Maria Lyra | National and Kapodistrian University of Athens (original) (raw)

Papers by Maria Lyra

Clinical Nuclear Medicine Physics with MATLAB®, 2021

In-111-Octreotide infusion, via intrahepatic catheterization is well established technique in our... more In-111-Octreotide infusion, via intrahepatic catheterization is well established technique in our Institution in hepatocellular carcinoma and neuroendocrine tumors treatment. In order to facilitate repetitive infusions of our patients, a method of implanted ports use, gave a simpler therapeutic way but also improved therapy results. Our aim is to show that radiopharmaceutical fluid flow through implanted port is rich; the absorbed dose in the tumor increased for best therapy results. Surgically implanted ports have been used in repetitive intra-arterial In-111 radiolabeled Octreotide infusions for 22 patients with hepatocellular carcinoma and similarly 18 patients with neuroendocrine tumors in a continuous base. A percutaneous implantation procedure facilitates safe and less invasive radiopharmaceutical infusions for the treatment. We have focused on the interventional techniques for percutaneous implantation of a vascular access device, consisting of an implantable port, to perform In-111 Octreotide infusions. Hepatic arterial infusion radiotherapy employs a hepatic artery catheter as a conduit to achieve a high concentration of radiolabeled agent to liver tumors. It is performed using less-invasive percutaneous image guided procedures. Various techniques were used to ensure high concentration of radiopharmaceutical in liver tumors, as there are many anatomical hepatic arterial variations and complicated blood flow patterns. These techniques are composed of arterial redistribution by embolization, percutaneous catheter placement, evaluation and management of flow patterns that reflect In-111 Octreotide distribution. Using fluid flow theory, we describe blood flow alterations that could be performed to obtain selective radiopharmaceutical distribution to the target area and avoid side effects caused by the accumulation of the radiolabeled agent into non tumor areas. By steady, laminar and disturbed flow equations, the rich distribution of our agent in the scintigraphy imaging of the tumor, by the implanted ports technique, can be explained. The factors affecting hepatic arterial flow in tumor feeding artery were analyzed. The patency rate of the hepatic artery was significantly higher in patients with catheter placement using fixed port method than those undergo fully interventional catheterization. A ratio of 5: 1 to 3: 1 flow increase was calculated through poiseuille flow and Reynolds number for circular pipe. We consider that in continuous therapy, it is important to use the simplest fixed port method for percutaneous catheter placement instead of interventional catheterization, in order to increase absorbed dose into tumor for best response of radionuclide therapy.

Recent Patents on Medical Imaging, Apr 1, 2012

Nuclear Medicine Communications, Jul 1, 1999

IFMBE proceedings, 2016

An assessment of the morphological parameters in renal imaging is an integral point of the evalua... more An assessment of the morphological parameters in renal imaging is an integral point of the evaluation of kidneys’ diseases and organ growth in children. The aim of this study is to create useful pathophysiological tools that will help as to a more accurate and detailed diagnosis in kidney studies.

Recent Patents on Medical Imaging, Jul 6, 2010

Springer eBooks, 2001

The evaluation of cortical damage to the kidneys, especially in children, is currently performed ... more The evaluation of cortical damage to the kidneys, especially in children, is currently performed by means of Tc99m-DMSA renal scan. The routine involves the acquisition of planar images and their qualitative and quantitative evaluation. Many recent studies have dealt with the possible advantage that single photon emission tomography (SPECT) could possess on qualitative criteria. This study attempts to quantitatively deal with the issue by the calculation of an index, through the digitised slices' data. The results exhibit a clear advantage of tomographic and 3D reconstructed images over the conventional planar ones.

CRC Press eBooks, Aug 10, 2021

Poster: "ECR 2011 / C-1833 / 3D volume visualization and estimation in kidneys scintigraphy&... more Poster: "ECR 2011 / C-1833 / 3D volume visualization and estimation in kidneys scintigraphy" by: "M. Lyra, M. Gavrilelli, V. Lyra; Athens/GR"

Journal of Medical Physics, Feb 1, 1986

ABSTRACT

... [14] Phinou PC, Lyra M, Jordanou J, Pappas D, Limouris G, Vlahos L ;Patient-specific Dosimetr... more ... [14] Phinou PC, Lyra M, Jordanou J, Pappas D, Limouris G, Vlahos L ;Patient-specific Dosimetry of I-131-MIBG Therapy of Adrenal Tumours using I-123-MIBG Diagnostic Imaging(2006); World Journal of Nuclear Medicine, Vol 5, No 3,pp188-195 [15] Rollo FD et al. ...

