Ilza Rosa Batista

Higher striatal dopamine transporter density in PTSD: an in vivo SPECT study with [ 99m Tc]TRODAT-1

RationaleSome evidence suggests a hyperdopaminergic state in posttraumatic stress disorder (PTSD). The 9-repetition allele (9R) located in the 3′ untranslated region of the dopamine transporter (DAT) gene (SLC6A3) is more frequent among PTSD patients. In vivo molecular imaging studies have shown that healthy 9R carriers have increased striatal DAT binding. However, no prior study evaluated in vivo striatal DAT density in PTSD.ObjectivesThe objective of this study was to evaluate in vivo striatal DAT density in PTSD.MethodsTwenty-one PTSD subjects and 21 control subjects, who were traumatized but asymptomatic, closely matched comparison subjects evaluated with the Clinician-Administered PTSD Scale underwent a single-photon emission computed tomography scan with [99mTC]-TRODAT-1. DAT binding potential (DAT-BP) was calculated using the striatum as the region of the interest and the occipital cortex as a reference region.ResultsPTSD patients had greater bilateral striatal DAT-BP (mean ± SD; left, 1.80 ± 0.42; right, 1.78 ± 0.40) than traumatized control subjects (left, 1.62 ± 0.32; right, 1.61 ± 0.31; p = 0.039 for the left striatum and p = 0.032 for the right striatum).ConclusionsThese results provide the first in vivo evidence for increased DAT density in PTSD. Increases in DAT density may reflect higher dopamine turnover in PTSD, which could contribute to the perpetuation and potentiation of exaggerated fear responses to a given event associated with the traumatic experience. Situations that resemble the traumatic event turn to be interpreted as highly salient (driving attention, arousal, and motivation) in detriment of other daily situations.

Memory Networks in Tinnitus: A Functional Brain Image Study

Tinnitus is characterized by the perception of sound in the absence of an external auditory stimulus. The network connectivity of auditory and non-auditory brain structures associated with emotion, memory and attention are functionally altered in debilitating tinnitus. Current studies suggest that tinnitus results from neuroplastic changes in the frontal and limbic temporal regions. The objective of this study was to use Single-Photon Emission Computed Tomography (SPECT) to evaluate changes in the cerebral blood flow in tinnitus patients with normal hearing compared with healthy controls. Methods: Twenty tinnitus patients with normal hearing and 17 healthy controls, matched for sex, age and years of education, were subjected to Single Photon Emission Computed Tomography using the radiotracer ethylenedicysteine diethyl ester, labeled with Technetium 99 m (99 mTc-ECD SPECT). The severity of tinnitus was assessed using the “Tinnitus Handicap Inventory” (THI). The images were processed and analyzed using “Statistical Parametric Mapping” (SPM8). Results: A significant increase in cerebral perfusion in the left parahippocampal gyrus (pFWE <0.05) was observed in patients with tinnitus compared with healthy controls. The average total THI score was 50.8+18.24, classified as moderate tinnitus. Conclusion: It was possible to identify significant changes in the limbic system of the brain perfusion in tinnitus patients with normal hearing, suggesting that central mechanisms, not specific to the auditory pathway, are involved in the pathophysiology of symptoms, even in the absence of clinically diagnosed peripheral changes.

Neurophysiological studies and non-motor symptoms prior to ataxia in a patient with machado-joseph disease: trying to understand the natural history of brain degeneration.

