Target Definition in Prostate, Head, and Neck

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Target definition is a major source of errors in both prostate and head and neck external-beam radiation treatment. Delineation errors remain constant during the course of radiation and therefore have a large impact on the dose to the tumor. Major sources of delineation variation are visibility of the target including its extensions, disagreement on the target extension, and interpretation or lack of delineation protocols. The visibility of the target can be greatly improved with the use of multimodality imaging. Both in the head and neck and the prostate, computed tomography (CT)–magnetic resonance imaging coregistration decreases the target volume and its variability. CT-positron emission tomography delineation is promising for delineation in head and neck cancer. Despite the better visibility, a different interpretation of the target extension remains a major source of error. The use of coregistration of CT with a second modality, together with improved guidelines for delineation and an online anatomical atlas, increases agreement between observers in prostate, lung, and nasopharynx tumors. Delineation errors should not be treated differently from other geometrical errors. Similar margin recipes for the correction of setup errors and organ motion should be adapted to incorporate the effect of delineation errors. A calculation of a 3-dimensional clinical target volume-planning target volume margin incorporating delineation errors for the head and neck is around 6.1 to 9.7 mm. Given the good local control of IMRT with smaller margins and smaller pathological specimens, it is likely that the delineated CTV frequently overestimates the actual volume.

Section snippets

Geometrical Error Sources

Several geometrical uncertainties are involved in the delineation process. First, the imaging modalities have a limited resolution, in particular in the direction perpendicular to the slice planes,6, 7 causing the partial volume effect.8 Second, there is a certain amount of observer “noise” (ie, when the same observer is asked to delineate the target volume twice, the answer will not be the same [intraobserver variation]).8, 9, 10 More important are interpretation differences between different

Prostate Cancer

The definition of the target area in prostate cancer conformal radiotherapy has been fairly straightforward. Apart from inclusion or exclusion of the draining lymph nodes in the radiation fields, either the prostate or the prostate including the seminal vesicles is outlined. We will focus on the delineation of the prostate with or without seminal vesicles. Several attempts have been made to decrease the variability of prostate delineation, mostly aiming at the localization of the prostate apex.

Image Coregistration

The use of image registration to combine multiple-image modalities for radiotherapy treatment planning is currently applied in many clinics.17, 82, 83 Frequently, information from multiple modalities or multiple scans of the same modality is important for the target volume definition of a given case.84 Numerous image registration methods are available (eg,83, 84, 85 each with characteristic strengths and weaknesses). Less attention has been given to the tools used to present these data to the

Conclusion

It is necessary to translate reductions in geometrical uncertainties into a possible reduction of target margins. Various methods have been proposed to define the impact of geometrical deviations on the target margin. For example, Bel and coworkers showed,26, 30 through simulation, that a margin for random variations of 0.7 times the SD of the random variations and 2.5 times the systematic variation is adequate to keep a 95% dose coverage. Aaltonen and coworkers97 described an analysis based on

References (106)

  • K. Kagawa et al.

    Initial clinical assessment of CT-MRI image fusion software in localization of the prostate for 3D conformal radiation therapy

    Int J Radiat Oncol Biol Phys

    (1997)
  • M.L. Kessler et al.

    Integration of multimodality imaging data for radiotherapy treatment planning

    Int J Radiat Oncol Biol Phys

    (1991)
  • C. Rasch et al.

    The potential impact of CT-MRI matching on tumor volume delineation in advanced head and neck cancer

    Int J Radiat Oncol Biol Phys

    (1997)
  • C. Weltens et al.

    Interobserver variations in gross tumor volume delineation of brain tumors on computed tomography and impact of magnetic resonance imaging

    Radiother Oncol

    (2001)
  • H.M. Kooy et al.

    Image fusion for stereotactic radiotherapy and radiosurgery treatment planning

    Int J Radiat Oncol Biol Phys

    (1994)
  • L.R. Schad et al.

    Correction of spatial distortion in magnetic resonance angiography for radiosurgical treatment planning of cerebral arteriovenous malformations

    Magn Reson Imaging

    (1992)
  • A.F. Thornton et al.

    The clinical utility of magnetic resonance imaging in 3-dimensional treatment planning of brain neoplasms

    Int J Radiat Oncol Biol Phys

    (1992)
  • A. Bel et al.

    High-precision prostate cancer irradiation by clinical application of an offline patient setup verification procedure, using portal imaging

    Int J Radiat Oncol Biol Phys

    (1996)
  • L. Ekberg et al.

    What margins should be added to the clinical target volume in radiotherapy treatment planning for lung cancer?

    Radiother Oncol

    (1998)
  • J. Hanley et al.

    Measurement of patient positioning errors in three-dimensional conformal radiotherapy of the prostate

    Int J Radiat Oncol Biol Phys

    (1997)
  • T.E. Schultheiss et al.

    Incidence of and factors related to late complications in conformal and conventional radiation treatment of cancer of the prostate

    Int J Radiat Oncol Biol Phys

    (1995)
  • C.D. Mubata et al.