MedPress Neurology and Neurosurgery, May 11, 2022

Lung status during pulmonary embolism and patient follow-up, should be evaluated and the accurate... more Lung status during pulmonary embolism and patient follow-up, should be evaluated and the accurate estimation of lungs volume is important; By 3-dimensional (3D) medical imaging data and diagnosis of patient embolism become much more reliable. A method for lungs' volume determination by Tc99m SPECT images and the definition of an Index of Lung Perfusion homogeneity (LPI) is demonstrated. Volumes of reconstructed transverse slices were estimated by counting the voxels inside each slice of SPECT data of the lung perfusions studies. For the lung lobe's edge and the background subtraction, an edge detection algorithm was produced. The total lung lobe volume was derived by summing the 2D SPECT slices' volumes. Non-uniform attenuation compensation was performed by quantitative filtered back-projection. A lung lobe segment volume analysis was also determined for the identification of lung section volumes with diminished radionuclide concentration. A follow-up correlation of the 3D SPECT of each lung perfusion tomography was studied by Lung Shaded surface display and Volume Rendering in 3D image post-processing. Lung Perfusion Index (LPI) is the ratio of lung segment volume over the whole organ volume and indicates the grade of the lung section perfusion situation. In follow-up patient studies, comparison of Lung Perfusion Index (LPI) in the repeat scans constitutes the Pulmonary Improvement Factor (PIF). In order to evaluate the accuracy of these measurements, 5 cylindrical phantoms, [1000-1500] ml volume, containing Tc99m activity dispersed in an imitation lung tissue (a mixture of styrofoam beds with water) were acquired under conditions similar to those of the patients' study. Using the regression equation derived from the phantom study, the accuracy of the volumes of the lungs' lobes was calculated. The method is simple and fast with a relative error of up to 3% for length, 11% for the area and 8% for volume determinations. The precision of the estimation varied, depending on the size and clinical status of the lung lobe. This method has been developed to assist in the accurate interpretation of 3D SPECT perfusion lung imaging by volume and semiquantitative lung perfusion index determination.

Radiation Protection Dosimetry, 1992

It is seen that a great many ideas and useful procedures are suggested by this working group. A... more It is seen that a great many ideas and useful
procedures are suggested by this working group.
Addressing many members from outside the EC it
is worthwhile to continue this collaboration between
EC and EFOMP for the future. even if communication
due to missing organizational structures is
more difficult than inside the EE.

Biomedical Journal of Scientific and Technical Research, Feb 25, 2019

Monte Carlo [MC] method is a modeling tool, capable of achieving a close adherence to reality, co... more Monte Carlo [MC] method is a modeling tool, capable of achieving a close adherence to reality, concerning the analysis of complex systems. Generally is a method for estimation of the solution of mathematical problems by means of random numbers

Cancer Biotherapy and Radiopharmaceuticals, Apr 1, 2005

Thirteen (13) patients with liver neuroendocrine carcinomas metastases, positive for somatostatin... more Thirteen (13) patients with liver neuroendocrine carcinomas metastases, positive for somatostatin receptors, confirmed by scintigraphy were infused with 4070-7030 MBq per session of In-111-octreotide after selective hepatic catheterization, exploiting the catastrophic activity of Indium Auger and Internal Conversion electron emission on cell DNA. Evaluation of the treatment was assessed by ultrasonography (US) as well as by computed tomography and/or magnetic resonance imaging scans. US appears to be the imaging procedure of choice because the examination is sensitive for evaluating lesions' edema and cystic components, provides precise measurement of tumor size, and is inexpensive. Degeneration US signs were classified in stage I (an echolucent rim in the periphery of the lesion), stage IIa (lesion with large cystic spaces), stage IIb (tiny cystic spaces) and stage III (absorption of the cystic component or stable cystic remnants).

