RESUMEN

PET detectors use signal multiplexing to reduce the total number of electronics channels needed to cover a given area. Using measured thin-beam calibration data, we tested a principal component based multiplexing scheme for scintillation detectors. The highly-multiplexed detector signal is no longer amenable to standard calibration methodologies. In this study we report results of a prototype multiplexing circuit, and present a new method for calibrating the detector module with multiplexed data. A [Formula: see text] mm3 LYSO scintillation crystal was affixed to a position-sensitive photomultiplier tube with [Formula: see text] position-outputs and one channel that is the sum of the other 64. The 65-channel signal was multiplexed in a resistive circuit, with 65:5 or 65:7 multiplexing. A 0.9 mm beam of 511 keV photons was scanned across the face of the crystal in a 1.52 mm grid pattern in order to characterize the detector response. New methods are developed to reject scattered events and perform depth-estimation to characterize the detector response of the calibration data. Photon interaction position estimation of the testing data was performed using a Gaussian Maximum Likelihood estimator and the resolution and scatter-rejection capabilities of the detector were analyzed. We found that using a 7-channel multiplexing scheme (65:7 compression ratio) with 1.67 mm depth bins had the best performance with a beam-contour of 1.2 mm FWHM (from the 0.9 mm beam) near the center of the crystal and 1.9 mm FWHM near the edge of the crystal. The positioned events followed the expected Beer-Lambert depth distribution. The proposed calibration and positioning method exhibited a scattered photon rejection rate that was a 55% improvement over the summed signal energy-windowing method.

Asunto(s)

Cámaras gamma , Procesamiento de Imagen Asistido por Computador/métodos , Fotones , Tomografía de Emisión de Positrones/instrumentación , Tomografía de Emisión de Positrones/métodos , Calibración , Electrónica , Humanos , Tomografía de Emisión de Positrones/normas

RESUMEN

A PET detector featuring a pseudo-monolithic crystal is being developed as a more cost-effective alternative to a full monolithic crystal PET detector. This work evaluates different methods to localize the scintillation events in quartered monolithic crystals that are optically coupled. A semi-monolithic crystal assembly was formed using four 26 × 26 × 10 mm3 LYSO crystals optically coupled together using optical adhesive, to mimic a 52 × 52 × 10 mm3 monolithic crystal detector. The crystal assembly was coupled to a 64-channel multi-anode photomultiplier tube using silicon grease. The detector was calibrated using a 34 × 34 scan grid. Events were first filtered and depth separated using a multi-Lorentzian fit to the collected light distribution. Next, three different techniques were explored to generate the look up tables for the event positioning. The first technique was 'standard interpolation' across the interface. The second technique was 'central extrapolation', where a bin was placed at the midpoint of the interface and events positioned within the interface region were discarded. The third technique used a 'central overlap' method where an extended region was extrapolated at each interface. Events were then positioned using least-squares minimization and maximum likelihood methods. The least-squares minimization applied to the look up table generated with the standard interpolation technique had the best full width at half maximum (FWHM) intrinsic spatial resolution and the lowest bias. However, there were discontinuities in the event positioning that would most likely lead to artifacts in the reconstructed image. The central extrapolation technique also had discontinuities and a 30% sensitivity loss near the crystal-crystal interfaces. The central overlap technique had slightly degraded performance metrics, but it still provided ~2.1 mm intrinsic spatial resolution at the crystal-crystal interface and had a symmetric and continuously varying response function. Results using maximum likelihood positioning were similar to least-squares minimization for the central overlap data.

