| 1. |
- Adjeiwaah, Mary, 1980-, et al.
(author)
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Dosimetric Impact of MRI Distortions : A Study on Head and Neck Cancers
- 2019
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 103:4, s. 994-1003
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Journal article (peer-reviewed)abstract
- Purpose: To evaluate the effect of magnetic resonance (MR) imaging (MRI) geometric distortions on head and neck radiation therapy treatment planning (RTP) for an MRI-only RTP. We also assessed the potential benefits of patient-specific shimming to reduce the magnitude of MR distortions for a 3-T scanner.Methods and Materials: Using an in-house Matlab algorithm, shimming within entire imaging volumes and user-defined regions of interest were simulated. We deformed 21 patient computed tomography (CT) images with MR distortion fields (gradient nonlinearity and patient-induced susceptibility effects) to create distorted CT (dCT) images using bandwidths of 122 and 488 Hz/mm at 3 T. Field parameters from volumetric modulated arc therapy plans initially optimized on dCT data sets were transferred to CT data to compute a new plan. Both plans were compared to determine the impact of distortions on dose distributions.Results: Shimming across entire patient volumes decreased the percentage of voxels with distortions of more than 2 mm from 15.4% to 2.0%. Using the user-defined region of interest (ROI) shimming strategy, (here the Planning target volume (PTV) was the chosen ROI volume) led to increased geometric for volumes outside the PTV, as such voxels within the spinal cord with geometric shifts above 2 mm increased from 11.5% to 32.3%. The worst phantom-measured residual system distortions after 3-dimensional gradient nonlinearity correction within a radial distance of 200 mm from the isocenter was 2.17 mm. For all patients, voxels with distortion shifts of more than 2 mm resulting from patient-induced susceptibility effects were 15.4% and 0.0% using bandwidths of 122 Hz/mm and 488 Hz/mm at 3 T. Dose differences between dCT and CT treatment plans in D-50 at the planning target volume were 0.4% +/- 0.6% and 0.3% +/- 0.5% at 122 and 488 Hz/mm, respectively.Conclusions: The overall effect of MRI geometric distortions on data used for RTP was minimal. Shimming over entire imaging volumes decreased distortions, but user-defined subvolume shimming introduced significant errors in nearby organs and should probably be avoided.
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| 2. |
- Adjeiwaah, Mary, et al.
(author)
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Quantifying the Effect of 3T Magnetic Resonance Imaging Residual System Distortions and Patient-Induced Susceptibility Distortions on Radiation Therapy Treatment Planning for Prostate Cancer
- 2018
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 100:2, s. 317-324
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Journal article (peer-reviewed)abstract
- Purpose: To investigate the effect of magnetic resonance system- and patient-induced susceptibility distortions from a 3T scanner on dose distributions for prostate cancers.Methods and Materials: Combined displacement fields from the residual system and patient-induced susceptibility distortions were used to distort 17 prostate patient CT images. VMAT dose plans were initially optimized on distorted CT images and the plan parameters transferred to the original patient CT images to calculate a new dose distribution.Results: Maximum residual mean distortions of 3.19 mm at a radial distance of 25 cm and maximum mean patient-induced susceptibility shifts of 5.8 mm were found using the lowest bandwidth of 122 Hz per pixel. There was a dose difference of <0.5% between distorted and undistorted treatment plans. The 90% confidence intervals of the mean difference between the dCT and CT treatment plans were all within an equivalence interval of (−0.5, 0.5) for all investigated plan quality measures.Conclusions: Patient-induced susceptibility distortions at high field strengths in closed bore magnetic resonance scanners are larger than residual system distortions after using vendor-supplied 3-dimensional correction for the delineated regions studied. However, errors in dose due to disturbed patient outline and shifts caused by patient-induced susceptibility effects are below 0.5%.
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| 3. |
- Aksnessaether, Bjorg Y., et al.
(author)
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In Reply to Sari et al
- 2020
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 107:2, s. 388-389
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Journal article (peer-reviewed)
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| 4. |
- Aksnessaether, Bjorg Y., et al.
