Recent developments in PET instrumentation, including advances in silicon photomultipliers and electronics, are fueling the development of novel PET systems improving flexibility and reducing costs. Among the improvements, ultra-high resolution time-of-flight (TOF) enables the use of limited angle geometry without sacrificing image quality. In this work, we present simulation results for a PET system under development, with ultra-high TOF resolution and depth-of-interaction (DOI). The proposed system is arranged for long axial field-of-view scanning using flat detector panels. We evaluate the performance of the system for varying TOF and DOI resolutions while incorporating geometric corrections during reconstruction. Results demonstrate the promising performance of a 2-panel, 70 ps TOF resolution system with 2.5 mm DOI resolution, as evidenced by traditional and task-based image quality metrics.

Introducción La cirugía funcional constituye una alternativa terapéutica para los pacientes con enfermedad de Parkinson (EP). Es conocido que tanto la subtalamotomía como la palidotomía bilaterales provocan complicaciones neurológicas, por lo que en las técnicas ablativas no resulta recomendable el abordaje bilateral del GPi en la EP y se sugiere tener precaución con la indicación de la subtalamotomía bilateral. Nuestro grupo ha perfeccionado la técnica quirúrgica para la ablación del núcleo subtalámico buscando disminuir la aparición de las discinesias inducidas por la cirugía y obtener mejor efecto terapéutico, por lo que el abordaje del NST en un segundo tiempo quirúrgico en el hemisferio opuesto al que se realizó previamente la palidotomía, evitaría las complicaciones derivadas de la palidotomía bilateral y puede ser una alternativa segura para los pacientes aun cuando estos presenten cuadros de discinesias. Nos propusimos evaluar el efecto y la seguridad de la combinación de la lesión del GPi y del NST en hemisferios cerebrales opuestos en pacientes con EP. Método Se realizó un estudio retrospectivo que incluyó a todos los pacientes operados en el CIREN en un periodo de 22 años, a los que se les realizó una palidotomía contralateral al hemicuerpo más afectado; seguida de una subtalamotomía del hemisferio opuesto en un segundo tiempo quirúrgico. El efecto sobre la condición neurológica fue evaluado mediante la sección III de la escala de MDS-UPDRS. Se evaluó la seguridad según escala de efectos adversos y escala de Clavien y Dindo. Resultados Ambas intervenciones quirúrgicas tuvieron un impacto positivo en el tratamiento farmacológico de los pacientes reduciéndose significativamente las dosis de L-dopa. Se observó una mejoría significativa en la condición motora de los pacientes con relación a las discinesias, así como a la rigidez, la bradicinesia y el temblor. Conclusiones La combinación palidotomía/subtalamotomía mostró ser una alternativa efectiva para el tratamiento de la EP complicada, capaz de permitir un mejor control motor y una reducción de la dosis de L-dopa con una baja tasa de complicaciones; permitiendo además evitar las complicaciones derivadas de la palidotomía y de la subtalamotomía bilaterales, demostrando ser una alternativa segura para los pacientes aun cuando estos presenten cuadros de discinesias.

The radiation sensitive part of the wide-field, small gamma camera Sentinella (TM) 108 consists of a monolithic, 102 x 102 mm(2) wide CsI(Na) crystal coupled to four position-sensitive photomultipliers. These are read out via a resistor mesh reducing the 256 PMT channels to four digitized values which allow for an image reconstruction, based on polynomials, with high spatial resolution. The sensor areas between neighboring PMTs suffer from reduced detection efficiency for scintillation light. The corresponding lack of signal amplitude translates to a poor uniformity and additional image compression in the border regions of the images after the first step of reconstruction. These effects cannot be completely eliminated by a global calibration procedure alone.We have developed and evaluated two classes of algorithms to compensate for this reduction of signal amplitude. Corrections are applied for each detected event separately, maintaining the real-time capability of the gamma camera. Algorithm 1 is based on a four-parameter, geometric calculation of the four output signals. This model aims to attack the underlying lack of detection efficiency without further assumptions on the true event distribution, preserving the global polynomial image decompression. Algorithm 2, to the contrary, starts from measured reference distributions of point sources which are used to model local deformations and energy loss without further information on the underlying detector geometry. Here too, a good image quality has been obtained after application of the deduced corrections.These algorithms are applied in the first step of event reconstruction. Within an energy interval of +/-0.2E(p) around the photopeak position of Tc-99m, E-p = 140.5 keV, and comparing several cameras, global uniformities around 5- 8% have been obtained with both models. Measured energy resolutions are about 9-14%.

