Comparison of the use of a clinically implemented deep learning segmentation model with the simulated study setting for breast cancer patients receiving radiotherapy.

Background: Deep learning (DL) models for auto-segmentation in radiotherapy have been extensively studied in retrospective and pilot settings. However, these studies might not reflect the clinical setting. This study compares the use of a clinically implemented in-house trained DL segmentation model for breast cancer to a previously performed pilot study to assess possible differences in performance or acceptability.

Evaluation of a clinically introduced deep learning model for radiotherapy treatment planning of breast cancer.

Deep learning (DL) models are increasingly studied to automate the process of radiotherapy treatment planning. This study evaluates the clinical use of such a model for whole breast radiotherapy. Treatment plans were automatically generated, after which planners were allowed to manually adapt them.

Acceptance procedure for the linear accelerator component of the 1.5 T MRI-linac.

Purpose: To develop and implement an acceptance procedure for the new Elekta Unity 1.5 T MRI-linac.

Methods: Tests were adopted and, where necessary adapted, from AAPM TG106 and TG142, IEC 60976 and NCS 9 and NCS 22 guidelines.

Clinical value of (dedicated) 3 Tesla and 7 Tesla MRI for cT1 glottic carcinoma: A feasibility study.

Objective: To assess the feasibility of the clinical use of 3 Tesla and 7 Tesla Magnetic Resonance Imaging for early (cT1) glottic carcinoma, including structural assessment of technical image quality and visibility of the tumor; and if feasible, to correlate MRI findings to routine diagnostics.

Methods: Prospective feasibility study. Twenty patients with primary clinical T1 glottic carcinoma underwent both routine clinical staging and CT.

Spiraling contaminant electrons increase doses to surfaces outside the photon beam of an MRI-linac with a perpendicular magnetic field.

The transverse magnetic field of an MRI-linac sweeps contaminant electrons away from the radiation beam. Films oriented perpendicular to the magnetic field and 5 cm from the radiation beam edge show a projection of the divergent beam, indicating that contaminant electrons spiral along magnetic field lines and deposit dose on surfaces outside the primary beam perpendicular to the magnetic field. These spiraling contaminant electrons (SCE) could increase skin doses to protruding regions of the patient along the cranio-caudal axis.

Beam characterisation of the 1.5 T MRI-linac.

As a prerequisite for clinical treatments it was necessary to characterize the Elekta 1.5 T MRI-linac 7 MV FFF radiation beam. Following acceptance testing, beam characterization data were acquired with Semiflex 3D (PTW 31021), microDiamond (PTW 60019), and Farmer-type (PTW 30013 and IBA FC65-G) detectors in an Elekta 3D scanning water phantom and a PTW 1D water phantom.

Systematic review of the diagnostic value of magnetic resonance imaging for early glottic carcinoma.

Objective: In early glottic cancer, accurate assessment of tumor extension, including depth infiltration, is of great importance for both staging, therapeutic approach and systematic comparison of data. Our goal was to assess the diagnostic value of MRI in pre-therapeutic staging of primary early stage (T1 and T2) glottic carcinoma.

Study Design: Systematic review of literature.

First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment.

The integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery.

(1) H MRS in the human spinal cord at 7 T using a dielectric waveguide transmitter, RF shimming and a high density receive array.

Multimodal MRI is the state of the art method for clinical diagnostics and therapy monitoring of the spinal cord, with MRS being an emerging modality that has the potential to detect relevant changes of the spinal cord tissue at an earlier stage and to enhance specificity. Methodological challenges related to the small dimensions and deep location of the human spinal cord inside the human body, field fluctuations due to respiratory motion, susceptibility differences to adjacent tissue such as vertebras and pulsatile flow of the cerebrospinal fluid hinder the clinical application of (1) H MRS to the human spinal cord. Complementary to previous studies that partly addressed these problems, this work aims at enhancing the signal-to-noise ratio (SNR) of (1) H MRS in the human spinal cord.

Dielectric waveguides for ultrahigh field magnetic resonance imaging.

Purpose: The design of RF coils for MRI transmit becomes increasingly challenging at high frequencies required for MRI at 7T and above. Our goal is to show a proof of principle of a new type of transmit coil for higher field strengths.

Method: We demonstrate an alternative transmit coil design based on dielectric waveguide principles which transfers energy via evanescent wave coupling.

MRI of the carotid artery at 7 Tesla: quantitative comparison with 3 Tesla.

Purpose: To evaluate the 7 Tesla (T) MRI of the carotid arteries, as quantitatively compared with 3T.

Materials And Methods: The 7T MRI of the carotid arteries was performed in six healthy subjects and in two patients with carotid stenosis. The healthy group was scanned at 3T and at 7T, using current coil setups at both field strengths.

Improved RF performance of travelling wave MR with a high permittivity dielectric lining of the bore.

