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Title: Advances in image-guided radiation therapy-the role of PET-CT

Abstract

In the era of image-guided radiation therapy (IGRT), the greatest challenge remains target delineation, as the opportunity to maximize cures while simultaneously decreasing radiation dose to the surrounding normal tissues is to be realized. Over the last 2 decades, technological advances in radiographic imaging, biochemistry, and molecular biology have played an increasing role in radiation treatment planning, delivery, and evaluation of response. Previously, fluoroscopy formed the basis of radiation treatment planning. Beginning in the late 1980s, computed tomography (CT) has become the basis for modern radiation treatment planning and delivery, coincident with the rise of 3-dimensional conformal radiation therapy (3DCRT). Additionally, multi-modality anatomic imaging registration was the solution pursued to augment delineation of tumors and surrounding structures on CT-based treatment planning. Although these imaging modalities provide the customary anatomic details necessary for radiation treatment planning, they have limitations, including difficulty with identification of small tumor deposits, tumor extension, and distinction from scar tissues. To overcome these limitations, PET and, more recently, PET-CT have been innovative regarding the extent of disease appraisal, target delineation in the treatment planning, and assessment of therapy response. We review the role of functional imaging in IGRT as it reassures transformations on the field of radiationmore » oncology. As we move toward the era of IGRT, the use of multi-modality imaging fusion, and the introduction of more sensitive and specific PET-CT tracers may further assist target definition. Furthermore, the potential to predict early outcome or even detect early recurrence of tumor, may allow for the tailoring of intervention in cancer patients. The convergence of a biological target volume, and perhaps multi-tracer tumor, molecular, and genetic profile tumors will probably be vital in cancer treatment selection. Nevertheless, prospective clinical experience with outcome is encouraged and needs to be expanded to entirely exploit the benefits of the IGRT.« less

Authors:
 [1];  [2];  [2]
  1. Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA (United States). E-mail: heronD2@upmc.edu
  2. Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, PA (United States)
Publication Date:
OSTI Identifier:
20783352
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Dosimetry; Journal Volume: 31; Journal Issue: 1; Other Information: DOI: 10.1016/j.meddos.2005.12.006; PII: S0958-3947(05)00204-9; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BIOCHEMISTRY; COMPUTERIZED TOMOGRAPHY; FLUOROSCOPY; IMAGES; MOLECULAR BIOLOGY; NEOPLASMS; PLANNING; RADIATION DOSES; RADIOTHERAPY

