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To explore the impact of personality on the decision process and satisfaction rates in pseudophakic presbyopic correction.Department of Ophthalmology, University Hospital of Alexandroupolis, Greece.Prospective, comparative study.A consistent consultation was conducted in patients with cataract that explained the benefits and the drawbacks of bilateral trifocal correction, which was offered at no extra cost. In all participants, personality was evaluated by The Traits Personality Questionnaire 5. Data modeling with decision trees and multiple regression analysis identified the contributions of personality traits to the decision process and postoperative satisfaction.Of 120 participants (60 men and 60 women), 81 (67.5%, 24 men, 57 women) selected premium correction. In men, low neuroticism and high extraversion were the primary personality contributors for selecting premium surgery. In women, all personality traits contributed to the selection process. Women were more demanding in the expected postoperative distant acuity than men (0.1 vs 0.2 logMAR) to present high satisfaction. For both men and women, openness to experience, conscientiousness, and extraversion are primary contributors for optimal satisfaction rates.Men and women demonstrate differences in the selection process for premium pseudophakic surgery and differences in the expected postoperative visual acuity. It seems that the personality of the patient plays a significant role in the perceived outcome after premium surgery.

Ferredoxin reductase (FDXR) has already been reported as a promising biomarker for estimating radiation doses in radiotherapy. This study aimed to investigate the responsiveness of FDXR on pediatric population exposed to ionizing radiation (X-rays) during pediatric interventional cardiology (IC) procedures.Peripheral blood was collected by venipuncture from 24 pediatric donors before and 24 hours after the IC procedure. To estimate the effective dose, demographic data and Air Kerma-Area Product (PKA) were recorded for each patient. The relative quantification (RQ) of the FDXR gene in irradiated patient blood samples compared to the non-irradiated blood samples was determined using qPCR analysis. The relative values of FDXR were log- transformed.The effective dose ranged from 0.002 mSv to 8.004 mSv. Over this radiation exposure range, the FDXR gene expression varied randomly with the effective dose. Up-regulation in FDXR expression was observed in 17 patients and down-regulation in 7 patients.Further studies in a larger cohort of pediatric patients along with the record of clinical data are needed to determine whether FDXR gene expression is an effective biomarker for radiation exposure estimation in pediatric imaging.

Background An imaging-based predictor of response could provide prognostic information early during treatment course in patients with multiple myeloma (MM). Purpose To investigate if very early changes in bone marrow relative fat fraction (rFF) and apparent diffusion coefficient (ADC) histogram metrics, occurring after one cycle of induction therapy in participants with newly diagnosed MM, could help predict overall best response status. Materials and Methods This prospective study included participants with MM who were enrolled between August 2014 and December 2017. Histogram metrics were extracted from ADC and rFF maps from MRI examinations performed before treatment and after the first treatment cycle. Participants were categorized into the very good partial response (VGPR) or better group and the less than VGPR group per the International Myeloma Working Group response criteria. ADC and rFF map metrics for predicting treatment response were compared using the Wilcoxon rank test, and the false discovery rate (FDR) was used to correct for multiple comparisons. Results A total of 23 participants (mean age, 65 years ± 11 [SD]; 13 men) were evaluated. There was no evidence of a difference in ADC metrics between the two responder groups after correcting for multiple comparisons. The rFF histogram changes between pretreatment MRI and MRI after the first treatment cycle (ΔrFF) that provided significant differences between the VGPR or better and less than VGPR groups were as follows: ΔrFF_10th Percentile (median, 0.5 [95% CI: 0, 1] vs -2.5 [95% CI: -5.1, 0.1], respectively), ΔrFF_90th Percentile (median, 2 [95% CI: 1, 6.8] vs -0.5 [95% CI: -1, 0]), ΔrFF_Mean (median, 3.4 [95% CI: 0.3, 7.6] vs -1.1 [95% CI: -1.8, -0.7]), and ΔrFF_Root Mean Squared (median, 3.2 [95% CI: 0.3, 6.1] vs -0.7 [95% CI: -1.3, -0.4]) (FDR-adjusted

The aim of the study was to measure and evaluate the radiation dose to the eye lens and forehead of interventional radiologists (IRs). The study included 96 procedures (lower-limb percutaneous transluminal angioplasties, embolisations/chemoembolisations and vertebroplasties) performed by 6 IRs. A set of seven thermoluminescence dosemeters was allocated to each physician. The highest dose per procedure was found for the left eye lens of the primary operator in vertebroplasties (1576 μSv). Left and right eye doses were linearly correlated to left and right forehead doses, respectively. A workload-based estimation of the annual dose to participating IRs revealed that the occupational dose limit for the eye lens can be easily exceeded. The left eye dose of ΙRs must be routinely monitored on a personalised basis. Τhe left eye dose measurement provides a reliable assessment of the ipsilateral forehead dose, along with valid estimations for the right eye and right forehead doses.

In frame-based Gamma Knife (GK) stereotactic radiosurgery two treatment planning workflows are commonly employed; one based solely on magnetic resonance (MR) images and the other based on magnetic resonance/computed tomography (MR/CT) co-registered images. In both workflows, target localization accuracy (TLA) can be deteriorated due to MR-related geometric distortions and/or MR/CT co-registration uncertainties. In this study, the overall TLA following both clinical workflows is evaluated for cases of multiple brain metastases.A polymer gel-filled head phantom, having the Leksell stereotactic headframe attached, was CT-imaged and irradiated by a GK Perfexion unit. A total of 26 4-mm shots were delivered at 26 locations directly defined in the Leksell stereotactic space (LSS), inducing adequate contrast in corresponding T2-weighted (T2w) MR images. Prescribed shot coordinates served as reference locations. An additional MR scan was acquired to implement the "mean image" distortion correction technique. The TLA for each workflow was assessed by comparing the radiation-induced target locations, identified in MR images, with corresponding reference locations. Using T1w MR and CT images of 15 patients (totaling 81 lesions), TLA in clinical cases was similarly assessed, considering MR-corrected data as reference. For the MR/CT workflow, both global and region of interest (ROI)-based MR/CT registration approaches were studied.In phantom measurements, the MR-corrected workflow demonstrated unsurpassed TLA (median offset of 0.2 mm) which deteriorated for MR-only and MR/CT workflows (median offsets of 0.8 and 0.6 mm, respectively). In real-patient cases, the MR-only workflow resulted in offsets that exhibit a significant positive correlation with the distance from the MR isocenter, reaching 1.1 mm (median 0.6 mm). Comparable results were obtained for the MR/CT-global workflow, although a maximum offset of 1.4 mm was detected. TLA was improved with the MR/CT-ROI workflow resulting in median/maximum offsets of 0.4 mm/1.1 mm.Subpixel TLA is achievable in all workflows. For the MR/CT workflow, a ROI-based MR/CT co-registration approach could considerably increase TLA and should be preferred instead of a global registration.

Magnetic resonance spectroscopy (MRS) has contributed important academic insights in motor neuron diseases (MNDs), particularly in amyotrophic lateral sclerosis (ALS). Over the past three decades momentous methodological advances took place, including the emergence of high-field magnetic resonance imaging (MRI) platforms, multi-voxel techniques, whole-brain protocols, novel head-coil designs, and a multitude of open-source imaging suites. Technological advances in MRS are complemented by important conceptual developments in MND, such as the recognition of the importance of extra-motor brain regions, multi-timepoint longitudinal study designs, assessment of asymptomatic mutation carriers, description of genotype-associated signatures, and the gradual characterisation of non-ALS MND phenotypes. We have conducted a systematic review of published MRS studies in MND to identify important emerging research trends, key lessons from pioneering studies, and stereotyped shortcomings. We also sought to highlight notable gaps in the current literature so that research priorities for future studies can be outlined. While MRS remains relatively underutilised in MND compared to other structural, diffusivity and functional imaging modalities, our review suggests that MRS can not only advance our academic understanding of MND biology, but has a multitude of practical benefits for clinical and pharmaceutical trial applications.

