In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The ge... more In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The geometrical projectors considered were the conventional geometrical Siddon ray-tracer ͑S-RT͒ and the orthogonal distance-based ray-tracer ͑OD-RT͒, based on computing the orthogonal distance from the center of image voxel to the line-of-response. A comparison of these geometrical projectors was performed using different point spread function ͑PSF͒ models. The Monte Carlobased method under consideration involves an extensive model of the system response matrix based on Monte Carlo simulations and is computed off-line and stored on disk. Methods: Comparisons were performed using simulated and experimental data of the commercial small animal PET scanner rPET. Results: The results demonstrate that the orthogonal distance-based ray-tracer and Siddon raytracer using PSF image-space convolutions yield better images in terms of contrast and spatial resolution than those obtained after using the conventional method and the multiray-based S-RT. Furthermore, the Monte Carlo-based method yields slight improvements in terms of contrast and spatial resolution with respect to these geometrical projectors. Conclusions: The orthogonal distance-based ray-tracer and Siddon ray-tracer using PSF imagespace convolutions represent satisfactory alternatives to factorizing the system matrix or to the conventional on-the-fly ray-tracing methods for list-mode reconstruction, where an extensive modeling based on Monte Carlo simulations is unfeasible.
ADVERTIMENT. La consulta d'aquesta tesi queda condicionada a l'acceptació de les següents... more ADVERTIMENT. La consulta d'aquesta tesi queda condicionada a l'acceptació de les següents condicions d'ús: La difusió d'aquesta tesi per mitjà del servei TDX (www.tdx.cat) ha estat autoritzada pels titulars dels drets de propietat intel·lectual únicament per a usos privats emmarcats en activitats d'investigació i docència. No s'autoritza la seva reproducció amb finalitats de lucre ni la seva difusió i posada a disposició des d'un lloc aliè al servei TDX. No s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant al resum de presentació de la tesi com als seus continguts. En la utilització o cita de parts de la tesi és obligat indicar el nom de la persona autora. ADVERTENCIA. La consulta de esta tesis queda condicionada a la aceptación de las siguientes condiciones de uso: La difusión de esta tesis por medio del servicio TDR (www.tdx.cat) ha sido autorizada por los titulares de los ...
The treatment of malignant melanoma or sarcomas on a limb using extremity perfusion with tumour n... more The treatment of malignant melanoma or sarcomas on a limb using extremity perfusion with tumour necrosis factor (TNF-alpha) and melphalan can result in a high degree of systemic toxicity if there is any leakage from the isolated blood territory of the limb into the systemic vascular territory. Leakage is currently controlled by using radiotracers and heavy external probes in a procedure that requires continuous manual calculations. The aim of this work was to develop a light, easily transportable system to monitor limb perfusion leakage by controlling systemic blood pool radioactivity with a portable gamma camera adapted for intraoperative use as an external probe, and to initiate its application in the treatment of MM patients. A special collimator was built for maximal sensitivity. Software for acquisition and data processing in real time was developed. After testing the adequacy of the system, it was used to monitor limb perfusion leakage in 16 patients with malignant melanoma to be treated with perfusion of TNF-alpha and melphalan. The field of view of the detector system was 13.8 cm, which is appropriate for the monitoring, since the area to be controlled was the precordial zone. The sensitivity of the system was 257 cps/MBq. When the percentage of leakage reaches 10% the associated absolute error is +/-1%. After a mean follow-up period of 12 months, no patients have shown any significant or lasting side-effects. Partial or complete remission of lesions was seen in 9 out of 16 patients (56%) after HILP with TNF-alpha and melphalan. The detector system together with specially developed software provides a suitable automatic continuous monitoring system of any leakage that may occur during limb perfusion. This technique has been successfully implemented in patients for whom perfusion with TNF-alpha and melphalan has been indicated.
