Nikolaos Papanikolaou

Champalimaud Foundation

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Nicholas Gourtsoyiannis

King's College London

Panayiotis Mavroidis

University of North Carolina at Chapel Hill

Kostas Marias

Foundation for Research and Technology Hellas

S Stathakis

The University of Texas Health Science Center at San Antonio

Celso Matos

Champalimaud Foundation

Thomas G. Maris

University of Crete

João Santinha

University of Lisbon

C Esquivel

The University of Texas Health Science Center at Houston

Georgios C. Manikis

Foundation for Research and Technology Hellas

Apostolos H. Karantanas

University Hospital of Heraklion

Cooperative Institutions

National and Kapodistrian University of Athens

108

University of Crete

University Hospital of Heraklion

Istituti di Ricovero e Cura a Carattere Scientifico

The University of Texas Health Science Center at San Antonio

Maastricht University Medical Centre

Foundation for Research and Technology Hellas

Aristotle University of Thessaloniki

University of Milan

University General Hospital Attikon

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NON-INVASIVE MYOCARDIAL IRON ASSESSMENT IN THALASSAEMIC PATIENTS. T2 relaxometry and magnetization transfer ratio measurements

Acta Radiologica (2000)

Nikolaos Papanikolaou Abraham A. Ghiatas Antonis Kattamis C. Ladis Nikolaos Kritikos

Purpose: To compare T2 relaxometry and magnetization transfer ratio (MTR) measurements of myocardial tissue in normal volunteers and thalassaemic patients for assessment of the myocardial iron levels. Material and Methods: All examinations were done on a 1 T MR system using a multi-echo spin-echo sequence with 8 echoes for T2 measurements and a gradient echo sequence for MTR measurements. Diastolic cardiac triggering was used in both sequences. Ten patients and 10 normal subjects were included in the study. T2 and MTR measurements were correlated with serum ferritin levels. Results: Regression analysis between T2 and MTR measurements and ferritin demonstrated a reversed linear relationship, (r=−0.932, p<0.05) and (r=−0.824, p<0.05), respectively. Mean T2 relaxation time and mean MTR of the normal subjects (57.95±4.9 ms and 43.70±3.3%) was significantly higher than that of the thalassaemic patients (38.8±6.2 ms and 26.40±6.1%) (p<0.01), respectively. Conclusion: MTR measurements can be used to complement T2 measurements for non-invasive myocardial iron assessment.

Magnetization transfer

10.1034/j.1600-0455.2000.041004348.x

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Citations (17)

Use of polymer gel dosimetry for the determination of the detector size effect on profile measurements of a 5 mm diameter photon beam

Journal of Physics Conference Series (2006)

E. Pappas Thomas G. Maris Antonios E. Papadakis Fotini Zacharopoulou John Damilakis

Narrow photon beams of less than 10 mm in diameter play a significant role in modern radiotherapy since they are increasingly used in stereotactic radiosurgery and in IMRT. The conventional treatment planning systems rely on narrow beam profile measurements either for relative dose calculations or for beam modeling. However, these measurements are problematic since narrow beams are characterized by large dose gradients and electronic dis-equilibrium. The aim of the current study was to investigate the detectors' size effect on the profile measurement of a 5 mm diameter 6 MV x-ray narrow beam using polymer gel MRI dosimetry.

Dose profile

10.1088/1742-6596/56/1/040

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Citations (1)

Prevalence of polyps and diverticulosis of the large bowel in the Cretan population

International Journal of Colorectal Disease (2001)

Gregorios A. Paspatis Nikolaos Papanikolaou E. Zois Emmanuel I. Michalodimitrakis

Diverticulosis

10.1007/s003840100304

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Citations (49)

Bipolar electrocoagulation vs conventional monopolar hot biopsy forceps in the endoscopic treatment of diminutive rectal adenomas

Colorectal Disease (2005)

Gregorios Paspatis Emmanouil Vardas Ioanna Charoniti Nikolaos Papanikolaou C. Barbatzas

