Inter-observer variation in gross tumour volume delineation of oesophageal cancer on MR, CT and PET/CT.

Background: The aim of our study was to assess the inter-observer variability in delineation of the gross tumour volume (GTV) of oesophageal cancer on magnetic resonance (MR) in comparison to computed tomography (CT) and positron emission tomography and CT (PET/CT).

Patients And Methods: Twenty-three consecutive patients with oesophageal cancer treated with chemo-radiotherapy were enrolled. All patients had PET/CT and MR imaging in treatment position.

HaN-Seg: The head and neck organ-at-risk CT and MR segmentation challenge.

Background And Purpose: To promote the development of auto-segmentation methods for head and neck (HaN) radiation treatment (RT) planning that exploit the information of computed tomography (CT) and magnetic resonance (MR) imaging modalities, we organized HaN-Seg: The Head and Neck Organ-at-Risk CT and MR Segmentation Challenge.

Materials And Methods: The challenge task was to automatically segment 30 organs-at-risk (OARs) of the HaN region in 14 withheld test cases given the availability of 42 publicly available training cases. Each case consisted of one contrast-enhanced CT and one T1-weighted MR image of the HaN region of the same patient, with up to 30 corresponding reference OAR delineation masks.

Comparison of conventional and hippocampus-sparing radiotherapy in nasopharyngeal carcinoma: In silico study and systematic review.

Background And Purpose: Radiation-induced damage to the hippocampi can cause cognitive decline. International recommendations for nasopharyngeal cancer (NPC) radiotherapy (RT) lack specific guidelines for protecting the hippocampi. Our study evaluates if hippocampi-sparing (HS) RT in NPC ensures target coverage and meets recommended dose limits for other at-risk organs.

vOARiability: Interobserver and intermodality variability analysis in OAR contouring from head and neck CT and MR images.

Background: Accurate and consistent contouring of organs-at-risk (OARs) from medical images is a key step of radiotherapy (RT) cancer treatment planning. Most contouring approaches rely on computed tomography (CT) images, but the integration of complementary magnetic resonance (MR) modality is highly recommended, especially from the perspective of OAR contouring, synthetic CT and MR image generation for MR-only RT, and MR-guided RT. Although MR has been recognized as valuable for contouring OARs in the head and neck (HaN) region, the accuracy and consistency of the resulting contours have not been yet objectively evaluated.

HaN-Seg: The head and neck organ-at-risk CT and MR segmentation dataset.

Purpose: For the cancer in the head and neck (HaN), radiotherapy (RT) represents an important treatment modality. Segmentation of organs-at-risk (OARs) is the starting point of RT planning, however, existing approaches are focused on either computed tomography (CT) or magnetic resonance (MR) images, while multimodal segmentation has not been thoroughly explored yet. We present a dataset of CT and MR images of the same patients with curated reference HaN OAR segmentations for an objective evaluation of segmentation methods.

Assessment of set-up errors in the radiotherapy of patients with head and neck cancer: standard vs. individual head support.

Background The aim of the study was to (a) compare the accuracy of two different immobilization strategies for patients with head and neck tumors, and (b) compare the set-up errors on treatment units with different portal imaging systems. Patients and methods Variations in the position of the isocenter (IC) relative to the reference point determined on the computed tomography simulator were measured in a vertical (anterior-posterior), longitudinal (superior-inferior), and lateral (medial-lateral) direction in 120 head and neck cancer patients irradiated with curative intent. Depending on the treatment unit (unit A - 2D/2D image previews; unit B- 2D image previews) and the time of irradiation, patients were divided into 6 groups of 20 patients.

Quality control in cone-beam computed tomography (CBCT) EFOMP-ESTRO-IAEA protocol (summary report).

The aim of the guideline presented in this article is to unify the test parameters for image quality evaluation and radiation output in all types of cone-beam computed tomography (CBCT) systems. The applications of CBCT spread over dental and interventional radiology, guided surgery and radiotherapy. The chosen tests provide the means to objectively evaluate the performance and monitor the constancy of the imaging chain.

Treating lung cancer with dynamic conformal arc therapy: a dosimetric study.

