Characterization of breast calcification types using dual energy x-ray method.

Calcifications are products of mineralization whose presence is usually associated with pathological conditions. The minerals mostly seen in several diseases are calcium oxalate (CaC2O4), calcium carbonate (CaCO3) and hydroxyapatite (HAp). Up to date, there is no in vivo method that could discriminate between minerals. To this aim, a dual energy x-ray method was developed in the present study. An analytical model was implemented for the determination of the Calcium/Phosphorus mass ratio ([Formula: see text]). The simulation was carried out using monoenergetic and polyenergetic x-rays and various calcification thicknesses (100-1000 [Formula: see text]) and types (CaC2O4, CaCO3, HAp). The experimental evaluation of the method was performed using the optimized irradiation conditions obtained from the simulation study. X-ray tubes, combined with energy dispersive and energy integrating (imaging) detectors, were used for the determination of the [Formula: see text] in phantoms of different mineral types and thicknesses. Based on the results of the experimental procedure, statistical significant difference was observed between the different types of minerals when calcification thicknesses were 300 [Formula: see text] or higher.

Polynomial dual energy inverse functions for bone Calcium/Phosphorus ratio determination and experimental evaluation.

An X-ray dual energy (XRDE) method was examined, using polynomial nonlinear approximation of inverse functions for the determination of the bone Calcium-to-Phosphorus (Ca/P) mass ratio. Inverse fitting functions with the least-squares estimation were used, to determine calcium and phosphate thicknesses. The method was verified by measuring test bone phantoms with a dedicated dual energy system and compared with previously published dual energy data. The accuracy in the determination of the calcium and phosphate thicknesses improved with the polynomial nonlinear inverse function method, introduced in this work, (ranged from 1.4% to 6.2%), compared to the corresponding linear inverse function method (ranged from 1.4% to 19.5%).

Dual Energy Method for Breast Imaging: A Simulation Study.

Dual energy methods can suppress the contrast between adipose and glandular tissues in the breast and therefore enhance the visibility of calcifications. In this study, a dual energy method based on analytical modeling was developed for the detection of minimum microcalcification thickness. To this aim, a modified radiographic X-ray unit was considered, in order to overcome the limited kVp range of mammographic units used in previous DE studies, combined with a high resolution CMOS sensor (pixel size of 22.5 µm) for improved resolution. Various filter materials were examined based on their K-absorption edge. Hydroxyapatite (HAp) was used to simulate microcalcifications. The contrast to noise ratio (CNR tc ) of the subtracted images was calculated for both monoenergetic and polyenergetic X-ray beams. The optimum monoenergetic pair was 23/58 keV for the low and high energy, respectively, resulting in a minimum detectable microcalcification thickness of 100 µm. In the polyenergetic X-ray study, the optimal spectral combination was 40/70 kVp filtered with 100 µm cadmium and 1000 µm copper, respectively. In this case, the minimum detectable microcalcification thickness was 150 µm. The proposed dual energy method provides improved microcalcification detectability in breast imaging with mean glandular dose values within acceptable levels.

Bone calcium/phosphorus ratio determination using dual energy X-ray method.

Non-invasive dual energy methods have been used extensively on osteoporosis diagnosis estimating parameters, such as, Bone Mineral Density (BMD) and Bone Mineral Content (BMC). In this study, an X-ray dual energy method (XRDE) was developed for the estimation of the bone Calcium-to-Phosphorous (Ca/P) mass ratio, as a bone quality index. The optimized irradiation parameters were assessed by performing analytical model simulations. X-ray tube output, filter material and thickness were used as input parameters. A single exposure technique, combined with K-edge filtering, was applied. The optimal X-ray spectra were selected according to the resulted precision and accuracy values. Experimental evaluation was performed on an XRDE system incorporating a Cadmium Telluride (CdTe) photon counting detector and three bone phantoms with different nominal mass Ca/P ratios. Additionally, the phantoms' mass Ca/P ratios were validated with energy-dispersive X-ray spectroscopy (EDX). Simulation results showed that the optimum filter atomic number (Z) ranges between 57 and 70. The optimum spectrum was obtained at 100 kVp, filtered with Cerium (Ce), with a surface density of 0.88 g/cm(2). All Ca/P ratio measurements were found to be accurate to within 1.6% of the nominal values, while the precision ranged between 0.91 and 1.37%. The accuracy and precision values of the proposed non-invasive method contributes to the assessment of the bone quality state through the mass Ca/P ratio determination.

