International Journal of Radiation Oncology*Biology*Physics
Physics contributionIMRT boost dose planning on dominant intraprostatic lesions: Gold marker-based three-dimensional fusion of CT with dynamic contrast-enhanced and 1H-spectroscopic MRI
Introduction
The use of defining a biologic target volume (BTV) and intensity-modulated radiotherapy (IMRT) for advanced “dose painting,” as proposed by Ling et al. (1) has been gradually introduced into clinical practice. This has been made possible by advanced imaging techniques. Prostate magnetic resonance imaging (MRI) techniques can be fused with planning computed tomography (CT), and this has been shown to enable improved target delineation (2, 3). Functional MRI techniques have been developed. Dynamic contrast-enhanced MRI (DCE-MRI) can visualize prostate cancer neovascularity (4, 5). 1H-spectroscopic MRI (MRSI) has been shown to provide a high specificity for prostate cancer (6, 7). These techniques can lead to a more accurate staging and localization of prostate cancer (8, 9, 10, 11, 12) and are valid methods for early evaluation of the RT effect (13).
The “classic” whole-prostate dose escalation has improved treatment outcomes (14, 15, 16). Nevertheless, intraprostatic failures do occur and can be detected by MRI (17). Cellini et al. (18) performed an MRI-based analysis of intraprostatic failure and concluded that, in all their observed cases, local recurrence originated within the initial tumor volume. Strategies, mainly for brachytherapy and small-size (<50 cm3) prostates, have been tested to detect the so-called dominant intraprostatic lesion (DIL) by MRSI, and an extra boost dose has been given to this DIL to increase the therapeutic ratio (19, 20, 21, 22, 23). To acquire high-resolution anatomic MRI data, an endorectal coil is usually inserted, causing deformation of the prostate gland. Consequently, accurate image registration with the initial planning CT scan (without an endorectal coil) is often difficult. CT–MRI matching can be done by mutual information-based automatic registration (24) or manually by visual approximation (19, 22). To overcome the difficulties in registration, we developed a gold marker-based three-dimensional (3D) CT-MRI fusion protocol (25), in which an endorectal balloon (ERB) is used during CT and treatment that has the same dimensions as the MRI endorectal coil (26). ERBs have also been used in prostate RT for their rectal wall-sparing effect (27, 28, 29). In our daily practice, fiducial gold markers are used for position verification and correction procedures (26, 30, 31, 32). These markers are clearly visible on both CT and T2*-weighted MRI. Reliable and accurate image fusion is feasible using the above-mentioned conditions (25, 33).
To date, the combination of two functional MRI techniques (DCE-MRI and MRSI), gold markers, and an ERB for biologic image-guided external beam RT has not been described. The purpose of this study was to demonstrate the feasibility of the fusion of these functional MRI techniques with CT, using gold markers as fiducials, and to integrate these images into inverse treatment planning to define a BTV for high-dose intraprostatic DIL boosting with IMRT. The next goal was to make an estimation of the potential gains, in terms of tumor control probability (TCP), and rectal toxicity, by analyzing the normal tissue complication probability (NTCP).
Section snippets
Methods and materials
This pilot study was performed during a 6-month period, to December 2004. Patients with biopsy-proven prostate cancer were selected for our study. At the start of this study, only patients with unilateral prostate cancer were selected. The patient exclusion criteria were previous hormonal therapy, positive lymphadenectomy, contraindications to MRI (e.g., cardiac pacemakers, intracranial clips), and contraindications to endorectal coil insertion (e.g., anorectal surgery, inflammatory bowel
Imaging and postprocessing
The marker implantation posed no problems. This procedure took 5 min/patient in the urology outpatient clinic. The ERB was tolerated well, and no problems arose during the imaging procedures. The planning CT scan took 15 min total, and MRI at the radiology department took 1 h (10 min of patient preparation and 50 min of imaging), which was rather strenuous for this elderly patient population. In 1 patient, MRI was interrupted because of lower back pain, but eventually could be finished.
Discussion
In this study, we have shown the feasibility of using combined functional imaging techniques of the prostate gland to integrate them into inverse treatment planning and to define a BTV (1) for high-dose intraprostatic IMRT boosting. This MRI-based BTV was then superimposed onto a treatment planning CT scan with a CT-MRI gold marker-based fusion protocol. With two different IMRT plans and the commonly used TCP and NTCP models, preliminary data were produced to investigative the potential gains
Conclusion
In this study, we demonstrated the feasibility of integrating two functional prostate MRI techniques into inverse treatment planning for the definition of a DIL for DIL-IMRT. In all patients, the combination of DCE-MRI, identifying regions of neovascularity suggestive of prostate cancer, and MRSI, detecting tumor nodules with high specificity, yielded a clearly defined single DIL volume. This DIL volume could be accurately transferred to the RT planning system, by CT-MRI registration using
Acknowledgments
The authors thank Johannes H. A. M. Kaanders for his helpful collaboration in the preparation of this manuscript.