Background: Lung cancer patients are often in poor physical condition, and a shorter treatment time would reduce their discomfort. Dynamic conformal arc therapy (DCAT) offers a shorter treatment time than conventional 3D conformal radiotherapy (3D CRT) and is usually available even in departments without inverse planning possibilities. We examined its suitability as a treatment modality for lung cancer patients.

Influence of the Integral Quality Monitor transmission detector on high energy photon beams: A multi-centre study.

Purpose: The influence of the Integral Quality Monitor (IQM) transmission detector on photon beam properties was evaluated in a preclinical phase, using data from nine participating centres: (i) the change of beam quality (beam hardening), (ii) the influence on surface dose, and (iii) the attenuation of the IQM detector.

Methods: For 6 different nominal photon energies (4 standard, 2 FFF) and square field sizes from 1×1cm to 20×20cm, the effect of IQM on beam quality was assessed from the PDD values obtained from the percentage dose depth (PDD) curves, measured with and without IQM in the beam path. The change in surface dose with/without IQM was assessed for all available energies and field sizes from 4×4cm to 20×20cm.

Reducing the dosimetric impact of positional errors in field junctions for craniospinal irradiation using VMAT.

Aim: To improve treatment plan robustness with respect to small shifts in patient position during the VMAT treatment by ensuring a linear ramp-like dose profile in treatment field overlap regions.

Background: Craniospinal irradiation (CSI) is considered technically challenging because the target size exceeds the maximal field size, which necessitates using abutted or overlapping treatment fields. Volumetric modulated arc therapy (VMAT) is increasingly being examined for CSI, as it offers both better dose homogeneity and better dose conformance while also offering a possibility to create field junctions which are more robust towards small shifts in patient position during the treatment.

Partitioning of oleic acid into phosphatidylcholine membranes is amplified by strain.

Partitioning of fatty acids into phospholipid membranes is studied on giant unilamellar vesicles (GUVs) utilizing phase-contrast microscopy. With use of a micropipet, an individual GUV is transferred from a vesicle suspension in a mixed glucose/sucrose solution into an isomolar glycerol solution with a small amount of oleic acid added. Oleic acid molecules intercalate into the phospholipid membrane and thus increase the membrane area, while glycerol permeates into the vesicle interior and thus via osmotic inflation causes an increase of the vesicle volume.

Frequency-dependent electrodeformation of giant phospholipid vesicles in AC electric field.

A model of vesicle electrodeformation is described which obtains a parametrized vesicle shape by minimizing the sum of the membrane bending energy and the energy due to the electric field. Both the vesicle membrane and the aqueous media inside and outside the vesicle are treated as leaky dielectrics, and the vesicle itself is modeled as a nearly spherical shape enclosed within a thin membrane. It is demonstrated (a) that the model achieves a good quantitative agreement with the experimentally determined prolate-to-oblate transition frequencies in the kilohertz range and (b) that the model can explain a phase diagram of shapes of giant phospholipid vesicles with respect to two parameters: the frequency of the applied alternating current electric field and the ratio of the electrical conductivities of the aqueous media inside and outside the vesicle, explored in a recent paper (S.

Growth and shape transformations of giant phospholipid vesicles upon interaction with an aqueous oleic acid suspension.

The interaction of two types of vesicle systems was investigated: micrometer-sized, giant unilamellar vesicles (GUVs) formed from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and submicrometer-sized, large unilamellar vesicles (LUVs) formed from oleic acid and oleate, both in a buffered aqueous solution (pH 8.8). Individual POPC GUVs were transferred with a micropipette into a suspension of oleic acid/oleate LUVs, and the shape changes of the GUVs were monitored using optical microscopy.

Electroformation in a flow chamber with solution exchange as a means of preparation of flaccid giant vesicles.

A recently described technique [Estes and Mayer, Biochim. Biophys. Acta 1712 (2005) 152-160] for the preparation of giant unilamellar vesicles (GUVs) in solutions with high ionic strength is examined.

The frequency dependence of phospholipid vesicle shapes in an external electric field.

Experiments show that phospholipid vesicles exposed to AC electric field undergo a shape transition from prolate to oblate ellipsoidal shape when the frequency of the field is increased. A theoretical model, based on the minimization of total free energy of the vesicle, was devised to explain this phenomenon. The model exhibits the same frequency-dependent prolate-to-oblate shape transition as observed in the experiment.