Analysis of interfractional set-up errors and intrafractional organ motions during IMRT for head and neck tumors to define an appropriate planning target volume (PTV)- and planning organs at risk volume (PRV)-margins

2006 ◽  
Vol 78 (3) ◽  
pp. 283-290 ◽  
Author(s):  
Minoru Suzuki ◽  
Yasumasa Nishimura ◽  
Kiyoshi Nakamatsu ◽  
Masahiko Okumura ◽  
Hisayuki Hashiba ◽  
...  
Keyword(s):  
At Risk ◽  
Head And Neck ◽  
Planning Target Volume ◽  
Organs At Risk ◽  
Target Volume ◽  
Head And Neck Tumors ◽  
Neck Tumors ◽  
Set Up

scholarly journals Use of a Head-Tilting Baseplate During Tomotherapy to Shorten the Irradiation Time and Protect the Hippocampus and Lens in Hippocampal Sparing-Whole Brain Radiotherapy

2021 ◽  
Vol 20 ◽  
pp. 153303382098682
Author(s):  
Kosei Miura ◽  
Hiromasa Kurosaki ◽  
Nobuko Utsumi ◽  
Hideyuki Sakurai
Keyword(s):  
At Risk ◽  
Planning Target Volume ◽  
Irradiation Time ◽  
Organs At Risk ◽  
Absorbed Dose ◽  
Whole Brain Radiotherapy ◽  
Target Volume ◽  
Whole Brain ◽  
Brain Radiotherapy ◽  
Hippocampal Sparing

Purpose: The aim of this study is to comparatively examine the possibility of reducing the exposure dose to organs at risk, such as the hippocampus and lens, and improving the dose distribution of the planned target volume with and without the use of a head-tilting base plate in hippocampal-sparing whole-brain radiotherapy using tomotherapy. Methods: Five paired images of planned head computed tomography without and with tilt were analyzed. The hippocampus and planning target volume were contoured according to the RTOG 0933 contouring atlas protocol. The hippocampal zone to be avoided was delineated using a 5-mm margin. The prescribed radiation dose was 30 Gy in 10 fractions. The absorbed dose to planning target volume dose, absorbed dose to the organ at risk, and irradiation time were evaluated. The paired t-test was used to analyze the differences between hippocampal-sparing whole-brain radiotherapy with head tilts and without head tilts. Results: Hippocampal-sparing whole-brain radiotherapy with tilt was not superior in planning target volume doses using the homogeneity index than that without tilt; however, it showed better values, and for Dmean and D2%, the values were closer to 30 Gy. Regarding the hippocampus, dose reduction with tilt was significantly greater at Dmax, Dmean, and Dmin, whereas regarding the lens, it was significantly greater at Dmax and Dmin. The irradiation time was also predominantly shorter. Conclusion: In our study, a tilted hippocampal-sparing whole-brain radiotherapy reduced the irradiation time by >10%. Therefore, our study indicated that hippocampal-sparing whole-brain radiotherapy with tomotherapy should be performed with a tilt. The head-tilting technique might be useful during hippocampal-sparing whole-brain radiotherapy. This method could decrease the radiation exposure time, while sparing healthy organs, including the hippocampus and lens.

scholarly journals Biology-guided Radiotherapy for Lung SBRT Reduces Planning Target Volume and Organs at Risk Doses

2019 ◽  
Vol 105 (1) ◽  
pp. S254
Author(s):  
J. Liang ◽  
A. Da Silva ◽  
C. Han ◽  
J. Neylon ◽  
A. Amini ◽  
...  
Keyword(s):  
At Risk ◽  
Planning Target Volume ◽  
Organs At Risk ◽  
Target Volume ◽  
Lung Sbrt

Dose volume histogram analysis for organs at risk when using 6 external beam techniques for radical prostatic irradiation