Patient-specific dosimetry in peptide receptor radionuclide therapy: a clinical review.

Neuroendocrine tumours (NETs) belong to a relatively rare class of neoplasms. Nonetheless, their prevalence has increased significantly during the last decades. Peptide receptor radionuclide therapy (PRRT) is a relatively new treatment approach for inoperable or metastasised NETs. The therapeutic effect is based on the binding of radiolabelled somatostatin analogue peptides with NETs' somatostatin receptors, resulting in internal irradiation of tumours. Pre-therapeutic patient-specific dosimetry is essential to ensure that a treatment course has high levels of safety and efficacy. This paper reviews the methods applied for PRRT dosimetry, as well as the dosimetric results presented in the literature. Focus is given on data concerning the therapeutic somatostatin analogue radiopeptides (111)In-[DTPA(0),D-Phe(1)]-octreotide ((111)In-DTPA-octreotide), (90)Y-[DOTA(0),Tyr(3)]-octreotide ((90)Y-DOTATOC) and (177)Lu-[DOTA(0),Tyr(3),Thr(8)]-octreotide ((177)Lu-DOTATATE). Following the Medical Internal Radiation Dose (MIRD) Committee formalism, dosimetric analysis demonstrates large interpatient variability in tumour and organ uptake, with kidneys and bone marrow being the critical organs. The results are dependent on the image acquisition and processing protocol, as well as the dosimetric imaging radiopharmaceutical.

A meshless point collocation treatment of transient bioheat problems.

A meshless numerical method is proposed for the solution of the transient bioheat equation in two and three dimensions. The Pennes bioheat equation is extended in order to incorporate water evaporation, tissue damage, and temperature-dependent tissue properties during tumor ablation. The conductivity of the tissue is not assumed constant but is treated as a local function to simulate local variability due to the existence of usually unclear interfacing of healthy and pathological segments. In this way, one avoids the need for accurate identification of the boundaries between pathological and healthy regions, which is a typical problem in medical practice, and sidesteps, evidently, the corresponding mathematical treatment of such boundaries, which is usually a tedious procedure with some inevitable degree of approximation. The numerical results of the new method for test applications of the bioheat transfer equation are validated against analytical predictions and predictions of other numerical methods. 3D simulations are presented that involve the modeling of tumor ablation and account for metabolic heat generation, blood perfusion, and heat ablation using realistic values for the various parameters. An evaluation of the effective medium approximation to homogenize conductivity fields for use with the bioheat equation is also provided.

Heart rate variability in Parkinson's disease unaffected by deep brain stimulation.

OBJECTIVES: Our aim was to investigate the impact of subthalamic nucleus deep brain stimulation (STN-DBS) on the cardiovagal control of patients with advanced Parkinson's disease. MATERIALS AND METHODS: Twenty-four patients (mean age: 62.1 ± 9.4 years) were examined 3 days before and 6 months after DBS by a questionnaire, blood pressure monitoring and a battery of neurophysiological tests: time domain analysis of RR interval variation during normal and deep breathing (DB), Valsalva manoeuvre, and tilt test. By off-line, performed frequency domain analysis of heart rate variation, total power (TP), low frequency band (LF) band, high-frequency (HF) band, and their normalized units were estimated. The neurophysiological measurements were compared to those of 24 healthy controls. RESULTS: The values of time domain variables were pre- and postoperatively lower in patients than in controls. A significant reduction was found in LF band after the implantation. Orthostatic hypotension was present in 45.8% of the patients preoperatively and 12.5% postoperatively. There was no correlation between DBS-related changes of motor function and corresponding neurophysiological measurements, but patients with more than 60% motor improvement had higher time domain parameters' values than the others. CONCLUSIONS: STN-DBS offered no considerable impact on autonomic cardiovascular control.

