Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2008 Sep 1;72(1):236-46.
doi: 10.1016/j.ijrobp.2008.04.051.

Intrafractional motion of the prostate during hypofractionated radiotherapy

Yaoqin Xie  1 , David Djajaputra, Christopher R King, Sabbir Hossain, Lijun Ma, Lei Xing
Affiliations

Intrafractional motion of the prostate during hypofractionated radiotherapy

Yaoqin Xie et al. Int J Radiat Oncol Biol Phys. .

Abstract

Purpose: To report the characteristics of prostate motion as tracked by the stereoscopic X-ray images of the implanted fiducials during hypofractionated radiotherapy with CyberKnife.

Methods and materials: Twenty-one patients with prostate cancer who were treated with CyberKnife between January 2005 and September 2007 were selected for this retrospective study. The CyberKnife uses a stereoscopic X-ray system to obtain the position of the prostate target through the monitoring of implanted gold fiducial markers. If there is a significant deviation, the treatment is paused while the patient is repositioned by moving the couch. The deviations calculated from X-ray images acquired within the time interval between two consecutive couch motions constitute a data set.

Results: Included in the analysis were 427 data sets and 4,439 time stamps of X-ray images. The mean duration for each data set was 697 sec. At 30 sec, a motion >2 mm exists in about 5% of data sets. The percentage is increased to 8%, 11%, and 14% at 60 sec, 90 sec, and 120 sec, respectively. A similar trend exists for other values of prostate motion.

Conclusions: With proper monitoring and intervention during treatment, the prostate shifts observed among patients can be kept within the tracking range of the CyberKnife. On average, a sampling rate of approximately 40 sec between consecutive X-rays is acceptable to ensure submillimeter tracking. However, there is significant movement variation among patients, and a higher sampling rate may be necessary in some patients.

PubMed Disclaimer

Conflict of interest statement

Conflicts of Interest Notification: No actual or potential conflicts of interest exist.

Figures

Figure 1
Figure 1
Flowchart of the patient setup and delivery process in CyberKnife treatment.
Figure 2
Figure 2
Histogram of the time span of the studied data sets.
Figure 3
Figure 3
Histogram of the fiducial center of mass movement in different directions.
Figure 4
Figure 4
Histogram of the prostate movement as a function of time duration and shift.
Figure 5
Figure 5
Rolling averages of prostate center of mass movement.
Figure 6
Figure 6
Patterns of prostate movement: (a) stable target at baseline, (b) continuous drift, (c) transient excursion, (d) persistent excursion, (e) high-frequency excursion, and (f) irregular movement (red: superior/inferior direction; green: left/right direction; blue: anterior/posterior direction; black: vector length of the shift).
Figure 7
Figure 7
Prostate movement behaviors for one of the patients in different data sets (red: superior/inferior direction; green: left/right direction; blue: anterior/posterior direction; black: vector length of the shift).
Figure 7
Figure 7
Prostate movement behaviors for one of the patients in different data sets (red: superior/inferior direction; green: left/right direction; blue: anterior/posterior direction; black: vector length of the shift).
Figure 8
Figure 8
Rigid Body Error curve of three fiducials for four representative patients (red: Fiducial 1; green: Fiducial 2; blue: Fiducial 3).
Figure 9
Figure 9
Prostate movement behaviors depicted by stereoscopic imaging of two different sample rates for two patients. (a) patient 1, (b) patient 2.
Figure 10
Figure 10
Percentage of data sets for the prostate target as a function of time duration and movement threshold.
See this image and copyright information in PMC

References

    1. Nichol AM, Brock KK, Lockwood GA, et al. A magnetic resonance imaging study of prostate deformation relative to implanted gold fiducial markers. Int J Radiat Oncol Biol Phys. 2007;67:48–56. - PubMed
    1. Zietman AL, DeSilvio ML, Slater JD, et al. Comparison of conventional-dose vs high-dose conformal radiation therapy in clinically localized adenocarcinoma of the prostate: a randomized controlled trial. Jama. 2005;294:1233–1239. - PubMed
    1. Pollack A, Zagars GK, Starkschall G, et al. Prostate cancer radiation dose response: results of the M. D. Anderson phase III randomized trial. Int J Radiat Oncol Biol Phys. 2002;53:1097–1105. - PubMed
    1. King CR, Lehmann J, Adler JR, et al. CyberKnife radiotherapy for localized prostate cancer: rationale and technical feasibility. Technol Cancer Res Treat. 2003;2:25–30. - PubMed
    1. Van den Heuvel F, Powell T, Seppi E, et al. Independent verification of ultrasound based image-guided radiation treatment, using electronic portal imaging and implanted gold markers. Med Phys. 2003;30:2878–2887. - PubMed

Publication types