SPECT imaging in psychiatry. A review

Advances in Injectable Hydrogels Based on Diverse Gelation Methods for Biomedical Imaging

The injectable hydrogels can deliver the loads directly to the predetermined sites and form reservoirs to increase the enrichment and retention of the loads in the target areas. The preparation and injection of injectable hydrogels involve the sol-gel transformation of hydrogels, which is affected by factors such as temperature, ions, enzymes, light, mechanics (self-healing property), and pH. However, tracing the injection, degradation, and drug release from hydrogels based on different ways of gelation is a major concern. To solve this problem, contrast agents are introduced into injectable hydrogels, enabling the hydrogels to be imaged under techniques such as fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, and radionuclide imaging. This review details methods for causing the gelation of imageable hydrogels; discusses the application of injectable hydrogels containing contrast agents in various imaging techniques, and finally explores the potential and challenges of imageable hydrogels based on different modes of gelation.

Inclusion of quasi-vertex views in a brain-dedicated multi-pinhole SPECT system for improved imaging performance

With brain-dedicated multi-detector systems employing pinhole apertures the usage of detectors facing the top of the patient's head (i.e. quasi-vertex (QV) views) can provide the advantage of additional viewing from close to the brain for improved detector coverage. In this paper, we report the results of simulation and reconstruction studies to investigate the impact of the QV views on the imaging performance of AdaptiSPECT-C, a brain-dedicated stationary SPECT system under development. In this design, both primary and scatter photons from regions located inferior to the brain can contribute to SPECT projections acquired by the QV views, and thus degrade AdaptiSPECT-C imaging performance. In this work, we determined the proportion, origin, and nature (i.e. primary, scatter, and multiple-scatter) of counts emitted from structures within the head and throughout the body contributing to projections from the different AdaptiSPECT-C detector rings, as well as from a true vertex view detector. We simulated phantoms used to assess different aspects of image quality (i.e. uniform activity concentration sphere, and Derenzo), as well as anthropomorphic phantoms with different count levels emulating clinical ¹²³I activity distributions (i.e. DaTscan and perfusion). We determined that attenuation and scatter in the patient's body greatly diminish the probability of the photons emitted outside the volume of interest reaching to detectors and being recorded within the 15% photopeak energy window. In addition, we demonstrated that the inclusion of the residual of such counts in the system acquisition does not degrade visual interpretation or quantitative analysis. The addition of the QV detectors improves volumetric sensitivity, angular sampling, and spatial resolution leading to significant enhancement in image quality, especially in the striato-thalamic and superior regions of the brain. Besides, the use of QV detectors improves the recovery of clinically relevant metrics such as the striatal binding ratio and mean activity in selected cerebral structures. Our findings proving the usefulness of the QV ring for brain imaging with ¹²³I agents can be generalized to other commonly used SPECT imaging agents labelled with isotopes, such as ^99mTc and likely ¹¹¹In.

Hypoactivity in the Paraterminal Gyrus Following Bilateral Anterior Capsulotomy

OBJECTIVE

Bilateral anterior capsulotomy (BAC) is one of the ablative neurosurgical procedures used to treat major depressive disorder or obsessive-compulsive disorder when all other therapies fail. Tristolysis, a reduction in sadness, is the most striking clinical effect of BAC and is seen in the first 1 to 2 weeks after surgery. This retrospective study measured regional cerebral blood flow (rCBF) following surgery to identify which cortical regions were impacted and could account for this clinical effect.

METHODS

All patients had their capsulotomies done in Vancouver by the same team. Pre- and postoperative single-photon emission computed tomography perfusion scans were analyzed for 10 patients with major depressive disorder and 3 with obsessive-compulsive disorder. rCBF was measured semiquantitatively by calculating the ratio between an identified region of interest and a whole brain reference area.

RESULTS

Decreased rCBF was found in the paraterminal gyri. Increased rCBF was found in the dorsolateral prefrontal cortices and in the left lateral temporal lobe.

CONCLUSIONS

BAC causes hypoactivity in the paraterminal gyri and is the most likely explanation for its tristolytic effect, suggesting that the paraterminal gyrus is the limbic cortical locus for the emotion of sadness. Increased activity in the dorsolateral prefrontal cortices may be occurring via connectional diaschisis, and suppression by overactive paraterminal gyri during depression may account for some of the neurocognitive deficits observed during depressive episodes.

Radiobromine and radioiodine for medical applications

The halogens bromine and iodine have similar chemical properties and undergo similar reactions due to their closeness in Group 17 of the periodic chart. There are a number of bromine and iodine radionuclides that have properties useful for diagnosis and therapy of human diseases. The emission properties of radiobromine and radioiodine nuclides with half-lives longer than 1 h are summarized along with properties that make radionuclides useful in PET/SPECT imaging and β/Auger therapy, such that the reader can assess which of the radionuclides might be useful for medical applications. An overview of chemical approaches that have been used to radiolabel molecules with radiobromine and radioiodine nuclides is provided with examples. Further, references to a large variety of different organ/cancer-targeting agents utilizing the radiolabeling approaches described are provided.