To assess whether a cold biopsy from a diminutive rectal adenoma followed by destruction with bipolar (gold probe) electrocoagulation using large probes and high power setting would be a safe and efficient alternative to conventional monopolar hot biopsy forceps (MHBF).Eligible patients were those undergoing colonoscopy, fulfilling the criteria of additional clearing colonoscopy and having at least one suspected rectal adenoma < or = 5 mm. At the time of endoscopy patients were randomized to receive treatment for their diminutive rectal adenomas either with cold biopsy followed by repeated gold probe electrocoagulation (Group A) using a 10 Fr catheter with setting 8 (40 W) for 1 second or with MHBF (Group B). These patients were followed up with a colonoscopy at 2-4 months.A total number of 24 (15 males, 9 females; mean age 56 years) patients were included in group A and 26 (14 males, 12 females; mean age 58 years) in group B. A total number of 38 and 37 diminutive rectal adenomas was detected in patients of Group A and Group B, respectively. At follow up colonoscopy residual adenoma tissue was found in 2 (5.2%) adenomas of 38 in Group A and in 4 (10.8%) of 37 in Group B (P > 0.3). No complications related to colonoscopy or endoscopic treatments in both groups occurred.Our data suggest that the use of cold biopsy followed by bipolar electrocoagulation using large probes and high power setting for destroying diminutive rectal adenoma seems to be equally effective and safe as MHBF.

Electrocoagulation

Diminutive

Polypectomy

10.1111/j.1463-1318.2004.00725.x

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Citations (15)

AI trustworthiness in prostate cancer imaging: a look at algorithmic and system transparency^*

Sara Colantonio Andrea Berti Rossana Buongiorno Giulio Del Corso Eva Pachetti

A responsible approach to artificial intelligence and machine learning technologies, grounded in sound scientific foundations, technical robustness, rigorous testing and validation, risk-based continuous monitoring and alignment with human values is imperative to guarantee their favorable impact and prevent any adverse effects they may have on individuals and communities. An essential aspect of responsible development is transparency, which constitutes a fundamental principle of the European approach towards artificial intelligence. Transparency can be achieved at different levels, such as data origin and use, system development, operation and usage. In this paper, we present the techniques implemented and delivered in the EU H2020 ProCAncer-I project to meet the transparency requirements at the different levels required.Clinical Relevance: This paper examines the primary transparency hurdles in artificial intelligence for medical imaging diagnostics, and presents the approaches that the EU H2020 project ProCAncer-I is taking to address them.

Trustworthiness

Robustness

10.1109/ieeeconf58974.2023.10404432

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Citations (0)

Innovations in thoracic imaging: CT, radiomics, AI and x‐ray velocimetry

Respirology (2022)

Rozemarijn Vliegenthart Andreas Fouras Colin Jacobs Nikolaos Papanikolaou

Abstract In recent years, pulmonary imaging has seen enormous progress, with the introduction, validation and implementation of new hardware and software. There is a general trend from mere visual evaluation of radiological images to quantification of abnormalities and biomarkers, and assessment of ‘non visual’ markers that contribute to establishing diagnosis or prognosis. Important catalysts to these developments in thoracic imaging include new indications (like computed tomography [CT] lung cancer screening) and the COVID‐19 pandemic. This review focuses on developments in CT, radiomics, artificial intelligence (AI) and x‐ray velocimetry for imaging of the lungs. Recent developments in CT include the potential for ultra‐low‐dose CT imaging for lung nodules, and the advent of a new generation of CT systems based on photon‐counting detector technology. Radiomics has demonstrated potential towards predictive and prognostic tasks particularly in lung cancer, previously not achievable by visual inspection by radiologists, exploiting high dimensional patterns (mostly texture related) on medical imaging data. Deep learning technology has revolutionized the field of AI and as a result, performance of AI algorithms is approaching human performance for an increasing number of specific tasks. X‐ray velocimetry integrates x‐ray (fluoroscopic) imaging with unique image processing to produce quantitative four dimensional measurement of lung tissue motion, and accurate calculations of lung ventilation.

