Bickerstaff’s brainstem encephalitis: case report and Tc99m brain SPECT findings

A 21-year-old healthy female suffered from an upper respiratory tract infection and 2 days later developed diplopia, unsteady gait, dysarthria and a profound disturbance of consciousness with rapid development of coma. Brain MRI and Tc99m brain perfusion SPECT, EEG, neurophysiological tests and CSF analysis results were unspecific. The detection of serum anti-GQ1b IgG autoantibodies at high titre led to the diagnosis of Bickerstaff’s brainstem encephalitis (BBE). Clinical symptoms resolved after treatment with plasma exchange and the outcome was good. Brain MRI was normal, and Tc99m brain perfusion SPECT demonstrated hypoperfusion of the whole cerebral hemispheres and basal ganglia with relative sparing of the thalami and the brainstem. Similar to brain MRI, the sensitivity of Tc99m brain perfusion SPECT in detecting brainstem lesions in typical BBE patients seems to be low.     

SPECT脑血流灌注显像在眩晕患者中的初步应用

目的评价乙撑双半胱氨酸二乙酯（＾９９ｍＴｃ－ＥＣＤ）ＳＰＥＣＴ脑血流灌注显像对眩晕患者的诊断价值。方法对１９列眩晕患者和２０例正常对照者进行ＳＰＥＣＴ脑血流灌注显像。结果突发性耳聋组和诊断未明确组的患者全部出现局部脑血流量下降,且多数分布在颞叶;梅尼埃病患者组则较少出现局部脑血流量下降（４０％,２／５）;正常对照组未发现局部脑血流量下降。结论＾９９ｍＴｃ－ＥＣＤＳＰＥＣＴ脑血流灌注显像有助于眩晕患     

Thallium-201 versus Tc99m-glucoheptonate SPECT for evaluation of recurrent brain tumours: a within-subject comparison with pathological correlation.

BACKGROUND: Thallium-201 (Tl-201) is the most commonly used tracer for functional imaging of recurrent brain tumours. However, the physical properties of Tl-201 are not particularly suitable for this application, thus, a technetium-99 (Tc99m) labelled alternative with more favourable physical properties has been sought. The aim of this study was to compare the ability of Tl-201 and Tc99m-glucoheptonate single photon emission computed tomography (SPECT) to detect viable recurrent tumour and differentiate post-radiation gliosis. METHOD: Brain SPECT with Tl-201 and Tc99m-glucoheptonate was performed in 20 patients with malignant brain tumour in whom recurrent disease was suspected. Tracer uptake in the mass was defined as high, moderate or low and was correlated with histological verification of the lesion in all cases. RESULTS: Recurrent tumour was demonstrated in 17 patients by both Tl-201 and Tc99m-glucoheptonate SPECT and confirmed by surgical resection in all 17 patients. Three patients had no tracer uptake on either Tl-210 or Tc99m-glucoheptonate SPECT and surgical resection revealed only fibrotic tissue with areas of necrosis. Tc99m-glucoheptonate images were found to correlate more closely with the surgical findings with regard to the location of tumour margin, extent of tumour invasion and intratumoural necrosis. CONCLUSION: Tc99m-glucoheptonate brain SPECT is an accurate agent for SPECT imaging of recurrent brain tumours and may provide more information about the location of the tumour margin and its extent and intratumoural necrosis than Tl-201. Tc99m-glucoheptonate may be a viable replacement for Tl-201.     

Superiority of HMPAO ictal SPECT to ECD ictal SPECT in localizing the epileptogenic zone

PURPOSE: We examined diagnostic performances of Tc-99m hexamethylpropylene amine oxime (HMPAO) and Tc-99m electron capture detection (ECD) ictal single-photon emission computed tomography (SPECT) to localize the epileptogenic zones in mesial temporal lobe epilepsy (TLE) and neocortical epilepsy (NE). METHODS: Epileptogenic zones were identified by invasive EEG or surgical outcome. Ictal SPECT was performed with stabilized Tc-99m HMPAO (TLE, 17; NE, 23) and with Tc-99m ECD (TLE, 7; NE, 7). Single-blind visual interpretation was used to localize the epileptogenic zones. Asymmetric index was calculated. Subtraction ictal SPECT was coregistered to a magnetic resonance imaging (MRI) template. RESULTS: In TLE, the sensitivity of Tc-99m HMPAO SPECT was 82% (14 of 17) and that of Tc-99m ECD SPECT was 71% (five of seven). The asymmetric index (AI; 25 +/- 10) of Tc-99m HMPAO SPECT was larger (p = 0.05) than the AI (13 +/- 13) of Tc-99m ECD SPECT in patients with TLE. In NE, the sensitivity of Tc-99m HMPAO SPECT was 70% (16 of 23), but that of Tc-99m ECD SPECT was 29% (two of seven). The AI (15 +/- 10) of Tc-99m HMPAO SPECT was significantly larger (p = 0.02) than the AI (4.8 +/- 6) of Tc-99m ECD SPECT in patients with NE. Subtraction ictal SPECT coregistered to MRI supported the visual assessment. CONCLUSIONS: We concluded that the sensitivity of Tc-99m ECD ictal SPECT is similar to that of Tc-99m HMPAO ictal SPECT in TLE; however, ictal hyperperfusion was higher with the Tc-99m HMPAO SPECT. In patients with NE, Tc-99m HMPAO ictal SPECT also was superior to Tc-99m ECD ictal SPECT in sensitivity and degree of hyperperfusion.     