Spinocerebellar ataxia type 3 or Machado–Joseph disease is the most common spinocerebellar ataxia. In this neurological disease, anatomical, physiological, clinical, and functional neuroimaging demonstrate a degenerative process besides the cerebellum. We performed neurophysiological and neuroimaging studies—polysomnography, transcranial sonography, vestibular-evoked myogenic potential, single-photon emission computed tomography (SPECT) with 99mTc-TRODAT-1, and a formal neuropsychological evaluation in a patient with sleep complaints and positive testing for Machado–Joseph disease, without cerebellar atrophy, ataxia, or cognitive complaints. Polysomnography disclosed paradoxical high amplitude of submental muscle, characterizing REM sleep without atonia phenomenon. Transcranial sonography showed hyperechogenicity of the substantia nigra. There was an absence of vestibular-evoked myogenic potentials on both sides in the patient under study, in opposite to 20 healthy subjects. Brain imaging SPECT with 99mTc-TRODAT-1 demonstrated a significant lower DAT density than the average observed in six healthy controls. Electroneuromyography was normal. Neuropsychological evaluation demonstrated visuospatial and memory deficits. Impairment of midbrain cholinergic and pontine noradrenergic systems, dysfunction of the pre-synaptic nigrostriatal system, changes in echogenicity of the substantia nigra, and damage to vestibulo-cervical pathways are supposed to occur previous to cerebellar involvement in Machado–Joseph disease.

Dopamine transporter shown by SPECT in patients with periodic leg movement after acute physical exercise.

PURPOSE This study aimed to evaluate dopamine transporter (DAT) density in patients with periodic leg movement (PLM) shown by [(99mt)Tc]TRODAT-1 single-photon emission computed tomography (SPECT) imaging and to determine the influence of acute physical exercise (maximal exercise test [MET]) on DAT densities. METHODS Sixteen healthy male volunteers between 45 and 65 yr of age were selected to participate in the study. Each subject (eight subjects in the control group and eight subjects in the patients with PLM experimental group) underwent baseline polysomnography (PSG) to evaluate sleep patterns and PLM index values. After obtaining PSG baselines, SPECT baselines were determined using [(99mt)Tc]TRODAT-1, a selective DAT imaging ligand. Subsequently, the volunteers performed the MET in the morning, followed by a SPECT 2 h later and PSG that night to assess the effect of acute physical exercise on DAT and sleep patterns. RESULTS The baseline SPECT results showed marginally significantly lower DAT densities in the striatal region of the experimental group. After the MET, no significant differences were observed between groups. The results also showed a significant reduction in the PLM index in the experimental group and a significantly increased percentage of stage 1 non-REM sleep in both groups after MET. CONCLUSIONS Our results show that patients with PLM had a marginally lower DAT density in the left putamen region compared with the control group. Although the effect of acute physical exercise (MET) reduced PLM symptoms, the results suggest that this improvement was not due to DAT availability.

Dopamine Transporter Imaging Using 99mTc-TRODAT-1 SPECT in Parkinson’s Disease

Background Although the decrease in striatal dopamine transporter (DAT) density has been described in North American, European, and Asian Parkinson’s disease (PD) patients, studies on this issue are required in the rest of the world. This study examined the diagnostic utility of DAT imaging in Brazilian PD patients. Material/Methods Twenty PD patients (13 males, 7 females, median age: 62 years, median age at disease onset: 56 years, median disease duration: 5 years, and median UPDRS-III score: 29) and 9 age- and sex-matched healthy subjects underwent single-photon emission computerized tomography (SPECT) using 99mTc-TRODAT-1. Results PD patients showed a significant decrease in the striatum, caudate nucleus, and putamen DAT densities compared with data from healthy subjects. Striatal 99mTc-TRODAT-1 bindings had the highest diagnostic accuracy compared to those estimates from caudate nucleus and putamen. For the diagnosis of PD, a striatal 99mTc-TRODAT-1 binding cut-off value of 0.90 was associated with a sensitivity of 100% and a specificity of 89%. There was no significant difference between striatal 99mTc-TRODAT-1 binding values provided by different readers, contrary to 99mTc-TRODAT-1 binding estimates in the caudate nucleus. Conclusions Striatal DAT imaging using 99mTc-TRODAT-1 can be considered a marker for differentiating PD patients from healthy individuals, with a good interobserver reproducibility.

Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs

The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and 450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes. Projection data are acquired in a photon-counting strategy, where CCD frames are stored at 50 frames per second, with a radius of rotation of 35 mm and magnification factor of one. The image reconstruction software tool is based on the maximum likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity attainable with the seven-pinhole imaging device, together with the linearity for quantification on the tomographic images, and to test the instrument in obtaining tomographic images of different mouse organs. A spatial resolution better than 500 µm and a sensitivity of 21.6 counts·s-1·MBq-1 were reached, as well as a correlation coefficient between activity and intensity better than 0.99, when imaging 99mTc sources. Images of the thyroid, heart, lungs, and bones of mice were registered using 99mTc-labeled radiopharmaceuticals in times appropriate for routine preclinical experimentation of <1 h per projection data set. Detailed experimental protocols and images of the aforementioned organs are shown. We plan to extend the instruments field of view to fix larger animals and to combine data from both detectors to reduce the acquisition time or applied activity.

SPEM: a state-of-the-art instrument for high resolution molecular imaging of small animal organs

OBJECTIVE To describe the Single Photon Emission Microscope (SPEM), a state-of-the-art instrument for small animal SPECT imaging, and characterize its performance presenting typical images of different animal organs. METHODS SPEM consists of two independent imaging devices based on high resolution scintillators, high sensitivity and resolution Electron-Multiplying CCDs and multi-pinhole collimators. During image acquisition, the mouse is placed in a rotational vertical holder between the imaging devices. Subsequently, an appropriate software tool based on the Maximum Likelihood algorithm iteratively produces the volumetric image. Radiopharmaceuticals for imaging kidneys, heart, thyroid and brain were used. The mice were injected with 74 to 148 MBq/0,3mL and scanned for 40 to 80 minutes, 30 to 60 minutes afterwards. During this procedure, the animals remained under ketamine/xilazine anesthesia. RESULTS SPEM images of different mouse organs are presented, attesting the imaging capabilities of the instrument. CONCLUSION SPEM is an innovative technology for small animal SPECT imaging providing high resolution images with appropriate sensitivity for pre-clinical research. Its use with appropriate radiotracers will allow translational investigation of several animal models of human diseases, their pharmacological treatment and the development of potential new therapeutic agents.

Case 241: Hemiparkinsonism- Hemiatrophy—SPECT with 99mTc TRODAT-1 and Muscle MR Imaging Abnormalities

History A 43-year-old right-handed man presented with a history of progressive mild left-sided weakness and slowness of movements. Symptoms began 4 years earlier, and the patient noticed a progressive decline in his daily routine due to gait difficulties in the past year. There was no history of head trauma, surgery, drug therapy, smoking, or alcohol abuse, nor was there any relevant family history. Examination revealed normal cognition (29 of 30 points on the Mini-Mental State Examination and 27 of 30 points on the Montreal Cognitive Assessment) and normal cerebellar, sensory, cranial nerve, and autonomic function. There was mild left-sided weakness involving the upper and lower limbs (medical research council graded muscle strength as 4+ out of 5) that was associated with facial hypomimia and a rigid akinetic syndrome only in the patients left hemibody (Unified Parkinsons Disease Rating Scale [UPDRS] part III [motor examination], 23 out of 52 points). Mild atrophy in the left upper and lower limbs without pain, swelling, or skin lesions was noted at physical examination. Routine blood chemistry was normal, as were serum creatine kinase and aldolase levels and thyroid, hepatic, and renal function. T1- and T2-weighted, fluid-attenuated inversion recovery, diffusion- and perfusion-weighted, and contrast material-enhanced brain magnetic resonance (MR) imaging results were normal, without basal ganglia hyperintensity, lacunae, calcification, or heavy metal deposits. Muscle MR imaging and single photon emission computed tomography (SPECT) with technetium 99m (99mTc) tropane dopamine transporter (TRODAT)-1 were performed for further evaluation. This patient received levodopa and benserazide (200 and 50 mg, respectively) four times a day and amantadine (100 mg) three times a day without adequate improvement (UPDRS score decreased from 23 to 20 points).