Although rehabilitation practice for most patients consists of a combined use of thermotherapy that is produced from diathermy devices resulting faster and deeper heating to the patient, major concerns about occupational exposure to electromagnetic radiation for the operators must be considered. In most occasions, physiotherapists have involved multi-hour treatment sessions to different patients, resulting overuse of the diathermy device. Recently, our team along with other groups have raised serious concerns about the occupational safety aspects related to microwave diathermy (MWD) use. Driven by these recent reports, in this work, we tried to investigate the in vitro effects of a physiotherapist routine MWD device regarding its potential inflammatory biological effects that could be evoked in human cultured monocytes. Our results show that MWD does not alter the integrity of the cell membrane and, consequently, the viability of monocytes as assessed by Trypan blue and MTT measurements. Then again, members of the MAPK family (p38 and ERK1/2) were activated upon MWD exposure at 5-30 min, eventually leading to a time-dependent considerable increase in TNF-α production, a key pro-inflammatory mediator. Our results are indicative of a stress-activated phenomenon of monocytes upon MWD radiation, which could trigger potential hazardous cellular outcomes due to thermal and/or non-thermal bystander effects. Our results deserve further investigation, planned by our team in due course, to delineate the clinical correlations of these findings.

The inconsistency of volumetric results often seen in MR neuroimaging studies can be partially attributed to small sample sizes and variable data analysis approaches. Increased sample size through multi-scanner studies can tackle the former, but combining data across different scanner platforms and field-strengths may introduce a variability factor capable of masking subtle statistical differences. To investigate the sample size effect on regression analysis between depressive symptoms and grey matter volume (GMV) loss in Alzheimer's disease (AD), a retrospective multi-scanner investigation was conducted. A cohort of 172 AD patients, with or without comorbid depressive symptoms, was studied. Patients were scanned with different imaging protocols in four different MRI scanners operating at either 1.5 T or 3.0 T. Acquired data were uniformly analyzed using the computational anatomy toolbox (CAT12) of the statistical parametric mapping (SPM12) software. Single- and multi-scanner regression analyses were applied to identify the anatomical pattern of correlation between GM loss and depression severity. A common anatomical pattern of correlation between GMV loss and increased depression severity, mostly involving sensorimotor areas, was identified in all patient subgroups imaged in different scanners. Analysis of the pooled multi-scanner data confirmed the above finding employing a more conservative statistical criterion. In the retrospective multi-scanner setting, a significant correlation was also exhibited for temporal and frontal areas. Increasing the sample size by retrospectively pooling multi-scanner data, irrespective of the acquisition platform and parameters employed, can facilitate the identification of anatomical areas with a strong correlation between GMV changes and depression symptoms in AD patients.

Language fMRI has become an integral part of the planning process in brain surgery. However, fMRI may suffer from confounding factors both on the patient side, as well as on the provider side. In this study, we investigate how patient-related confounds affect the ability of the patient to perform language fMRI tasks (feasibility), the task sensitivity from an image contrast point of view, and the anatomical specificity of expressive and receptive language fMRI protocols. 104 patients were referred for language fMRI in the context of presurgical procedures for epilepsy and brain tumor surgery. Four tasks were used: (1) a verbal fluency (VF) task to map vocabulary use, (2) a semantic description (SD) task to map sentence formation/semantic integration skills, (3) a reading comprehension (RC) task and (4) a listening comprehension (LC) task. Feasibility was excellent in the LC task (100%), but in the acceptable to mediocre range for the rest of the tasks (SD: 87.50%, RC: 85.57%, VF: 67.30%). Feasibility was significantly confounded by age (p = 0.020) and education level (p = 0.003) in VF, by education level (p = 0.004) and lesion laterality (p = 0.019) in SD and by age (p = 0.001), lesion laterality (p = 0.007) and lesion severity (p = 0.048) in RC. All tasks were comparable regarding sensitivity in generating statistically significant image contrast (VF: 90.00%, SD: 92.30%, RC: 93.25%, LC: 88.46%). The lobe of the lesion (p = 0.005) and the age (p = 0.009) confounded contrast sensitivity in the VF and SD tasks respectively. Both VF and LC tasks demonstrated unilateral lateralization of posterior language areas; only the LC task showed unilateral lateralization of anterior language areas. Our study highlights the effects of patient-related confounding factors on language fMRI and proposes LC as the most feasible, less confounded, and efficiently lateralizing task in the clinical presurgical context.

Introduction Socioeconomic status (SES) has been shown to be a prognostic factor for overall survival in a variety of hematologic malignancies, especially for patients who require continuous care such as those with multiple myeloma (MM). Patients and Methods We retrospectively collected data from 223 patients with symptomatic MM diagnosed and treated in our department from January 2005 to December 2019. The modified Kuppuswamy scale, slightly modified, was used for the SES assessment. The Kaplan-Meier estimator of survival and Cox regression analysis were used. Results In our cohort of 223 patients with MM, low SES was an independent poor prognostic factor for overall survival (OS), in addition to higher International Staging System stage and high-risk cytogenetics (hazard ratio for low SES on Cox regression analysis, 2.092; 95% confidence interval [CI], 1.36-3.2; log-rank P = .000). Patients with low SES had inferior survival compared with the whole patient cohort (median OS: low SES, 28 months; 95% CI, 18-37.9; high SES, 68 months; 95% CI, 55.6-80.4; log-rank P = .000). The low SES effect on OS was more evident for the elderly patients who were not transplant eligible and in those with a diagnosis of MM International Staging System stage I. The effect of low SES on OS was attenuated by time, and ethnic origin had no effect on OS. Conclusions The results of the present study have shown that low SES is an independent poor prognostic factor for survival of patients with MM.

Microwave diathermies (MWDs) are electromagnetic (EM) radiation emitting systems that are used by physiotherapists for thermotherapy treatment. Although this form of therapy is widely available in most physiotherapy units worldwide, management of the equipment is not obligatory addressed either by clinical engineers or medical physicists. A novel quality control (QC) protocol for MWD equipment, examining mechanical, electrical and electronic condition, the power output and EM radiation distribution in the electrotherapy room, was used during a national QC survey. The results of the survey revealed serious concerns about the safety of users and coexisting patients. The proposed approach could result in the introduction of EM-screened rooms, ensuring that MWD users and other persons in the vicinity will not be exposed to EM radiation over reference levels. International bodies could develop specific directives for EM radiation exposure in Physiotherapy Units, to conform to the proposed acceptance and functioning criteria for MDWs.

Rehabilitation practice for many patients consisting of a combined use of magneto therapy resulting emission of low frequency magnetic fields to the patient, elicit concerns about occupational exposure to electromagnetic radiation (EMR) for the operators. The time extended use of the device periodically leads to mechanical failures or troubleshooting of the machine which, in most cases, are not perceived by the operator of the device. All device’s efficient functionality have a major impact on the completion of the treatment procedure in a large percentage of specific clinical conditions. If the device’s operating condition is technically out of order or in a mode of over-activity, operators are mainly seeking solutions by reviewing the clinical case of the patient. This eliminates their contribution during the primary therapeutic plan or increases the treatment sessions. In this work, an extended survey is presented including 75 physiotherapy centres concerning usability and maintenance issues of magneto therapy devices throughout Greek territory combined with extended measurements of Electromagnetic Radiation in the unit room were performed. Physiotherapists’ perceptions revealed lack of technical support, maintenance and safe use of magneto therapy devices that extract auxiliary observations upon their clinical practice routines. Additionally safety measurements have not revealed field strengths over International Reference Levels which could result health risks for users and coexisting patients. The pilot survey that conducted in Attica and Western Greece confirms that magnetic fields strength that are measured are in accordance with the statutory legislation but will, at the same time, revealed lack of maintenance of the devices. Deficiency in topics such as proper equipment function will necessitate the creation of quality safety protocols, concerning the use of magneto-therapy, with the main aim the improvement of treatment procedures for the higher performance of therapeutic rehabilitation services to patients. Finally in this work, the proposal of a QC protocol for magnetotherapy devices is proposed for evaluation.

Self-monitoring is a crucial component of human empathy and necessary for the formation and repair of social relations. Several studies have brought to light possible neuronal substrates associated with self-monitoring, but the information that they have provided is inconclusive. The authors, therefore, studied a large group of patients with dementia to assess what brain structures are necessary for the self-monitoring function.

The purpose of this study was to analyze and to compare results regarding the penumbra size, flatness and symmetry obtained using six different measuring systems.Beam profile measurements were performed in standard water phantom set-up for two photon beams for various square field sizes and for five electron beams for several applicator sizes at several depths. Six measuring systems were used: three ionization chambers; a Semiflex (31002, PTW), a Markus (23343, PTW) and a Roos (34001, PTW); Two semiconductor detectors; a p-type diode (60008, PTW) and an e-type diode (60017, PTW) and a one dimensional Linear Array (LA48, PTW).Our results indicate that penumbra size determination is strongly dependent on the measuring system. For the photon measurements the diodes showed the narrowest penumbra followed by the LA48, while the largest penumbra was presented by the Semiflex. The unshielded diode overestimates the penumbra in large field sizes and big depths. The parallel plate ionization chambers overestimate the penumbra width of electron beam profiles. The LA48 presents the most symmetric beam profiles.Regarding penumbra size determination, the LA48 can be considered acceptable in terms of accuracy, and is the most time-effective system. It is also adequate for symmetry and flatness measurements. For greatest possible accuracy silicon diode is recommended. Parallel plate ionization chambers are not appropriate for penumbra measurements.