SU-E-I-88: Realistic Pathological Simulations of the NCAT and Zubal Anthropomorphic Models, Based on Clinical PET/CT Data.

PURPOSE: In the present study a patient-specific dataset of realistic PET simulations was created, taking into account the variability of clinical oncology data. Tumor variability was tested in the simulated results. A comparison of the produced simulated data was performed to clinical PET/CT data, for the validation and the evaluation of the procedure. METHODS: Clinical PET/CT data of oncology patients were used as the basis of the simulated variability inserting patient-specific characteristics in the NCAT and the Zubal anthropomorphic phantoms. GATE Monte Carlo toolkit was used for simulating a commercial PET scanner. The standard computational anthropomorphic phantoms were adapted to the CT data (organ shapes), using a fitting algorithm. The activity map was derived from PET images. Patient tumors were segmented and inserted in the phantom, using different activity distributions. RESULTS: The produced simulated data were reconstructed using the STIR opensource software and compared to the original clinical ones. The accuracy of the procedure was tested in four different oncology cases. Each pathological situation was illustrated simulating a) a healthy body, b) insertion of the clinical tumor with homogenous activity, and c) insertion of the clinical tumor with variable activity (voxel-by-voxel) based on the clinical PET data. The accuracy of the presented dataset was compared to the original PET/CT data. Partial Volume Correction (PVC) was also applied in the simulated data. CONCLUSIONS: In this study patient-specific characteristics were used in computational anthropomorphic models for simulating realistic pathological patients. Voxel-by-voxel activity distribution with PVC within the tumor gives the most accurate results. Radiotherapy applications can utilize the benefits of the accurate realistic imaging simulations, using the anatomicaland biological information of each patient. Further work will incorporate the development of analytical anthropomorphic models with motion and cardiac correction, combined with pathological patients to achieve high accuracy in tumor imaging. This research was supported by the Joint Research and Technology Program between Greece and France; 2009-2011 (protocol ID: 09FR103).

SU-E-I-90: Fast and Robust Algorithm Towards Vessel Lumen and Stent Strut Detection in Optical Coherence Tomography.

PURPOSE: Optical Coherence Tomography (OCT) is a catheter-based imaging method that employs near-infrared light to produce high-resolution cross-sectional intravascular images. We propose a new segmentation technique for automatic lumen area extraction and stent strut detection in intravascular OCT images for the purpose of quantitative analysis of neointimal hyperplasia (NIH). METHODS: Two clinical dataset of frequency-domainOCT scans of the human femoral artery were analyzed. First, a segmentation method based on Fuzzy C-Means (FCM) clustering and Wavelet Transform (WT) was applied towards inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived from the local maxima of the wavelet transform into the FCM membership function. RESULTS: The inner lumen contour and the position of stent strut were extracted with very high accuracy. Compared with manual segmentation by an expert physician, the automatic segmentation had an average overlap value of 0.917 ± 0.065 for all OCT images included in the study. The strut detection procedure successfully identified 6.7 ± 0.5 struts for each OCT image. CONCLUSIONS: A new fast and robust automatic segmentation technique combining FCM and WT for lumen border extraction and strut detection in intravascular OCT images was designed and implemented. The proposed algorithm may be employed for automated quantitative morphological analysis of in-stent neointimal hyperplasia.

Portable biomedical devices: a critical issue during telecare services design.

OBJECTIVES: The selection of a portable biomedical device (PBD) is a key issue regarding telecare service design. The objective of this study is to investigate the accuracy parameters of a PBD under different settings and levels. METHODS AND MATERIALS: By using a commercial PBD, trials were performed in a referral cardiology center and on the Olympia Explorer of the Royal Olympia Cruises, and the Superfast XII of Superfast Ferries. Data were collected (February 2004 - June 2006) by performing: (1) 'in hospital' standalone trials; (2) 'in hospital' comparative trials; and (3) 'on board' trials. Semistructured interviews were also conducted with several subjects, their cardiologists and crewmembers. RESULTS: We investigated the accuracy parameters, namely the data precision (DP), the peripheral modules reliability (PMR) and the data transmission quality (DTQ). Although the outcomes of the comparative trials, via a statistical method verifying the DP (more than 95%), the trials 'on board' and 'in hospital' revealed a number of critical variables for the PMR and DTQ parameters. CONCLUSION: Telecare services design has accuracy parameter investigation needs. These parameters should be investigated simultaneously, while a compromise between them can act as a driving force to the telecare services success. The compromise is achieved by a smooth fit between DP and PMR with this fit varying within settings and levels.

