Explorando el oscuro continente: imagen médica y cerebro / Exploring the dark continent: medical image and brain

Introducción. Hasta finales del siglo XIX, el sistema nervioso central es prácticamente inaccesible a la observación directa. El descubrimiento en 1895 de los rayos X y su posterior aplicación médica constituyen un cambio de paradigma que revoluciona por completo la manera en que se practica la neurología. La posibilidad de visualizar el interior del encéfalo tiene un impacto mayúsculo en la práctica clínica y enriquece el diagnóstico y el tratamiento de patologías cerebrales de una forma hasta entonces inimaginable. Desarrollo. El propósito de este trabajo es describir el nacimiento y el desarrollo de la imagen médica cerebral: partimos del descubrimiento de los rayos X y del inicio de la radiografía hasta llegar a la aparición en la década de los setenta de la tomografía computarizada y la resonancia magnética, técnicas que cambiarían el mundo del diagnóstico por imagen. En este breve recorrido por la historia de la neurorradiología también se incluye el origen de la angiografía y otras técnicas actualmente en desuso, pero que en su momento constituyeron una auténtica revolución; tal es el caso de la ventriculografía o la neumoencefalografía. Conclusiones. Los procedimientos y técnicas descritos en este artículo han permitido visualizar el interior del cerebro, facilitando el diagnóstico y el tratamiento de múltiples procesos neurológicos (AU)

Introduction. Until the late 19th century, direct observation of the central nervous system was practically impossible. The discovery of X-rays in 1895 and their subsequent application in the field of medicine brought about a shift of paradigm that completely revolutionised the way in which neurology was practised. The possibility of viewing the inside of the brain had a pronounced impact on clinical practice, and enriched the diagnosis and treatment of brain pathologies in a manner that was unimaginable up until then. Development. The aim of this study is to describe the birth and development of medical imaging of the brain, from the discovery of X-rays and the early days of radiography to the appearance of computerised tomography and magnetic resonance in the 60s, both of which are techniques that were to change the world of diagnostic imaging forever. This brief overview of the history of radiology also includes the origins of angiography and other techniques that are no longer in use, but which were ground-breaking innovations in their time, such as ventriculography or pneumoencephalography. Conclusions. The procedures and techniques described in this article made it possible to view the inside of the brain, thereby facilitating the diagnosis and treatment of a number of neurological processes (AU)

Integrated PET/CT in lung cancer imaging: history and technical aspects.

Integrated PET/CT is a new anatomo-metabolic imaging modality combining two different techniques: Computed Tomography (CT) that provides very detailed anatomic information and Positron Emission Tomography (PET) that provides metabolic information. Integrated PET/CT has several advantages. One of the advantages is the use of CT data for attenuation correction that is significantly faster compared to that in conventional PET systems. Due to the use of CT data for attenuation correction, artefacts can be generated on PET images related to the use of intravenous or oral CT contrast agents, CT beam-hardening artefacts due to metallic implants and motion artefacts (respiratory motion, physical bowel motion, cardiac motion). The purpose of this review is to discuss some technical considerations concerning the CT protocol that can be used for PET/CT in lung cancer imaging and to give a short overview of the initial results of staging of non-small cell lung cancer (NSCLC).

Impacto de la imagen por resonancia magnética (IRM) en la práctica médica / Images´s impact for magnetic resonance (IMR) in the medical practice

No disponible

The evolution of medical imaging: from Geiger counters to MRI--a personal saga.

This article traces the evolution of medical imaging, from the crude images of the thyroid gland obtained using Geiger and scintillation counters, to the automatic scanners built to image brain tumors and organs, to gamma cameras, to digital imaging. A computed tomography scanner built in Aberdeen in the late 1960s led to the present-day gamma-camera tomographs, the main workhorse of nuclear medicine. The gradual evolution of the steps needed for clinical magnetic resonance imaging (MRI) are described, along with the rapid development of this novel form of body imaging. A brief account is also given of the present-day use of MRI in clinical medicine worldwide, with some modern cutting-edge applications, and its possible future.

Molecular imaging of the brain: a historical perspective.

The rapid expansion of modern molecular imaging methods since the time of their initial conception in the 1970s has given rise to numerous discoveries of molecular mechanisms that underlie brain function in health and disease. Uses in clinical diagnosis and therapy monitoring are still evolving. Future clinical trials, in which molecular imaging is imbedded and correlated with clinical outcomes, will be critical to advancing new uses for patient management. Receptor occupancy studies are already well integrated into many drug development studies and clinical trials; such studies will provide a basis for new studies that will further advance clinical uses of brain molecular imaging.

Inovações e trajetórias tecnológicas no território das imagens médicas / Technological inovations in the medical imaging area

O campo das imagens médicas é uma das áreas da medicina onde o desenvolvimento e a incorporação de novas tecnologias à prática clínica e aos sistemas de saúde têm sido particularmente significativo. Essa tese tem por objeto o estudo do progresso técnico relacionado a três tecnologias de imagem introduzidas no cuidado à saúde nos últimos trinta anos: a tomografia computadorizada, a imagem por ressonância magnética e a tomografia por emissão de pósitrons. Sua proposta foi caracterizar a trajetória de desenvolvimento destas tecnologias de imagem, buscando reconhecer os diferentes fatores e mecanismos envolvidos na dinâmica deste processo. Para tal, utilizou-se de um conjunto de ferramentas oriundas do campo da economia da inovação - os conceitos de paradigma e trajetória tecnológica, de design dominante e de sistemas tecnológicos - que trabalham com a visão de multideterminação do desenvolvimento tecnológico, reconhecendo as inter-relações entre vários condicionantes como o progresso científico, as necessidades clínicas, o mercado e as políticas públicas. O conhecimento dos fatores e mecanismos intervenientes no desenvolvimento dessas tecnologias traz elementos que permitem uma melhor compreensão do processo de inovação tecnológica no setor de imagens. Elas podem auxiliar na avaliação de propostas de intervenção e na formulação de políticas referentes a estes equipamentos, seja no que diz respeito a políticas industriais, seja no que se refere a decisões internas ao sistema de saúde relacionadas com o acesso, uso e financiamento destas tecnologias e procedimentos.