Background The cerebellum has a crucial role in mood regulation. While cerebellar grey matter (GM) alterations have been previously reported in bipolar disorder (BD), cerebro-cerebellar white matter (WM) connectivity alterations and cerebellar GM profiles have not been characterised in the context of predominant polarity (PP) and onset polarity (OP) subphenotypes of BD patients which is the aim of the present study. Methods Forty-two euthymic BD patients stratified for PP and OP and 42 healthy controls (HC) were included in this quantitative neuroimaging study to evaluate cerebellar GM patterns and cerebro-cerebellar WM connections. Diffusion tensor tractography was used to characterise afferent and efferent cerebro-cerebellar tract integrity. False discovery rate corrections were applied in post-hoc comparisons. Results BD patients exhibited higher fractional anisotropy (FA) in fronto-ponto-cerebellar tracts bilaterally compared to HC. Subphenotype-specific FA profiles were identified within the BD cohort. Regarding PP subgroups, we found FA changes in a) left contralateral fronto-ponto-cerebellar tract (depressive-PP > HC) and b) contralateral/ipsilateral fronto-ponto-cerebellar tracts bilaterally (manic-PP > HC). Regarding OP subgroups, we observed FA changes in a) left/right contralateral fronto-ponto-cerebellar tracts (depressive-OP > HC) and b) all fronto-ponto-cerebellar, most parieto-ponto-cerebellar and right contralateral occipito-ponto-cerebellar tracts (manic-OP>HC). In general, greater and more widespread cerebro-cerebellar changes were observed in manic-OP patients than in depressive-OP patients compared to HC. Manic-OP showed higher FA compared to depressive-OP patients in several afferent WM tracts. No GM differences were identified between BD and HC and across BD subgroups. Conclusions Our findings highlight fronto-ponto-cerebellar connectivity alterations in euthymic BD. Polarity-related subphenotypes have distinctive cerebro-cerebellar WM signatures with potential clinical and pathobiological implications.

This work provides characterization of system-related geometric distortions present in MRIs used in Gamma Knife (GK) stereotactic radiosurgery (SRS) treatment planning. A custom-made phantom, compatible with the Leksell stereotactic frame model G and encompassing 947 control points (CPs), was utilized. MR images were obtained with and without the frame, thus allowing discrimination of frame-induced distortions. In the absence of the frame and following compensation for field inhomogeneities, measured average CP disposition owing to gradient nonlinearities was 0.53 mm. In presence of the frame, contrarily, detected distortion was greatly increased (up to about 5 mm) in the vicinity of the frame base due to eddy currents induced in the closed loop of its aluminum material. Frame-related distortion was obliterated at approximately 90 mm from the frame base. Although the region with the maximum observed distortion may not lie within the GK treatable volume, the presence of the frame results in distortion of the order of 1.5 mm at a 7 cm distance from the center of the Leksell space. Additionally, severe distortions observed outside the treatable volume could possibly impinge on the delivery accuracy mainly by adversely affecting the registration process (e.g. the position of the lower part of the N-shaped fiducials used to define the stereotactic space may be miss-registered). Images acquired with a modified version of the frame developed by replacing its front side with an acrylic bar, thus interrupting the closed aluminum loop and reducing the induced eddy currents, were shown to benefit from relatively reduced distortion. System-related distortion was also identified in patient MR images. Using corresponding CT angiography images as a reference, an offset of 1.1 mm was detected for two vessels lying in close proximity to the frame base, while excellent spatial agreement was observed for a vessel far apart from the frame base.

This work focuses on MR-related sequence dependent geometric distortions, which are associated with B 0 inhomogeneity and patient-induced distortion (susceptibility differences and chemical shift effects), in MR images used in stereotactic radiosurgery (SRS) applications. Emphasis is put on characterizing distortion at target brain areas identified by gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) paramagnetic contrast agent uptake. A custom-made phantom for distortion detection was modified to accommodate two small cylindrical inserts, simulating small brain targets. The inserts were filled with Gd-DTPA solutions of various concentrations (0–20 mM). The phantom was scanned at 1.5 T unit using both the reversed read gradient polarity (to determine the overall distortion as reflected by the inserts centroid offset) and the field mapping (to determine B 0 inhomogeneity related distortion in the vicinity of the inserts) techniques. Post-Gd patient images involving a total of 10 brain metastases/targets were also studied using a similar methodology. For the specific imaging conditions, contrast agent presence was found to evidently affect phantom insert position, with centroid offset extending up to 0.068 mm mM−1 (0.208 ppm mM−1). The Gd-DTPA induced distortion in patient images was of the order of 0.5 mm for the MRI protocol used, in agreement with the phantom results. Total localization uncertainty of metastases-targets in patient images ranged from 0.35 mm to 0.87 mm, depending on target location, with an average value of 0.54 mm (2.24 ppm). This relative wide range of target localization uncertainty results from the fact that the B 0 inhomogeneity distortion vector in a specific location may add to or partly counterbalance Gd-DTPA induced distortion, thus increasing or decreasing, respectively, the total sequence dependent distortion. Although relatively small, the sequence dependent distortion in Gd-DTPA enhanced brain images can be easily taken into account for SRS treatment planning and target definition purposes by carefully inspecting both the forward and reversed polarity series.

To estimate (a) organ doses and organ-specific radiation-induced cancer risk from a single low-dose CT (LDCT) for lung cancer screening (LCS) and (b) the theoretical cumulative risk of radiation-induced cancer for a typical cohort to be subjected to repeated annual LCS LDCT. Sex- and body size-specific organ dose data from scan projection radiography (SPR) and helical CT exposures involved in LCS 256-slice LDCT were determined using Monte Carlo methods. Theoretical life attributable risk (LAR) of radiogenic cancer from a single 256-slice chest LDCT at age 55–80 years and the cumulative LAR of cancer from repeated annual LDCT studies up to age 80 years were estimated and compared to corresponding nominal lifetime intrinsic risks (LIRs) of being diagnosed with cancer. The effective dose from LCS 256-slice LDCT was estimated to be 0.71 mSv. SPR was found to contribute 6–12 % to the total effective dose from chest LDCT. The radiation-cancer LAR from a single LDCT study was found to increase the nominal LIR of cancer in average-size 55-year-old males and females by 0.008 % and 0.018 %, respectively. Cumulative radiogenic risk of cancer from repeated annual scans from the age of 55–80 years was found to increase the nominal LIR of cancer by 0.13 % in males and 0.30 % in females. Modern scanners may offer sub-millisievert LCS LDCT. Cumulative radiation risk from repeated annual 256-slice LDCT LCS examinations was found to minimally aggravate the lifetime intrinsic cancer risk of a typical screening population. • Effective dose from lung cancer screening low-dose CT may be

Considering the high incidence of depressive symptoms in Alzheimer’s disease (AD), we conducted a large-sample study to investigate the pattern of gray matter (GM) abnormalities that differentiates depressive from non-depressive AD patients. We included 201 AD patients who underwent MRI assessment and categorized them into depressive and non-depressive subgroups based on the Geriatric Depression Scale (GDS; cut-off score: ≤9). We performed whole-brain voxel-based morphometry analysis in 173 patients after MRI quality control and used between-group comparisons and regression analysis models to analyze the volumetric data controlling for nuisance variables. Depressive AD patients had extensive GM volume loss mainly in the paracentral region, specifically in post- and pre-central gyrus, supplementary motor areas and thalamus compared to non-depressive patients. Similar findings were obtained for the group of 173 patients using regression analysis and GDS score as predictor variable. We provided the first clear demonstration of a unique pattern of GM atrophy that characterizes AD patients with depression which is consistent with regions implicated in the phenomenon of psychomotor retardation that characterizes depression.