The centralized radiopharmacy set up in Spain by the Cetir Medical Group allows optimal use of ra... more The centralized radiopharmacy set up in Spain by the Cetir Medical Group allows optimal use of radiopharmaceuticals and complies with laws (Directive 89/343/EEC and Royal Decree 479/1993/Spain) governing their use. More than 220,000 individual patient doses have been supplied since the unit was established in November 1995. In this paper, we describe the infrastructure of the centralized radiopharmacy, including the operations and procedures involved, and how we believe we have achieved our original objectives.
Serial measurements of plasma activity, plasma protein binding and urine excretion were obtained ... more Serial measurements of plasma activity, plasma protein binding and urine excretion were obtained in order to study 99Tcm-MAG3 (MAG) and 131I-Hippuran (OIH) kinetics after simultaneous injection of both tracers in 21 patients with various renal diseases. Results were compared on the basis of a compartmental model, calculating the rate constants as well as the clearance and volume of distribution. Protein binding was calculated in 10 patients (mean: MAG = 54.7%, OIH = 33.8%). The dependence of time, tracer and patient factors was shown by ANOVA. Time was independent, with tracer and patient factors and their interaction being significant. The mean value of the renal excretion constant was equal for the two tracers (k12 = 0.052 min-1). The clearance values were found to be highly correlated (r = 0.982) with a ratio of 0.57 between them. The volumes of distribution in litres were 4.1 (MAG) and 7.0 (OIH). One-hour urine excretion was nearly the same for both tracers (MAG: 64%, OIH: 63% of the injected dose).
Simplified methods based on a single blood sample have been proposed to estimate the clearance of... more Simplified methods based on a single blood sample have been proposed to estimate the clearance of 131I-hippuran (HIP) and 99Tcm-mercaptoacetyltriglycine (MAG). The blood sample is usually drawn at that time which yields a minimum error between the estimated clearance and that obtained by the standard nine-sample method. In this paper, we establish the regression equations to obtain the HIP and MAG clearances using one sample withdrawn during a fixed time interval. As HIP has long been the agent of choice, we have also established regression equations to estimate the clearance of HIP using one sample after MAG administration. Our results suggest that it is possible to obtain plasma samples 30-50 min post-injection which result in an error of the estimate only slightly higher than the minimum.
The Journal of Thoracic and Cardiovascular Surgery, 2003
laser revascularization metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial... more laser revascularization metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial Technetium 99m-labeled tetrofosmin and iodine 123-labeled Objective: Transmyocardial laser revascularization is a new technique that improves symptoms in patients with refractory angina not amenable to conventional revascularization. The aim of this study was to assess whether transmyocardial laser revascularization produces changes in innervation, perfusion scintigraphy, or both that could explain the benefit to patients. Downloaded from Figure 4. 123 I-MIBG left anterior oblique 45°planar scans. The patient was referred for right coronary and left circumflex artery disease. TMR was performed on the inferior and lateral areas. The planar scans showed an inferolateral moderate defect before the operation, a severe defect at 3 months, and a partial recovery at 12 months. Muxí et al Cardiopulmonary Support and Physiology laser revascularization metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial Technetium 99m-labeled tetrofosmin and iodine 123-labeled Continuing Medical Education Activities
The purpose of our study was to evaluate the performance and clinical usefulness of an automated ... more The purpose of our study was to evaluate the performance and clinical usefulness of an automated injector system (AIS) that administers an automated injection for ictal SPECT after calculating the volume of tracer to be injected over time. Methods: To test the AIS, repeated injections were performed at different times after tracer preparation. The clinical study consisted of 56 patients with drug-resistant, complex partial seizures. Tracer for ictal SPECT was injected using automated injection in 27 patients and manual injection (MI) in the remaining 29. Injection time (T I ) was measured in seconds from seizure onset to the end of volume injection. The SISCOM (Subtraction Ictal Spect Co-registered to MRI) procedure was used to locate the epileptogenic seizure focus with SPECT. The definition of seizure focus was made by consensus of the epilepsy unit using conventional diagnostic methods. Results: During the experimental phase, there were no system failures, and the error in injected doses when using automated injection was lower than with MI. During the clinical phase, T I using manual injection was 41 s with a range of 14-103 s, compared with an AIS average of 33 s with a range of 19-63 s (P , 0.05). Ictal SPECT and SISCOM successfully localized the seizure focus in 21 of the 27 patients (78%) by AIS and in 19 of the 29 patients (65%) by MI (P 5 0.14). Furthermore, nursing staff found the AIS method more convenient than the MI method. Conclusion: An AIS can improve the quality of work of the nursing staff in the neurology ward and allow a finer adjustment of the injection dose. Early results using an AIS would indicate a reduction in injection time and improved SPECT accuracy.