2000 ◽  
Vol 2 (1) ◽  
pp. 17-25 ◽  
Author(s):  
T. Haycocks ◽  
J. Mui ◽  
H. Alasti ◽  
C. Catton
Keyword(s):  
At Risk ◽  
Organs At Risk ◽  
Area Under The Curve ◽  
Target Volume ◽  
Dose Volume Histograms ◽  
Treatment Techniques ◽  
Dose Volume ◽  
Femoral Heads ◽  
Curve Method ◽  
Set Up

Ten patients with prostate cancer were each planned with 3 conventional and 3 conformal isocentric treatment techniques to compare the relative radiation doses to the bladder and rectal walls, and femoral head using dose volume histograms (DVH). The DVH were calculated for each organ and each technique, and the plans were ranked using the area under the curve method and also by the relative radiation dose given to specific normal tissue volumes.The results show that for the planning target volume chosen, the 4 field non-coplanar technique delivers the least dose to the bladder, the 6 field coplanar technique delivers the least dose to the rectum and the 3 field oblique technique delivers the least dose to the femoral heads. The 4-field technique with no shielding contributes the most dose to the bladder and rectum and the 6 field coplanar technique contributes the most dose to the femoral heads.No technique was shown to be optimal for all the organs at risk, but both the 6 field and 4 field non-coplanar field arrangements were shown to be superior techniques for minimising both the bladder and rectal dosage. The choice of technique will therefore depend on other factors such as the total prescribed dose, the ease of set-up and the ease of verification of isocentre reproducibility.

scholarly journals Set-up Errors and Determination of Planning Target Volume Margins Protocol for Different Anatomical Sites in a Newly Established Tertiary Radiotherapy Centre in India

2020 ◽  
Vol 6 (02) ◽  
pp. 81-87
Author(s):  
Avik Mandal ◽  
Pritanjali Singh ◽  
Soumen Bera ◽  
Avajeet Kumar ◽  
Dharmendra Singh ◽  
...  
Keyword(s):  
Head And Neck ◽  
Planning Target Volume ◽  
Random Error ◽  
Target Volume ◽  
Curative Intent ◽  
Image Guided Radiotherapy ◽  
Image Guided ◽  
Number Of Patients ◽  
Set Up ◽  
The Brain

Abstract Objective Our study aimed to assess the set-up errors for image-guided radiotherapy at a newly established tertiary radiation center in India and to establish the departmental protocol of clinical target volume–planning target volume (CTV–PTV) margins for different anatomical sites. Materials and Methods This study enrolled the first 200 patients who were treated with curative intent at All India Institute of Medical Sciences, Patna, from February 2019 to September 2019. Number of patients were 53, 26, 53, 11, 6, 47, and 4 for head and neck, brain, breast, thorax, abdomen, pelvis, and craniospinal irradiation (CSI), respectively. The translational vectors for total 1,463 kV cone-beam computed tomography (CBCT) images were collected from the treatment record. Results For the systematic error, the largest value is found for the thoracic subset on the X and Y directions, and for breast patients on Z axis, whereas the smallest values were found for CSI. For random error, the largest value was found for pelvic in the X, Y direction, and for breast subset on Z axis, whereas the smallest values on X and Z axes were found in the brain and for head and neck on the Y axis. Largest value for systemic error is smaller than 5 mm in all directions and for all anatomical subsets. The highest random error value is 5.07 mm in Y axis for pelvic subset. The largest values for CTV–PTV margin are found for thoracic subset and the smallest for CSI followed by the brain. Significant reduction of set-up error observed for the last hundred patients as compared to the first half of the patient population. Conclusion Use of thermoplastic cast along with breast board and respiratory motion management should be recommended to reduce set-up error for breast and thoracic subset. Six degrees of freedom robotic couch system can also further rectify the set-up error in image-guided radiotherapy.

scholarly journals The Capabilities and Characteristics of Helical Tomotherapy and Co-Planar Dual Arcs Volumetric-Modulated arc Therapy Associated with Hippocampal Sparing During Prophylactic Cranial Irradiation