Regional cerebral blood flow in patients with systemic lupus erythematosus.

Patients with systemic lupus erythematosus (SLE) with or without definite neuropsychiatric symptoms/signs were studied. Technetium-99m (Tc-99m) hexamethylpropylenamine (HMPAO) brain images were used to detect basal ganglion and cerebral cortex regional cerebral blood flow (rCBF) in patients with SLE with brain involvement. One hundred nine female patients with SLE were investigated using Tc-99m HMPAO brain images with fan-beam single-photon emission computed tomography (SPECT) and surface three-dimensional (3D) display. These patients were separated into 2 subgroups: group 1, 74 cases with definite neuropsychiatric symptoms/signs; and group 2, 35 cases without any neuropsychiatric symptoms/signs. Fan-beam SPECT demonstrated unilateral or bilateral hypoperfusion of basal ganglia or thalamus in 22% and 9% of patients in groups 1 and 2, respectively. Local hypoactivity anomalies were found in the brain cortex of 89% and 20% of patients in groups 1 and 2, respectively, using surface 3D display of the brain. In either group 1 or group 2 patients, parietal and frontal lobes are the most common areas and cerebellum and thalamus are the least common areas of brain involvement, respectively. This study suggests that in comparison with traditional brain imaging techniques, Tc-99m HMPAO brain imaging with fan-beam SPECT in combination with surface 3D display may provide objective information for detection of anomalies of rCBF in patients with SLE.     

多梗塞性痴呆和Alzheimer型痴呆的SPECT和MRI比较研究

对２２例多梗塞性痴呆，１５例Ａｌｚｈｅｉｍｅｒ型痴呆病人和２４例同龄，同利手健康对照组作了单光子发射计算机断层显角和磁共振成象检查。结果发现ＳＰＥＣＴ在ＭＩＤ病人主要表现为多发性，局灶性脑放射性减低，两侧不对称，以额皮质，皮质下明显；ＤＡＴ病人主要表现为大脑皮质放射性对称性降低，以颞顶枕明显。     

SPECT scan in somatization disorder patients: an exploratory study of eleven cases.

OBJECTIVE: There are no previous studies using single photon emission computed tomography (SPECT) scans in somatization disorder (SD) patients. The aim of this paper is to assess SPECT imaging abnormalities in SD patients and study any relation to laterality. METHOD: Eleven SD patients from the Somatization Disorder Unit of Miguel Servet University Hospital, Zaragoza, Spain, not fulfilling criteria for any other psychiatric disorder and showing normal computed tomography (CT) and magnetic resonance imaging (MRI) images were studied with SPECT. Patients with DSM-IV axis I comorbidity were ruled out because it has been demonstrated that SPECT scans can show abnormalities in patients with depression and anxiety disorders. The technique used for SPECT was 99mTc-D,1,hexamethylpropyleneamide-oxime (99mTc-HMPAO) in four patients and 99mTc-bicisate in the other seven. The SPECT scans were evaluated without knowledge of clinical data and entirely by visual inspection. RESULTS: Seven out of 11 (63.6%) SD patients showed hypoperfusion in SPECT imaging. In four cases there was hypoperfusion in the non-dominant hemisphere and the predominance of pain symptoms took place in the contralateral hemibody. In the other three patients hypoperfusion was bilateral. The anatomical regions affected were cerebellum (four cases), frontal and prefrontal areas (three cases), temporoparietal areas (two cases) and the complete hemisphere (one case). CONCLUSIONS: A proportion of SD patients may present hypoperfusion in SPECT images, uni- or bilaterally, in different brain areas. Possible aetiological explanations for this finding are discussed. Controlled studies are necessary to confirm or refute this hypothesis.     