The role of cognitive variables was compared in two single cases of schizophrenia hypofrontality.... more The role of cognitive variables was compared in two single cases of schizophrenia hypofrontality. SPECT procedures and neuropsychological tests were used to study frontal brain function. After cognitive rehabilitation, neuropsychological performance were enhanced in both patients, but only one of them showed enhanced the frontal blood flow. The brain perfusion changes after cognitive rehabilitation could be associated with the cognitive-dependent hypofrontality. ᮊ
As part of the radioiodinated 4-amino-N-1-(3-(4-fluorophenoxy)- propyl)-4-methyl-4-piperidinyl)5-... more As part of the radioiodinated 4-amino-N-1-(3-(4-fluorophenoxy)- propyl)-4-methyl-4-piperidinyl)5-iodo-2-methoxybenzamide (123I-R91150) characterization study, ketanserin challenges were performed on healthy volunteers with the aim of assessing the specificity of 123I-R91150 binding to subtype 2A of the 5-hydroxytryptamine receptor (5-HT2A), the sensitivity of 123I-R91150 SPECT in measuring ligand displacement, the relationship be- tween ketanserin plasma concentrations and 123I-R91150 dis- placement, and the suitability of the
Tkcniques de reconstrucció d'imatges en SPECT Introducció L'ecpectacular avenq en la tecnologia m... more Tkcniques de reconstrucció d'imatges en SPECT Introducció L'ecpectacular avenq en la tecnologia medica que s'ha produit en els darrers anys, i l'augment de potencia de c?~lcul dels ordinadors, han generalitzat la utilizació de tecniques cada vegada més sofisticades en l'kmbit del diagnbstic per la imatge. En l'actualitat disposem de tecniques d'obtenció d'imatges biomediques que, en aportar informació complementaria morfolbgica i funcional, estan augmentant la capacitat de diagnbstic mitjancant tecniques no invasives. Com a exemple cal destacar la tomografia per ordinador de raigs X (SO)-imprbpiarnent coneguda com a TC o tomografia computeritzada-, l'ecografia, la ressonhncia magnetita nuclear (RMN) i la tomografia d'emissió de fotons, en les dues vessants, emissió de fotó únic (SPECT, single photon emission computed tomography) o emissió de dos fotons d'aniquilació (PET, positron emission tomogra
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2005
Dopamine transporter (DAT) ligands have been developed for in vivo imaging of the dopaminergic sy... more Dopamine transporter (DAT) ligands have been developed for in vivo imaging of the dopaminergic system in SPECT. Although the visual analysis of SPECT images is, in general, suitable for clinical assessment, the accurate quantification of the striatal uptake might increase the sensitivity of the technique and help in the early diagnosis, follow-up, and eventual treatment response of Parkinson's disease (PD). This work is focused on assessment of the quantification of specific uptake of (99m)Tc-DAT ligands when compensation for all degrading phenomena is performed. The SimSET Monte Carlo (MC) code was used to generate a set of SPECT projections of a numeric striatal phantom with different specific uptake ratios (SURs). An absolute quantification method (AQM), which performs a MC-based scatter compensation and a fully 3-dimensional (3D) reconstruction, was implemented. The scatter estimate was included in the reconstruction algorithm. The use of attenuation, point-spread-function (...