International Journal of Biomedical Imaging, 2011

Single photon emission computed tomography (SPECT) imaging is widely implemented in nuclear medic... more Single photon emission computed tomography (SPECT) imaging is widely implemented in nuclear medicine as its clinical role in the diagnosis and management of several diseases is, many times, very helpful (e.g., myocardium perfusion imaging). The quality of SPECT images are degraded by several factors such as noise because of the limited number of counts, attenuation, or scatter of photons. Image filtering is necessary to compensate these effects and, therefore, to improve image quality. The goal of filtering in tomographic images is to suppress statistical noise and simultaneously to preserve spatial resolution and contrast. The aim of this work is to describe the most widely used filters in SPECT applications and how these affect the image quality. The choice of the filter type, the cutoff frequency and the order is a major problem in clinical routine. In many clinical cases, information for specific parameters is not provided, and findings cannot be extrapolated to other similar SPECT imaging applications. A literature review for the determination of the mostly used filters in cardiac, brain, bone, liver, kidneys, and thyroid applications is also presented. As resulting from the overview, no filter is perfect, and the selection of the proper filters, most of the times, is done empirically. The standardization of image-processing results may limit the filter types for each SPECT examination to certain few filters and some of their parameters. Standardization, also, helps in reducing image processing time, as the filters and their parameters must be standardised before being put to clinical use. Commercial reconstruction software selections lead to comparable results interdepartmentally. The manufacturers normally supply default filters/parameters, but these may not be relevant in various clinical situations. After proper standardisation, it is possible to use many suitable filters or one optimal filter.

PubMed, Dec 15, 2015

Background: Many radionuclides have been used for several decades in cancer treatment. (131)I, (9... more Background: Many radionuclides have been used for several decades in cancer treatment. (131)I, (90)Y, (89)Sr, (111)In, (177)Lu and (223)Ra are some of the most widely used radioisotopes. Therapeutic results and side effects can be associated only if the absorbed dose is well estimated. Knowledge of the absorbed dose during radionuclide therapy is the only method that can compare therapeutic results between different therapeutic techniques such as external radiotherapy and radio immunotherapy. Accurate patient specific estimation of the absorbed dose to the tumor and normal tissue can be achieved with voxel based internal dosimetry. Objective: The aim of this study is to develop a computer algorithm that calculates absorbed dose at every voxel of quantitative SPET scintigraphy image and establish a general internal dosimetry protocol for therapy by radionuclides. Material and methods: SPET scintigraphy images of known (131)I activities were obtained. The known activity of (131)I was contained in a cylindrical phantom of 16cm radius. A numerical factor was determined to convert the measured count rate from the SPET images to activity. The algorithm that calculate absorbed dose at every voxel of the scintigraphy image was developed by MATLAB. MATLAB is a high level computer language with interactive environment and performs mathematical calculations by matrices. The scintigraphy images were imported in MATLAB and were converted to 3-dimensional matrices. Every element of the matrix was assigned with the respective count rate. The matrix was multiplied with the conversion factor and the new elements represented the activity at every voxel. A cumulative activity matrix was made from activity matrices that were obtained at different time points. The absorbed dose at every voxel of the cumulative activity matrix was computed with the convolution method. A3- dimensional convolution matrix with size 5x5x5 was created. The elements of this matrix are numerical factors that convert cumulative activity to absorbed dose. The convolution between these two matrices was made using the 'convn' function of MATLAB. This function convolves the cumulative activity matrix with the convolution matrix and gives a new matrix with numeric elements that represent absorbed dose at every voxel. Furthermore, regions of interest can be drawn on the images and dose volume histograms and mean absorbed doses can be calculated. Results: SPET scintigraphy images were obtained for 64MBq (131)I activity. A cumulative activity of 230GBq*s was calculated and the voxel convolution method showed that mean absorbed dose was 20.6Gy. Maximum dose of 50Gy was calculated for the central voxel in the activity. A region of interest was drawn and the dose volume histogram was calculated. The results were compared to MIRDOSE3.1 program. A mean dose of 20.1Gy was calculated with MIRDOSE3.1 for the same cumulative activity in 0.85cm diameter. Conclusion: Patient specific voxel internal dosimetry can be performed accurately with MATLAB. Dose volume histograms and mean dose can be calculated.