
much larger coverage in CBCT for a single rotation, scan time on the order of
seconds in 4DCT versus minutes in 4DCBCT, arc detector versus flat panel de-
tector geometry employed with different anti-scatter setups, and external surro-
gates in 4DCT versus internal tracking in 4DCBCT of respiratory motion. To
date, investigations of accuracy of respiratory-correlated fan beam versus cone
beam CT imaging in the presence of respiratory motion in the ground truth set-
ting have been limited. Researchers have compared 3DCBCT image to the 4DCT
maximum intensity projection (MIP) reconstructed image of anthropomorphic
respiratory phantoms and found contradictory results [25] [26]. Nevertheless,
T.-C. Lee et al.
325
the relative accuracy of 4DCBCT and 4DCT in the ground truth setting is un-
known.
We had shown the uptake accuracy in 4D phased-match CT attenuation cor-
rected 4DPET could be significantly compromised due to patient’s irregular
breathing pattern and the nature of acquisition time difference between two
modalities [27]. In this work, we will focus on the impact of respiratory motion
on CT acquisition by comparing the accuracy of 4DCT and 4DCBCT in the
ground truth setting with an anthropomorphic respiratory phantom. These re-
sults may be informative for treatment planning, treatment verification, longitu-
dinal response assessment, and adaptive radiotherapy for thoracic and abdomin-
al cancers.
2. Methods
2.1. Anthropomorphic Phantom
The Quasar programmable respiratory motion phantom (Modus Medical De-
vices Inc., ON, Canada) was used for this study. A custom insert was designed,
consisting of a water-filled 24 mm outer-diameter sphere simulating a lung le-
sion, surrounded by polystyrene pellets comparable to the density of lung. The
Quasar phantom has a mount for an infrared marker which moves at a 1:1 ratio
to the phantom insert. The motion of the infrared marker was captured with an
RPM camera (RPM, Varian Medical Systems, Palo Alto, CA). An image of the
phantom is shown in
Figure 1. The motion of the Quasar phantom is one di-
mensional (superior-inferior) and can be programmed using sinusoidal breath-
ing traces or representative patient traces distributed with the phantom.
2.2. Phantom Motion
To evaluate the fidelity of the 4DCT and 4DCBCT studies, the water sphere was
driven by 10 sinusoidal respiratory waveforms (period 3, 4, 5, 6, 7 seconds, 15
and 30 mm amplitude) and 20 patient-derived respiratory waveforms provided
by the Quasar software (10 patient waveforms with period 4.2 ± 0.7 - 6.6 ± 1.6
seconds, nominal 15 and 30 mm peak-to-peak amplitude, mean 9.9 ± 1.2 - 19.8
± 2.3 mm amplitude). It should be noted that the patient-specific respiratory
Figure 1. On left, programmable respiratory phantom with custom anthropomorphic in-
sert. The mount for the infrared marker cubic is indicated with a red arrow. On right,
representative CT slice of phantom geometry.

剩余12页未读，继续阅读

资源推荐
资源评论
weixin_38631331
  • 粉丝: 5
  • 资源: 907
上传资源 快速赚钱
voice
center-task 前往需求广场，查看用户热搜

最新资源