Tracing and cataloguing knowledge in an e-health cardiology environment.

In an e-health cardiology environment, the current knowledge engineering systems can support two knowledge processes; the knowledge tracing, and the knowledge cataloguing. We have developed an n-tier system capable of supporting these processes by enabling human collaboration in each phase along with, a prototype scalable knowledge engineering tactic. A knowledge graph is used as a dynamic information structure. Biosignal data (values of HR, QRS, and ST variables) from 86 patients were used; two general practitioners defined and updated the patients' clinical management protocols; and feedback was inserted retrospectively. Several calibration tests were also performed. The system succeeded in formulating three knowledge catalogues per patient, namely, the "patient in life", the "patient in time", and the "patient in action". For each patient the clinically accepted normal limits of each variable were predicted with an accuracy of approximately 95%. The patients' risk-levels were identified accurately, and in turn, the errors were reduced. The data and the expert-oriented feedback were also time-stamped correctly and synchronized under a common time-framework. Knowledge processes optimization necessitates human collaboration and scalable knowledge engineering tactics. Experts should be responsible for resenting or rejecting a process if it downgrades the provided healthcare quality.

Optimizing the interventional cardiology facility: services integration in routine workflow.

OBJECTIVES: Integration of administrative and clinical data, imaging, and expert services, although challenging,is a key requirement in contemporary interventional cardiology facilities (ICF). We propose a workflow-oriented hybrid system to support the ICF and investigate its feasibility and effectiveness ina referral medical center. METHODS: We have developed a Java-powered hybrid system (NetCARDIO), able to support over web synchronous and asynchronous data management, realtime multimedia data telemonitoring and continuous telementoring. Data regarding procedural rates, treatment planning and radiation exposure were collected over a two-year period of routine NetCARDIO implementation(July 2002 to June 2004) and compared with data from an immediately preceding period of equal duration (January 2000 to December 2001). RESULTS: During the NetCARDIO period, 163 +/- 17 coronary procedures per month were performed vs.77 +/- 15 during the control period (p <0.001). Percutaneous coronary intervention was delivered 'ad hoc' in 88% of eligible patients vs. 45% (p <0.001). Mean fluoroscopy time per coronary lesion treated decreased from 594 +/- 82 s to 540 +/- 94 s(p < 0.001). Annual radiation exposure of expert interventionists was decreased by 22%. Electronic storage significantly reduced archiving costs. CONCLUSIONS: Real-time multimodal services sharing combined with powerful database capabilities is feasible through a web-based structure, significantly enhancing performance and cost-effectiveness of ICF. Further research is needed to promote integration of additional data sources and services.

Inter-scale wavelet analysis for speckle reduction in thyroid ultrasound images.

A wavelet-based method for speckle suppression in ultrasound images of the thyroid gland is introduced. The classification of image pixels as speckle or part of important image structures is accomplished within the framework of back-propagation tracking and singularity detection of wavelet transform modulus maxima, derived from inter-scale analysis. A comparative study with other de-speckling techniques, employing quantitative indices, demonstrated that our method achieved superior speckle reduction performance and edge preservation properties. Moreover, a questionnaire regarding qualitative imaging parameters, emanating from various visual observations, was employed by two experienced physicians in order to evaluate the algorithm's speckle suppression efficiency.

A hybrid multi-scale model for thyroid nodule boundary detection on ultrasound images.

