ABSTRACT
In this work, it is shown how a tilt can be introduced into a segmented surface through several piston terms, by using the classical Ronchi test. We have developed tilt error simulations by adding multiple constant terms to each point on the sagitta surface of a segment using ray tracing. Thereby a comparison between simulated Ronchigrams for piston and tilt has been performed for two adjacent segments, so that it is possible to appreciate the tilt and piston effects on the shape of the patterns. As a result, we show the behavior of the central maximum of the fringes in the presence of tilt and/or piston. Additionally we present evidence of introducing tilting without changing the surface shape by adding multiple pistons, and a description of how to characterize both piston and tilt using the Ronchi test.
Subject(s)
Adenocarcinoma/diagnostic imaging , Adenocarcinoma/secondary , Choline/analogs & derivatives , Fluorine Radioisotopes , Multimodal Imaging , Positron-Emission Tomography , Prostatic Neoplasms/pathology , Tomography, X-Ray Computed , Aged , Clavicle , Humans , Lymphatic Metastasis/diagnostic imaging , MaleABSTRACT
La Tomografía por Emisión de Positrones con 18F-Fluorodeoxiglucosa (PET-FDG) es una técnica de diagnóstico por imagen cuyo uso se ha generalizado en España durante la última década. Para optimizar la utilización de esta tecnología es necesario ajustarse a una serie de indicaciones concretas, en las cuales la PET-FDG ha demostrado sobradamente su superioridad con respecto a los métodos convencionales de diagnóstico. Dichas indicaciones incluyen: la estadificación de tumores pulmonares y linfomas; la reestadificiación de tumores de tiroides, colorrectales, de cabeza-cuelli, linfomas y melanomas; la localización de tumores de origen desconocido; la caracterización del nódulo pulmonar solitario; y por último, el diagnóstico diferencial recidiva/radionecrosis en tumores cerebrales (AU)
This work details the Positron Emission Tomography technique with 18F-Fluorodeoxiglucose (PET-FDG), the use of which is becoming more generalized in our country. It also explains that in order to optimize the use of this technology, it is necessary to meet a series of specific indications, where its superiority has been demonstrated with respect to conventional diagnostic methods (AU)
Subject(s)
Humans , Male , Female , Positron-Emission Tomography/methods , Neoplasms/diagnosis , Positron-Emission Tomography , Neoplasm Recurrence, Local/diagnosis , Neoplasm Staging/methods , Diagnosis, DifferentialABSTRACT
La Tomografía por Emisión de Positrones con 18F-fluorodeoxiglucosa (PET-FDG) es una técnica de diagnóstico por imagen cuyo uso se ha generalizado en España durante la última década. Existen una serie de indicaciones concretas, en las cuales la PET-FDG ha demostrado sobradamente su superioridad con respecto a los métodos convencionales de diagnóstico. Es recomendable, por ello, realizar un estudio PET-FDG únicamente en las siguientes situaciones: la estadificación de tumores pulmonares y linfomas, la re-estadificación de tumores de tiroides, colorrectales, de cabeza-cuello, linfomas y melanomas; la localización de tumores de origen desconocido; la caracterización del nódulo pulmonar solitario; y, por último, el diagnóstico diferencial recidiva/radionecrosis en tumores cerebrales (AU)
Subject(s)
Humans , Tomography, Emission-Computed , Neoplasms/diagnosis , Diagnosis, Differential , Patient Selection , Fluorodeoxyglucose F18ABSTRACT
La tomografía por emisión de positrones con 18-Fluorodesoxiglucosa (PET-FDG) ha ido ampliando progresivamente sus aplicaciones oncológicas en los últimos años, entre ellas a los tumores con origen endocrino. En la glándula tiroidea, aunque no se ha demostrado su utilidad para la distinción entre patología benigna y maligna, es la prueba de elección en los carcinomas diferenciados (foliculares y papilares) ante elevación persistente de tiroglobulina y rastreos corporales con 131-I negativos. Asimismo, también se han obtenido buenos resultados utilizándolo como método de seguimiento de los tumores anaplásicos y medulares. En cuanto a las neoplasias de origen neuroendocrino, la PET-FDG es especialmente útil en tumores con bajo grado de diferenciación y alto índice proliferativo. En este ámbito, se encuentran en desarrollo nuevos radiofármacos PET, fundamentalmente para la evaluación de tumores carcinoides y feocromocitomas (AU)
Subject(s)
Humans , Tomography, Emission-Computed/methods , Endocrine Gland Neoplasms , Carcinoid Tumor , Pheochromocytoma , Neuroendocrine Tumors , Fluorodeoxyglucose F18ABSTRACT
We used a LED in a Ronchi tester to obtain two main improvements: (i) We can choose one of two wavelength bands to illuminate and record the ronchigram, and (ii) we can change the irradiance of the illumination source according to the optical system under test and the detector array. This can be done by use of an adequate electronic circuit.