Microwave diathermy (MWD) is a therapeutic system that has been in use for some decades now in all physiotherapy settings, following the regulations of national facility establishments. The validity of diathermy devices is probably reduced as their working time increases, introducing the need for the device to be controlled/reset by qualified personnel in order to maintain its effectiveness in sessions and to accurately deliver the energy output that the physiotherapist asks for. However, while MWD has been a vital tool for practising physiotherapists, there is no clear evidence of a health burden due to incorrect usability. Additionally, due to the fact that physiotherapy rooms contain physiotherapeutic equipment it is observed that during the use of the diathermy device there is spatial heterogeneity in the interior space. In this work, the results are presented of the first national survey for quality control of MWD systems installed in physiotherapy rooms existing in urban and rural areas in Greece. Serious concerns about the technical status of the equipment as well as staff and patient safety, regarding the levels of non-ionising radiation emitted from MWD devices, are discussed. Additional evaluation is included of measurements in empty physiotherapy rooms while the MWD unit is transmitting at three different input powers (50 W/100 W/150 W-these are the therapeutic protocols used most frequently by physiotherapists) and in fully equipped physiotherapy rooms. Field strengths measured around MWDs normally working at different angles, distances and times compared to international limits revealed great spatial and time heterogeneity, raising serious concerns about the safety of occupational workers or other patients.

The purpose of this study was to use magnetoencephalography (MEG) to identify epileptic zones in patients with brain tumors before undergoing tumor surgery. The MEG data were recorded with a 122-channel biomagnetometer. Equivalent current dipoles (ECD) were calculated for epileptic spikes on MEG recordings according to the single dipole model. Eight patients (five males and three females) within the age range (43-73 years; mean ± SD = 55.12 ± 9.77) were examined by MEG before neurosurgery operation. Four patients had meningioma grade I, three had glioblastoma grade IV and one had astrocytoma grade II. All the patients showed ECD at their MEG's before surgical operation except a female one with meningioma who showed no ECD. Tumors observed in the frontal areas show posteriorly located ECD. We conclude that the MEG is a valuable clinical tool for the localization of epileptic foci in patients with brain tumors before surgical tumor operation.

Following the clinical introduction of the Elekta Unity MR-linac, there is an urgent need for development of dosimetry protocols and tools, not affected by the presence of a magnetic field. This work presents a benchmarking methodology comprising 2D/3D passive dosimetry and involving on-couch adaptive treatment planning, a unique step in MR-linac workflows. Two identical commercially available 3D-printed head phantoms (featuring realistic bone anatomy and MR/CT contrast) were employed. One phantom incorporated a film dosimetry insert, while the second was filled with polymer gel. Gel dose-response characteristics were evaluated under the Unity irradiation and read-out conditions, using vials and a cubic container filled with gel from the same batch. Treatment plan for the head phantoms involved a hypothetical large C-shape brain lesion, partly surrounding the brainstem. An IMRT step-and-shoot 7-beam plan was employed. Pre-treatment on-couch MR-images were acquired in order for the treatment planning system to calculate the virtual couch shifts and perform adaptive planning. Absolute 2D and relative 3D measurements were compared against calculations related to both adapted and original plans. Real-time dose accumulation monitoring in the gel-filled phantom was also performed. Results from the vials and cubic container suggest that gel dose-response is linear in the dose range investigated and signal integrity is mature at the read-out timings considered. Head phantom 2D and 3D measurements agreed well with calculations with 3D gamma index passing rates above 90% in all cases, even with the most stringent criteria used (2 mm/2%). By exploiting the 3D information provided by the gel, comparison also involved DVHs, dose-volume and plan quality metrics, which also reflected the agreement between adapted and delivered plans within ±4%. No considerable discrepancies were detected between adapted and original plans. A novel methodology was developed and implemented, suitable for QA procedures in Unity. TPS calculations were validated within the experimental uncertainties involved.

The aim of this study is to evaluate the effect of iDose(4) iterative reconstruction algorithm on radiation dose and imaging quality at chest-abdomen-pelvis (CAP) CT examinations. Seventeen patients were considered; all patients had a previous CT scan with the standard filter back-projection (FBP) protocol and a follow-up scan with the iDose(4) protocol at the same scanner. Image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were objectively calculated. Two radiologists evaluated noise, sharpness, contrast, diagnostic confidence and artefacts. Radiation exposure quantities were calculated. iDose(4) resulted in 46 % dose reduction combined with significantly lower noise and higher SNR and CNR compared with FBP. iDose(4) images had significantly lower subjective image noise and enhanced sharpness and contrast. Diagnostic confidence was high and image artefacts were minor for both algorithms. iDose(4) provides great potential for reducing patient radiation burden while improving imaging quality in CAP CT examinations.

Risk-benefit analysis of triple-rule-out 256-slice computed tomography angiography (TRO-CTA) requires data on associated cancer risks, currently not available. The aim of the current study was to provide estimates of patient radiation burden and lifetime attributable risk (LAR) of radiation-induced cancer in patients undergoing typical 256-slice TRO-CTA.Standard step-and-shoot 256-slice TRO-CTA exposures were simulated on 31 male and 31 female individual-specific voxelized phantoms using a Monte Carlo CT dosimetry software. Dose images were generated depicting the dose deposition on the exposed body region of the patient. Organ doses were obtained for all primarily irradiated radiosensitive organs. Organ doses were correlated to patient body size. TRO-CTA effective dose was estimated from (a) organ doses and (b) dose-length product data. Recently published sex-, age-, and organ-specific cancer risk factors were used to estimate the total LAR of radiation-induced cancer. The theoretical risks of radiation-induced cancer to the lung and breast following a 256-slice TRO-CTA were compared with the corresponding nominal risks for each of the studied patients.The highest organ doses were observed for the breast, heart, esophagus, and lung. Mean effective dose estimated using organ dose data was found to be 6.5 ± 1.0 mSv for female and 3.8 ± 0.7 mSv for male individuals subjected to 256-slice TRO-CTA. The associated mean LARs of cancer was found to be 41 per 10 female and 17 per 10 male patients. The total radiation-induced cancer risk was found to markedly decrease with patient age. TRO-CTA exposure was found to increase the intrinsic risks of developing lung or breast cancer during the remaining lifetime by less than 0.5% and 0.1%, respectively.The mean theoretical risk of radiation-induced cancer for a patient cohort subjected to step-and-shoot 256-slice TRO-CTA may be considered to be low compared with the intrinsic risk of developing cancer.

Purpose To evaluate the usefulness of a time-efficient MRI method for the quantitative determination of tissue iron in the liver and heart of β-thalassemic patients using spin-spin relaxation rate, R2, measurements. Materials and Methods Images were obtained at 1.5 T from aqueous Gd-DTPA solutions (0.106–8 mM) and from the liver and heart of 46 β-thalassemic patients and 10 controls. The imaging sequence used was a respiratory-triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin-echo (SE) pulse sequence (TR = 2000 msec, TEmin = 5 msec, echo spacing (ES) = 5 msec, matrix = 192 × 256, slice thickness = 10 mm). Liver iron concentration (LIC) measurements were obtained for 22 patients through biopsy specimens excised from the relevant liver segment. Biopsy specimens were also evaluated regarding iron grade and fibrosis. Serum ferritin (SF) measurements were obtained in all patients. Results A statistically significant difference was found between patients and healthy controls in mean liver (P < 0.004) and myocardium (P < 0.004) R2 values. The R2 values correlated well with Gd DTPA concentration (r = 0.996, P < 0.0001) and LIC (r = 0.874, P < 0.0001). A less significant relationship (r = 0.791, P < 0.0001) was found between LIC measurements and SF levels. R2 measurements appear to be significantly affected (P = 0.04) by different degrees of hepatic fibrosis. The patients' liver R2 values did not correlate with myocardial R2 values (r = 0.038, P < 0.21). Conclusion Tissue iron deposition in β-thalassemic patients may be adequately quantified using R2 measurements obtained with a 16-echo MRI sequence with short ES (5 msec), even in patients with a relatively increased iron burden. J. Magn. Reson. Imaging 2006. © 2005 Wiley-Liss, Inc.