A hybrid model for thyroid nodule boundary detection on ultrasound images is introduced. The segmentation model combines the advantages of the "á trous" wavelet transform to detect sharp gray-level variations and the efficiency of the Hough transform to discriminate the region of interest within an environment with excessive structural noise. The proposed method comprise three major steps: a wavelet edge detection procedure for speckle reduction and edge map estimation, based on local maxima representation. Subsequently, a multiscale structure model is utilised in order to acquire a contour representation by means of local maxima chaining with similar attributes to form significant structures. Finally, the Hough transform is employed with 'a priori' knowledge related to the nodule's shape in order to distinguish the nodule's contour from adjacent structures. The comparative study between our automatic method and manual delineations demonstrated that the boundaries extracted by the hybrid model are closely correlated with that of the physicians. The proposed hybrid method can be of value to thyroid nodules' shape-based classification and as an educational tool for inexperienced radiologists.

Clinical-oriented collaboration over the Web during interventional radiology procedures.

Multidisciplinary collaboration is a key requirement in several contemporary interventional radiology procedures (IRPs). We proposed a hybrid system (NetAngio) to enable "on the fly" heterogeneous collaboration to support IRP providing intraoperating essential services, and investigate its feasibility and effectiveness in a referral medical center. We have developed a Web-based, cost-effective structure, able to support real-time mentoring, image manipulation, and education services beyond the boundaries of the single institution and potentially allow sub specialists to participate in opinion and decision making in more complex cases. Supported services based on a Motion Joint Photographic Experts Group (MJPEG) coder/decoder (CODEC) can be easily accessible by authorized collaborators, within a user-friendly interface by using a typical Web-browser. Ten interventional radiologists, two vascular surgeons and two medical physicists participated in 33 "fully collaborative" cases during a 13-month period from January 2004 to February 2005. In addition, fifteen 90-minute open seminars and finally, 75 expert's module activations, and 255 learner's module activations were performed during the evaluation period. Collaborative procedures are able to enhance outcomes performance especially in more complex cases where the simultaneous presence of a remote expert interventionist and a medical physicist or a surgeon is required. Further research is needed to promote integration of additional data sources and services.

Operational criteria for selecting a cDNA microarray data normalization algorithm.

Microarray technology allows gene expression profiling at a global level. Many algorithms for the normalization of raw microarray data have been proposed, but no attempt has yet been made to propose operationally verifiable criteria for their comparative evaluation, which is necessary for the selection of the most appropriate method for a given dataset. This study develops a set of operational criteria for assessing the impact of various normalization algorithms in terms of accuracy (bias), precision (variance) and over-fitting (information reduction). The use of these criteria is illustrated by applying the three most widely used algorithms (global median normalization, spiked-in based normalization and lowess) on a specifically designed, multiply-controlled dataset.

Advanced soft computing diagnosis method for tumour grading.

OBJECTIVE: To develop an advanced diagnostic method for urinary bladder tumour grading. A novel soft computing modelling methodology based on the augmentation of fuzzy cognitive maps (FCMs) with the unsupervised active Hebbian learning (AHL) algorithm is applied. MATERIAL AND METHODS: One hundred and twenty-eight cases of urinary bladder cancer were retrieved from the archives of the Department of Histopathology, University Hospital of Patras, Greece. All tumours had been characterized according to the classical World Health Organization (WHO) grading system. To design the FCM model for tumour grading, three experts histopathologists defined the main histopathological features (concepts) and their impact on grade characterization. The resulted FCM model consisted of nine concepts. Eight concepts represented the main histopathological features for tumour grading. The ninth concept represented the tumour grade. To increase the classification ability of the FCM model, the AHL algorithm was applied to adjust the weights of the FCM. RESULTS: The proposed FCM grading model achieved a classification accuracy of 72.5%, 74.42% and 95.55% for tumours of grades I, II and III, respectively. CONCLUSIONS: An advanced computerized method to support tumour grade diagnosis decision was proposed and developed. The novelty of the method is based on employing the soft computing method of FCMs to represent specialized knowledge on histopathology and on augmenting FCMs ability using an unsupervised learning algorithm, the AHL. The proposed method performs with reasonably high accuracy compared to other existing methods and at the same time meets the physicians' requirements for transparency and explicability.

