Quality assurance for dynamic tumor tracking using the Vero4DRT system

Purpose: We perform quality assurance (QA) for indirect dynamic tumor tracking (DTT) using four-dimensional radiation therapy (the Vero4DRT™ system).Methods: A single photon beam was set with a 40 × 40 mm2 field size at a gantry angle of zero degrees and a low monitor unit setting of 200. Doses were measured using a 0.016 cm3 ionization chamber inserted in a phantom under stationary, DTT, and non-DTT conditions for sinusoidal (peak-to-peak) amplitude [A] and breathing period [T] (20 mm, 2 s; 20 mm, 4 s; and 40 mm, 4 s). The stationary condition was measured for comparison. Dose profiles were measured using Gafchromic EBT3 films in the phantom under the same conditions.Results: For chamber measurement, the relative doses were as follows: 0.99 with non-DTT and 1.00 with DTT at A = 20 mm and T = 2 s; 0.99 with non-DTT and 1.00 with DTT at A = 20 mm and T = 4 s; and 0.84 with non-DTT and 1.00 with DTT at A = 40 mm and T = 4 s. For film measurement, the spatial distances between the 90% dose of the dose profiles were as follows: 6.53 mm for non-DTT and 0.40 mm for DTT at A = 20 mm and T = 2 s; 6.33 mm for non-DTT and 0.15 mm for DTT at A = 20 mm and T = 4 s; and 10.61 mm for non-DTT and 0.17 mm with DTT at A = 40 mm and T = 4 s.Conclusion: Our results showed high dosimetric and geometric accuracy for DTT using four-dimensional modeling and marked reduction of the blurring effects on dose distribution. We recommend the use of a QA procedure for DTT performed using the Vero4DRT™ system

Observation of domain wall bimerons in chiral magnets

Topological defects embedded in or combined with domain walls have been proposed in various systems, some of which are referred to as domain wall skyrmions or domain wall bimerons. However, the experimental observation of such topological defects remains an ongoing challenge. Here, using Lorentz transmission electron microscopy, we report the experimental discovery of domain wall bimerons in chiral magnet Co-Zn-Mn(110) thin films. By applying a magnetic field, multidomain structures develop, and simultaneously, chained and isolated bimerons arise as the localized state between the domains with the opposite in-plane components of net magnetization. The multidomain formation is attributed to magnetic anisotropy and dipolar interaction, and domain wall bimerons are stabilized by the Dzyaloshinskii-Moriya interaction. In addition, micromagnetic simulations show that domain wall bimerons appear for a wide range of conditions in chiral magnets with cubic magnetic anisotropy. Our results promote further study in various fields of physics.Comment: 30 pages, 10 figures (including Supplementary Materials

A case of laparoscopic and endoscopic cooperative surgery for sigmoidovesical fistula

We performed laparoscopic and endoscopic cooperative surgery (LECS) for partial colectomy with partial cystectomy in an 80-year-old woman with sigmoidovesical fistula secondary to sigmoid diverticulitis. LECS was designed for local resection of the stomach for gastric submucosal tumors using the endoscopic submucosal dissection (ESD) technique. While conventional open abdominal surgery is very invasive, LECS has enabled surgeons to perform minimally invasive surgery. Although there have been no reported cases in which the bladder was laparoscopically resected after sigmoidovesical fistula division, we were able to safely resect the fistula and preserve the urethral opening by performing laparoscopic and cystoscopic cooperative surgery. There are no previously reported cases in which LECS was performed for partial sigmoidectomy and partial cystectomy ; therefore, we report this as a valuable case, with a review of the literature. We hope that further studies involving more patients will lead to the establishment of this procedure

Structural analysis of radiation-induced chromosome aberrations by atomic force microscope (AFM) before and after Giemsa staining

12th International Congress of Radiation Researc

Effect of interfacial serum proteins on melanoma cell adhesion to biodegradable poly(L-lactic acid) microspheres coated with hydroxyapatite.

We have measured the interaction forces between a murine melanoma cell and a poly(L-lactic acid) (PLLA) microsphere coated with/without hydroxyapatite (HAp) nanoparticles (i.e., an HAp/PLLA or a bare PLLA microsphere) in a serum-free culture medium, using atomic force microscopy (AFM) with colloid probe technique, in order to investigate how the HAp-nanoparticle coating as well as interfacial serum proteins influence the cell-microsphere adhesion. The cell adhesion force of the HAp/PLLA microspheres was 1.4-fold stronger than that of the bare PLLA microspheres. When the microspheres were pretreated with a culture medium supplemented with 10% fetal bovine serum, the cell adhesion force of the HAp/PLLA microspheres was increased by a factor of 2.1; in contrast, no change was observed in the cell adhesion force of the bare PLLA microspheres before/after the pretreatment. Indeed, the cell adhesion force of the HAp/PLLA was 2.8-fold larger than that of the bare PLLA after the pretreatment. Additionally, we have investigated the effect of interfacial serum proteins on the zeta potentials of these microspheres. On the basis of the obtained results, possible mechanism of cell adhesion to the HAp/PLLA and bare PLLA microspheres in the presence/absence of the interfacial serum proteins is discussed