Purpose. Coronary artery ectasia (CAE) is defined as a dilatation of an arterial segment to a diameter at least 1.5 times that of the adjacent artery. It is characterized by slow flow, predisposing to thrombosis. The TIMI frame count (TFC) technique has been successfully used for the assessment of coronary flow velocity using coronary angiograms (CA). Our aim was to compare TFC with magnetic resonance peak flow velocity (PFV) for the evaluation of the coronary flow in patients with CAE. Methods. Fifteen male patients with CAE, aged 45–60 yrs, and 15 age-matched male controls were studied by both techniques. Only patients without coronary obstructive disease were included. Magnetic resonance coronary angiography (MRA) was performed with a 1.5T scanner. The most ectatic part of the proximal 1/3 of the vessel involved was examined. Velocity-encoded MR images were acquired in a double oblique imaging plane, which was perpendicular to the same ectatic segment. The findings were compared with TFC results. Results. Ten patients had RCA ectasia and five LAD ectasia. In CAE patients, peak flow velocity was 10.7 ± 1.4 cm/sec in RCA and 11.4 ± 2.3 cm/sec in LAD. TFC was 42.9 ± 7.4 in RCA and 52.0 ± 20.1 in LAD. In controls, peak flow velocity was 18.1 ± 1.9 in RCA and 21.0 ± 1.7 cm/sec in LAD. TFC was 20.4 ± 1.59 in RCA and 19.8 ± 1.12 in LAD. Controls had significantly higher peak flow velocity (p < 0.001) and lower TFC (p < 0.001) in both RCA and LAD, compared to patients with CAE. In patients with CAE, there was a negative correlation between PFV and TFC measurements (r = 0.74, p < 0.001). Conclusion. Coronary flow in CAE patients can be assessed both by TFC and PFV. The noninvasive nature of PFV gives the opportunity for serial, easily repeatable, flow evaluation in these patients.

This work seeks to verify multi-shot clinical applications of stereotactic radiosurgery with a Leksell Gamma Knife model C unit employing a polymer gel-MRI based experimental procedure, which has already been shown to be capable of verifying the precision and accuracy of dose delivery in single-shot gamma knife applications. The treatment plan studied in the present work resembles a clinical treatment case of pituitary adenoma using four 8 mm and one 14 mm collimator helmet shots to deliver a prescription dose of 15 Gy to the 50% isodose line (30 Gy maximum dose). For the experimental dose verification of the treatment plan, the same criteria as those used in the clinical treatment planning evaluation were employed. These included comparison of measured and GammaPlan calculated data, in terms of percentage isodose contours on axial, coronal and sagittal planes, as well as 3D plan evaluation criteria such as dose-volume histograms for the target volume, target coverage and conformity indices. Measured percentage isodose contours compared favourably with calculated ones despite individual point fluctuations at low dose contours (e.g., 20%) mainly due to the effect of T2 measurement uncertainty on dose resolution. Dose-volume histogram data were also found in a good agreement while the experimental results for the percentage target coverage and conformity index were 94% and 1.17 relative to corresponding GammaPlan calculations of 96% and 1.12, respectively. Overall, polymer gel results verified the planned dose distribution within experimental uncertainties and uncertainty related to the digitization process of selected GammaPlan output data.

Objectives The purpose of this study was to compare the results of magnetic resonance angiography (MRA) with X-ray coronary angiography (XCA) in a pediatric population. Background Coronary artery abnormalities in Kawasaki disease (KD) develop in about 15% to 25% of young patients, mostly in the form of aneurysms. Methods Thirteen patients (12 male), age three to eight years, were studied. The maximal diameter and length of the aneurysm were recorded. Coronary MRA was performed using a 1.5 T Philips Intera CV magnetic resonance scanner with an electrocardiographically triggered pulse sequence. It was a three-dimensional segmented k-space gradient–echo sequence (TE = 2.1 ms, TR = 7.5 ms, flip angle = 30°, slice thickness = 1.5 mm) employing a T2-weighted preparation pre-pulse and a frequency selective fat-saturation pre-pulse. Data acquisition was performed in mid-diastole. All scans were carried out with the patient free breathing using a two-dimensional real-time navigator beam. All patients underwent XCA within a week. Results In six patients, aneurysms of the coronary arteries were identified, while coronary ectasia alone was present in the remaining seven patients. Magnetic resonance angiography and XCA diagnosis of coronary artery aneurysm agreed completely. Maximal aneurysm diameter and length and ectasia diameter by MRA and XCA were similar. No stenotic lesion was identified by either technique. Conclusions In conclusion, MRA is a reliable diagnostic tool, equivalent to XCA for coronary artery aneurysm identification in patients with KD. Magnetic resonance angiography may prove to be of great value for the serial non-invasive evaluation of these patients.

Coronary artery ectasia (CAE) is defined as a dilatation of an arterial segment to a diameter at least 1.5 times that of the adjacent normal artery. The correct follow-up of ectatic vessels is hampered by the need for repeat angiograms. In this work we compared quantitative coronary angiography (QCA) measurements of the diameter of the proximal most ectatic part of coronary vessels, with corresponding measurements obtained by magnetic resonance angiography (MRA) using both gradient echo and turbo spin echo imaging sequences. Fifteen patients (14 male), aged 45-65 years, with known CAE were prospectively studied. Two electrocardiogram (ECG)-triggered pulse sequences were implemented for coronary magnetic resonance angiography. The first was a three-dimensional (3D), segmented, k-space gradient-echo sequence, employing a T2-weighted preparation prepulse and a frequency-selective, fat-saturation prepulse to enhance "white blood" (WB) contrast of the coronary arteries. The second sequence was an M2D dual Inversion Recovery (IR) Turbo Spin-Echo with a linear k-space acquisition scheme, providing "black-blood" (BB) contrast of the coronaries. All scans were carried out with the patient free breathing using a 2D, real-time Navigator beam, for respiratory motion tracking and gating. All patients underwent QCA, and the diameter of the proximal most ectatic part of each vessel was measured and compared with "white-blood" and "black-blood" MRA measurements. The average length of continuously visualized LM, LAD, LCx, and RCA by MRA was 2.5 +/- 0.3, 5.8 +/- 0.8, 3.9 +/- 1.0, and 7.2 +/- 1.2 cm, respectively. There were no statistically significant differences between diameter measurements of the proximal most ectatic part of each vessel, obtained with WB and BB sequences. There was a close correlation between MRA and QCA measurements (r = 0.87, p < 0.001). Bland-Altman analysis showed no systematic differences between the examined methods, over the whole range of vessel diameters measured. Coronary MRA is in close correlation with QCA for CAE detection. Magnetic resonance angiography, being noninvasive, may prove of significant value for the efficient follow-up of these patients.

In cine cardiac magnetic resonance imaging (MRI) studies, for any preset imaging parameters the number of phases per cardiac cycle for a single slice is proportional to breath-hold duration. We investigated the relationship between the accuracy of measurement of left ventricular (LV) end-diastolic and end-systolic volumes (EDV and ESV, respectively), mass and ejection fraction (EF), and the number of phases acquired per cardiac cycle. Twelve adult volunteers underwent cardiac MRI and five complete LV functional studies were obtained with 8, 11, 14, 17, and 20 phases per cardiac cycle. We calculated LV volumes, EF, and mass for each acquisition, and compared them using the 20-phase acquisition as the reference standard. The scan duration was proportional to the number of phases acquired. There was a systematic underestimation of LV, EDV, and EF, with decreasing number of phases. Differences from the reference standard became significant for the 8-phase acquisition (p0.05). Subgroup analysis showed that only those with slower heart rates (65/min) had significant differences in EDV, but not in EF, for the 8-phase acquisition. For those with faster heart rates, no differences were detected between the different acquisitions. There were no significant differences between all acquisitions for the LV ESV and mass. We conclude that at least 11 phases per cardiac cycle are needed to maintain accuracy for cine cardiac MRI studies. Decreasing the number of phases per cardiac cycle beyond this cutoff may introduce significant error of measurement, particularly for the left ventricular EDV and EF and especially for those with bradycardia, and should be avoided.

VIPAR polymergels and 3D MRI techniques were evaluated for their ability to provide experimental verification of 3D dose distributions in a simulation of a 192 Ir prostate monotherapy clinical application. A real clinical treatment plan was utilized, generated by post-irradiation, CT based calculations derived from Plato™ BPS and Swift™ treatment planning systems. The simulated treatment plan involved the use of 10 catheters and 39 source positions within a glass vessel of appropriate dimensions, homogeneously filled with the VIPAR gel. 3D high resolution MR scanning of the gel produced T2 relaxation time maps, from which 3D dose distributions were derived via an appropriate calibration procedure. Results were compared to corresponding dose distributions obtained from the Plato and Swift treatment planning systems. Quantitative comparison, on a point by point basis, was based on user adopted acceptance criteria of 5% dose-difference and 3 mm distance-to-agreement. Significant deviations between experimental and calculated dose distributions were found for doses lower than 50% due to the reduced dose resolution of the method in the low dose, low dose gradient region. Measurement errors were observed at 1.0–1.5 mm around each catheter due to MR imaging susceptibility artifacts. For most remaining points the acceptance criteria were fulfilled. Systematic offsets of the order of 1–2 mm, observed between measured and corresponding calculated isocontours at specific segments, are attributed to the 1 mm uncertainty in catheter reconstruction and 1 mm uncertainty in the alignment of the MR and CTimaging planes.