Evaluation of the effect of methylphenidate by computed tomography, electroencephalography, neuropsychological tests, and clinical symptoms in children with attention-deficit/hyperactivity disorder: A prospective cohort study

BACKGROUND

Stimulant drugs are the most commonly used treatments for attention-deficit/hyperactivity disorder (ADHD), although the mechanism of action of these drugs is still not entirely understood.

OBJECTIVE

The aim of this study was to investigate the effects of the psychostimulant drug methylphenidate (MPH) on regional cerebral blood flow (rCBF), electrical activity of the brain, and clinical symptoms in children with ADHD using single-photon emission computed tomography (SPECT), electroencephalography (EEG), and neuropsychological tests.

METHODS

In this prospective cohort study, pediatric outpatients received MPH for 3 months at a mean dose of 1 mg/kg · d (range, 0.5-1.5 mg/kg · d). They were then administered the Wechsler Intelligence Scale for Children-Revised, the Bender Visual-Motor Gestalt Test (BGT), EEG, and SPECT of the brain. The parents and/or teacher of each child were asked to complete the Conners' Parent Rating Scale (CPRS), the Conners' Teacher Rating Scale (CTRS), and the Turgay Diagnostic and Statistical Manual of Mental Disorders Fourth Edition-based Child and Adolescent Behavior Disorders Screening and Rating Scale (T-DSM-IV-S). All of the evaluations were performed at baseline and after 3 months of MPH treatment. Each child underwent a Stroop test as an activation method 15 minutes before the SPECT procedure.

RESULTS

Sixty patients were assessed for inclusion. Twenty-one children (18 boys [85.7%], 3 girls [14.3%]; mean [SD] age, 9.7 [1.7] years; range, 8-13 years) with a diagnosis of ADHD were included in and completed the study. Mean (SD) BGT scores before MPH treatment compared with after MPH treatment were significantly decreased (9.8 [4.2] vs 6.3 [3.4]; Z = -3.27; P = 0.001). After treatment with MPH, the visual SPECT results suggested that low rCBF was normalized in the right frontotemporal areas in 10 children with ADHD. After treatment, 12 patients (57.1%) had no change in EEG activity, 5 (23.8%) had improvement, and 4 (19.0%) had worsening activity. Patients who had improvement or no worsening on EEG after MPH treatment were associated with significant improvement after MPH treatment compared with before treatment in mean (SD) CTRS scores (25.9 [14.3] vs 35.0 [14.4]; P = 0.003), teachers' T-DSM-IV-S total score (25.1 [14.2] vs 38.4 [18.7]; P = 0.005), and CPRS scores (mothers scores: 29.7 [16.6] vs 42.6 [17.2], P = 0.002; fathers' scores: 29.4 [16.8] vs 41.9 [23.7], P = 0.004). No significant difference was found in these scores in the patients whose EEG findings showed deterioration after MPH treatment. The quantitative values for SPECT observed before treatment compared with those observed after 3 months of MPH treatment were not found to be significantly different in any areas of the brain.

CONCLUSIONS

MPH use over 3 months was associated with improvement from baseline in visual-motor function and behavioral disorders in these children and adolescents with ADHD. However, no significant difference in rCBF or electrical activity in the brain was observed in this small study.

Brain SPECT imaging of neuropsychiatric disorders

Brain imaging has become an integral part of the evaluation of neurological and psychiatric disorders. Functional imaging techniques, SPECT and PET, together with structural modalities, CT and MRI, are widely employed. Functional imaging studies are routinely used in the diagnostic workup of patients with well-characterized neurological disorders, such as epilepsy and brain tumors, and have a growing role in research on psychiatric disorders without known mechanisms such as depression and schizophrenia. Furthermore, many well-defined neurological disorders manifest prominent psychiatric symptomatology which may pose difficulties in differential diagnosis. This review addresses the current knowledge of SPECT findings in patients who present with psychiatric phenomena, associated with disorders at the interface of neurology and psychiatry.

Diagnostic utility of endocrine and neuroimaging screening tests in first-onset adolescent psychosis

OBJECTIVE

To determine the diagnostic utility of endocrine and neuroimaging screening tests in first-onset adolescent psychosis.

METHOD

111 consecutively admitted adolescents (aged 13 through 19 years) who presented with a first-onset psychosis and who had an unremarkable medical history and normal physical examination were given a battery of endocrine and neuroimaging screening tests. Diagnostic utility of a screening test was defined as an abnormal result (a positive test) that either led to a previously unknown or unsuspected medical diagnosis or played an important role in the clinical care of the patient.

RESULTS

15.4% of the endocrine screening tests and 11.0% of the neuroimaging screening tests were identified as positive. However, no endocrine and no neuroimaging tests met criteria for diagnostic utility. The direct cost of this screening battery was $636.95 per patient.

CONCLUSION

Routine endocrine and neuroimaging screening tests in first-onset adolescent psychosis provide no diagnostic utility and are not cost-effective. Selective use of appropriate endocrine and neuroimaging diagnostic tests in populations with symptoms suggestive of organic disorders should replace routine screening procedures.