Patients with head and neck cancers can develop salivary hypofunction after radiotherapy. The use... more Patients with head and neck cancers can develop salivary hypofunction after radiotherapy. The use of pilocarpine during radiotherapy treatment has been shown to be an effective treatment, although its usefulness is being discussed. The aim of this study was: (1) to determine the value of a semiquantitative scintigraphy method for measuring the uptake and excretory salivary function of patients with head and neck irradiated tumours; and (2) to study the usefulness of pilocarpine as a salivary gland protector during radiotherapy. We prospectively studied 49 patients (mean age 61 years, range 29-87 years) with head and neck cancer in need of radiotherapy. Patients were divided into two groups consecutively: group P (26 patients) received 5 mg of pilocarpine three times per day starting the day before radiation therapy, and group NP (23 patients) received radiotherapy without pilocarpine and were used as the control group. Salivary gland scintigraphy and a visual analogue scale (VAS) of...
After reviewing the main methods existing to calculate the rate of the mucociliary transport, the... more After reviewing the main methods existing to calculate the rate of the mucociliary transport, the authors describe their personal technique. A 99mTechnetium Sulphur Colloid drop is deposited in the nasal fossa, which is carried away by the cilia down to the rhinopharynx and followed by a gamma camera. To calculate the transport rate, a new method of quantification has been introduced, based on the formation of a parametric image. A study was carried out in 14 males without any pathology of the upper airways, obtaining a mean velocity of 5.3 mm per min (range 3.3.-8.2).
An In-111 leukocyte scan was performed in a cirrhotic patient with ascitic fluid infection to rul... more An In-111 leukocyte scan was performed in a cirrhotic patient with ascitic fluid infection to rule out an abdominal abscess. Scintigraphy showed localized uptake in the area between the liver and right lung 30 minutes after reinjection of the labeled cells. The 24-hour study was negative. No purulent collection was demonstrated in any location.
Quantification accuracy in SPECT imaging is impaired by a number of factors including noise, atte... more Quantification accuracy in SPECT imaging is impaired by a number of factors including noise, attenuation, collimator/detector response and scatter. Recent advances in SPECT technology have considerably improved the possibilities of quantification in nuclear neuroimaging. On the one hand, fan-beam collimators on multihead systems offer a good trade-off between resolution and noise. On the other hand, transmission imaging systems which enable us to obtain attenuation maps are now available. The scattering and the spatially variant fan-beam collimator response are relevant degrading effects in neuro-transmission SPECT studies. Monte Carlo simulation (MC) is the most general method for detailed modelling of scatter although it implies long computation times. The scattering in the collimator was neglected for low energy photons as those of 99mTc agents. Thus, the scattering models in 99mTc brain neurotransmission studies were focused on scatter interactions inside the object. The SimSET Monte Carlo code was used and the collimator module included a new probability density function per unit of solid angle for fan-beam collimators. This modelling of the collimator/detector blurring effect accelerated the code in a 2-fold factor. The assessment of the Monte Carlo-based scatter estimate is based on comparison with sinograms which in turn are based on simulated projection data of numerical phantoms. The numerical phantom was implemented by using experimental data obtained from a CT image of an anthropomorphic striatal phantom. The fully D reconstruction which included attenuation and PSF corrections was based on composite images of the 8 slices showing the basal ganglia activity, 128×128 pixels each. Good agreement was found between the original and the estimated scatter distributions. Our findings indicate that the proposed methodology is expected to be useful for obtaining accurate scattering distributions in SPECT projections.
To develop a small-animal SPECT system using a low cost commercial portable gamma camera equipped... more To develop a small-animal SPECT system using a low cost commercial portable gamma camera equipped with a pinhole collimator, a continuous scintillation crystal and a position-sensitive photomultiplier tube. The gamma camera was attached to a variable radius system, which enabled us to optimize sensitivity and resolution by adjusting the radius of rotation to the size of the object. To investigate the capability of the SPECT system for small animal imaging, the dependence of resolution and calibration parameters on radius was assessed and acquisitions of small phantoms and mice were carried out. Resolution values, ranging from 1.0mm for a radius of 21.4mm and 1.4mm for a radius of 37.2mm were obtained, thereby justifying the interest of a variable radius SPECT system. The image quality of phantoms and animals were satisfactory, thus confirming the usefulness of the system for small animal SPECT imaging.