2021 ◽  
Vol 20 ◽  
pp. 153303382110439
Author(s):  
Dandan Wang ◽  
Xingmin Ma ◽  
Lu Fu ◽  
Jiabing Gu ◽  
Tong Bai ◽  
...  
Keyword(s):  
At Risk ◽  
Planning Target Volume ◽  
Helical Tomotherapy ◽  
Organs At Risk ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Cranial Irradiation ◽  
Prophylactic Cranial Irradiation ◽  
Target Coverage ◽  
Arc Therapy

Objective: To investigate the features of helical tomotherapy and co-planar dual Arcs volumetric-modulated arc therapy during prophylactic cranial irradiation associated with bilateral hippocampal tissue sparing. Materials and methods: Helical tomotherapy and co-planar dual arcs volumetric-modulated arc therapy treatment plans were generated with a dose of 30 Gy/10 fractions in 16 patients treated with prophylactic cranial irradiation. The dose to the bilateral hippocampal tissues, organs at risk, and planning target volume were determined when the average dose of bilateral hippocampal tissues was reduced by approximately 4 Gy as an observation point. Changes in dosimetry when sparing the bilateral hippocampal tissues were determined for both modalities. Results: When bilateral hippocampal tissues were restricted to 8 Gy, D40%mean-bilateral hippocampal tissues = 7.64 ± 0.41 Gy in helical tomotherapy, while D40%mean-bilateral hippocampal tissues = 10.96 ± 0.38 Gy in co-planar dual arcs volumetric-modulated arc therapy volumetric-modulated arc therapy. Helical tomotherapy was associated with significantly lower doses to organs at risk, including Dmean-bilateral hippocampal tissues ( P = .03), D98%-bilateral hippocampal tissues ( P = .01), D2%-bilateral hippocampal tissues ( P = .01), Dmean-inner ear ( P = .02), Dmean-parotid glands ( P = .02), Dmax-lens ( P = .02), and Dmax-brainstem ( P = .02), but not Dmax-optic nerves ( P = .87). Helical tomotherapy provided better target coverage, with lower average D2%-PTV ( P = .02), higher average D98%-PTV ( P = .02), and better conformal index (0.87 vs 0.84, P = .02) and homogeneity index (0.15 vs 0.21, P = .05). With smaller bilateral hippocampal tissues doses, the planning target volume dose changed across 3 dosimetry regions for both modalities; the plateau region (>20.0 Gy for helical tomotherapy versus >16.0 Gy for co-planar dual arcs volumetric-modulated arc therapy), gradient region (20.0-12.0 Gy vs 16.0-11.0 Gy), and falling region (<12.0 Gy vs <11.0 Gy). The average delivery duration of helical tomotherapy was almost 7.7 times longer than that of co-planar dual arcs volumetric-modulated arc therapy. Conclusions: Helical tomotherapy was better at sparing the bilateral hippocampal tissues and organs at risk and had better target coverage but a significantly longer treatment duration than co-planar dual arcs volumetric-modulated arc therapy. Further dose decreases in the bilateral hippocampal tissues would yield worse target dose coverage.

scholarly journals The Informatics of the Planning Target Volume -- why it cannot and should not be changed

2017 ◽  
Vol 8 (1) ◽  
pp. 1-9
Author(s):  
Alexis Andrew Miller ◽  
Scott Turner
Keyword(s):  
At Risk ◽  
Planning Target Volume ◽  
Outcomes Research ◽  
Organs At Risk ◽  
Daily Practice ◽  
Target Volume ◽  
High Dose ◽  
Radiation Oncologists

The ICRU defined the Planning Target Volume (PTV) as a static and geometrical volume in 1993. Radiation oncologists continue to manually alter PTVs in their daily practice when critical organs at risk (OAR) are too close to high dose PTVs. This practice is examined and shown to be non-standard (defies the ICRU definitions), inaccurate (all DVHs look perfect when the plan is manifestly NOT perfect), and useless for outcomes research (automatically analysed DVHs will find situations where the PTV_unaltered overlaps the OAR_unaltered, but will fail to find situations where an OAR_unaltered would be overlapped by a PTV_unaltered, but is not overlapped by a PTV_altered.

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