(author)
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Second Cancers in Patients With Locally Advanced Prostate Cancer Randomized to Lifelong Endocrine Treatment With or Without Radical Radiation Therapy : Long-Term Follow-up of the Scandinavian Prostate Cancer Group-7 Trial
- 2020
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 106:4, s. 706-714
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Journal article (peer-reviewed)abstract
- Background: Curative radiation therapy (RT) constitutes a cornerstone in prostate cancer (PC) treatment. We present long-term follow-up estimates for second cancer (SC) risk and overall survival (OS) in patients randomized to hormone therapy (ET) alone or combined with 70 Gy prostatic RT in the Scandinavian Prostate Cancer Group-7 (SPCG-7) study. We explored the effect of salvage RT (≥60 Gy to the ET group) and reported causes of death.Methods and Materials: The SPCG-7 study (1996-2002) was a randomized controlled trial that included 875 men with locally advanced nonmetastatic PC. In this analysis, including data from the Norwegian and Swedish Cancer and Cause of Death registries for 651 Norwegian and 209 Swedish study patients, we estimated hazard ratios (HRs) for SC and death, and cumulative incidences of SC.Results: Median follow-up of the 860 (431 ET and 429) ET + RT patients was 12.2 years for SC risk analysis and 12.6 years for the OS analysis. Eighty-three of the Norwegian ET patients received salvage RT, and median time to salvage RT was 5.9 years. We found 125 and 168 SCs in the ET and ET + RT patients, respectively. With ET alone as reference, ET + RT patients had an HR of 1.19 (95% confidence interval [CI], 0.92-1.54) for all SCs and 2.54 (95% CI, 1.14-5.69) for urinary bladder cancer (UBC). The total number of UBC was 31 (23 in ET + RT; 8 in ET), and the vast majority (85%) were superficial. The HR for SC in salvage RT patients was 0.48 (95% CI, 0.24-0.94). Median OS was 12.8 (95% CI, 11.8-13.8) and 15.3 (95%, CI 14.3-16.4) years in the ET and ET + RT groups, respectively. Compared with ET alone, the risk of death was reduced in ET + RT patients (HR, 0.73; 95% CI, 0.62-0.86) and in ET patients receiving salvage RT (HR, 0.44; 95% CI, 0.30-0.65).Conclusions: Although the risk of UBC was increased in PC patients who received RT in addition to ET, this disadvantage is outweighed by the OS benefit of RT confirmed in our study. The risk of SC, and especially UBC, should be discussed with patients and be reflected in follow-up programs.
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| 5. |
- Bosco, Cecilia, et al.
(author)
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Prostate Cancer Radiation Therapy and Risk of Thromboembolic Events
- 2017
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In: International Journal of Radiation Oncology, Biology, Physics. - : ELSEVIER SCIENCE INC. - 0360-3016 .- 1879-355X. ; 97:5, s. 1026-1031
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Journal article (peer-reviewed)abstract
- Purpose: To investigate the risk of thromboembolic disease (TED) after radiation therapy (RT) with curative intent for prostate cancer (PCa).Patients and Methods: We identified all men who received RT as curative treatment (n=9410) and grouped according to external beam RT (EBRT) or brachytherapy (BT). By comparing with an age-and county-matched comparison cohort of PCa-free men (n = 46,826), we investigated risk of TED after RT using Cox proportional hazard regression models. The model was adjusted for tumor characteristics, demographics, comorbidities, PCa treatments, and known risk factors of TED, such as recent surgery and disease progression.Results: Between 2006 and 2013, 6232 men with PCa received EBRT, and 3178 underwent BT. A statistically significant association was found between EBRT and BT and risk of pulmonary embolism in the crude analysis. However, upon adjusting for known TED risk factors these associations disappeared. No significant associations were found between BT or EBRT and deep venous thrombosis.Conclusion: Curative RT for prostate cancer using contemporary methodologies was not associated with an increased risk of TED.
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| 6. |
- Daşu, Alexandru, et al.
(author)
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Secondary malignancies from prostate cancer radiation treatment : a risk analysis of the influence of target margins and fractionation patterns
- 2011
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier BV. - 0360-3016 .- 1879-355X. ; 79:3, s. 738-746
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Journal article (peer-reviewed)abstract
- PURPOSE: This study explores the implications for cancer induction of treatment details such as fractionation, planning target volume (PTV) definition, and interpatient variations, which are relevant for the radiation treatment of prostate carcinomas.METHODS AND MATERIALS: Treatment planning data from 100 patients have been analyzed with a risk model based on the United Nations Scientific Committee on the Effects of Atomic Radiation competition model. The risk model can account for dose heterogeneity and fractionation effects characteristic for modern radiotherapy. Biologically relevant parameters from clinical and experimental data have been used with the model.RESULTS: The results suggested that changes in prescribed dose could lead to a modification of the risks for individual organs surrounding the clinical target volume (CTV) but that the total risk appears to be less affected by changes in the target dose. Larger differences are observed for modifications of the margins between the CTV and the PTV because these have direct impact onto the dose level and dose heterogeneity in the healthy tissues surrounding the CTV. Interpatient anatomic variations also have to be taken into consideration for studies of the risk for cancer induction from radiotherapy.CONCLUSIONS: The results have shown the complex interplay between the risk for secondary malignancies, the details of the treatment delivery, and the patient heterogeneity that may influence comparisons between the long-term effects of various treatment techniques. Nevertheless, absolute risk levels seem very small and comparable to mortality risks from surgical interventions, thus supporting the robustness of radiation therapy as a successful treatment modality for prostate carcinomas.
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| 7. |
- Dasu, Alexandru, et al.