In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The ge... more In the present work, the authors compare geometrical and Monte Carlo projectors in detail. The geometrical projectors considered were the conventional geometrical Siddon ray-tracer ͑S-RT͒ and the orthogonal distance-based ray-tracer ͑OD-RT͒, based on computing the orthogonal distance from the center of image voxel to the line-of-response. A comparison of these geometrical projectors was performed using different point spread function ͑PSF͒ models. The Monte Carlobased method under consideration involves an extensive model of the system response matrix based on Monte Carlo simulations and is computed off-line and stored on disk. Methods: Comparisons were performed using simulated and experimental data of the commercial small animal PET scanner rPET. Results: The results demonstrate that the orthogonal distance-based ray-tracer and Siddon raytracer using PSF image-space convolutions yield better images in terms of contrast and spatial resolution than those obtained after using the conventional method and the multiray-based S-RT. Furthermore, the Monte Carlo-based method yields slight improvements in terms of contrast and spatial resolution with respect to these geometrical projectors. Conclusions: The orthogonal distance-based ray-tracer and Siddon ray-tracer using PSF imagespace convolutions represent satisfactory alternatives to factorizing the system matrix or to the conventional on-the-fly ray-tracing methods for list-mode reconstruction, where an extensive modeling based on Monte Carlo simulations is unfeasible.
ADVERTIMENT. La consulta d'aquesta tesi queda condicionada a l'acceptació de les següents... more ADVERTIMENT. La consulta d'aquesta tesi queda condicionada a l'acceptació de les següents condicions d'ús: La difusió d'aquesta tesi per mitjà del servei TDX (www.tdx.cat) ha estat autoritzada pels titulars dels drets de propietat intel·lectual únicament per a usos privats emmarcats en activitats d'investigació i docència. No s'autoritza la seva reproducció amb finalitats de lucre ni la seva difusió i posada a disposició des d'un lloc aliè al servei TDX. No s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant al resum de presentació de la tesi com als seus continguts. En la utilització o cita de parts de la tesi és obligat indicar el nom de la persona autora. ADVERTENCIA. La consulta de esta tesis queda condicionada a la aceptación de las siguientes condiciones de uso: La difusión de esta tesis por medio del servicio TDR (www.tdx.cat) ha sido autorizada por los titulares de los ...
The treatment of malignant melanoma or sarcomas on a limb using extremity perfusion with tumour n... more The treatment of malignant melanoma or sarcomas on a limb using extremity perfusion with tumour necrosis factor (TNF-alpha) and melphalan can result in a high degree of systemic toxicity if there is any leakage from the isolated blood territory of the limb into the systemic vascular territory. Leakage is currently controlled by using radiotracers and heavy external probes in a procedure that requires continuous manual calculations. The aim of this work was to develop a light, easily transportable system to monitor limb perfusion leakage by controlling systemic blood pool radioactivity with a portable gamma camera adapted for intraoperative use as an external probe, and to initiate its application in the treatment of MM patients. A special collimator was built for maximal sensitivity. Software for acquisition and data processing in real time was developed. After testing the adequacy of the system, it was used to monitor limb perfusion leakage in 16 patients with malignant melanoma to be treated with perfusion of TNF-alpha and melphalan. The field of view of the detector system was 13.8 cm, which is appropriate for the monitoring, since the area to be controlled was the precordial zone. The sensitivity of the system was 257 cps/MBq. When the percentage of leakage reaches 10% the associated absolute error is +/-1%. After a mean follow-up period of 12 months, no patients have shown any significant or lasting side-effects. Partial or complete remission of lesions was seen in 9 out of 16 patients (56%) after HILP with TNF-alpha and melphalan. The detector system together with specially developed software provides a suitable automatic continuous monitoring system of any leakage that may occur during limb perfusion. This technique has been successfully implemented in patients for whom perfusion with TNF-alpha and melphalan has been indicated.
The centralized radiopharmacy set up in Spain by the Cetir Medical Group allows optimal use of ra... more The centralized radiopharmacy set up in Spain by the Cetir Medical Group allows optimal use of radiopharmaceuticals and complies with laws (Directive 89/343/EEC and Royal Decree 479/1993/Spain) governing their use. More than 220,000 individual patient doses have been supplied since the unit was established in November 1995. In this paper, we describe the infrastructure of the centralized radiopharmacy, including the operations and procedures involved, and how we believe we have achieved our original objectives.