Asunto(s)

Óptica y Fotónica , Tomografía de Emisión de Positrones/instrumentación , Conteo por Cintilación/instrumentación , Silicio/química , Artefactos , Calibración , Humanos , Tomografía de Emisión de Positrones/métodos , Factores de Tiempo

RESUMEN

To reduce the number of output channels and associated cost in PET detectors, strategies to multiplex the signal channels have been investigated by several researchers. This work aims to find an optimal multiplexing strategy for detector modules consisting of a monolithic LYSO scintillator coupled to a 64-channel PMT. We apply simulated multiplexing strategies to measured data from two continuous miniature crystal element (cMiCE) detector modules. The strategies tested include standard methods such as row column summation and its variants, as well as new data-driven methods involving the principal components of measured data and variants of those components. The detector positioning resolution and bias are measured for each multiplexing strategy and the results are compared. The mean FWHM over the entire detector was 1.23 mm for no multiplexing (64 channels). Using 16 principal component channels yielded a mean FWHM resolution of 1.21 mm, while traditional row/column summation (16 channels) yielded 1.28 mm. Using 8 principal component output channels resulted in a resolution of 1.30 mm. Using the principal components of the calibration data to guide the multiplexing scheme appears to be a viable method for reducing the number of output data channels. Further study is needed to determine if the depth-of-interaction resolution can be preserved with this multiplexing scheme.

Asunto(s)

Algoritmos , Tomografía de Emisión de Positrones/métodos , Calibración , Tomografía de Emisión de Positrones/instrumentación , Tomografía de Emisión de Positrones/normas

RESUMEN

Modern field programmable gate arrays (FPGAs) are capable of performing complex discrete signal processing algorithms with clock rates well above 100 MHz. This, combined with FPGA's low expense, ease of use, and selected dedicated hardware make them an ideal technology for a data acquisition system for a positron emission tomography (PET) scanner. The University of Washington is producing a high-resolution, small-animal PET scanner that utilizes FPGAs as the core of the front-end electronics. For this scanner, functions that are typically performed in dedicated circuits, or offline, are being migrated to the FPGA. This will not only simplify the electronics, but the features of modern FPGAs can be utilized to add significant signal processing power to produce higher quality images. In this paper we report on an all-digital pulse pile-up correction algorithm that has been developed for the FPGA. The pile-up mitigation algorithm will allow the scanner to run at higher count rates without incurring large data losses due to the overlapping of scintillation signals. This correction technique utilizes a reference pulse to extract timing and energy information for most pile-up events. Using pulses acquired from a Zecotech Photonics MAPD-N with an LFS-3 scintillator, we show that good timing and energy information can be achieved in the presence of pile-up utilizing a moderate amount of FPGA resources.

RESUMEN

Objetivo: Evaluar los efectos de la rizotomía sacral percutánea por radiofrecuencia en pacientes con lesión de la médula espinal sobre parámetros urodinámicos (capacidad cistométrica máxima [CCM] y presión del detrusor a capacidad cistométrica máxima [PdetCCM]). Material y Métodos: En este estudio prospectivo se evaluó a 8 pacientes con LME (4 hombres y 4 mujeres) con una media de edad de 31,3 años (de 22 a 41). El intervalo medio entre la lesión de la médula espinal y la rizotomía fue de 53,5 meses (entre 20 y 96). A todos los pacientes se les practicó un bloqueo anestésico bajo control fluoroscópico de la tercera raíz sacral de forma bilateral con bupivacaína 0,5%. Se eligió para rizotomía sacral percutánea por radiofrecuencia a los que respondieron con un aumento en la capacidad vesical. Se procedió a la evaluación urodinámica de todos los pacientes a los 6 y los 12 meses tras la realización del procedimiento. Se consignaron tanto la CCM como la PdetCCM. Resultados: Todos los pacientes mostraron una mejora significativa en la CCM a los 12 meses. El volumen vesical medio aumentó de los 100,2±57,1 a 282,9±133,4 ml (p < 0,05). La PdetCCM se redujo de 82,4±31,7 a 69,9±28,7 cm H2O (p = 0,2). Tres pacientes con disreflexia autonómica experimentaron un alivio total de los síntomas tras el procedimiento. A los 12 meses se observó una reaparición de la hiperactividad del detrusor en todos los pacientes. Un paciente presentó abolición de las erecciones reflejas tras el procedimiento. No se observaron complicaciones de importancia en relación con la rizotomía. Conclusiones: La rizotomía sacral percutánea por radiofrecuencia es una técnica mínimamente invasiva, de baja morbilidad, que puede aumentar la CCM. Existe una tendencia hacia la reducción de la PdetCCM en pacientes con LME a los 12 meses, a pesar de que no se alcanza un nivel estadísticamente significativo (AU)