Citation Formats

Heron, Dwight E., Smith, Ryan P., and Andrade, Regiane S.. Advances in image-guided radiation therapy-the role of PET-CT. United States: N. p., 2006. Web. doi:10.1016/j.meddos.2005.12.006.
Heron, Dwight E., Smith, Ryan P., & Andrade, Regiane S.. Advances in image-guided radiation therapy-the role of PET-CT. United States. doi:10.1016/j.meddos.2005.12.006.
Heron, Dwight E., Smith, Ryan P., and Andrade, Regiane S.. Sat . "Advances in image-guided radiation therapy-the role of PET-CT". United States. doi:10.1016/j.meddos.2005.12.006.
@article{osti_20783352,
title = {Advances in image-guided radiation therapy-the role of PET-CT},
author = {Heron, Dwight E. and Smith, Ryan P. and Andrade, Regiane S.},
abstractNote = {In the era of image-guided radiation therapy (IGRT), the greatest challenge remains target delineation, as the opportunity to maximize cures while simultaneously decreasing radiation dose to the surrounding normal tissues is to be realized. Over the last 2 decades, technological advances in radiographic imaging, biochemistry, and molecular biology have played an increasing role in radiation treatment planning, delivery, and evaluation of response. Previously, fluoroscopy formed the basis of radiation treatment planning. Beginning in the late 1980s, computed tomography (CT) has become the basis for modern radiation treatment planning and delivery, coincident with the rise of 3-dimensional conformal radiation therapy (3DCRT). Additionally, multi-modality anatomic imaging registration was the solution pursued to augment delineation of tumors and surrounding structures on CT-based treatment planning. Although these imaging modalities provide the customary anatomic details necessary for radiation treatment planning, they have limitations, including difficulty with identification of small tumor deposits, tumor extension, and distinction from scar tissues. To overcome these limitations, PET and, more recently, PET-CT have been innovative regarding the extent of disease appraisal, target delineation in the treatment planning, and assessment of therapy response. We review the role of functional imaging in IGRT as it reassures transformations on the field of radiation oncology. As we move toward the era of IGRT, the use of multi-modality imaging fusion, and the introduction of more sensitive and specific PET-CT tracers may further assist target definition. Furthermore, the potential to predict early outcome or even detect early recurrence of tumor, may allow for the tailoring of intervention in cancer patients. The convergence of a biological target volume, and perhaps multi-tracer tumor, molecular, and genetic profile tumors will probably be vital in cancer treatment selection. Nevertheless, prospective clinical experience with outcome is encouraged and needs to be expanded to entirely exploit the benefits of the IGRT.},
doi = {10.1016/j.meddos.2005.12.006},
journal = {Medical Dosimetry},
number = 1,
volume = 31,
place = {United States},
year = {Sat Apr 01 00:00:00 EST 2006},
month = {Sat Apr 01 00:00:00 EST 2006}
}
  • Imaging plays a vital role in radiation therapy and with recent advances in technology considerable emphasis has been placed on cone-beam CT (CBCT). Attaching a kV x-ray source and a flat panel detector directly to the linear accelerator gantry has enabled progress in target localization techniques, which can include daily CBCT setup scans for some treatments. However, with an increasing number of CT scans there is also an increasing concern for patient exposure. An intensity-weighted region-of-interest (IWROI) technique, which has the potential to greatly reduce CBCT dose, in conjunction with the chord-based backprojection-filtration (BPF) reconstruction algorithm, has been developed andmore » its feasibility in clinical use is demonstrated in this article. A nonuniform filter is placed in the x-ray beam to create regions of two different beam intensities. In this manner, regions outside the target area can be given a reduced dose but still visualized with a lower contrast to noise ratio. Image artifacts due to transverse data truncation, which would have occurred in conventional reconstruction algorithms, are avoided and image noise levels of the low- and high-intensity regions are well controlled by use of the chord-based BPF reconstruction algorithm. The proposed IWROI technique can play an important role in image-guided radiation therapy.« less
  • Purpose: Measuring changes in lung perfusion resulting from radiation therapy dose requires registration of the functional imaging to the radiation therapy treatment planning scan. This study investigates registration accuracy and utility for positron emission tomography (PET)/computed tomography (CT) perfusion imaging in radiation therapy for non–small cell lung cancer. Methods: {sup 68}Ga 4-dimensional PET/CT ventilation-perfusion imaging was performed before, during, and after radiation therapy for 5 patients. Rigid registration and deformable image registration (DIR) using B-splines and Demons algorithms was performed with the CT data to obtain a deformation map between the functional images and planning CT. Contour propagation accuracy andmore » correspondence of anatomic features were used to assess registration accuracy. Wilcoxon signed-rank test was used to determine statistical significance. Changes in lung perfusion resulting from radiation therapy dose were calculated for each registration method for each patient and averaged over all patients. Results: With B-splines/Demons DIR, median distance to agreement between lung contours reduced modestly by 0.9/1.1 mm, 1.3/1.6 mm, and 1.3/1.6 mm for pretreatment, midtreatment, and posttreatment (P<.01 for all), and median Dice score between lung contours improved by 0.04/0.04, 0.05/0.05, and 0.05/0.05 for pretreatment, midtreatment, and