We have studied motor performance in a man with Parkinson's disease (PD) in whom thermolytic lesions of the left subthalamic and left globus pallidus nuclei interrupted the basal ganglia (BG)-thalamo-cortical motor circuit in the left hemisphere. This allowed us to study remaining motor capabilities in the absence of aberrant BG activity typical of PD. Movements of the left arm were slow and parkinsonian whereas movement speed and simple reaction times (RT) of the right (operated) arm were within the normal range with no obvious deficits in a range of daily life activities. Two main abnormalities were found with the right hand. (a) Implicit sequence learning in a probabilistic serial reaction time task was absent. (b) In a go/no-go task when the percent of no-go trials increased, the RT superiority with the right hand was lost. These deficits are best explained by a failure of the cortex, deprived of BG input, to facilitate responses in a probabilistic context. Our findings confirm the idea that it is better to stop BG activity than allowing faulty activity to disrupt the motor system but dispute earlier claims that interrupting BG output in PD goes without an apparent deficit. From a practical viewpoint, our observations indicate that the risk of persistent dyskinesias need not be viewed as a contraindication to subthalamotomy in PD patients since they can be eliminated if necessary by a subsequent pallidotomy without producing deficits that impair activities of daily life.

Background: Stereotactic thermocoagulative lesions of the subthalamic nucleus (STN) have been shown to induce significant motor improvement in patients with Parkinson's disease (PD).Patients and methods: 89 patients with PD were treated with unilateral subthalamotomy. 68 patients were available for evaluations after 12 months, 36 at 24 months and 25 at 36 months.Results: The Unified Parkinson's Disease Rating Scale (UPDRS) motor scores improved significantly contralaterally to the lesion in the "off'' and "on'' states throughout the follow-up, except for the "on'' state at the last evaluation. Axial features and signs ipsilateral to the lesion progressed steadily throughout the study. Levodopa daily doses were significantly reduced by 45%, 36% and 28% at 12, 24 and 36 months post-surgery. 14 patients (15%) developed postoperative hemichorea-ballism which required pallidotomy in eight. These 14 patients had significantly higher dyskinesia scores (levodopa induced) preoperatively than the entire cohort.Conclusion: Unilateral subthalamotomy was associated with significant and sustained motor benefit contralateral to the lesion. Further work is needed to ascertain what factors led to severe, persistent chorea-ballism in a subset of patients. Subthalamotomy may be considered an option in circumstances when deep brain stimulation is not viable.

Summary Background: The treatment of malignant melanoma or sarcomas on a limb using extremity perfusion with tumour necrosis factor (TNF-α) 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. Methods: 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-α and melphalan. Results: 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-α and melphalan. Conclusion: 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-α and melphalan has been indicated.

Introduction. Participation of apoptotic death mechanisms in drug resistant temporal lobe epilepsy (DRTLE) is currently under great debate. We have investigated if there is neuronal loss and the immunodetection to different markers in neocortical tissue death in eigth patients with DRTLE. The neocortexes of five patients deceased due to non-neurological causes, paired in age and gender were evaluated as control tissue. Methods. The evaluation of neuronal loss was made by means of a stereological study and with immunohistochemical techniques with the synaptophysin marker. Immunopositivity to different apoptotic markers (annexin V, caspase 3 and 8, bcl-2 and p53) and detection of deoxyribonucleic acid (DNA) fragmentation (TUNEL) were analyzed and double labeling with synaptophysin was performed in every case. The results were evaluated with confocal microscope and analyzed with the Zeiss LSM 5 Image Browser Program, 2.80.1113 (Germany). Results. A statistically significant decrease in the total number of cells (p < 0.05) and the synaptophysin cells+ (p<0.01) in the neocortex (layer IV) of the patients with DRTLE when compared with the control tissue was found. No significant differences were found in the apoptotic markers bcl-2, p53, caspase 3 and 8 for any of the neocortex layers while there was a statistically significant increase in the number of TUNEL cells+ (p<0.05) and annexin V+ (p<0.05) in the neocortical layer IV of the patients. Conclusions. This group of evidence speaks in favor of the existence of an effect on the neuronal number in the neocortex layer IV that may be associated with noncaspase dependent apoptotic death process, without being able to rule out death by necrosis. Key words: Drug resistant temporal lobe epilepsy. Apoptosis. Necrosis. Neuronal loss. Neurología 2008;23(9):555-565.

Current testbenches for nuclear imaging devices aim to simulate only a single stage of the system at a time. This approach is useful in early design stages where accuracy is not necessary. However, it would be desirable that different tools could be combined to achieve more detailed simulations. In this work, we present a high precision testbench that has been developed to test nuclear imaging systems. Its accuracy lies in the possibility of linking different simulation tools using the right one for each part of the system. High energy events are simulated using Geant4 (High Energy Simulator). Analog and digital electronics are verified using Cadence Spectre and ModelSim. This testbench structure allows testing any physical topology, scintillation crystals, Photomultiplier Tubes (PMTs), Avalanche Photodiodes (APDs), with any kind of ASIC, discrete analog and digital electronics, thus reducing the prototyping and design time. New system developments can be easily verified using behavioral and circuital description models for analog and digital electronics. Finally, a dual-head continuous LSO scintillation crystal Positron Emission Tomography (PET) system has been used as an example for evaluation of the testbench.