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Introduction: To evaluate the effects of percutaneous radiofrequency sacral rhizotomy in spinal cord injured (SCI) patients on urodynamic parameters (maximum cystometric capacity — MCC and detrusor pressure at maximum cystometric capacity - PdetMCC). Material and Methods: This prospective study assessed eight patients with SCI (four men and four women) with a mean age of 31.3 years (22 to 41). Mean interval period between spinal cord lesion and rhizotomy was 53.5 months (20 to 96). All patients underwent an anesthetic block of the 3rd sacral root bilaterally using 0.5% bupivacaine under fluoroscopic control. Those who responded with an increase on bladder capacity were selected to undergo the percutaneous radiofrequency sacral rhizotomy. All patients underwent urodynamic evaluation at 6 and 12months following the procedure. MCC and PdetMCC were recorded. Results: All patients presented a significant improvement on MCC after 12 months. The mean vesical volume increased from 100.2±57.1 to 282.9±133.4 ml (p<0.05). The PdetMCC reduced from 82.4±31.7 to 69.9±28.7 cmH2O (p = 0.2). Three patients with autonomic dysreflexia had complete relief of symptoms after the procedure. At 12 months, recurrence of detrusor hyperactivity was observed in all patients. One patient presented abolishment of reflex erections after the procedure. No major complications related to the rhizotomy were noted.C onclusions: Percutaneous radiofrequency sacral rhizotomy is a minimally invasive technique with low morbidity able to increase MCC. There is a trend towards the reduction of the PdetMCC in SCI patients at 12 months, although statistical significance was not reached (AU)

Asunto(s)

Humanos , Masculino , Femenino , Adulto , Traumatismos de la Médula Espinal/diagnóstico , Traumatismos de la Médula Espinal/cirugía , Disreflexia Autónoma/diagnóstico , Disreflexia Autónoma/patología , Vejiga Urinaria Neurogénica/diagnóstico , Incontinencia Urinaria/diagnóstico , Vejiga Urinaria Neurogénica/complicaciones , Rizotomía/instrumentación , Rizotomía/métodos , Rizotomía , Urodinámica , Ablación por Catéter , Anestésicos Locales

RESUMEN

INTRODUCTION: To evaluate the effects of percutaneous radiofrequency sacral rhizotomy in spinal cord injured (SCI) patients on urodynamic parameters (maximum cystometric capacity - MCC and detrusor pressure at maximum cystometric capacity - PdetMCC). MATERIAL AND METHODS: This prospective study assessed eight patients with SCI (four men and four women) with a mean age of 31.3years (22 to 41). Mean interval period between spinal cord lesion and rhizotomy was 53.5 months (20 to 96). All patients underwent an anesthetic block of the 3rd sacral root bilaterally using 0.5% bupivacaine under fluoroscopic control. Those who responded with an increase on bladder capacity were selected to undergo the percutaneous radiofrequency sacral rhizotomy. All patients underwent urodynamic evaluation at 6 and 12 months following the procedure. MCC and P(det)MCC were recorded. RESULTS: All patients presented a significant improvement on MCC after 12 months. The mean vesical volume increased from 100.2±57.1 to 282.9±133.4ml (p<0.05). The P(det)MCC reduced from 82.4±31.7 to 69.9±28.7cmH(2)O (p=0.2). Three patients with autonomic dysreflexia had complete relief of symptoms after the procedure. At 12 months, recurrence of detrusor hyperactivity was observed in all patients. One patient presented abolishment of reflex erections after the procedure. No major complications related to the rhizotomy were noted. CONCLUSIONS: Percutaneous radiofrequency sacral rhizotomy is a minimally invasive technique with low morbidity able to increase MCC. There is a trend towards the reduction of the P(det)MCC in SCI patients at 12 months, although statistical significance was not reached.

