Planning Study of Flattening Filter Free Beams for Volumetric Modulated Arc Therapy in Squamous Cell Carcinoma of the Scalp - Figure 1

<p><b>Delineated planning target volume (PTV) for squamous cell carcinoma of the scalp (A), and two different beam setups in VMAT plans:</b> (B) Two 360° arcs were used with half-field beam. (C) Eight half-field quarter-arcs (90°) were used in VMAT plan.</p

Planning Study of Flattening Filter Free Beams for Volumetric Modulated Arc Therapy in Squamous Cell Carcinoma of the Scalp

<div><p>Purpose</p><p>Flattening filter free (FFF) beams show the potential for a higher dose rate and lower peripheral dose. We investigated the planning study of FFF beams with their role for volumetric modulated arc therapy (VMAT) in squamous cell carcinoma of the scalp.</p><p>Methods and Materials</p><p>One patient with squamous cell carcinoma which had involvement of entire scalp was subjected to VMAT using TrueBeam linear accelerator. As it was a rare skin malignancy, CT data of 7 patients with brain tumors were also included in this study, and their entire scalps were outlined as target volumes. Three VMAT plans were employed with RapidArc form: two half-field full-arcs VMAT using 6 MV standard beams (HFF-VMAT-FF), eight half-field quarter-arcs VMAT using 6 MV standard beams (HFQ-VMAT-FF), and HFQ-VMAT using FFF beams (HFQ-VMAT-FFF). Prescribed dose was 25×2 Gy (50 Gy). Plan quality and efficiency were assessed for all plans.</p><p>Results</p><p>There were no statistically significant differences among the three VMAT plans in target volume coverage, conformity, and homogeneity. For HFQ-VMAT-FF plans, there was a significant decrease by 12.6% in the mean dose to the brain compared with HFF-VMAT-FF. By the use of FFF beams, the mean dose to brain in HFQ-VMAT-FFF plans was further decreased by 7.4% compared with HFQ-VMAT-FF. Beam delivery times were similar for each technique.</p><p>Conclusions</p><p>The HFQ-VMAT-FF plans showed the superiority in dose distributions compared with HFF-VMAT-FF. HFQ-VMAT-FFF plans might provide further normal tissue sparing, particularly in the brain, showing their potential for radiation therapy in squamous cell carcinoma of the scalp.</p></div

Cumulative survival of patients stratified by the number of lymph node metastases (pN).

<p>Cumulative survival of patients stratified by the number of lymph node metastases (pN).</p

The mean doses of organs at risk, MU, beam-on time, and mean dose rate (MDR) for treatment plans created with different planning techniques.

<p><i>Abbreviations:</i> HFF-VMAT-FF = two half-field full-arcs VMAT with conventional flattened (FF) beam; HFQ-VMAT-FF = eight half-field quarter-arcs VMAT with FF beam; HFQ-VMAT-FFF = eight half-field quarter-arcs VMAT with flattening filter free (FFF) beam.</p><p>* Body: it is the region of the CT which was scanned.</p><p>* <i>P</i> value corresponds to the paired <i>t</i> test: a = HFF-VMAT-FF vs HFQ-VMAT-FF, b = HFQ-VMAT-FF vs HFQ-VMAT-FFF.</p><p>The mean doses of organs at risk, MU, beam-on time, and mean dose rate (MDR) for treatment plans created with different planning techniques.</p

Isodose distributions for one patient with squamous cell carcinoma in axial, coronal, and sagittal planes.

<p>(A) HFF-VMAT-FF: two half-field full-arcs VMAT with conventional flattened (FF) beam; (B) HFQ-VMAT-FF: eight half-field quarter-arcs VMAT with FF beam; (C) HFQ-VMAT-FFF: eight half-field quarter-arcs VMAT with flattening filter free (FFF) beam.</p

Dosimetric parameters of PTV for treatment plans created with different planning techniques.

<p><i>Abbreviations:</i> HFF-VMAT-FF = two half-field full-arcs VMAT with conventional flattened (FF) beam; HFQ-VMAT-FF = eight half-field quarter-arcs VMAT with FF beam; HFQ-VMAT-FFF = eight half-field quarter-arcs VMAT with flattening filter free (FFF) beam; CI = conformity index; HI = homogeneity index.</p><p>* <i>P</i> value corresponds to the paired <i>t</i> test: a = HFF-VMAT-FF vs HFQ-VMAT-FF, b = HFQ-VMAT-FF vs HFQ-VMAT-FFF.</p><p>Dosimetric parameters of PTV for treatment plans created with different planning techniques.</p

Planning Study of Flattening Filter Free Beams for Volumetric Modulated Arc Therapy in Squamous Cell Carcinoma of the Scalp - Figure 4

<p><b>Dose-volume histogram (DVH) comparison for the PTV and brain with different planning techniques:</b> (a) HFF-VMAT-FF: two half-field full-arcs VMAT with conventional flattened (FF) beam; (b) HFQ-VMAT-FF: eight half-field quarter-arcs VMAT with FF beam; (c) HFQ-VMAT-FFF: eight half-field quarter-arcs VMAT with flattening filter free (FFF) beam.</p

Synthesis and Characterization of an Osmapentalene Derivative Containing a β‑Agostic Os···H–C(sp³) Interaction

Treatment of cyclopropaosmapentalene (<b>1</b>) with EtCCEt in the presence of AgBF₄ gave a new type of polycyclic metallaaromatic complex with a structure containing an sp³ carbon and a β-agostic Os···H–C­(sp³) interaction. This result strongly supported our proposed intermediate in the reaction of cyclopropaosmapentalene <b>1</b> with alkynes that produced photothermal osmium carbolong complexes. When EtCCCOMe was used, the reaction gave a more thermally stable ketone-coordinated complex as the major product. The DFT study indicated that the difference in the two reactions is of thermodynamic origin

Patient, tumor, and treatment characteristics before and after propensity score matching.

Patient, tumor, and treatment characteristics before and after propensity score matching.</p

Multivariate Cox regression analysis of prognostic factors in matched population.

Multivariate Cox regression analysis of prognostic factors in matched population.</p