Functional neuroimaging strategy in temporal lobe epilepsy: a comparative study of 18FDG-PET and 99mTc-HMPAO-SPECT.

We performed 99mTc-hexamethylpropyleneamineoxime-single-photon emission computed tomography (SPECT) and 18F-fluorodeoxyglucose-positron emission tomography (PET) in 20 epileptic patients with well-lateralized temporal electroencephalographic focus, normal computed tomographic scan, and brain magnetic resonance imaging (MRI) either normal (n = 10) or showing nonspecific changes in the epileptogenic temporal lobe (n = 10). In patients with a normal MRI, PET exhibited focal hypometabolism in 80%, whereas SPECT showed corresponding hypoperfusion in only 20%. In patients with an abnormal MRI, PET and SPECT yielded 100% and 90% sensitivity, respectively. The metabolic and regional cerebral blood flow disturbances were topographically concordant with electroencephalographic and MRI findings in all these patients. Only patients with a large and pronounced hypometabolism on PET images exhibited hypoperfusion on SPECT. Spatial resolution appeared to be the critical factor responsible for the higher sensitivity of PET. However, this superiority of PET did not prove clinically useful in patients whose SPECT was abnormal, particularly when brain MRI showed nonspecific changes in the epileptogenic temporal lobe.     

Imaging of perfusion, angiogenesis, and tissue elasticity after stroke

Blood flow interruption in a cerebral artery causes brain ischemia and induces dramatic changes of perfusion and metabolism in the corresponding territory. We performed in parallel positron emission tomography (PET) with [(15)O]H(2)O, single photon emission computed tomography (SPECT) with [(99m)Tc]hexamethylpropylene-amino-oxime ([(99m)Tc]HMPAO) and ultrasonic ultrafast shear wave imaging (SWI) during, immediately after, and 1, 2, 4, and 7 days after middle cerebral artery occlusion (MCAO) in rats. Positron emission tomography and SPECT showed initial hypoperfusion followed by recovery at immediate reperfusion, hypoperfusion at day 1, and hyperperfusion at days 4 to 7. Hyperperfusion interested the whole brain, including nonischemic areas. Immunohistochemical analysis indicated active angiogenesis at days 2 to 7, strongly suggestive that hyperperfusion was supported by an increase in microvessel density in both brain hemispheres after ischemia. The SWI detected elastic changes of cerebral tissue in the ischemic area as early as day 1 after MCAO appearing as a softening of cerebral tissue whose local internal elasticity decreased continuously from day 1 to 7. Taken together, these results suggest that hyperperfusion after cerebral ischemia is due to formation of neovessels, and indicate that brain softening is an early and continuous process. The SWI is a promising novel imaging method for monitoring the evolution of cerebral ischemia over time in animals.     

Voxel-Based Mapping of Cortical Ischemic Damage Using Tc 99M L, L-Ethyl Cysteinate Dimer Spect in Acute Stroke

BACKGROUND AND PURPOSE: When performed soon after stroke onset, single-photon emission computed tomography (SPFCT) with hexamethylpropylenamine oxime or Tc 99m L,L-ethyl cysteinate dimer (ECD) has significant added predictive value compared to neurological scores. With ECD SPECT, the degree of tracer uptake reduction predicts neurological recovery, and using a 40% threshold to characterize irreversibly damaged tissue (IDT), significant correlations have been observed. However, correlations between this uptake threshold and tissue outcomes have not been assessed. The purpose of this study was to validate the 40% ECD uptake threshold for the probabilistic mapping of IDT using an automatic, voxel-based approach. METHODS: In 10 acute stroke patients, the authors first compared early ECD SPECT and late coregistered magnetic resonance imaging (MRI) data and assessed for IDT and "tissue at risk" (i.e., tissue with ECD uptake below and above 40%) the percentage of voxels ultimately infarcted and noninfarcted on late brain MRI. They then assessed the correlations between the volumes of brain tissue compartments and subsequent neurological recovery. Finally, to assess whether visual SPECT analysis is reliable compared to the more complex voxel-based approach, the authors compared the predictive value of the 2 methods for neurological recovery. RESULTS: The majority of IDT voxels (average = 84%), defined by ECD uptake < 40%, evolved toward infarction, and 51.8% to 100% of at-risk voxels (average = 89%) escaped infarction. The extent of IDT correlated significantly with neurological recovery (P = .0009). There was good agreement between visual and voxel-based analyses (P = .0004). CONCLUSION: The results support the validity of the ECD uptake thresholds chosen, suggesting that ECD uptake can reflect neuronal viability and that ECD SPECT can be useful for the early detection of potentially salvageable tissue and irreversible damage. These preliminary results encourage the use of this method in a clinical setting for fast decision making in choosing acute therapy.     