ABSTRACT
We present an algorithm that uses a square grid in a Ronchi test. We assume that the point coordinates of this pattern (termed a bironchigram) are affected by Gaussian errors. To calculate the optical path difference, we apply only one nonlinear least-squares fit to the dot coordinates. The relevant equations are deduced, and experimental results are shown.
ABSTRACT
Segmented mirrors will be used in the telescopes of the Pierre Auger Fluorescence detector. To align the segments, we have developed four methods in which (a) the image of the stop border, (b) the image of a screen with concentric circles, and (c) the Ronchi pattern are used. In addition to these, we have developed a new method, (d), in which instead of the Ronchi ruling, we have used a circular grid. In this case we obtain a moiré pattern for each segment by means of which the experimental setup is simplified, and the sensitivity of the alignment is improved.
ABSTRACT
Sagittal sections of the brain-stem made by MRI reveal differences in the angle formed by the medulla and the cord. In order to study the normal mobility of this region of the CNS during flexion and extension of the head, sagittal MRI studies were made in the sagittal plane in 18 young volunteers. The volunteers were in dorsal decubitus with the cervical spine first flexed and then extended, with the movement localized to the cranio-cervical junction as far as possible. T1-weighted sequences were used, with body coils in 16 cases and surface coils in two. Measurements were related to global cranio-cervical range of movement, movement at the cranio-cervical junction and spino-medullary movement. Variations in the depth of the free space in front of the medulla, pons and spinal cord during movement were also noted. We also checked for downward shift of the lower part of the 4th ventricle and modification of the shape of the ventricle during flexion-extension. The global range of cranio-cervical movement was between 31 and 100 degrees (average 63 degrees). The range between the cranium and C1C2 was 4 to 39 degrees (average 19 degrees) and the spino-medullary range was from 1 to 32 degrees (average 14 degrees). During flexion, the free space narrowed in front of the pons 11 times, in front of the medulla 14 times and in front of the cervical cord 11 times. There was a downward shift of the lower part of the 4th ventricle during flexion in 4 cases but no change in shape was noted. Though this study is open to criticism from several aspects, it may be concluded that variations of the spino-medullary angle in the sagittal plane during flexion-extension do occur, that they are closely correlated with movements at the cranio-cervical junction, moves forward during flexion.
Subject(s)
Magnetic Resonance Imaging , Medulla Oblongata/physiology , Spinal Cord/physiology , Adult , Biomechanical Phenomena , Female , Humans , Male , Medulla Oblongata/anatomy & histology , Movement , Spinal Cord/anatomy & histologyABSTRACT
Fetal magnetic resonance (MR) imaging was performed at 33 weeks of gestation for investigation of a posterior fossa abnormality found at ultrasound screening. Fetal movements were abolished by vecuronium injected under ultrasound guidance into the umbilical vein. MR images showed atrophy of the left cerebellar lobe with cisternal dilatation. These were confirmed postnatally by CT scan.
Subject(s)
Brain/abnormalities , Magnetic Resonance Imaging/methods , Neuromuscular Nondepolarizing Agents/administration & dosage , Prenatal Diagnosis , Adult , Female , Humans , Pregnancy , Pregnancy Trimester, Third , Umbilical VeinsSubject(s)
Magnetic Resonance Spectroscopy , Optic Nerve , Cranial Nerve Neoplasms/diagnosis , Cranial Nerve Neoplasms/diagnostic imaging , Humans , Magnetic Resonance Spectroscopy/methods , Optic Nerve/diagnostic imaging , Optic Nerve Diseases/diagnosis , Optic Nerve Diseases/diagnostic imaging , Tomography, X-Ray ComputedABSTRACT
A prospective study of 52 boxers, 20-60 years, 13 of them amateurs and 39 professionals, has been made using magnetic resonance imaging (MRI) at 0.15 T. Twelve of the boxers were still active, while the other 40 had retired after about 10 years of boxing. Multi-slices in two planes without gap were performed using T1 and T2 weighted sequences. The findings were correlated to the number of matches, the number of knock outs, the severity of head trauma, the style of the boxer, and to the clinical findings and the findings at EEG. There was a good correspondence between the presence of lesions and the style of the boxer. The changes noted--mainly atrophic--occurred among those with capacity to 'stand punishment'. MRI offers an opportunity to evaluate the effect of trauma and the information obtained may be used to prevent disabilities among boxers.