In this work, three-dimensional (3-D) MRI techniques are employed in N-Vinylpyrrolidone-Argon-(VIPAR-) based polymer gel dosimetry. VIPAR gels were irradiated using a Nucletron microSelection 192Ir HDR brachytherapy remote afterloading system with single source dwell position and intravascular brachytherapy irradiation protocols. A single VIPAR gel and a single irradiation are adequate to obtain the full calibration curve needed. The 3-D dose distributions obtained with the 3-D MRI method were found to be in good agreement with the corresponding Monte Carlo calculations, for brachytherapy and intravascular irradiations. The method allows the reconstruction of isodose contours over any plane, with increased spatial resolution and accuracy following a single MR acquisition. VIPAR gel measurements using a 3-D MRI readout technique can be of particular use in the experimental dosimetry of brachytherapy sources, as well as for dose verification purposes when complex irradiation regimes and three-dimensional dose gradients are investigated.

The purpose of this study was to evaluate radiation dose reduction in coronary computerised tomography angiography (CCTA), using a commercially available iterative reconstruction (IR) algorithm as well as the behaviour of the image noise.A total cohort of 47 patients underwent CCTA examination on a 64-slice multi-detector CT. They were divided into four groups according to the time when the examination was performed (before or after the installation of iDose) and the acquisition protocol followed (prospective or retrospective electrocardiography-ECG gated). The images acquired with reduced dose settings were reconstructed using two levels (L4 and L6) of the iDose4 algorithm. Image noise was measured in all cases.In retrospective acquisition, images acquired with a 46% lower radiation dose and reconstructed with iDose4 L6 provided noise comparable to that in the full-dose filtered back-projection images. For the prospective acquisition mode, a slight decrease (26%) in radiation dose resulted in noise improvement in low-dose images reconstructed with iDose4 L4 (16% noise removal) and L6 (30% noise removal).The fact that image quality is improved while radiation exposure is reduced indicates that there is room for a further reduction in exposure settings. Additionally, the combination of iDose4 with prospective acquisition is able to significantly reduce the radiation dose associated with CCTA at values of about 2 mSv and even lower.

Purpose To propose, verify, and implement a simple and efficient methodology for the improvement of total geometric accuracy in multiple brain metastases gamma knife (GK) radiation surgery. Methods and Materials The proposed methodology exploits the directional dependence of magnetic resonance imaging (MRI)-related spatial distortions stemming from background field inhomogeneities, also known as sequence-dependent distortions, with respect to the read-gradient polarity during MRI acquisition. First, an extra MRI pulse sequence is acquired with the same imaging parameters as those used for routine patient imaging, aside from a reversal in the read-gradient polarity. Then, “average” image data are compounded from data acquired from the 2 MRI sequences and are used for treatment planning purposes. The method was applied and verified in a polymer gel phantom irradiated with multiple shots in an extended region of the GK stereotactic space. Its clinical impact in dose delivery accuracy was assessed in 15 patients with a total of 96 relatively small ( Results Phantom study results showed that use of average MR images eliminates the effect of sequence-dependent distortions, leading to a total spatial uncertainty of less than 0.3 mm, attributed mainly to gradient nonlinearities. In brain metastases patients, non-eliminated sequence-dependent distortions lead to target localization uncertainties of up to 1.3 mm (mean: 0.51 ± 0.37 mm) with respect to the corresponding target locations in the “average” MRI series. Due to these uncertainties, a considerable underdosage (5%-32% of the prescription dose) was found in 33% of the studied targets. Conclusions The proposed methodology is simple and straightforward in its implementation. Regarding multiple brain metastases applications, the suggested approach may substantially improve total GK dose delivery accuracy in smaller, outlying targets.

One aim of the current study was to determine normalized dose data for maternal radiosensitive organs and embryo/fetus from 256-slice CT pulmonary angiography (CTPA) performed on pregnant patients suspected of having pulmonary embolism. A second aim was to provide reliable maternal and fetal doses and associated radiation cancer risk estimates from 256-slice CTPA and lung perfusion scintigraphy (LPS) for comparison. Methods: Mathematic anthropomorphic phantoms were generated to simulate the average woman at early pregnancy and at the third, sixth, and ninth months of gestation. In each phantom, 0–3 additional 1.5-cm-thick fat tissue layers were added to derive 4 phantoms representing pregnant women with different body sizes. Monte Carlo methods were used to simulate low-dose 256-slice CTPA exposures on each of the 16 generated phantoms. Normalized organ and embryo/fetal dose data were derived for exposures at 80, 100, and 120 kV. Maternal effective dose and embryo/fetal dose from 256-slice CTPA and associated lifetime attributable risks of radiation cancer were determined for different body sizes and gestational stages and compared with corresponding data from LPS. Results: For an average-sized pregnant patient at the first trimester, the 256-slice CTPA exposure resulted in a maternal effective dose of 1 mSv and an embryo/fetal dose of 0.05 mGy. However, maternal effective dose considerably increased with body size, whereas embryo/fetal dose increased with both body size and gestational stage. Compared with LPS, low-dose CTPA to an average-sized pregnant patient resulted in a 30% higher maternal effective dose but a 3.4–6 times lower embryo/fetal dose. Nevertheless, LPS was associated with less aggregated radiation risk for an average-sized pregnant patient, with the difference from CTPA being increased further for larger patients. Conclusion: Compared with CTPA performed with a modern wide-area CT scanner, LPS remains comparatively more dose-efficient.

In this work the extent of the linear dose response and the dynamic dose range of N-vinylpyrrolidone-argon based (VIPAR) polymer gels were investigated. VIPAR gels were irradiated using a 6 MV linear accelerator up to 60 Gy and a Nucletron microSelectron 192Ir HDR brachytherapy source to much higher doses to cover a dose range of two orders of magnitude. They were then MR scanned at 1.5 T to obtain T2-maps. VIPAR gel measurements obtained from the two irradiation regimes were calibrated against ion chamber measurements and dose calculations derived using the AAPM TG-43 protocol respectively. A satisfying agreement between the calibration results derived using the 6 MV x-rays and the 192Ir source was found for doses up to 60 Gy, implying that the response of the VIPAR gels is independent of photon energy and dose rate. A linear R2 dose response up to approximately 40 Gy and a dynamic dose range up to at least approximately 250 Gy were observed. VIPAR gel dose measurements derived using the monoexponentially fitted brachytherapy calibration data were found to be quite accurate.

Magnetoencephalography (MEG) recordings were evaluated for 25 healthy female volunteers, in five different gustatory states: normal, sweet, bitter, sour and salty. The study population was divided in two groups according to age: group A (10-19 years old) and group B (20-30 years old). There was a higher count of low frequencies (2 Hz) and a lower count of high frequencies (7 Hz) with increasing age, in all studied states. We compared each state for the frequencies of 2 Hz and 7 Hz between the two groups. Statistically significant differences were found in the normal and sweet states for the frequencies of 2 Hz and 7 Hz and in the salty taste in the frequency of 7 Hz. We also intra-compared the five states in group A and the five states in group B for the 2 Hz and 7 Hz frequencies. The results were not statistically significant. A differentiation in the distribution of the frequencies with increasing age may provide new insights into the age-dependence of taste quality brain centers.

