Experimental assessment of inter-centre variation in stopping-power and range prediction in particle therapy.

Purpose: Experimental assessment of inter-centre variation and absolute accuracy of stopping-power-ratio (SPR) prediction within 17 particle therapy centres of the European Particle Therapy Network.

Material And Methods: A head and body phantom with seventeen tissue-equivalent materials were scanned consecutively at the participating centres using their individual clinical CT scan protocol and translated into SPR with their in-house CT-number-to-SPR conversion. Inter-centre variation and absolute accuracy in SPR prediction were quantified for three tissue groups: lung, soft tissues and bones.

Evaluation of two commercial CT metal artifact reduction algorithms for use in proton radiotherapy treatment planning in the head and neck area.

Purpose: To evaluate two commercial CT metal artifact reduction (MAR) algorithms for use in proton treatment planning in the head and neck (H&N) area.

Methods: An anthropomorphic head phantom with removable metallic implants (dental fillings or neck implant) was CT-scanned to evaluate the O-MAR (Philips) and the iMAR (Siemens) algorithms. Reference images were acquired without any metallic implants in place.

Temporal relationship of sleep apnea and acromegaly: a nationwide study.

Purpose: Patients with acromegaly have an increased risk of sleep apnea, but reported prevalence rates vary largely. Here we aimed to evaluate the sleep apnea prevalence in a large national cohort of patients with acromegaly, to examine possible risk factors, and to assess the proportion of patients diagnosed with sleep apnea prior to acromegaly diagnosis.

Methods: Cross-sectional multicenter study of 259 Swedish patients with acromegaly.

Inter-centre variability of CT-based stopping-power prediction in particle therapy: Survey-based evaluation.

Background And Purpose: Stopping-power ratios (SPRs) are used in particle therapy to calculate particle range in patients. The heuristic CT-to-SPR conversion (Hounsfield Look-Up-Table, HLUT), needed for treatment planning, depends on CT-scan and reconstruction parameters as well as the specific HLUT definition. To assess inter-centre differences in these parameters, we performed a survey-based qualitative evaluation, as a first step towards better standardisation of CT-based SPR derivation.

Doubling of water intake increases daytime blood pressure and reduces vertigo in healthy subjects.

We studied the effect of increased water intake on ambulatory blood pressure (BP) in healthy individuals. Blood pressure was recorded after 2 weeks of either regular (RWI) or extra water intake (EWI, an additional 30 ml water/kg body weight per day) in 20 healthy subjects (10 males, 10 females). The extra water intake (RWI: 1.

Portal dose image verification: the collapsed cone superposition method applied with different electronic portal imaging devices.

Two different commercial electronic portal imaging devices (EPIDs), one based on a liquid ion chamber matrix and the other based on a fluoroscopic CCD camera, were used to acquire readings that, through a calibration procedure, provided images proportional to the absolute dose to a virtual water slab located at the EPID plane. The transformation of the matrix ion chamber image into a portal dose image (PDI) was based on a published relationship between dose rate and ionization current. For the fluoroscopic CCD-camera-based system, the transformation was based on a deconvolution with a radial light scatter kernel.

Portal dose image verification: formalism and application of the collapsed cone superposition method.

A formalism tailored for portal dose image verification is proposed to facilitate the comparison of calculated and measured portal dose distributions. Each portal image is converted into a dose proportional image and normalized to the reference beam calibration dose per monitor unit. The calculated or measured dose to a detector phantom is accordingly normalized so as to enable direct comparison.