(author)
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What is the Clinically Relevant Relative Biologic Effectiveness? A Warning for Fractionated Treatments With High Linear Energy Transfer Radiation
- 2008
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 70:3, s. 867-874
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Journal article (peer-reviewed)abstract
- PURPOSE: To study the clinically relevant relative biologic effectiveness (RBE) of fractionated treatments with high linear energy transfer (LET) radiation and to identify the important factors that might influence the transfer of tolerance and curative levels from low LET radiation. These are important questions in the light of the growing interest for the therapeutic use of radiation with higher LET than electrons or photons.METHODS AND MATERIALS: The RBE of various fractionated schedules was analyzed with theoretical models for radiation effect, and the resulting predictions were compared with the published clinical and experimental data regarding fractionated irradiation with high LET radiation.RESULTS: The clinically relevant RBE increased for greater doses per fraction, in contrast to the predictions from single-dose experiments. Furthermore, the RBE for late-reacting tissues appeared to modify more quickly than that for early-reacting tissues. These aspects have quite important clinical implications, because the increased biologic effectiveness reported for this type of radiation would otherwise support the use of hypofractionation. Thus, the differential between acute and late-reacting tissues could put the late-reacting normal tissues at more risk from high LET irradiation; however, at the same time, it could increase the therapeutic window for slow-growing tumors.CONCLUSIONS: The modification of the RBE with the dose per fraction must be carefully taken into consideration when devising fractionated treatments with high LET radiation. Neglecting to do so might result in an avalanche of complications that could obscure the potential advantages of the therapeutic use of this type of radiation.
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| 8. |
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| 9. |
- Fransson, Per, et al.
(author)
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Five-year prospective patient evaluation of bladder and bowel symptoms after dose-escalated radiotherapy for prostate cancer with the Beamcath (R) technique
- 2006
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 66:2, s. 430-438
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Journal article (peer-reviewed)abstract
- Purpose: Late side effects were prospectively evaluated up to 5 years after dose-escalated external beam radiotherapy (EBRT) and were compared with a previously treated series with conventional conformal technique.Methods and Materials: Bladder and bowel symptoms were prospectively evaluated with the Prostate Cancer Symptom Scale (PCSS) questionnaire up to 5 years posttreatment. In all, 257 patients completed the questionnaire 5 years posttreatment. A total of 168 patients were treated with the conformal technique at doses <71 Gy, and 195 were treated with the dose-escalated stereotactic BeamCath® technique comprising three dose levels: 74 Gy (n = 68), 76 Gy (n = 74), and 78 Gy (n = 53).Results: For all dose groups analyzed together, 5 years after treatment, urinary starting problems decreased and urinary incontinence increased in comparison to baseline values. No increase in other bladder symptoms or frequency was detected. When comparing dose groups after 5 years, both the 74-Gy and 78-Gy groups reported increased urinary starting problems compared with patients given the conventional dose (<71 Gy). No increased incontinence was seen in the 76-Gy or the 78-Gy groups. Bowel symptoms were slightly increased during the follow-up period in comparison to baseline. Dose escalation with stereotactic EBRT (74–78 Gy) did not increase gastrointestinal late side effects after 5 years in comparison to doses <71 Gy.Conclusion: Dose-escalated EBRT with the BeamCath® technique with doses up to 78 Gy is tolerable, and the toxicity profile is similar to that observed with conventional doses <71 Gy.
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| 10. |
- Jonsson, Joakim H, et al.
(author)
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Internal fiducial markers and susceptibility effects in MRI : simulation and measurement of spatial accuracy
- 2012
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In: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier BV. - 0360-3016 .- 1879-355X. ; 82:5, s. 1612-1618
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Journal article (peer-reviewed)abstract
- BACKGROUND: It is well-known that magnetic resonance imaging (MRI) is preferable to computed tomography (CT) in radiotherapy target delineation. To benefit from this, there are two options available: transferring the MRI delineated target volume to the planning CT or performing the treatment planning directly on the MRI study. A precondition for excluding the CT study is the possibility to define internal structures visible on both the planning MRI and on the images used to position the patient at treatment. In prostate cancer radiotherapy, internal gold markers are commonly used, and they are visible on CT, MRI, x-ray, and portal images. The depiction of the markers in MRI are, however, dependent on their shape and orientation relative the main magnetic field because of susceptibility effects. In the present work, these effects are investigated and quantified using both simulations and phantom measurements.METHODS AND MATERIALS: Software that simulated the magnetic field distortions around user defined geometries of variable susceptibilities was constructed. These magnetic field perturbation maps were then reconstructed to images that were evaluated. The simulation software was validated through phantom measurements of four commercially available gold markers of different shapes and one in-house gold marker.RESULTS: Both simulations and phantom measurements revealed small position deviations of the imaged marker positions relative the actual marker positions (<1 mm).CONCLUSION: Cylindrical gold markers can be used as internal fiducial markers in MRI.
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