Serial measurements of plasma activity, plasma protein binding and urine excretion were obtained ... more Serial measurements of plasma activity, plasma protein binding and urine excretion were obtained in order to study 99Tcm-MAG3 (MAG) and 131I-Hippuran (OIH) kinetics after simultaneous injection of both tracers in 21 patients with various renal diseases. Results were compared on the basis of a compartmental model, calculating the rate constants as well as the clearance and volume of distribution. Protein binding was calculated in 10 patients (mean: MAG = 54.7%, OIH = 33.8%). The dependence of time, tracer and patient factors was shown by ANOVA. Time was independent, with tracer and patient factors and their interaction being significant. The mean value of the renal excretion constant was equal for the two tracers (k12 = 0.052 min-1). The clearance values were found to be highly correlated (r = 0.982) with a ratio of 0.57 between them. The volumes of distribution in litres were 4.1 (MAG) and 7.0 (OIH). One-hour urine excretion was nearly the same for both tracers (MAG: 64%, OIH: 63% of the injected dose).
Simplified methods based on a single blood sample have been proposed to estimate the clearance of... more Simplified methods based on a single blood sample have been proposed to estimate the clearance of 131I-hippuran (HIP) and 99Tcm-mercaptoacetyltriglycine (MAG). The blood sample is usually drawn at that time which yields a minimum error between the estimated clearance and that obtained by the standard nine-sample method. In this paper, we establish the regression equations to obtain the HIP and MAG clearances using one sample withdrawn during a fixed time interval. As HIP has long been the agent of choice, we have also established regression equations to estimate the clearance of HIP using one sample after MAG administration. Our results suggest that it is possible to obtain plasma samples 30-50 min post-injection which result in an error of the estimate only slightly higher than the minimum.
The Journal of Thoracic and Cardiovascular Surgery, 2003
laser revascularization metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial... more laser revascularization metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial Technetium 99m-labeled tetrofosmin and iodine 123-labeled Objective: Transmyocardial laser revascularization is a new technique that improves symptoms in patients with refractory angina not amenable to conventional revascularization. The aim of this study was to assess whether transmyocardial laser revascularization produces changes in innervation, perfusion scintigraphy, or both that could explain the benefit to patients. Downloaded from Figure 4. 123 I-MIBG left anterior oblique 45°planar scans. The patient was referred for right coronary and left circumflex artery disease. TMR was performed on the inferior and lateral areas. The planar scans showed an inferolateral moderate defect before the operation, a severe defect at 3 months, and a partial recovery at 12 months. Muxí et al Cardiopulmonary Support and Physiology laser revascularization metaiodobenzylguanidine scintigraphy in the assessment of transmyocardial Technetium 99m-labeled tetrofosmin and iodine 123-labeled Continuing Medical Education Activities
The purpose of our study was to evaluate the performance and clinical usefulness of an automated ... more The purpose of our study was to evaluate the performance and clinical usefulness of an automated injector system (AIS) that administers an automated injection for ictal SPECT after calculating the volume of tracer to be injected over time. Methods: To test the AIS, repeated injections were performed at different times after tracer preparation. The clinical study consisted of 56 patients with drug-resistant, complex partial seizures. Tracer for ictal SPECT was injected using automated injection in 27 patients and manual injection (MI) in the remaining 29. Injection time (T I ) was measured in seconds from seizure onset to the end of volume injection. The SISCOM (Subtraction Ictal Spect Co-registered to MRI) procedure was used to locate the epileptogenic seizure focus with SPECT. The definition of seizure focus was made by consensus of the epilepsy unit using conventional diagnostic methods. Results: During the experimental phase, there were no system failures, and the error in injected doses when using automated injection was lower than with MI. During the clinical phase, T I using manual injection was 41 s with a range of 14-103 s, compared with an AIS average of 33 s with a range of 19-63 s (P , 0.05). Ictal SPECT and SISCOM successfully localized the seizure focus in 21 of the 27 patients (78%) by AIS and in 19 of the 29 patients (65%) by MI (P 5 0.14). Furthermore, nursing staff found the AIS method more convenient than the MI method. Conclusion: An AIS can improve the quality of work of the nursing staff in the neurology ward and allow a finer adjustment of the injection dose. Early results using an AIS would indicate a reduction in injection time and improved SPECT accuracy.