Asunto(s)

Ablación por Catéter/métodos , Rizotomía/métodos , Traumatismos de la Médula Espinal/complicaciones , Vejiga Urinaria Neurogénica/cirugía , Vejiga Urinaria Hiperactiva/cirugía , Adulto , Femenino , Estudios de Seguimiento , Humanos , Masculino , Bloqueo Nervioso , Tamaño de los Órganos , Estudios Prospectivos , Resultado del Tratamiento , Vejiga Urinaria/patología , Vejiga Urinaria Neurogénica/etiología , Vejiga Urinaria Neurogénica/patología , Vejiga Urinaria Hiperactiva/etiología , Urodinámica , Adulto Joven

RESUMEN

Modern Field Programmable Gate Arrays (FPGAs) are capable of performing complex discrete signal processing algorithms with clock rates above 100MHz. This combined with FPGA's low expense, ease of use, and selected dedicated hardware make them an ideal technology for a data acquisition system for a positron emission tomography (PET) scanner. The University of Washington is producing a high-resolution, small-animal PET scanner that utilizes FPGAs as the core of the front-end electronics. For this next generation scanner, functions that are typically performed in dedicated circuits, or offline, are being migrated to the FPGA. This will not only simplify the electronics, but the features of modern FPGAs can be utilizes to add significant signal processing power to produce higher resolution images. In this paper we report on an all-digital pulse pileup correction algorithm that is being developed for the FPGA. The pileup mitigation algorithm will allow the scanner to run at higher count rates without incurring large data losses due to the overlapping of scintillation signals. This correction technique utilizes a reference pulse to extract timing and energy information for most pileup events. Using pulses were acquired from a Zecotech Photonics MAPDN with an LFS-3 scintillator, we show that good timing and energy information can be achieved in the presence of pileup.

RESUMEN

Our laboratory has previously reported on the basic design concepts of an updated FireWire based data acquisition system for depth-of-interaction detector systems designed at the University of Washington. The new version of our data acquisition system leverages the capabilities of modern field programmable gate arrays (FPGA) and puts almost all functions into the FPGA, including the FireWire elements, the embedded processor, and pulse timing and integration. The design is centered around an acquisition node board (ANB) that includes 64 serial ADC channels, one high speed parallel ADC, FireWire 1394b support, the FPGA, a serial command bus and signal lines to support a rough coincidence window implementation to reject singles events from being sent on the FireWire bus. Adapter boards convert detector signals into differential paired signals to connect to the ANB. In this paper we discuss many of the design details, including steps taken to minimize the number of layers in the printed circuit board and to avoid skewing of parallel signals and unwanted bandwidth limitations.

RESUMEN

This work presents a row/column summing readout electronics for an 8×8 silicon photomultiplier array. The summation circuit greatly reduces the number of electronic channels, which is desirable for pursuing higher resolution positron emission tomography scanners. By using a degenerated common source topology in the summation circuit, more fan-in is possible and therefore a greater reduction in the number of electronic channels can be achieved. The timing signal is retrieved from a common anode, which allows the use of a single fast-sampling analog to digital converter (ADC) for the timing channel and slower, lower power ADCs for the 64 spatial channels. Preliminary results of one row summation of the 8×8 readout electronics exhibited FWHM energy resolution of 17.8% and 18.3% with and without multiplexing, respectively. The measured timing resolution is 2.9ns FWHM.

RESUMEN

Reports on postoperative complications of anti-incontinence surgery followed the widespread use of synthetic slings. In this paper we describe the more frequent complications, such as obstruction, pelvic hematoma, bladder and urethral injuries, to facilitate the management of these complications.

