Radionuclide Brain Imaging Research Articles

Radionuclide brain imaging correlates of cognitive impairment in Parkinson's disease (PD)

A subtle cognitive impairment can be detected early in the course of Parkinson's disease (PD). Executive, memory and visuospatial functions are specifically affected, but the underlying pathophysiological basis is not well elucidated yet and may be heterogeneous. The recent identification of a PD-related cognitive metabolic pattern (PDCP), including hypometabolism in associative frontal, parietal and posterior limbic structures, has integrated the classical notion of a striato-frontal syndrome at the basis of cognitive dys-function. Recent evidence suggests that whilst executive dys-function is seen in virtually all PD patients, visuospatial and memory impairment may share a higher risk for the subsequent development of dementia. By means of perfusion SPECT and [18F]FDG-PET, cortical dys-function may be highlighted since the early stages, it is more evident in PD patients with Mild Cognitive Impairment (MCI), and reaches the maximum in PD dementia (PDD). Posterior temporo–parieto–occipital dys-function in associative and limbic cortex, closely resembling that found in Alzheimer's disease patients, is found in PDD, with a more severe occipital hypometabolism and a relatively milder hypometabolism in medial temporal lobe structures. Furthermore, deficit of acetylcholinesterase (AchE) can be found by means of [11C]MP4A-PET already in early stage of PD, especially in posterior regions, then becoming more severe in PDD and in dementia with Lewy bodies (DLB). Administration of AchE inhibitors to PDD patients increased brain metabolism in bilateral frontal and left parietal regions, and left posterior cingulate. Finally, the recent availability of radiopharmaceuticals able to disclose amyloid brain deposition has allowed to demonstrate amyloid load in a part of patients with PDD, possibly due to diffuse rather than neuritic plaques. Brain PET and SPECT have strongly contributed to the understanding of the pathophysiology of cognitive impairment in PD and may serve as probes to monitor the effects of therapeutic interventions.

Benign Hereditary Chorea: Clinical, Neuroimaging, and Genetic Findings

Benign hereditary chorea is an autosomal dominant disease with an early onset of symptoms. In some families, symptoms tend to decrease in adulthood, suggesting that the disorder results from a developmental disturbance in the brain. Individuals with benign hereditary chorea, a nonprogressive disease, have normal or slightly below normal intelligence. The locus for benign hereditary chorea is on chromosome 14. Benign hereditary chorea is a result of mutations in the thyroid transcription factor 1 gene. Previous neuroimaging and pathological investigations of the brain showed no notable abnormalities in patients with this condition. In this study, 5 patients from 1 family with typical clinical features of benign hereditary chorea are presented. Clinical severity varied considerably in the family. Brain magnetic resonance imaging results were normal. Brain single photon emission computed tomography in 3 children, performed 1 hour after intravenous injection of 0.35 mCi/kg of body weight of technetium 99m ethyl cysteinate dimer, showed markedly decreased uptake in the right striatum and the right thalamus in 1 child. The oldest child had mildly reduced uptake in the right putamen and the left thalamus. Brain single photon emission computed tomographic findings in the youngest child were normal. Contrary to other reports of radionuclide brain imaging, notable brain single photon emission computed tomography changes were detected in 2 of 5 patients. Brain single photon emission computed tomography findings did not seem to correlate with the clinical status of the children.