The role of cognitive variables was compared in two single cases of schizophrenia hypofrontality.... more The role of cognitive variables was compared in two single cases of schizophrenia hypofrontality. SPECT procedures and neuropsychological tests were used to study frontal brain function. After cognitive rehabilitation, neuropsychological performance were enhanced in both patients, but only one of them showed enhanced the frontal blood flow. The brain perfusion changes after cognitive rehabilitation could be associated with the cognitive-dependent hypofrontality. ᮊ
As part of the radioiodinated 4-amino-N-1-(3-(4-fluorophenoxy)- propyl)-4-methyl-4-piperidinyl)5-... more As part of the radioiodinated 4-amino-N-1-(3-(4-fluorophenoxy)- propyl)-4-methyl-4-piperidinyl)5-iodo-2-methoxybenzamide (123I-R91150) characterization study, ketanserin challenges were performed on healthy volunteers with the aim of assessing the specificity of 123I-R91150 binding to subtype 2A of the 5-hydroxytryptamine receptor (5-HT2A), the sensitivity of 123I-R91150 SPECT in measuring ligand displacement, the relationship be- tween ketanserin plasma concentrations and 123I-R91150 dis- placement, and the suitability of the
Tkcniques de reconstrucció d'imatges en SPECT Introducció L'ecpectacular avenq en la tecnologia m... more Tkcniques de reconstrucció d'imatges en SPECT Introducció L'ecpectacular avenq en la tecnologia medica que s'ha produit en els darrers anys, i l'augment de potencia de c?~lcul dels ordinadors, han generalitzat la utilizació de tecniques cada vegada més sofisticades en l'kmbit del diagnbstic per la imatge. En l'actualitat disposem de tecniques d'obtenció d'imatges biomediques que, en aportar informació complementaria morfolbgica i funcional, estan augmentant la capacitat de diagnbstic mitjancant tecniques no invasives. Com a exemple cal destacar la tomografia per ordinador de raigs X (SO)-imprbpiarnent coneguda com a TC o tomografia computeritzada-, l'ecografia, la ressonhncia magnetita nuclear (RMN) i la tomografia d'emissió de fotons, en les dues vessants, emissió de fotó únic (SPECT, single photon emission computed tomography) o emissió de dos fotons d'aniquilació (PET, positron emission tomogra
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2005
Dopamine transporter (DAT) ligands have been developed for in vivo imaging of the dopaminergic sy... more Dopamine transporter (DAT) ligands have been developed for in vivo imaging of the dopaminergic system in SPECT. Although the visual analysis of SPECT images is, in general, suitable for clinical assessment, the accurate quantification of the striatal uptake might increase the sensitivity of the technique and help in the early diagnosis, follow-up, and eventual treatment response of Parkinson's disease (PD). This work is focused on assessment of the quantification of specific uptake of (99m)Tc-DAT ligands when compensation for all degrading phenomena is performed. The SimSET Monte Carlo (MC) code was used to generate a set of SPECT projections of a numeric striatal phantom with different specific uptake ratios (SURs). An absolute quantification method (AQM), which performs a MC-based scatter compensation and a fully 3-dimensional (3D) reconstruction, was implemented. The scatter estimate was included in the reconstruction algorithm. The use of attenuation, point-spread-function (...