Perfusion thresholds in human cerebral ischemia: historical perspective and therapeutic implications.

After middle cerebral artery occlusion (MCAO) in the laboratory animal, the ischemic penumbra has been documented as a severely hypoperfused, functionally impaired, but still viable cortex which can regain its function and escape infarction if it is reperfused before a certain time has elapsed. The penumbra surrounds the ischemic core of already irreversibly damaged tissue, and is progressively recruited into the core with increasing MCAO duration. In the animal, the threshold of cerebral blood flow (CBF) below which neuronal function is impaired and the tissue is at risk of infarction is around 22 ml/100 g/min (approximately 40% of normal) in the awake or lightly anesthetized monkey, and around 30--35 ml/100 g/min in the cat and the rat. The threshold of CBF below which the tissue becomes irreversibly damaged and will progress to infarction depends on the duration of ischemia, and is around 10 ml/100 g/min for 1--2 h (approximately 20% of normal) and around 18 ml/100 g/min for permanent ischemia in the monkey. Mildly reduced CBF down to the 40% threshold (termed 'oligemia') is normally well tolerated, and the affected tissue is not at risk of infarction under uncomplicated conditions (in the animal, however, selective neuronal death may occur even with only mildly reduced CBF values, but this sequela of stroke seems an exceptional encounter in man). Classic studies with carotid artery clamping in man have provided estimates for the penumbra threshold at around 20 ml/ 100 g/min for the whole brain, but only recently have imaging studies allowed to document the existence of the penumbra in acute stroke and given estimates of local CBF thresholds. With PET, the penumbra is characterized by a reduced CBF, an increased oxygen extraction fraction, and a relatively preserved oxygen consumption (CMRO(2)). In a series of PET studies performed 5--18 h after stroke onset, we have determined the threshold for penumbra to be around 20 ml/100 g/min, and documented that the extent of neurological recovery is proportional to the volume of penumbra that eventually escaped infarction. Within this time interval, the thresholds for irreversible damage were around 8 ml/ 100 g/min for CBF and around 0.9 ml/100 g/min for CMRO(2). Recent studies with diffusion-weighted and perfusion MR have reported similar relative thresholds for CBF of about 50 and 18% for penumbra and core, respectively. Although it is likely that the threshold for irreversibility will be lower with shorter duration since clinical onset, this has not been documented thus far. Because saving the penumbra will improve clinical outcome, it should constitute the main target of acute stroke therapy. We found evidence of penumbra in about one third of the cases studied between 5 and 18 h after onset, and as late as 16 h after symptom onset in occasional patients, suggesting the therapeutic window may be protracted in at least a fraction of the cases; similar experience has recently accrued from diffusion-weighted MR and perfusion MR. In the remaining patients, there was evidence of early extensive damage or early spontaneous reperfusion, which would make them inappropriate candidates for neuroprotective therapy. Recent evidence from PET studies of relative perfusion performed within 3 h of onset suggests that early thrombolysis indeed saves the tissue with CBF below a critical threshold of 12 ml/ 100 g/min, with a correlation between the volume of such tissue escaping infarction and subsequent neurological recovery. Thus, mapping the penumbra in the individual patient with physiologic imaging should allow to formulate a pathophysiological diagnosis, and in turn to design a rational management of the stroke patient and to increase the sensitivity of drug trials by appropriate patient selection.

What does positron emission tomography offer oncology?

The origins of positron emission tomography (PET) date back 70 years. Since the 1970s, however, its use has increased exponentially in the fields of neurology, cardiology and oncology. [18F]-Fluorodeoxyglucose (FDG) whole-body scanning is by far the most widely utilised and recognised application of PET in oncology. However, PET is a very versatile and powerful imaging modality capable of helping bridge the gap between the laboratory and the clinic. This article reviews the history and current applications of PET in oncology and then explores some of the newer applications and potential future uses of this versatile technology particularly in the area of cancer research.

Radiopharmaceuticals for nuclear endocrinology at the University of Michigan.

The historical background at the University of Michigan laid a foundation for the innovative development of radionuclides in diagnosis and treatment of endocrine diseases. From that background, Dr. William Beierwaltes, the chief of Nuclear Medicine, inspired two talented young chemists to synthesize unique radiopharmaceuticals that transformed diagnostic approaches to certain endocrine disorders. Dr. Raymond Counsell's 131-I-radiocholesterol, enabled imaging that defined function in the adrenal cortex, and thereby distinguished the different forms of Cushing's syndrome and of primary aldosteronism; in addition, this new technique differentiated benign adrenal cortical adenomas from other adrenal cortical tumors. Dr. Donald Wieland created metaiodobenzlylguanidine (MIBG), a compound that can be tagged with either 131-I or 123-I, and led to the scintigraphic depiction of adrenergic tumors, particularly pheochromocytomas and neuroblastoma, anywhere in the body of a patient. Treatments with large doses of MIBG have reduced the malignant forms of pheochromocytomas and brought remissions to children with neuroblastomas. MIBG also concentrated in the autonomic neurons and so the nerves of the heart were also portrayed. Subsequent novel syntheses included positron-emitting nuclides that, through positron emission tomography, have revealed the physiology and altered physiology of the human heart. These men and their discoveries exemplify the creative endeavors that compel us to seek further the wonders of nuclear science.