Application of travelling wave MR to human body imaging is restricted by the limited peak power of the available RF amplifiers. Nevertheless, travelling wave MR advantages like a large field of view excitation and distant location of transmit elements would be desirable for whole body MRI. In this work, improvement of the B1+ efficiency of travelling wave MR is demonstrated.

High-resolution MRI of the carotid arteries using a leaky waveguide transmitter and a high-density receive array at 7 T.

A setup for 7T MRI of the carotid arteries in the neck was designed and constructed. Separate dedicated arrays were used for transmit and receive. For the transmit array, single-side adapted dipole antennas were mounted on a dielectric pillow, which was shown to serve as a leaky waveguide, efficiently distributing B1 into the neck.

Animal-vegetal polarity in the plasma membrane of a molluscan egg: a quantitative freeze-fracture study.

Using freeze-fracture electron microscopy, the numerical particle distribution in the fertilized Nassarius egg plasma membrane has been analyzed in four areas at different positions along the animal-vegetal axis of the egg. These areas can be distinguished by distinct microvilli patterns and differences in microvilli densities. In all areas, more IMPs (intramembrane particles) are present on the P face than on the corresponding E face.

Gap junctions and rhombic particle arrays in the freeze-fractured mouse oocyte-follicle cell complex.

Intact follicles as well as defolliculated oocytes of the mouse were studied by freeze-fracture electron microscopy. In intact follicles the oocyte plasma membrane shows two prominent types of intra-membrane particle array:gap junctions and yet undescribed rhombic particle arrays. The gap junctions vary in size (from 5 to 500 IMPs) and shape.

Lateral mobility of plasma membrane lipids in dividing Xenopus eggs.

The lateral mobility of plasma membrane lipids was analyzed during first cleavage of Xenopus laevis eggs by fluorescence photobleaching recovery (FPR) measurements, using the lipid analogs 5-(N-hexadecanoyl)aminofluorescein ("HEDAF") and 5-(N-tetradecanoyl)aminofluorescein ("TEDAF") as probes. The preexisting plasma membrane of the animal side showed an inhomogeneous, dotted fluorescence pattern after labeling and the lateral mobility of both probes used was below the detection limits of the FPR method (D much less than 10(-10) cm2/sec). In contrast, the preexisting plasma membrane of the vegetal side exhibited homogeneous fluorescence and the lateral diffusion coefficient of both probes used was relatively high (HEDAF, D = 2.

The ultrastructural organization of gap junctions between follicle cells and the oocyte in Xenopus laevis.

The cellular contact sites between the full-grown oocyte of Xenopus laevis and the surface extensions of surrounding follicles cells were analysed by electron microscopy of ultrathin sections, freeze-fracture replicas and critical point-dried specimens. Evidence is given for the presence of clusters of intramembranous particles (IMPs) at the P-face which represent gap junctions in diverse forms. Most common are maculae (phi 0.

Lateral mobility of plasma membrane lipids in Xenopus eggs: regional differences related to animal/vegetal polarity become extreme upon fertilization.

Regional differences in the lateral mobility properties of plasma membrane lipids have been studied in unfertilized and fertilized Xenopus eggs by fluorescence photobleaching recovery (FPR) measurements. Out of a variety of commonly used lipid probes only the aminofluorescein-labeled fatty acids HEDAF (5-(N-hexadecanoyl)-aminofluorescein) and TEDAF (5-(N-tetradecanoyl)-aminofluorescein) appear to partition into the plasma membrane. Under all experimental conditions used these molecules show partial recovery upon photobleaching indicating the existence of lipidic microdomains.

Ultrastructural aspects of rapid plasma membrane growth in mitotic neuroblastoma cells.

In murine C1300 neuroblastoma cells, clone Neuro 2A, the major fraction of the necessary increase in cell surface area during the cell cycle occurs within a short period around mitosis. During this period cell cycle-related modulations in a number of structural, dynamic and transport properties are most prominent. In this study we have examined the mechanism of rapid plasma membrane growth during mitosis, and the resulting changes in the ultrastructural features of the plasma membrane, by scanning and freeze-fracture electron microscopy as well as by electron microscopy of ultrathin sections.

Freeze-fracture electron microscopy of membrane changes in progesterone-induced maturing oocytes and eggs of Xenopus laevis.

Using freeze-fracture electron microscopy, compositional changes were analysed in the surface membrane of Xenopus oocytes during maturation after in vitro progesterone treatment, as well as in eggs before and after fertilization. Investigated stages were as follows: (1) defolliculated full-grown oocytes; (2) defolliculated oocytes after 5 min exposure to 5 micrograms/ml progesterone; (3) ditto at germinal vesicle breakdown (GVBD) after 5 h progesterone treatment; (4) unfertilized eggs at oviposition and (5) zygotes 30 min post-fertilization. Comparing the patterns of intramembranous particle (IMP) density and IMP size during these stages the following changes were found: a transient decrease in IMP density was found after 5 min progesterone treatment; a 48% increase during maturation; a further 17% increase after fertilization.