Asunto(s)

Hematoma/etiología , Hematoma/terapia , Cabestrillo Suburetral/efectos adversos , Obstrucción del Cuello de la Vejiga Urinaria/etiología , Obstrucción del Cuello de la Vejiga Urinaria/terapia , Algoritmos , Femenino , Humanos , Obstrucción del Cuello de la Vejiga Urinaria/diagnóstico , Obstrucción del Cuello de la Vejiga Urinaria/fisiopatología

RESUMEN

Las complicaciones postoperatorias de la cirugía antiincontiencia, han comenzado a publicarse paralelamente al aumento proporcional del uso de la técnica de cabestrillo para la Incontinencia de orina de esfuerzo. En este trabajo de revisión describimos las complicaciones más frecuentes, como la obstrucción infravesical, el hematoma pélvico, lesiones uretrales y vesicales, con el fin de facilitar a quienes reproducen esta técnica una herramienta de diagnóstico y tratamiento para estas complicaciones (AU)

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Reports on postoperative complications of anti-incontinence surgery followed the widespread use of synthetic slings. In this paper we describe the more frequent complications, such as obstruction, pelvic hematoma, bladder and urethral injuries, to facilitate the management of these complications (AU)

Asunto(s)

Humanos , Masculino , Incontinencia Urinaria/complicaciones , Incontinencia Urinaria/terapia , Complicaciones Posoperatorias/epidemiología , Complicaciones Posoperatorias/terapia , Colgajos Quirúrgicos , Incontinencia Urinaria/epidemiología , Incontinencia Urinaria/cirugía , Complicaciones Posoperatorias/cirugía , Obstrucción del Cuello de la Vejiga Urinaria/complicaciones , Obstrucción del Cuello de la Vejiga Urinaria/fisiopatología , Obstrucción del Cuello de la Vejiga Urinaria/cirugía , Uretra/cirugía , Uretra

RESUMEN

Here we demonstrate a parametric positioning method on a continuous crystal detector. Three different models for the light distribution were tested. Diagnosis of the residues showed that the parametric model fits the experimental data better than Gaussian and Cauchy models in our particular experimental setup. Based on the correlation between the spread and the peak value of the light distribution model with the depth of interaction (DOI), we were able to estimate the three-dimensional position of a scintillation event. On our continuous miniature crystal element (cMiCE) detector module with 8 mm thick LYSO crystal, the intrinsic spatial resolution is 1.06 mm at the center and 1.27 mm at the corner using a maximum-likelihood estimation (MLE) method and the parametric model. The DOI resolution (full width at half maximum) is estimated to be approximately 3.24 mm. The positioning method using the parametric model outperformed the Gaussian and Cauchy models, in both MLE and weighted least-squares (WLS) fitting methods. The key feature of this technique is that it requires very little calibration of the detector, but still retains high resolution and high sensitivity.

Asunto(s)

Tomografía de Emisión de Positrones/instrumentación , Tomografía de Emisión de Positrones/métodos , Algoritmos , Cristalización , Diseño de Equipo , Interpretación de Imagen Asistida por Computador/métodos , Luz , Funciones de Verosimilitud , Modelos Estadísticos , Distribución Normal , Fotones , Física/métodos

RESUMEN

The University of Washington developed a Firewire based data acquisition system for the MiCES small animal PET scanner. Development work has continued on new imaging scanners that require more data channels and need to be able to operate within a MRI imaging system. To support these scanners, we have designed a new version of our data acquisition system that leverages the capabilities of modern field programmable gate arrays (FPGA). The new design preserves the basic approach of the original system, but puts almost all functions into the FPGA, including the Firewire elements, the embedded processor, and pulse timing and pulse integration. The design has been extended to support implementation of the position estimation and DOl algorithms developed for the cMiCE detector module. The design is centered around an acquisition node board (ANB) that includes 65 ADC channels, Firewire 1394b support, the FPGA, a serial command bus and signal lines to support a rough coincidence window implementation to reject singles events from being sent on the Firewire bus. Adapter boards convert detector signals into differential paired signals to connect to the ANB.

