Medical Diagnostic Center Ayios Therissos

Nicosia, Cyprus

Medical Diagnostic Center Ayios Therissos

Nicosia, Cyprus
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Seimenis I.,Medical Diagnostic Center Ayios Therissos | Tsekos N.V.,Houston Medical Robotics | Keroglou C.,University of Cyprus | Eracleous E.,Medical Diagnostic Center Ayios Therissos | And 2 more authors.
CardioVascular and Interventional Radiology | Year: 2012

Purpose The aim of this work was to develop and test a general methodology for the planning and performance of robot-assisted, MR-guided interventions. This methodology also includes the employment of software tools with appropriately tailored routines to effectively exploit the capabilities of MRI and address the relevant spatial limitations. Methods The described methodology consists of: (1) patient-customized feasibility study that focuses on the geometric limitations imposed by the gantry, the robotic hardware, and interventional tools, as well as the patient; (2) stereotactic preoperative planning for initial positioning of the manipulator and alignment of its end-effector with a selected target; and (3) real-time, intraoperative tool tracking and monitoring of the actual intervention execution. Testing was performed inside a standard 1.5T MRI scanner in which the MR-compatible manipulator is deployed to provide the required access. Results A volunteer imaging study demonstrates the application of the feasibility stage. A phantom study on needle targeting is also presented, demonstrating the applicability and effectiveness of the proposed preoperative and intraoperative stages of the methodology. For this purpose, a manually actuated, MR-compatible robotic manipulation system was used to accurately acquire a prescribed target through alternative approaching paths. Conclusions The methodology presented and experimentally examined allows the effective performance of MR-guided interventions. It is suitable for, but not restricted to, needle-targeting applications assisted by a robotic manipulation system, which can be deployed inside a cylindrical scanner to provide the required access to the patient facilitating real-time guidance and monitoring. © 2011 Springer Science+Business Media, LLC and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE).


Loizou C.P.,Intercollege | Murray V.,University of New Mexico | Pattichis M.S.,University of New Mexico | Seimenis I.,Medical Diagnostic Center Ayios Therissos | And 2 more authors.
IEEE Transactions on Information Technology in Biomedicine | Year: 2011

This study introduces the use of multiscale amplitude modulation-frequency modulation (AM-FM) texture analysis of multiple sclerosis (MS) using magnetic resonance (MR) images from brain. Clinically, there is interest in identifying potential associations between lesion texture and disease progression, and in relating texture features with relevant clinical indexes, such as the expanded disability status scale (EDSS). This longitudinal study explores the application of 2-D AM-FM analysis of brain white matter MS lesions to quantify and monitor disease load. To this end, MS lesions and normal-appearing white matter (NAWM) from MS patients, as well as normal white matter (NWM) from healthy volunteers, were segmented on transverse T2-weighted images obtained from serial brain MR imaging (MRI) scans (0 and 6-12 months). The instantaneous amplitude (IA), the magnitude of the instantaneous frequency (IF), and the IF angle were extracted from each segmented region at different scales. The findings suggest that AM-FM characteristics succeed in differentiating 1) between NWM and lesions; 2) between NAWM and lesions; and 3) between NWM and NAWM. A support vector machine (SVM) classifier succeeded in differentiating between patients that, two years after the initial MRI scan, acquired an EDSS ≤ 2 from those with EDSS > 2 (correct classification rate = 86%). The best classification results were obtained from including the combination of the low-scale IA and IF magnitude with the medium-scale IA. The AM-FM features provide complementary information to classical texture analysis features like the gray-scale median, contrast, and coarseness. The findings of this study provide evidence that AM-FM features may have a potential role as surrogate markers of lesion load in MS. © 2006 IEEE.


Konstantinou N.,University of Cyprus | Pettemeridou E.,University of Cyprus | Seimenis I.,Democritus University of Thrace | Eracleous E.,Medical Diagnostic Center Ayios Therissos | And 3 more authors.
Frontiers in Neurology | Year: 2016

Objectives: Characterize the scale and pattern of long-term atrophy in gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) in chronic moderate-severe traumatic brain injury (TBI) and its relationship to neurocognitive outcomes. Participants: The TBI group consisted of 17 males with primary diagnosis of moderate-severe closed head injury. Participants had not received any systematic, post-acute rehabilitation and were recruited on average 8.36 years post-injury. The control group consisted of 15 males matched on age and education. Main measures: Neurocognitive battery included widely used tests of verbal memory, visual memory, executive functioning, and attention/organization. GM, WM, and CSF volumes were calculated from segmented T1-weighted anatomical MR images. Voxel-based morphometry was employed to identify brain regions with differences in GM and WM between TBI and control groups. Results: Chronic TBI results in significant neurocognitive impairments, and significant loss of GM and WM volume, and significant increase in CSF volume. Brain atrophy is not widespread, but it is rather distributed in a fronto-thalamic network. The extent of volume loss is predictive of performance on the neurocognitive tests. Conclusion: Significant brain atrophy and associated neurocognitive impairments during the chronic stages of TBI support the notion that TBI results in a chronic condition with lifelong implications. © 2016 Konstantinou, Pettemeridou, Seimenis, Eracleous, Papacostas, Papanicolaou and Constantinidou.


Christoforou E.G.,University of Cyprus | Seimenis I.,Democritus University of Thrace | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Andreou E.,University of Cyprus | And 2 more authors.
International Journal of Medical Robotics and Computer Assisted Surgery | Year: 2014

Background: 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. Methods: 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. Results: 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. Conclusions: Robotic assistance provided by the developed manipulator may effectively facilitate the performance of various MRI-guided, minimally invasive interventions inside a cylindrical scanner. © 2013 John Wiley & Sons, Ltd.


Perisinakis K.,University of Crete | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Seimenis I.,Democritus University of Thrace | Tzedakis A.,University of Crete | And 2 more authors.
Medical Physics | Year: 2013

Purpose: 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. Methods: 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. Results: 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. Conclusions: 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. © 2013 American Association of Physicists in Medicine.


Perisinakis K.,University of Crete | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Seimenis I.,Democritus University of Thrace | Tzedakis A.,University of Crete | And 3 more authors.
International Journal of Cardiology | Year: 2013

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. © 2013 Elsevier Ireland Ltd © 2013 Published by Elsevier Ireland Ltd.


Perisinakis K.,University of Crete | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Seimenis I.,Democritus University of Thrace | Tzedakis A.,University of Crete | And 3 more authors.
Investigative Radiology | Year: 2012

Objectives: 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. Materials and Methods: 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. Results: 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%. Conclusion: 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. © 2012 by Lippincott Williams & Wilkins.


Perisinakis K.,University of Crete | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Seimenis I.,Democritus University of Thrace | Tzedakis A.,University of Crete | Damilakis J.,University of Crete
Journal of Nuclear Medicine | Year: 2014

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 averagesized 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. COPYRIGHT © 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.


Perisinakis K.,University of Crete | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Tzedakis A.,University of Crete | Papadakis A.E.,University of Crete | Damilakis J.,University of Crete
Investigative Radiology | Year: 2012

Objectives: 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. Materials and Methods: 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. Results: 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 5 female and 17 per 10 5 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. CONCLUSIONS:: 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. © 2012 by Lippincott Williams & Wilkins.


Perisinakis K.,University of Crete | Seimenis I.,Medical Diagnostic Center Ayios Therissos | Tzedakis A.,University of Crete | Papadakis A.E.,University of Crete | Damilakis J.,University of Crete
Circulation | Year: 2010

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. © 2010 American Heart Association, Inc.

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