The Clinical Role of SPECT in Patients with Brain Tumors

The introduction of computed tomography (CT) in the early 1970s effectively replaced radionuclide brain imaging as the main modality to evaluate the structure and morphology of brain tumors. There are, nevertheless, a number of management problems in patients with suspected brain tumors that can be addressed only by functional imaging. There is the need to determine whether a focal mass detected on CT or magnetic resonance imaging (MRI) is benign or malignant. Since the prognosis of the patient is related to the tumor grade, and because stereotactic biopsy recovers only a small fragment of the tumor, there is the need for an imaging technique that reflects the behavior and the malignancy of the tumor. After treatment, it is important to continue to determine the cause of clinical deterioration in patients with glioma who have received high doses of radiation. Progressive radiation necrosis may require surgical debulking. Detection and localization of solid tumor recurrence, on the other hand, may aid in designing treatment. Positron emission tomography (PET) using 1xF‐fluorodeoxyglucose (18FDG) has been the standard functional imaging modality in these patients. With the introduction of single‐photon emitting brain perfusion tracers in the last decade, brain single‐photon emission computed tomography (SPECT) has reemerged as a useful measure of brain function. Other tracers such as thallium‐201 (201TI) chloride have emerged as tumor markers and have also found a role in brain SPECT. This review evaluates the clinical value and potential of201TI and perfusion brain SPECT in patients with brain tumors

Feasibility of dual radionuclide brain imaging with I‐123 and Tc‐99m

A study was conducted to evaluate the feasibility of simultaneous dual radionuclide brain imaging with 123I and 99mTc using photopeak image subtraction techniques or offset photopeak image acquisition. The contribution of the photons from one radionuclide to a second radionuclide's photopeak energy window (crosstalk) was evaluated for SPECT and planar imaging of a brain phantom containing 123I and 99mTc for a range of activity levels and distribution properties approximating those in rCBF images of the adult human brain. Crosstalk was evaluated for 10% symmetrical energy windows centered on the 123I and 99mTc photopeaks and for 10% energy windows asymmetrically placed to the left and right of the center of the respective photopeaks. Major observations include: (1) in the centered photopeak windows, 99mTc crosstalk in the 123I window is 8.9% of the 99mTc seen in the 99mTc window and ranges from 37.5% to 75.0% of the 123I in the 123I window. 123I crosstalk is 37.8% of the 123I seen in the 123I window and ranges from 4.4% to 8.9% of the 99mTc seen in the 99mTc window; (2) the spatial distribution of a radionuclide's crosstalk photons differs from that observed in the radionuclide's photopeak window; (3) a 99mTc photopeak window offset to the left does not decrease 123I crosstalk, and the percentage of 99mTc scattered photons is significantly increased in the window.(ABSTRACT TRUNCATED AT 250 WORDS)

Conventional radionuclide brain imaging in the era of transmission and emission tomography

The clinical applications for conventional radionuclide brain imaging have declined considerably since the introduction of newer imaging modalities (computerized cranial tomography [CCT], nuclear magnetic resonance [NMR]). Currently, conventional brain imaging primarily serves as a complementary test when CCT is negative or equivocal and strong clinical suspicion remains. Selected areas in which radionuclide imaging may be the preferred modality include evaluation of cerebral perfusion in assessment of brain death, detection of early viral encephalitis, evaluation of major venous sinus patency, external marking for localization of intracranial tumor, and in selected cases of suspected subdural hematoma, brain tumor, and cerebrovascular disease. The concept of conventional radionuclide brain imaging will likely undergo considerable change in the near future as newer radiopharmaceuticals are introduced and wider application is made of single photon emission computerized tomography (SPECT) and positron emission tomography (PET) imaging.

Radionuclide Techniques for Brain Imaging

Over the past decade, many of the prime indications for radionuclide brain scanning have become instead indications for CCT, and nuclear medicine studies of the brain have assumed more of a complementary, supportive role. However, there is great promise for improvement in central nervous system radionuclide applications with advances anticipated in both radiopharmaceuticals and instrumentation. Nuclear medicine is continuing to function as a powerful research tool and, in the relatively near future, may regain its role as a major clinical test of the central nervous system.

The role of radionuclide brain imaging and computerized tomography in the early diagnosis of herpes simplex encephalitis

We have reviewed the medical records and radiographic examinations of 12 patients with herpes simplex encephalitis to assess the role of RN and CT in the early diagnosis of this disease. The initia RN study was positive in 83% (10/12) of cases while the initial CT study was positive in 75% (9/12) of cases. The earliest positive RN was seen on the second day after the onser of neurologic signs or symptoms while the earliest positive CT was seen on the third day. We describe various abnormal patterns encountered in HSE and discuss their diagnostic reliability. We make recommendations for the diagnosis of HSE based on our findings and on the information available in the literature.