RESUMEN

We present a clustering method to extract the depth of interaction (DOI) information from an 8 mm thick crystal version of our continuous miniature crystal element (cMiCE) small animal PET detector. This clustering method, based on the maximum-likelihood (ML) method, can effectively build look-up tables (LUT) for different DOI regions. Combined with our statistics-based positioning (SBP) method, which uses a LUT searching algorithm based on the ML method and two-dimensional mean-variance LUTs of light responses from each photomultiplier channel with respect to different gamma ray interaction positions, the position of interaction and DOI can be estimated simultaneously. Data simulated using DETECT2000 were used to help validate our approach. An experiment using our cMiCE detector was designed to evaluate the performance. Two and four DOI region clustering were applied to the simulated data. Two DOI regions were used for the experimental data. The misclassification rate for simulated data is about 3.5% for two DOI regions and 10.2% for four DOI regions. For the experimental data, the rate is estimated to be approximately 25%. By using multi-DOI LUTs, we also observed improvement of the detector spatial resolution, especially for the corner region of the crystal. These results show that our ML clustering method is a consistent and reliable way to characterize DOI in a continuous crystal detector without requiring any modifications to the crystal or detector front end electronics. The ability to characterize the depth-dependent light response function from measured data is a major step forward in developing practical detectors with DOI positioning capability.

Asunto(s)

Algoritmos , Aumento de la Imagen/instrumentación , Interpretación de Imagen Asistida por Computador/instrumentación , Tomografía de Emisión de Positrones/instrumentación , Transductores , Cristalización/métodos , Diseño de Equipo , Análisis de Falla de Equipo , Aumento de la Imagen/métodos , Interpretación de Imagen Asistida por Computador/métodos , Fantasmas de Imagen , Tomografía de Emisión de Positrones/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad

RESUMEN

Our laboratory has been developing a depth-of-interaction (DOI) detector design based on light sharing between pairs or quadlets of crystals. Work to date has been utilizing 2×2 mm cross section crystals carefully positioned on a multi-anode PMT. However, there is still significant light sharing in the PMT glass envelope and current PMT designs do not allow one-on-one coupling for arrays of smaller cross section crystals. One-on-one coupling is optimal for implementing the DOI estimator. An alternative to PMTs is to take advantage of progress in fabrication of metal resistive-layer semiconductor photodetectors to provide arrays with one-on-one crystal coupling. We report on our initial tests of one manufacturer's devices. The photodetector (MAPD) and scintillator combination (LFS-3) are both products of Zecotek. The LFS-3 crystal is a variant of LFS that has a better spectral match to the MAPD. Measurements show performance equivalent to or better than that obtained with PMTs and LSO, LFS, or LYSO crystals. For example, 2×2×20 mm crystals are providing 11% energy resolution. The high gain of such devices allow flexibility in designs for both the array and the supporting electronics. We are proceeding with the dMiCE development based on the use of MAPD and LFS-3 arrays.

RESUMEN

The authors quantified the collagen and elastic fibers in the bladder wall of ovariectomized rats with and without estradiol replacement. This study was conducted on 60 3-month-old Wistar rats. Group 1 remained intact; group 2 underwent bilateral ovariectomy and were sacrificed after 30 days; group 3 were sham operated and sacrificed after 30 days; group 4 had a bilateral ovariectomy and after 30 days were started on subcutaneous injections of 17beta-estradiol (10 microg/kg body weight) for 90 days; group 5 were sham operated and after 30 days were on started subcutaneous sesame oil replacement (0.2 ml/day) for 90 days; group 6 had a bilateral ovariectomy and after 30 days were started on subcutaneous sesame oil replacement (0.2 ml/day) for 90 days. Sirius red and Weigert's resorcin-fuchsin were used to stain collagen and elastic fibers on paraffin-embedded rat bladder sections. The M-42 grid system was used to quantitatively analyze the fibers. Ovariectomy had no effect on the volumetric density and absolute volume of the collagen and elastic fibers in the bladder wall of rats, or on the weight of the bladder. Estradiol replacement in castrated animals did not demonstrate any significant difference in the stereological parameters compared to the castrated group without hormonal replacement.

