scholarly journals Comparisons of 3-Dimensional Conformal and Intensity-Modulated Neutron Therapy for Head and Neck Cancers

2021 ◽  
Author(s):  
Natalie Viscariello ◽  
Matthew D. Greer ◽  
Upendra Parvathaneni ◽  
Jay J. Liao ◽  
George E. Laramore ◽  
...  
Keyword(s):  
Head And Neck ◽  
Spatial Proximity ◽  
Clinical Implementation ◽  
3 Dimensional ◽  
Dose Volume Histograms ◽  
Intensity Modulated ◽  
Therapeutic Ratio ◽  
Neutron Therapy ◽  
The Mean ◽  
Close Spatial Proximity

Abstract Purpose Neutron therapy is a high linear energy transfer modality that is useful for the treatment of radioresistant head and neck (H&N) cancers. It has been limited to 3-dimensioanal conformal-based fast-neutron therapy (3DCNT), but recent technical advances have enabled the clinical implementation of intensity-modulated neutron therapy (IMNT). This study evaluated the comparative dosimetry of IMNT and 3DCNT plans for the treatment of H&N cancers. Materials and Methods Seven H&N IMNT plans were retrospectively created for patients previously treated with 3DCNT at the University of Washington (Seattle). A custom RayStation model with neutron-specific scattering kernels was used for inverse planning. Organ-at-risk (OAR) objectives from the original 3DCNT plan were initially used and were then systematically reduced to investigate the feasibility of improving a therapeutic ratio, defined as the ratio of the mean tumor to OAR dose. The IMNT and 3DCNT plan quality was evaluated using the therapeutic ratio, isodose contours, and dose volume histograms. Results When compared with the 3DCNT plans, IMNT reduces the OAR dose for the equivalent tumor coverage. Moreover, IMNT is most advantageous for OARs in close spatial proximity to the target. For the 7 patients with H&N cancers examined, the therapeutic ratio for IMNT increased by an average of 56% when compared with the 3DCNT. The maximum OAR dose was reduced by an average of 20.5% and 20.7% for the spinal cord and temporal lobe, respectively. The mean dose to the larynx decreased by an average of 80%. Conclusion The IMNT significantly decreases the OAR doses compared with 3DCNT and provides comparable tumor coverage. Improvements in the therapeutic ratio with IMNT are especially significant for dose-limiting OARs near tumor targets. Moreover, IMNT provides superior sparing of healthy tissues and creates significant new opportunities to improve the care of patients with H&N cancers treated with neutron therapy.

scholarly journals Incidental Dose to Pelvic Nodal Regions in Prostate-Only Radiotherapy

2016 ◽  
Vol 16 (2) ◽  
pp. 211-217 ◽  
Author(s):  
Vedang Murthy ◽  
Shirley Lewis ◽  
Mayur Sawant ◽  
Siji N. Paul ◽  
Umesh Mahantshetty ◽  
...  
Keyword(s):  
Intensity Modulated Radiotherapy ◽  
Conventional Radiotherapy ◽  
Prostate Radiotherapy ◽  
3 Dimensional ◽  
Intensity Modulated ◽  
Treatment Techniques ◽  
Dose Volume ◽  
Internal Iliac ◽  
The Mean ◽  
Conformal Treatment

Objectives: Pelvic lymph nodal regions receive an incidental dose from conformal treatment of the prostate. This study was conducted to investigate the doses received by the different pelvic nodal regions with varying techniques used for prostate radiotherapy. Methods and Materials: Twenty patients of high-risk node-negative prostate cancer treated with intensity-modulated radiotherapy to the prostate alone were studied. Replanning was done for intensity-modulated radiotherapy, 3-dimensional conformal treatment, and 2-dimensional conventional radiotherapy with additional delineation of the pelvic nodal regions, namely, common iliac (upper and lower), presacral, internal iliac, obturator, and external iliac. Dose–volume parameters such as Dmean, D100%, D66%, D33%, V40, and V50 to each of the nodal regions were estimated for all patients. Results: The obturator nodes received the highest dose among all nodal regions. The mean dose received by obturator nodal region was 44, 29, and 22 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The mean dose was significantly higher when compared between 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment ( P < .001), 2-dimensional conventional radiotherapy and intensity-modulated radiotherapy ( P < .001), and 3-dimensional conformal treatment and intensity-modulated radiotherapy ( P < .001). The D33% of the obturator region was 64, 39, and 37 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The dose received by all other pelvic nodal regions was low and not clinically relevant. Conclusion: The incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques as used in the trials studying elective pelvic nodal irradiation. However, with intensity-modulated radiotherapy, this dose is lower, making elective pelvic irradiation more relevant. Advances in Knowledge: This study highlights that incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques.

Effectiveness and toxicity of hypofractionated high-dose intensity-modulated radiotherapy versus 2- and 3-dimensional radiotherapy in incurable head and neck cancer

Head & Neck ◽  
2015 ◽  
Vol 38 (S1) ◽  
pp. E1264-E1270 ◽  
Author(s):  
Kirsty M. van Beek ◽  
Johannes H. A. M. Kaanders ◽  
Geert O. Janssens ◽  
Robert P. Takes ◽  
Paul N. Span ◽  
...  
Keyword(s):  
Head And Neck Cancer ◽  
Head And Neck ◽  
Neck Cancer ◽  
Intensity Modulated Radiotherapy ◽  
Dose Intensity ◽  
High Dose ◽  
3 Dimensional ◽  
Intensity Modulated ◽  
High Dose Intensity

scholarly journals Lightning flash multiplicity in Eastern Mediterranean thunderstorms

2013 ◽  
Vol 1 (4) ◽  
pp. 3529-3552 ◽  
Author(s):  
Y. Yair ◽  
S. Shalev ◽  
Z. Erlich ◽  
A. Agrachov ◽  
E. Katz ◽  
...  
Keyword(s):  
Eastern Mediterranean ◽  
Eastern Mediterranean Region ◽  
Spatial Proximity ◽  
Lightning Flash ◽  
Temporal Separation ◽  
Mean Values ◽  
Temporal Succession ◽  
The Mean ◽  
One Year ◽  
Close Spatial Proximity

Abstract. Cloud-to-ground lightning flashes usually consist of one or several strokes coming in very short temporal succession and close spatial proximity. The common method for converting stroke data into flashes is using the National Lightning Detection Network (NALDN) thresholds of maximum temporal separation of 0.5 s and maximum lateral distance of 10 km radius between successive strokes. In the present study, we tested a location-based algorithm with several spatial and temporal ranges, and analyzed stroke data obtained by the Israel Lightning Location System (ILLS) during one year (1 August 2009–31 July 2010). We computed the multiplicity, the percentage of single stroke flashes and the geographical distribution of single vs. multiple-stroke flashes for thunderstorms in the Eastern Mediterranean region. Results show that for the NALDN thresholds, the percentage of single stroke flashes in Israel was 37% and the average multiplicity was 1.7. We re-analyzed the data with a spatial range that equals twice the ILLS location error and shorter times. For the new thresholds of maximum distance of 2.5 km and maximum allowed temporal separation of 0.2 s we find that the mean multiplicity of negative CGs is lowered to 1.4 and find a percentage of 58% of single stroke flashes. A unique severe storm from 30 October 2009 is analyzed and compared to the annual average of 2009/10, showing that large deviations from the mean values can occur in specific events.

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