Cranial Computerized Axial Transmission Tomography With and Without Contrast Enhancement Compared With Radionuclide Brain Imaging

<h3>To the Editor.—</h3> The article by Heath et al (Archives138:628-629, 1978) that prompted two editorials in theArchives(138:530-532, 1978) makes the statement: "Comparative studies of radionuclide imaging and CT [computerized tomographic] scans, with and without iodine enhancement, in diagnosing brain abscesses have not appeared in the literature." Two recent publications address themselves at least partially to this issue^1.2 We disagree with the statement that credits radionuclide imaging (RI) with an almost 100% sensitivity rate in detecting intracranial abscesses. Radionuclide imaging has inherent limitations; the resolution limit of presently available large field-of-view gamma cameras for brain lesions is about 1.5 cm. In clinical practice, a lesion below that limit is unlikely to be detected. Unless a scrupulous technique is used in positioning the head, structures in the posterior fossa may be poorly visualized. Pathologic findings near the base of the skull are also known to present greater diagnostic difficulty.

Cranial computerized axial transmission tomography with and without contrast enhancement compared with radionuclide brain imaging

Cranial computerized axial transmission tomography with and without contrast enhancement compared with radionuclide brain imaging

Radionuclide Brain Scan Findings in Superior Sagittal Sinus Thrombosis

Superior sagittal sinus thrombosis is a serious condition requiring early diagnosis. This paper presents our experience with two cases and describes the findings. In one case radionuclide brain imaging was the first study performed. In the other, the diagnosis was made at arteriography with scanning used for follow-up.

Radionuclide brain imaging—its role and relation to CT scanning

Separate CNS disease entities are discussed with either the complementary or exclusive indications for radionuclide brain imaging and computerized cranial tomography. Either modality alone has a potential overall precision somewhat in excess of 90° in the localization of cerebral lesions with the effectiveness of each modality differing according to the histology and anatomic location of the lesion. Most investigators agree that the combined application of the two procedures is far superior to their separate use. Routine dynamic isotope studies are essential and in addition, new radiopharmaceuticals and technological advances may improve the radionuclide evaluation of CNS disease. Areas discussed include: primary and secondary CNS neoplasms; acute cerebrovascular accidents: arteriovenous malformations; traumatic cerebrovascular disease: hydrocephalus and dementia; and intracranial inflammatory processes.

Role of the radionuclide brain image in the diagnosis of brainstem gliomas.

The noninvasive detection of brainstem gliomas remains difficult. Eleven of our patients with proven brainstem gliomas had radionuclide brain imaging prior to the initiation of therapy or confirmation of the diagnosis; six studies were positive. Pneumoencephalography remains the most reliable diagnostic test for brainstem glioma, and is invariably required for confirmation. Although angiography is useful in the evaluation of vasocularity it may not detect small infiltrating lesions. Radionuclide brain imaging is useful in the initial workup of patients with suspected brainstem gliomas.

Clinically Silent Brain Metastases: Can Radionuclide Scintigraphy Detect Them?

The role of static and dynamic radionuclide brain imaging in the detection of occult brain metastases was evaluated by reviewing the brain images and case histories of 136 patients with neoplastic disease (mostly lung cancer) who, at the time of the scintigraphic study, lacked clinical evidence of brain metastases. Static studies were normal in 121, equivocal in 13, and abnormal in 2. One of the patients with an abnormal study had dural metastases; the other had skull metastases. None of the 13 equivocal scans was found to be indicative of metastasic disease. Cerebral flood flow studies were performed in 99 of the 136 patients and all were negative for evidence of metastatic disease. The results of this study do not support the use of brain scintigraphy for routine screening of asymptomatic cancer patients.