    Imaging protocol for radical dose-escalated radiotherapy treatment of prostate cancer

    Int J Radiat Oncol Biol Phys

    (1998)
  • C. Weltens et al.

    Comparison of plastic and Orfit masks for patient head fixation during radiotherapyprecision and costs

    Int J Radiat Oncol Biol Phys

    (1995)
  • J.A. Antolak et al.

    Prostate target volume variations during a course of radiotherapy

    Int J Radiat Oncol Biol Phys

    (1998)
  • J.M. Balter et al.

    Measurement of prostate movement over the course of routine radiotherapy using implanted markers

    Int J Radiat Oncol Biol Phys

    (1995)
  • C.J. Beard et al.

    Analysis of prostate and seminal vesicle motionimplications for treatment planning

    Int J Radiat Oncol Biol Phys

    (1996)
  • L.A. Dawson et al.

    Target position variability throughout prostate radiotherapy

    Int J Radiat Oncol Biol Phys

    (1998)
  • J.C. Roeske et al.

    Evaluation of changes in the size and location of the prostate, seminal vesicles, bladder, and rectum during a course of external beam radiation therapy

    Int J Radiat Oncol Biol Phys

    (1995)
  • A. Tinger et al.

    A critical evaluation of the planning target volume for 3-D conformal radiotherapy of prostate cancer

    Int J Radiat Oncol Biol Phys

    (1998)
  • M. van Herk et al.

    prostate by three dimensional image registration

    Int J Radiat Oncol Biol Phys

    (1995)
  • M. Roach et al.

    Prostate volumes defined by magnetic resonance imaging and computerized tomographic scans for three-dimensional conformal radiotherapy

    Int J Radiat Oncol Biol Phys

    (1996)
  • J. Lattanzi et al.

    Daily CT localization for correcting portal errors in the treatment of prostate cancer

    Int J Radiat Oncol Biol Phys

    (1998)
  • S. Hamlet et al.

    Larynx motion associated with swallowing during radiation therapy

    Int J Radiat Oncol Biol Phys

    (1994)
  • P. Nowak et al.

    Treatment portals for elective radiotherapy of the neckan inventory in The Netherlands

    Radiother Oncol

    (1997)
  • V. Gregoire et al.

    CT-based delineation of lymph node levels and related CTVs in the node-negative neckDAHANCA, EORTC, GORTEC, NCIC, RTOG consensus guidelines

    Radiother Oncol

    (2003)
  • P. Levendag et al.

    Rotterdam and Brussels CT-based neck nodal delineation compared with the surgical levels as defined by the American Academy of Otolaryngology-Head and Neck Surgery

    Int J Radiat Oncol Biol Phys

    (2004)
  • I. Poon et al.

    A population-based atlas and clinical target volume for the head-and-neck lymph nodes

    Int J Radiat Oncol Biol Phys

    (2004)
  • L.M. Toonkel et al.

    MRI assisted treatment planning for radiation therapy of the head and neck

    Magn Reson Imaging

    (1988)
  • B. Emami et al.

    Influence of MRI on target volume delineation and IMRT planning in nasopharyngeal carcinoma

    Int J Radiat Oncol Biol Phys

    (2003)
  • T.L. Elliot et al.

    Accuracy of prostate volume measurements in vitro using three-dimensional ultrasound

    Acad Radiol

    (1996)
  • J.M. Wheatley et al.

    Validation of a technique of computer-aided tumor volume determination

    J Surg Res

    (1995)
  • X. Geets et al.

    Role of 11-C-methionine positron emission tomography for the delineation of the tumor volume in pharyngo-laryngeal squamous cell carcinomacomparison with FDG-PET and CT

    Radiother Oncol

    (2004)
  • J.F. Vansteenkiste et al.

    Positron emission tomography in the management of non-small cell lung cancer

    Hematol Oncol Clin North Am

    (2004)
  • J.F. Vansteenkiste et al.

    Potential use of FDG-PET scan after induction chemotherapy in surgically staged IIIa-N2 non-small-cell lung cancera prospective pilot study

    Ann Oncol

    (1998)
  • C.B. Caldwell et al.

    defined non-small-cell lung tumors on CTthe impact of 18FDG-hybrid PET fusion

    Int J Radiat Oncol Biol Phys

    (2001)
  • J. Bradley et al.

    Impact of FDG-PET on radiation therapy volume delineation in non-small-cell lung cancer

    Int J Radiat Oncol Biol Phys

    (2004)
  • P. Bowden et al.

    Measurement of lung tumor volumes using three-dimensional computer planning software

    Int J Radiat Oncol Biol Phys

    (2002)
  • O. Algan et al.

    Localization of the prostatic apex for radiation treatment planning

    Int J Radiat Oncol Biol Phys

    (1995)
  • J.A. Cox et al.

    Prostate cancercomparison of retrograde urethrography and computed tomography in radiotherapy planning

    Int J Radiat Oncol Biol Phys

    (1994)
  • R. Sharma et al.

    Enhancement of prostate tumor volume definition with intravesical contrasta three-dimensional dosimetric evaluation

    Int J Radiat Oncol Biol Phys

    (1997)
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