posttreatment (P<.001 for all). Distance between anatomic features reduced with DIR by median 2.5 mm and 2.8 for pretreatment and midtreatment time points, respectively (P=.001) and 1.4 mm for posttreatment (P>.2). Poorer posttreatment results were likely caused by posttreatment pneumonitis and tumor regression. Up to 80% standardized uptake value loss in perfusion scans was observed. There was limited change in the loss in lung perfusion between registration methods; however, Demons resulted in larger interpatient variation compared with rigid and B-splines registration. Conclusions: DIR accuracy in the data sets studied was variable depending on anatomic changes resulting from radiation therapy; caution must be exercised when using DIR in regions of low contrast or radiation pneumonitis. Lung perfusion reduces with increasing radiation therapy dose; however, DIR did not translate into significant changes in dose–response assessment.« less
  • Accurate patient setup and target localization are essential to advanced radiation therapy treatment. Significant improvement has been made recently with the development of image-guided radiation therapy, in which image guidance facilitates short treatment course and high dose per fraction radiotherapy, aiming at improving tumor control and quality of life. Many imaging modalities are being investigated, including x-ray computed tomography (CT), ultrasound imaging, positron emission tomography, magnetic resonant imaging, magnetic resonant spectroscopic imaging, and kV/MV imaging with flat panel detectors. These developments provide unique imaging techniques and methods for patient setup and target localization. Some of them are different; some aremore » complementary. This paper reviews the currently available kV x-ray CT systems used in the radiation treatment room, with a focus on the CT-on-rails systems, which are diagnostic CT scanners moving on rails installed in the treatment room. We will describe the system hardware including configurations, specifications, operation principles, and functionality. We will review software development for image fusion, structure recognition, deformation correction, target localization, and alignment. Issues related to the clinical implementation of in-room CT techniques in routine procedures are discussed, including acceptance testing and quality assurance. Clinical applications of the in-room CT systems for patient setup, target localization, and adaptive therapy are also reviewed for advanced radiotherapy treatments.« less
  • In order to quantify the differences between ultrasound-imaging and megavoltage-CT (MVCT) daily prostate localization in prostate-cancer radiotherapy and their dosimetric impacts, daily shifts were analyzed for a total of 140 prostate cancer patients; 106 positioned using ultrasound-based imaging [B-mode Acquisition and Targeting (BAT)], and 34 using the MVCT from a TomoTherapy Hi-Art unit. The shifts indicated by the two systems were compared statistically along the right/left (R/L), superior/inferior (S/I), and anterior/posterior (A/P) directions. The systematic and random variations among the daily alignments were calculated. Margins to account for these shifts were estimated. The mean shifts and standard deviations along themore » R/L, S/I, and A/P directions were -0.11{+-}3.80, 0.67{+-}4.67, and 2.71{+-}6.31 mm for BAT localizations and -0.98{+-}5.13, 0.27{+-}3.35, and 1.00{+-}4.22 mm for MVCT localizations, respectively. The systematic and random variations in daily shifts based on MVCT were generally smaller than those based on BAT, especially along the A/P direction. A t-test showed this difference to be statistically significant. The planning target volume margins in the A/P direction estimated to account for daily variations were 8.81 and 14.66 mm based on MVCT and BAT data, respectively. There was no statistically significant difference in the daily prostate movement pattern between the first few fractions and the remaining fractions. Dosimetric comparison of MVCT and BAT prostate alignments was performed for seven fractions from a patient. The degradation from the plan caused by the MVCT alignment is trivial, while that by BAT is substantial. The MVCT technique results in smaller variations in daily shifts than ultrasound imaging, indicating that MVCT is more reliable and precise for prostate localization. Ultrasound-based localization may overestimate the daily prostate motion, particularly in the A/P direction, negatively impacting prostate dose coverage and rectal sparing.« less
  • Purpose: Commercial CT-based image-guided radiotherapy (IGRT) systems allow widespread management of geometric variations in patient setup and internal organ motion. This document provides consensus recommendations for quality assurance protocols that ensure patient safety and patient treatment fidelity for such systems. Methods: The AAPM TG-179 reviews clinical implementation and quality assurance aspects for commercially available CT-based IGRT, each with their unique capabilities and underlying physics. The systems described are kilovolt and megavolt cone-beam CT, fan-beam MVCT, and CT-on-rails. A summary of the literature describing current clinical usage is also provided. Results: This report proposes a generic quality assurance program for CT-basedmore » IGRT systems in an effort to provide a vendor-independent program for clinical users. Published data from long-term, repeated quality control tests form the basis of the proposed test frequencies and tolerances.Conclusion: A program for quality control of CT-based image-guidance systems has been produced, with focus on geometry, image quality, image dose, system operation, and safety. Agreement and clarification with respect to reports from the AAPM TG-101, TG-104, TG-142, and TG-148 has been addressed.« less