Patients with head and neck cancers can develop salivary hypofunction after radiotherapy. The use... more Patients with head and neck cancers can develop salivary hypofunction after radiotherapy. The use of pilocarpine during radiotherapy treatment has been shown to be an effective treatment, although its usefulness is being discussed. The aim of this study was: (1) to determine the value of a semiquantitative scintigraphy method for measuring the uptake and excretory salivary function of patients with head and neck irradiated tumours; and (2) to study the usefulness of pilocarpine as a salivary gland protector during radiotherapy. We prospectively studied 49 patients (mean age 61 years, range 29-87 years) with head and neck cancer in need of radiotherapy. Patients were divided into two groups consecutively: group P (26 patients) received 5 mg of pilocarpine three times per day starting the day before radiation therapy, and group NP (23 patients) received radiotherapy without pilocarpine and were used as the control group. Salivary gland scintigraphy and a visual analogue scale (VAS) of...
After reviewing the main methods existing to calculate the rate of the mucociliary transport, the... more After reviewing the main methods existing to calculate the rate of the mucociliary transport, the authors describe their personal technique. A 99mTechnetium Sulphur Colloid drop is deposited in the nasal fossa, which is carried away by the cilia down to the rhinopharynx and followed by a gamma camera. To calculate the transport rate, a new method of quantification has been introduced, based on the formation of a parametric image. A study was carried out in 14 males without any pathology of the upper airways, obtaining a mean velocity of 5.3 mm per min (range 3.3.-8.2).
An In-111 leukocyte scan was performed in a cirrhotic patient with ascitic fluid infection to rul... more An In-111 leukocyte scan was performed in a cirrhotic patient with ascitic fluid infection to rule out an abdominal abscess. Scintigraphy showed localized uptake in the area between the liver and right lung 30 minutes after reinjection of the labeled cells. The 24-hour study was negative. No purulent collection was demonstrated in any location.
Quantification accuracy in SPECT imaging is impaired by a number of factors including noise, atte... more Quantification accuracy in SPECT imaging is impaired by a number of factors including noise, attenuation, collimator/detector response and scatter. Recent advances in SPECT technology have considerably improved the possibilities of quantification in nuclear neuroimaging. On the one hand, fan-beam collimators on multihead systems offer a good trade-off between resolution and noise. On the other hand, transmission imaging systems which enable us to obtain attenuation maps are now available. The scattering and the spatially variant fan-beam collimator response are relevant degrading effects in neuro-transmission SPECT studies. Monte Carlo simulation (MC) is the most general method for detailed modelling of scatter although it implies long computation times. The scattering in the collimator was neglected for low energy photons as those of 99mTc agents. Thus, the scattering models in 99mTc brain neurotransmission studies were focused on scatter interactions inside the object. The SimSET Monte Carlo code was used and the collimator module included a new probability density function per unit of solid angle for fan-beam collimators. This modelling of the collimator/detector blurring effect accelerated the code in a 2-fold factor. The assessment of the Monte Carlo-based scatter estimate is based on comparison with sinograms which in turn are based on simulated projection data of numerical phantoms. The numerical phantom was implemented by using experimental data obtained from a CT image of an anthropomorphic striatal phantom. The fully D reconstruction which included attenuation and PSF corrections was based on composite images of the 8 slices showing the basal ganglia activity, 128×128 pixels each. Good agreement was found between the original and the estimated scatter distributions. Our findings indicate that the proposed methodology is expected to be useful for obtaining accurate scattering distributions in SPECT projections.
To develop a small-animal SPECT system using a low cost commercial portable gamma camera equipped... more To develop a small-animal SPECT system using a low cost commercial portable gamma camera equipped with a pinhole collimator, a continuous scintillation crystal and a position-sensitive photomultiplier tube. The gamma camera was attached to a variable radius system, which enabled us to optimize sensitivity and resolution by adjusting the radius of rotation to the size of the object. To investigate the capability of the SPECT system for small animal imaging, the dependence of resolution and calibration parameters on radius was assessed and acquisitions of small phantoms and mice were carried out. Resolution values, ranging from 1.0mm for a radius of 21.4mm and 1.4mm for a radius of 37.2mm were obtained, thereby justifying the interest of a variable radius SPECT system. The image quality of phantoms and animals were satisfactory, thus confirming the usefulness of the system for small animal SPECT imaging.
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Papers by Javier Pavía