Velocimetry

10.1111/resp.14344

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Citations (31)

MR Imaging of the Liver Using an Ultrafast 3D Multi-Shot EPI Sequence

Acta Radiologica (1999)

Nikolaos Papanikolaou A. H. Karantanas Eleftherios Lavdas

Purpose: To compare a 3D echo planar imaging (EPI) sequence with four other T1-weighted sequences for imaging of the liver at 1 T. Material and Methods: Twenty volunteers were included in our imaging protocol. Spin-echo (SE), turbo SE (TSE), turbo field echo (TFE) in 2D and 3D acquisition mode, fast field echo (T1-FFE) and 3D EPI sequences were applied. Signal-to-noise (S/N) ratio of the liver, contrast-to-noise (C/N) ratio and relative contrast (ReCon) between the liver and the spleen, scanning time per slice and artifact levels were evaluated. Results: 3D EPI provided a statistically equivalent S/N ratio of the liver with SE and T1-FFE sequences ( p > 0.05), while it provided a statistically higher S/N ratio of the liver compared to TFE sequences ( p < 0.05). The TSE technique provided a statistically higher S/N ratio of the liver compared to 3D EPI ( p < 0.05). With regard to the liver-spleen C/N ratio, 3D EPI provided statistically equivalent results compared to all sequences except T1-FFE, where 3D EPI was superior. With regard to liver-spleen ReCon, 3D EPI was statistically equivalent to SE, TSE and T1-FFE, while it provided significantly higher liver-spleen ReCon than 3D TFE and significantly lower than 2D TFE. Conclusion: 3D EPI provided sufficient ReCon and C/N ratio and produced motion-free images in one breath-hold period. Further clinical studies are required to estimate the sensitivity, specificity and accuracy of the sequence.

Echo-planar imaging

10.3109/02841859909175561

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Citations (2)

Quantification of tumor burden in multiple myeloma by atlas-based semi-automatic segmentation of WB-DWI

Cancer Imaging (2020)

Sílvia D. Almeida João Santinha Francisco P. M. Oliveira Joana Ip M. V. Lisitskaya

Whole-body diffusion weighted imaging (WB-DWI) has proven value to detect multiple myeloma (MM) lesions. However, the large volume of imaging data and the presence of numerous lesions makes the reading process challenging. The aim of the current study was to develop a semi-automatic lesion segmentation algorithm for WB-DWI images in MM patients and to evaluate this smart-algorithm (SA) performance by comparing it to the manual segmentations performed by radiologists.An atlas-based segmentation was developed to remove the high-signal intensity normal tissues on WB-DWI and to restrict the lesion area to the skeleton. Then, an outlier threshold-based segmentation was applied to WB-DWI images, and the segmented area's signal intensity was compared to the average signal intensity of a low-fat muscle on T1-weighted images. This method was validated in 22 whole-body DWI images of patients diagnosed with MM. Dice similarity coefficient (DSC), sensitivity and positive predictive value (PPV) were computed to evaluate the SA performance against the gold standard (GS) and to compare with the radiologists. A non-parametric Wilcoxon test was also performed. Apparent diffusion coefficient (ADC) histogram metrics and lesion volume were extracted for the GS segmentation and for the correctly identified lesions by SA and their correlation was assessed.The mean inter-radiologists DSC was 0.323 ± 0.268. The SA vs GS achieved a DSC of 0.274 ± 0.227, sensitivity of 0.764 ± 0.276 and PPV 0.217 ± 0.207. Its distribution was not significantly different from the mean DSC of inter-radiologist segmentation (p = 0.108, Wilcoxon test). ADC and lesion volume intraclass correlation coefficient (ICC) of the GS and of the correctly identified lesions by the SA was 0.996 for the median and 0.894 for the lesion volume (p < 0.001). The duration of the lesion volume segmentation by the SA was, on average, 10.22 ± 0.86 min, per patient.The SA provides equally reproducible segmentation results when compared to the manual segmentation of radiologists. Thus, the proposed method offers robust and efficient segmentation of MM lesions on WB-DWI. This method may aid accurate assessment of tumor burden and therefore provide insights to treatment response assessment.

10.1186/s40644-020-0286-5

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Citations (20)

Comparison of echo planar imaging, gradient echo and fast spin echo MR scans of knee menisci

Computerized Medical Imaging and Graphics (2000)

Apostolos H. Karantanas Aristeidis Zibis Nikolaos Papanikolaou

Fast spin echo

Meniscus

Gradient echo

Cartilage damage

Medial meniscus

10.1016/s0895-6111(00)00027-6