Background This study provides data on the cumulative life attributable risk (LAR) of radiation-induced cancer from the combination of coronary CT angiography (CCTA), dynamic CT perfusion (CTP) and delayed enhancement (DE) CT scans, required for reliable risk–benefit analysis of the one-stop-shop CCTA+CTP+DECT cardiac examination. Methods Monte Carlo simulation of the dynamic CTP and DECT exposures on 62 adult individuals was employed to determine radiation absorbed dose to exposed radiosensitive organs. Corresponding data for CCTA were derived using patient chest circumference and previously published data. Individual-specific LARs of cancer were estimated using organ/tissue-specific radiogenic cancer risk factors. Total LAR from CCTA+CTP+DECT scans' sequence were estimated and compared to nominal intrinsic risk of cancer. Results The main contribution, up to 80%, to cumulative radiation burden from CCTA+CTP+DECT scan-sequence was found to originate from the CTP scan. The total LAR from CCTA+CTP+DECT for females was found 4–6 times higher, compared to males. The mean cumulative risk of radiogenic cancer associated with the complete CCTA+CTP+DECT scan sequence was found to marginally increase the intrinsic risk for cancer induction by less than 0.6% and 0.1% for females and males, respectively. Conclusions The radiation risk from the 256-slice CCTA+CTP+DECT scan sequence may be considered low and should not constitute an obstacle for the clinical endorsement of the one-stop-shop cardiac CT examination, given that its clinical value has been well verified. Nevertheless, every effort should be made towards optimization of the dynamic CTP component which is the main contributor to patient radiation burden.

Performing minimally invasive interventions under direct MRI guidance offers significant advantages. Required accessibility to the patient inside the MRI scanner is fairly limited, and employment of robotic assistance has been proposed. The development of MR-compatible robotic systems entails engineering challenges related to geometric constraints and the magnetic nature of the scanning environment.A novel, general-purpose, MR-compatible robotic manipulation system has been developed for the performance of minimally invasive interventions inside a cylindrical scanner under direct MRI guidance. The system is endowed with five degrees of freedom (DOF), is characterized by a unique kinematics structure and is manually actuated.The prototype system was shown to exhibit the required MR-compatibility characteristics and a task-space positioning ability of approximately 5 mm. Needle targeting testing demonstrated a 93% success rate in acquiring a 5 mm spherical target. Phantom testing was performed inside a 3 T scanner and results are reported for an experimental study simulating MRI-guided, manipulator-assisted, MR arthrography.Robotic assistance provided by the developed manipulator may effectively facilitate the performance of various MRI-guided, minimally invasive interventions inside a cylindrical scanner.

To determine patient-specific absorbed peak doses to skin, eye lens, brain parenchyma, and cranial red bone marrow (RBM) of adult individuals subjected to low-dose brain perfusion CT studies on a 256-slice CT scanner, and investigate the effect of patient head size∕shape, head position during the examination and bowtie filter used on peak tissue doses.The peak doses to eye lens, skin, brain, and RBM were measured in 106 individual-specific adult head phantoms subjected to the standard low-dose brain perfusion CT on a 256-slice CT scanner using a novel Monte Carlo simulation software dedicated for patient CT dosimetry. Peak tissue doses were compared to corresponding thresholds for induction of cataract, erythema, cerebrovascular disease, and depression of hematopoiesis, respectively. The effects of patient head size∕shape, head position during acquisition and bowtie filter used on resulting peak patient tissue doses were investigated. The effect of eye-lens position in the scanned head region was also investigated. The effect of miscentering and use of narrow bowtie filter on image quality was assessed.The mean peak doses to eye lens, skin, brain, and RBM were found to be 124, 120, 95, and 163 mGy, respectively. The effect of patient head size and shape on peak tissue doses was found to be minimal since maximum differences were less than 7%. Patient head miscentering and bowtie filter selection were found to have a considerable effect on peak tissue doses. The peak eye-lens dose saving achieved by elevating head by 4 cm with respect to isocenter and using a narrow wedge filter was found to approach 50%. When the eye lies outside of the primarily irradiated head region, the dose to eye lens was found to drop to less than 20% of the corresponding dose measured when the eye lens was located in the middle of the x-ray beam. Positioning head phantom off-isocenter by 4 cm and employing a narrow wedge filter results in a moderate reduction of signal-to-noise ratio mainly to the peripheral region of the phantom.Despite typical peak doses to skin, eye lens, brain, and RBM from the standard low-dose brain perfusion 256-slice CT protocol are well below the corresponding thresholds for the induction of erythema, cataract, cerebrovascular disease, and depression of hematopoiesis, respectively, every effort should be made toward optimization of the procedure and minimization of dose received by these tissues. The current study provides evidence that the use of the narrower bowtie filter available may considerably reduce peak absorbed dose to all above radiosensitive tissues with minimal deterioration in image quality. Considerable reduction in peak eye-lens dose may also be achieved by positioning patient head center a few centimeters above isocenter during the exposure.

The aim of this study was to determine the radiation burden and the lifetime attributable risk (LAR) of radiation-induced cancer in patients undergoing screening 256-slice computed tomography colonography (CTC) and compare CTC-related radiogenic risks to corresponding nominal lifetime intrinsic risk of cancer.A Monte Carlo simulation software dedicated for computed tomography (CT) dosimetry was used to determine absorbed doses to primarily exposed radiosensitive organs of 31 women and 29 men subjected to screening CTC on a 256-slice CT scanner. Effective dose was estimated from (a) organ dose data and (b) dose-length product. Organ-specific and total LARs of cancer were estimated using published risk factors. Cumulative LARs from repeated CTC studies on individuals participating in a colorectal cancer screening program were compared with corresponding lifetime intrinsic risks.The mean organ dose-derived effective dose was estimated to be 2.92 and 2.61 mSv for female and male individuals, respectively. The dose-length product method was found to overestimate effective dose from CTC by 26% and 13% in female and male individuals, respectively. Compared with previously published results for 64-slice CT scanners, 256-slice CTC was found to be associated with up to 45% less radiation burden. The cumulative LAR of radiation-induced cancer from repeated quinquennial screening CTC studies between the ages of 50 and 80 years was estimated to increase the lifetime intrinsic risk of cancer by less than 0.2%.The level of patient radiation burden and theoretical radiogenic cancer risks associated with screening CTC performed using modern low-dose protocols and techniques may not justify disapproval of CTC as a mass screening tool.

Background— Available data on the radiation burden from coronary computed tomography (CT) angiography (CCTA) are mostly limited to effective dose estimates. This study provides individualized estimates of doses and associated life attributable risks of radiation-induced cancer in a clinical patient population undergoing 256-slice CCTA. Methods and Results— Typical retrospectively and prospectively ECG-gated CCTA exposures in a 256-slice CT scanner were simulated on 52 patient-specific voxelized phantoms. Dose images depicting the dose deposition on the exposed region were generated, and normalized organ doses for all primarily irradiated radiosensitive organs were derived and correlated to patient body habitus. Lung, breast, and esophagus absorbed doses were then determined in 136 consecutive patients subjected to CCTA. Projected life attributable risks of radiation-induced cancer were estimated through the use of appropriate sex-, age- and organ-specific cancer risk factors and compared with corresponding nominal cancer risks. The total projected life attributable risk of radiogenic cancer after CCTA decreases steeply with age at exposure, and lung cancer constitutes the most probable detriment for both sexes. The relative risks of lung cancer associated with prospectively ECG-gated CCTA were 1.0032 and 1.0008 for women and men, respectively. The mean total projected life attributable risks were estimated to be 24.9±7.4 and 71.5±30.0 per 100 000 women undergoing prospectively and retrospectively ECG-gated CCTA, respectively. The corresponding values for men were 7.3±1.3 and 31.4±5.0 per 100 000 patients. Conclusions— The mean projected life attributable risks of radiation-induced cancer in a typical clinical patient cohort undergoing standard prospectively ECG-gated CCTA with a 256-slice scanner were found to inconsequentially increase the natural cancer incidence rates.

Computed tomography (CT) coronary angiography has been widely used since the introduction of 64-slice scanners and dual-source CT technology, but high radiation doses have been reported. Prospective ECG-gating using a 'step-and-shoot' axial scanning protocol has been shown to reduce radiation exposure effectively while maintaining diagnostic accuracy. 256-slice scanners with 80 mm detector coverage have been currently introduced into practice, but their impact on radiation exposure has not been adequately studied. The aim of this study was to assess radiation doses associated with CT coronary angiography using a 256-slice CT scanner. Radiation doses were estimated for 25 patients scanned with either prospective or retrospective ECG-gating. Image quality was assessed objectively in terms of mean CT attenuation at selected regions of interest on axial coronary images and subjectively by coronary segment quality scoring. It was found that radiation doses associated with prospective ECG-gating were significantly lower than retrospective ECG-gating (3.2 +/- 0.6 mSv versus 13.4 +/- 2.7 mSv). Consequently, the radiogenic fatal cancer risk for the patient is much lower with prospective gating (0.0176% versus 0.0737%). No statistically significant differences in image quality were observed between the two scanning protocols for both objective and subjective quality assessments. Therefore, prospective ECG-gating using a 'step-and-shoot' protocol that covers the cardiac anatomy in two axial acquisitions effectively reduces radiation doses in 256-slice CT coronary angiography without compromising image quality.