Asunto(s)

Colágeno/análisis , Estradiol/farmacología , Ovariectomía/veterinaria , Vejiga Urinaria/ultraestructura , Animales , Tejido Elástico , Estradiol/administración & dosificación , Terapia de Reemplazo de Estrógeno , Femenino , Ratas , Ratas Wistar , Vejiga Urinaria/química

RESUMEN

Six new phenol (anthraquinone or stilbene) glycosides with an acyl group at 6-position of the glucopyranose moiety were isolated from rhubarb (the roots of Rheum palmatum) cultivated in Japan, together with 22 known compounds. Most of these compounds were evaluated for cytotoxic activity against tumor and normal cells and for induction of DNA damage by spore rec-assay. Among them, emodin and aloe-emodin showed higher cytotoxic activities against human oral squamous cell carcinoma (HSC-2) and salivary gland tumor (HSG) cell lines than against normal human gingival fibroblasts (HGF). Chrysophanol 8-O-beta-(6'-acetyl)glucopyranoside, 4-(4'-hydroxyphenyl)-2-butanone 4'-O-beta-D-(2"-O-galloyl-6"-O-cinnamoyl) glucopyranoside, and 6"-O-(4'''-hydroxybenzoyl) resveratroloside exhibited relatively higher cytotoxic activities against all these cells. The other glycosides of anthraquinone or stilbene showed weaker cytotoxic activity against these tumor cell lines, but may be considered as cancer chemopreventive agents. Spore rec-assay with a recombination deficient mutant of Bacillus subtilis M45 demonstrated the DNA damage-inducing activity of emodin and aloe-emodin 15-O-beta-D-glucopyranoside among, rhubarb phenols.

Asunto(s)

Daño del ADN , Fenoles/aislamiento & purificación , Fenoles/toxicidad , Rheum/química , Bacillus subtilis/efectos de los fármacos , Carcinoma de Células Escamosas/tratamiento farmacológico , Ensayos de Selección de Medicamentos Antitumorales , Glicósidos/aislamiento & purificación , Glicósidos/toxicidad , Humanos , Pruebas de Sensibilidad Microbiana , Peso Molecular , Neoplasias de la Boca/tratamiento farmacológico , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Raíces de Plantas/química , Células Tumorales Cultivadas

RESUMEN

The Ca2+-activated pathways of Saccharomyces cerevisiae induce a delay in the onset of mitosis through the activation of Swe1, a negative regulatory kinase that inhibits the Cdc28-Clb complex. Calcineurin and Mpk1 activate Swe1 at the transcriptional and post-translational level, respectively, and both pathways are essential for the cell cycle delay. Our genetic screening identified the MCK1 gene, which encodes a glycogen synthetase kinase-3 family protein kinase, as a component of the Ca2+ signaling pathway. Genetic analyses indicated that Mck1 functions downstream of the Mpk1 pathway and down-regulates Hsl1, an inhibitory kinase of Swe1. In medium with a high concentration of Ca2+, Hsl1 was delocalized from the bud neck and destabilized in a manner dependent on both calcineurin and Mck1. Calcineurin was required for the dephosphorylation of autophosphorylated Hsl1. The E3 ubiquitin ligase complex SCF(Cdc4), but not the anaphase-promoting complex (APC), was essential for Hsl1 destabilization. The Ca2+-activated pathway may play a role in the rapid inactivation of Hsl1 at the cell cycle stage(s) when APC activity is low.