References (48)
- et al.
Towards multidimensional radiotherapy (MD-CRT)Biological imaging and biological conformality
Int J Radiat Oncol Biol Phys
(2000) - et al.
Definition of the prostate in CT and MRIA multi-observer study
Int J Radiat Oncol Biol Phys
(1999) - 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) - et al.
Use of MRI and spectroscopy in evaluation of external beam radiotherapy for prostate cancer
Int J Radiat Oncol Biol Phys
(2004) - et al.
Prostate cancer radiation dose responseResults of the M.D. Anderson phase III randomized trial
Int J Radiat Oncol Biol Phys
(2002) - et al.
Prostate cancer radiotherapy dose responseAn update of the Fox Chase experience
J Urol
(2004) - et al.
High-dose intensity modulated radiation therapy for prostate cancerEarly toxicity and biochemical outcome in 772 patients
Int J Radiat Oncol Biol Phys
(2002) - et al.
Analysis of intraprostatic failures in patients treated with hormonal therapy and radiotherapyImplications for conformal therapy planning
Int J Radiat Oncol Biol Phys
(2002) - et al.
Magnetic resonance spectroscopic imaging-guided brachytherapy for localized prostate cancer
Int J Radiat Oncol Biol Phys
(2002) - et al.
Static field intensity modulation to treat a dominant intra-prostatic lesion to 90 Gy compared to seven field 3-dimensional radiotherapy
Int J Radiat Oncol Biol Phys
(1999)
Inverse planning for HDR prostate brachytherapy used to boost dominant intraprostatic lesions defined by magnetic resonance spectroscopy imaging
Int J Radiat Oncol Biol Phys
Treatment planning for prostate implants using magnetic-resonance spectroscopy imaging
Int J Radiat Oncol Biol Phys
Towards integrating functional imaging in the treatment of prostate cancer with radiationThe registration of the MR spectroscopy imaging to ultrasound/CT images and its implementation in treatment planning
Int J Radiat Oncol Biol Phys
The effect of an endorectal balloon and off-line correction on the interfraction systematic and random prostate position variationsA comparative study
Int J Radiat Oncol Biol Phys
The influence of a rectal balloon tube as internal immobilization device on variations of volumes and dose-volume histograms during treatment course of conformal radiotherapy for prostate cancer
Int J Radiat Oncol Biol Phys
Acute gastrointestinal, genitourinary, and dermatological toxicity during dose-escalated 3D-conformal radiation therapy (3DCRT) using an intrarectal balloon for prostate gland localization and immobilization
Int J Radiat Oncol Biol Phys
Clinical use of on-line portal imaging for daily patient treatment verification
Int J Radiat Oncol Biol Phys
Daily prostate targeting using implanted radiopaque markers
Int J Radiat Oncol Biol Phys
Electronic portal imaging device detection of radio opaque markers for the evaluation of prostate position during megavoltage irradiationA clinical study
Int J Radiat Oncol Biol Phys
Magnetic resonance imaging in the radiation treatment planning of localized prostate cancer using intra-prostatic fiducial markers for computed tomography co-registration
Radiother Oncol
Comparison of rectal dose-wall histogram versus dose-volume histogram for modeling the incidence of late rectal bleeding after radiotherapy
Int J Radiat Oncol Biol Phys
Calculation of complication probability factors for non-uniform normal tissue irradiationThe effective volume method
Int J Radiat Oncol Biol Phys
Tolerance of normal tissue to therapeutic irradiation
Int J Radiat Oncol Biol Phys
Rectal wall sparing effect of three different endorectal balloons in 3D conformal and IMRT prostate radiotherapy
Int J Radiat Oncol Biol Phys
Cited by (158)
Nuclear magnetic resonance spectroscopy of human body fluids and in vivo magnetic resonance spectroscopy: Potential role in the diagnosis and management of prostate cancer
2020, Urologic Oncology: Seminars and Original InvestigationsProstate irradiation with focal dose escalation to the intraprostatic dominant nodule: a systematic review
2018, Prostate InternationalInter-operator variability in compartmental kinetic analysis of <sup>18</sup>F-fluoromisonidazole dynamic PET
2018, Clinical ImagingCitation Excerpt :Hypoxic tumors, in general, express more aggressive phenotype, are radio-resistant, and have thus an increased likelihood of loco-regional recurrence, distant metastasis, poor overall outcome [2–5]. Potential treatment strategies for overcoming tumor hypoxia and improving local control rates include the use of radio-sensitizing drugs and biological image-guided dose escalation to hypoxic tumor sub-regions [6–10]. Rational application of such strategies would require that hypoxia can be shown accurately in the clinical setting, that its extent and severity can be quantified accurately, and that these parameters indeed correlate with poor patient outcome when current standard treatment regimens are applied.