Statement of problem There is a need for achieving reliable chemical bond strength between veneering composites resins and casting alloys through the use of simplified procedures. Purpose The purpose of this study was to examine the shear bond strength of an indirect composite resin to a Ni-Cr alloy, using 4 primers and 2 airborne-particle-abrasion procedures. Material and methods Fifty-six Ni-Cr (Heraenium NA) discs, 10 mm in diameter and 1.5 mm in height, were fabricated. Twenty-four discs were airborne-particle abraded with 50-μm Al2O3 particles, while another 24 were airborne-particle abraded with 250-μm Al2O3 particles. The following primers were applied on 6 discs of each airborne-particle-abrasion treatment group: Solidex Metal Photo Primer (MPP50, MPP250), Metal Primer II (MPII50, MPII250), SR Link (SRL50, SRL250), and Tender Bond (TB50, TB250). The Rocatec system was used on another 6 discs, airborne-particle abraded according to the manufacturer's recommendations, which served as the control group (R). Two more discs were airborne-particle abraded with 50-μm and 250-μm Al2O3 particles, respectively, to determine the Al content on their surfaces, without any bonding procedure. The indirect composite resin used was Sinfony. Specimens were thermally cycled (5°C and 55°C, 30-second dwell time, 5000 cycles) and tested in shear mode in a universal testing machine. The failure mode was determined with an optical microscope, and selected specimens were subjected to energy dispersive spectroscopy (EDS). Mean bond strength values were analyzed using 2-way ANOVA followed by Tukey's multiple comparison tests (α=.05) and compared to the control group using 1-way ANOVA followed by Tukey's multiple comparison tests (α=.05). Results The groups abraded with 50-μm particles exhibited significantly higher bond strength compared to the groups abraded with 250-μm particles. Group MPII50 exhibited the highest mean value (17.4 ±2 MPa). Groups MPP50, MPP250, and TB50, TB250 showed adhesive failures and significantly lower bond strength compared to group R. Groups MPII50, MPII250, and SRL50, SRL250 showed combination failures and no significant difference compared with group R. EDS revealed interfacial rather than adhesive failures. Conclusions Airborne-particle abrasion with 50-μm Al 2 O 3 particles may result in improved bond strength, independent of the primer used. The bond strength of Metal Primer II and SR Link specimens was comparable to that of specimens treated with Rocatec. (J Prosthet Dent 2008;99:377-387)

Composite veneering materials are used as alternatives to porcelain in fixed prosthodontics. Mechanical retention of the resin on the metal framework has been associated with the formation of gaps at the resin/alloy interface, and failure of the restoration. Several chemical bonding systems have been introduced to promote resin adhesion. The purpose of the present study was to evaluate the shear bond strength of three photocured composites (Artglass, Solidex & Signum+) to a Ni-Cr alloy.72 wax disks covered with 150-mum diameter beads were cast and divided in two equal groups. In the first group, Metal Photo Primer was applied on the casting surface, while the Siloc system was used in the second. Each group was divided in three subgroups of 12 samples, in which the three composites were photocured. Half of the specimens of each subgroup were subjected to 1000 and 5000 thermal cycles (5 and 55 degrees C) respectively. All specimens were tested in shear in a universal testing machine. The Siloc-Solidex group showed the highest bond strength (17.3 +/- 3.7 MPa). No statistically significant difference was found between specimens treated with Metal Photo Primer or Siloc. Thermocycling did not significantly affect the bond strength values. Solidex showed an adhesive failure mode for both alloy surface treatments, while Artglass and Signum+ exhibited combination failures. Conclusively, the appropriate alloy surface treatment - resin combination can significantly improve the resin-alloy shear bond strength. Specifically, Solidex resin exhibited significantly higher bond values compared with Artglass and Signum+, for both surface treatments and thermocycling procedures.

We evaluated the ability of magnetic resonance imaging to perform a noninvasive assessment of coronary arteries, function and viability in one examination in a population with Kawasaki disease.Magnetic resonance angiography (MRA) can identify coronary abnormalities in patients with Kawasaki disease (KD). Contrast enhanced cardiovascular magnetic resonance (CeCMR) is the current gold standard for scar detection. Steady-state, free precession (SSFP) cine is a reliable technique to evaluate myocardial function and wall motion.Twenty patients with KD aged 7-12 yrs, were examined. Coronary MRA was performed using a 1.5 T system with two ECG-triggered pulse sequences. CeCMR images were acquired 15 minutes after the i.v. injection of 0.1 mmol/kg Gd-DTPA using an inversion recovery sequence. SSFP cines were acquired using 6-mm short-axis slices from the atrioventricular ring to the apex.Aneurysms of the coronary arteries were identified in 7 patients and coronary ectasia was present in the remaining 12 patients while 1 patient had both. Transmural anterior-apical scar was detected by ceCMR in two cases, while small inferior necrosis was identified in another 2 cases. Left ventricular function was deteriorated only in the two patients with antero-apical infarction. The presence of myocardial infarction was detected in the territory supplied by the involved coronary artery.In Kawasaki disease MRA, SSFP cine and ceCMR are able to perform noninvasive coronary artery evaluation, function and infarct detection in a single study.

In view of the need for dose-validation procedures on each individual intensity-modulated radiation therapy (IMRT) plan, dose-verification measurements by film, by ionization chamber, and by polymer gel-MRI dosimetry were performed for a prostate-treatment plan configuration. Treatment planning system (TPS) calculations were evaluated against dose measurements.Intensity-modulated radiation therapy (IMRT) treatments were planned on a commercial TPS. Kodak EDR-2 films were used for the verification of two-dimensional (2D) dose distributions at 1 coronal and 5 axial planes in a water-equivalent phantom. Full three-dimensional (3D) dose distributions were measured by use of a novel polymer gel formulation and a 3D magnetic resonance imaging (MRI) readout technique. Calculations were compared against measurements by means of isocontour maps, gamma-index maps (3% dose difference, 3-mm distance to agreement) and dose-volume histograms.A good agreement was found between film measurements and TPS predictions for points within the 60% isocontour, for all the examined plans (gamma-index1 for 96% of pixels). Three-dimensional dose distributions obtained with the polymer gel-MRI method were adequately matched with corresponding TPS calculations, for measurements in a gel phantom covering the planning-target volume (PTV).Measured 2D and 3D dose distributions suggest that, for the investigated prostate IMRT plan configuration, TPS calculations provide clinically acceptable accuracy.

In this work, the utilization of polymer gel-MRI dosimetry for measurements at distances relevant to clinical brachytherapy and intravascular applications [i.e., in the mm range, where steep three-dimensional (3-D) dose gradients exist] is investigated using N-vinylpyrrolidone-based gels. Transverse axis radial dose distributions, dose distributions parallel to the source axis, and 2-D dose distributions around the commonly used microSelectron 192Ir HDR source are measured for single source dwell position irradiations. Experimental results are found in good agreement with verified Monte Carlo calculations, even for distances less than 3 mm from the source. The effect of various MRI parameters, such as slice thickness, slice mispositioning, and in-plane resolution, on the accuracy of the method is also investigated. Possible limitations of the method are discussed, and its' overall potential in brachytherapy dosimetry is evaluated. Experimental 2-D dose distributions for an intravascular application following the Paris irradiation protocol are compared to corresponding commercial treatment planning system calculations. Results suggest that polymer gel-MRI dosimetry is capable of experimentally verifying dose distributions in relevant clinical intravascular applications.

Proton-electron double-resonance imaging (PEDRI) was used to assess renal function by monitoring the flow of the exogenous nitroxide free radical proxyl carboxylic acid (PCA) through normal and injured kidneys in the living rat. Kidney damage was induced by treatment with 2-bromoethylamine (BEA), which provides a well established model for human analgesic nephropathy. PCA clearance rates for liver, abdominal blood vessels, and renal tissues were determined from serial PEDRI images of normal rats (n = 6) and rats treated with BEA (n = 21). Different groups of BEA-treated animals were imaged on day 4 (n = 6), day 6 (n = 6), and day 9 (n = 9) after treatment. In BEA-treated rats, there was an increase in PCA half-life in all tissues studied. This increase was greatest in the kidney tissues and the effect progressed with time after treatment. The effect is probably due to BEA-induced damage to the tubules in the renal cortex and may not be related to the primary lesions in the renal medulla.