An extravascular component of contrast enhancement in cranial computed tomography. Part II. Contrast enhancement and the blood-tissue barrier.

The authors provide evidence of significant extravasation of contrast media responsible for the contrast enhancement of pathological tissue on computed tomography. The tissue-blood ratio of enhancement was calculated by the EMI scanner in 2 patients after injection of contrast material and prior to surgery; tumor-blood ratios for red blood cell and plasma tracers were calculated after surgery. The ratios of enhancement demonstrated the analogy between contrast enhancement and the leaking of radionuclide across the blood-brain barrier. This phenomenon may cause error if this technique is used for the measurement of cerebral blood volume. The area for complementary roles of CT and radionuclide brain imaging seems to be narrower than expected.

Nuclear medicine and ultrasound in the evaluation of neurologic diseases

Echoencephalography and radionuclide brain imaging are used to aid in the diagnosis of a variety of intracranial abnormalities. Because of technical considerations, A-mode rather than B-mode echography must, under most circumstances, be employed for examination of the head. There are technical limitations to echoencephalography, and it tends to be relatively subjective and dependent on the skill of the sonographer. These factors have, to some extent, been responsible for the more limited application of ultrasound to neurologic diagnosis, as compared to the application of radionuclides. The most common use of echoencephalography is in the detection of midline shifts associated with various sequelae of head trauma. Ultrasound has also been used to detect space-occupying lesions, either directly or more usually by determing associated midline displacements. The characterization and follow-up of known lesions with ultrasound has also been described. In the above instances its usefulness is usually as a noninvasive technique complementary to nuclear medicine studies, which under most circumstances are more effective than ultrasound. The evaluation of ventricular enlargement, which is not usually possible per se with radionuclides, is possible with ultrasound. Computerized transverse tomography (CTT) can be applied more efficiently in a routine way in many of the above circumstances, including evaluation of ventricular size. The combination of CTT and nuclear medicine procedures in the brain area is so effective and comprehensive that where these are both available the demand for ultrasound will probably decrease but will not be eliminated.

Brain Tumor Scanning with Radioisotopes.

Twenty-three authors have contributed to this volume derived from the proceedings of a symposium' on brain tumor scanning held in Buffalo .in 1968. The book is divided into three parts: bIOlogical principles, new scanning techniques, and clinical results. The highlight of this book is the considerable discussion of the biological principles, including such topics as Basic A spects of the A ccumulation of Substances in Brain Tumors; Factors Involved in the Uptake and Distribution of Radioactive Tracers in Brain Tumors and Brain; Concentration of Tracer Substances in Brain Tumors: A n Electron Microscope Evaluation; Correlation Between the Ultrastructure of Brain Tumors and Their Uptakes of 203Hg_ Chlormerodrin, and Comparative Studies on the Ultrastructure of Intracranial Tumors in 111an and Experimental A nimals. Although much of this material is scattered throughout the world literature, very little of it has appeared in radiological journals. It is obvious from the panel discussion which concludes this section of the book that much of this material is still controversial; nevertheless, the fundamental mechanisms which make a brain scan positive or negative are eruditely set forth. Some pages are devoted to the theoretical and clinical virtues of positron brain imaging; however, this is of limited interest, as the instrumentation is specialized and not in wide use. Hemodynamic radionuclide studies are covered in two chapters. A hint of the application of the autofluoroscope to these pursuits is given, but a mo~e scholarly discussion is devoted to the use of a twin probe system to assess hemispheric radionuclide transit following intravenous administration. The results of these activity histograms are correlated with a variety of intracranial afflictions. A formal dissertation on the use of the Anger camera is not included. The chapters dealing with the interpretive aspects of brain scanning are good, and there are numerous illustrations throughout the text. This book will be of interest to those engaged in radionuclide brain imaging; the first 75 pages, dealing with the basic biological mechanisms of radiopharmaceutical concentration or lack thereof, are particularly recommended.