Asunto(s)

Calcineurina/metabolismo , Señalización del Calcio/efectos de los fármacos , Calcio/farmacología , Proteínas F-Box , Regulación Fúngica de la Expresión Génica/efectos de los fármacos , Proteínas Quinasas Activadas por Mitógenos , Proteínas Quinasas/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/enzimología , Complejos de Ubiquitina-Proteína Ligasa , Ubiquitina-Proteína Ligasas , Ciclosoma-Complejo Promotor de la Anafase , Calcineurina/genética , Proteínas Quinasas Dependientes de Calcio-Calmodulina/química , Proteínas de Ciclo Celular/metabolismo , División Celular/efectos de los fármacos , Regulación hacia Abajo/efectos de los fármacos , Activación Enzimática , Epistasis Genética , Citometría de Flujo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Fase G2/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Genes Fúngicos/genética , Glucógeno Sintasa Quinasa 3 , Ligasas/metabolismo , Modelos Biológicos , Mutación , Péptido Sintasas/metabolismo , Proteínas Quinasas/genética , Proteínas Serina-Treonina Quinasas , Proteínas Tirosina Quinasas/química , Proteínas Tirosina Quinasas/genética , ARN de Hongos/genética , ARN de Hongos/metabolismo , Proteínas Ligasas SKP Cullina F-box , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Transcripción Genética

RESUMEN

Interest in clinical fluorodeoxyglucose (FDG) imaging with dual-headed gamma cameras continues to grow. In 1996, Jarritt and Acton published a review article of the use of gamma-camera systems for FDG imaging [1]. Since that article was published, considerable progress has been made in the adaptation of dual-headed camera systems for coincidence imaging. We review the basic principles of dual-headed coincidence imaging and some of the major limitations and challenges in the development of such technology. Since much of the current clinical experience with FDG imaging is based on the use of dedicated position emission tomographic (PET) systems, some comparisons of the performance limitations between dual-headed gamma-camera and dedicated PET systems are provided.

Asunto(s)

Cámaras gamma , Tomografía Computarizada de Emisión/instrumentación , Fluorodesoxiglucosa F18 , Humanos , Modelos Estadísticos , Radiometría , Sensibilidad y Especificidad

RESUMEN

UNLABELLED: The use of high-dose 131I antibody therapy requires accurate measurement of normal tissue uptake to optimize the therapeutic dose. One of the factors limiting the accuracy of such measurements is scatter and collimator septal penetration. This study evaluated two classes of energy-based scatter corrections for quantitative 131I imaging: window-based and spectrum-fitting. METHODS: The window-based approaches estimate scatter from data in two or three energy windows placed on either side of the 364-keV photopeak using empirical weighting factors. A set of images from spheres in an elliptical phantom were used to evaluate each of the window-based corrections. The spectrum-fitting technique estimates detected scatter at each pixel by fitting the observed energy spectrum with a function that models the photopeak and scatter, and which incorporates the response function of the camera. This technique was evaluated using a set of Rollo phantom images. RESULTS: All of the window-based methods performed significantly better than a single photopeak window (338-389 keV), but the weighting factors were found to depend on the object being imaged. For images contaminated with scatter, the spectrum-fitting method significantly improved quantitation over photopeak windowing. Little difference, however, between any of the methods was observed for images containing small amounts of scatter. CONCLUSION: Most clinical 131I imaging protocols will benefit from qualitative and quantitative improvements provided by the spectrum-fitting scatter correction. The technique offers the practical advantage that it does not require phantom-based calibrations. Finally, our results suggest that septal penetration and scatter in the collimator and other detector-head components are important sources of error in quantitative 131I images.

Asunto(s)

Cámaras gamma , Radioisótopos de Yodo , Fantasmas de Imagen , Dosis de Radiación , Radiometría , Cintigrafía/métodos , Dispersión de Radiación