Ureteral injuries during gynecologic surgery: treatment with a minimally invasive approach.

PURPOSE: To report the safety and efficacy of percutaneous nephrostomy and primary antegrade recanalization for treatment of iatrogenic ureteral strictures after gynecologic surgery. PATIENTS AND METHODS: Ten women had symptoms suggestive of ureteral obstruction during the immediate postoperative period (5 days-1 week after surgery). Under analgesia and conscious sedation, standard percutaneous nephrostomy was performed, and a long 7F sheath was placed in the upper ureter. The obstructions were traversed with the aid of a 0.0035-inch Glidewire and a 5F angled Glide catheter (Terumo, Japan). Subsequently, the areas were dilated with angioplasty balloons to a maximum diameter of 7 mm. Finally, an 8F percutaneous internal/external nephroureteral drainage stent was inserted to secure ureteral patency. Follow-up was carried out by serial nephrostomography until removal of the stent and by renal ultrasonography thereafter. RESULTS: Twelve obstructions with a mean length of 1.4 cm (range 0.4-1.9 cm) were managed. The technical success rate was 100%. No major complications occurred, and normal renal function was restored. The mean follow-up was 12 months. In 60% of the patients, a patent ureter was depicted at 1 week, whereas in four patients, repeat dilation of the obstructed segment was required. The stents were removed after a mean period of 4.8 weeks. CONCLUSION: Percutaneous nephrostomy and primary antegrade ureteral balloon dilation is safe and efficacious for treating ureteral injury after pelvic surgery and obviates open surgical manipulations.

An image-analysis system based on support vector machines for automatic grade diagnosis of brain-tumour astrocytomas in clinical routine.

An image-analysis system based on the concept of Support Vector Machines (SVM) was developed to assist in grade diagnosis of brain tumour astrocytomas in clinical routine. One hundred and forty biopsies of astrocytomas were characterized according to the WHO system as grade II, III and IV. Images from biopsies were digitized, and cell nuclei regions were automatically detected by encoding texture variations in a set of wavelet, autocorrelation and parzen estimated descriptors and using an unsupervised SVM clustering methodology. Based on morphological and textural nuclear features, a decision-tree classification scheme distinguished between different grades of tumours employing an SVM classifier. The system was validated for clinical material collected from two different hospitals. On average, the SVM clustering algorithm correctly identified and accurately delineated 95% of all nuclei. Low-grade tumours were distinguished from high-grade tumours with an accuracy of 90.2% and grade III from grade IV with an accuracy of 88.3% The system was tested in a new clinical data set, and the classification rates were 87.5 and 83.8%, respectively. Segmentation and classification results are very encouraging, considering that the method was developed based on every-day clinical standards. The proposed methodology might be used in parallel with conventional grading to support the regular diagnostic procedure and reduce subjectivity in astrocytomas grading.

Comparison of the efficacy of tolterodine and oxybutynin in different urodynamic severity grades of idiopathic detrusor overactivity.

OBJECTIVE: To compare the efficacy of tolterodine and oxybutynin in the treatment of specific, according to their urodynamic grade of severity, populations with overactive detrusor. METHODS: In this open, randomized, two-way crossover study 128 women with urodynamically confirmed, idiopathic detrusor overactivity were recruited. Patients were categorized in 4 grades of severity groups, according to the characteristics of the first overactive detrusor contraction during filling cystometrogram: high volume-low pressure (grade-group I), high volume-high pressure (grade-group II), low volume-low pressure (grade-group III) and low volume-high pressure (grade-group IV). The primary outcome measure was average volume of voided urine per micturition. RESULTS: 107 patients successfully completed the study protocol and were included in the analyses: 40 in group IV, 36 in III, 25 in II and 6 in group I. In groups IV and III both oxybutynin and tolterodine significantly increased the average volume of voided urine per micturition but the differences between the drugs were not significant (p > 0.05). In group II neither of the drugs achieved significant changes in the outcome measure (p > 0.05). CONCLUSIONS: Tolterodine and oxybutynin are clinically equipotent in treating detrusor overactivity in specific severity groups of patients, although urodynamic effects are somewhat different.