Infantile Spasms: Localized Cerebral Lesions on SPECT

Summary: Ten infantile spasms (IS) patients had single photon emission computed tomography (SPECT) with [^99mTc]HMPAO, EEG, and magnetic resonance imaging (MRI) studies. SPECT showed localized cerebral hypo-perfusion in 7 infants (4 unifocal; 3 multifocal) always involving the temporal regions either unilaterally or bilaterally. EEGs obtained in near time of the SPECT studies showed focal abnormalities in all 7 infants with hypoper-fusion on SPECT, with complete correspondence of the abnormalities in 5. MRI showed localized cerebral lesionsin only 3 of the 10 infants, all of whom had corresponding areas of hypoperfusion on SPECT. Our study indicates that localized cerebral abnormalities (especially of the temporal lobes) may often be associated with IS and that such patients may have localized cerebral hypoperfusion on SPECT even when the MRI is normal.     

Cerebral Perfusion in Patients With Syndrome X: A Single Photon Emission Computed Tomography Study

OBJECTIVE: To test the hypothesis that syndrome X is a systemic vascular disorder, the authors studied 40 patients with this diagnosis using technetium-99m hexamethylpropylene amine oxime and single photon emission computed tomography (SPECT) brain images. Twenty-three of 25 cases with definite myocardial perfusion defects diagnosed by thallium-201 myocardial perfusion SPECT also had multiple hypoperfusion areas in the brain versus 2 of 15 patients without thallium myocardial defects. The parietal lobes were the most common hypoperfusion areas, and cerebellum was the least common. Syndrome X is a systemic vascular disorder with a high incidence of hypoperfusion lesions of the brain and is usually coincident with myocardial defects.     

应用单光子发射计算机断层扫描脑血流灌注显像评价颈内动脉球囊闭塞试验后大脑耐受性

目的 评估单光子发射计算机断层扫描(SPECT)脑血流灌注显像在球囊闭塞试验(BOT)中的评价效用.方法 31例颈内动脉瘤患者接受了暂时性BOT.在闭塞球囊排空前5min,大约740MBq锝标双半胱乙脂(99mTc-ECD)由静脉注入,随后进行单光子发射计算机断层扫描.所得图像进行视觉分析、分级(正常、轻度、中度和重度灌注减低)并计算患侧/健侧(L/N)感兴趣区内放射性计数比值.结果 SPECT提示了24例受试者在暂时性球囊闭塞后出现了异常灌注,而只有4例出现了神经症状.正常血流灌注组L/N比值范围为0.98±0.03(7例),轻度血流灌注减低组L/N比值范围为0.89±0.03(11例),中度血流灌注减低组L/N比值范围为0.81±0.03(7例),重度血流灌注减低组L/N比值范围为0.66±0.04(6例),各组间的差异有统计学意义(P=0.000).结论 BOT联合负荷SPECT评价颈内动脉闭塞后的大脑耐受性是一种易行、客观、敏感的方法,所得初步结果需更多病人数量来证实.     

Nicergoline augmentation treatment of late onset depression

Background: Elderly patients with depression have more ischemic lesions on magnetic resonance imaging (MRI) of the brain than those without depression. Therefore, late onset depression might be associated with neurobiological etiology, especially vascular lesions of the brain. Recently nicergoline, which is an ergoline derivative and increases cerebral blood flow, has been reported to be effective for vascular depression. However, it remains unclear whether late onset depression without ischemic lesions or vascular risk factors can be improved by this compound. Methods: The present study reports the case of a 69‐year‐old woman with depression, which consisted of mild depressive mood, severe loss of drive and appetite, and moderate cognitive impairment that developed over 8 months. Treatment with 150 mg of sulpiride, 40 mg of paroxetine hydrochloride, and 0.5 mg of etizolam everyday for 5 months had no effect on the patient. MRI of the brain showed mild cortical atrophy in the bilateral frontal and parietal lobes with no remarkable ischemic lesions. A mild decrease of relative cerebral blood flow (CBF) in the atrophic regions was shown by ^99mTc‐HMPAO single photon emission computed tomography (SPECT). After sulpiride treatment was discontinued, the patient took 15 mg of nicergoline daily in addition to selective serotonin reuptake inhibitor (SSRI) treatment. Results: The patient's symptoms were improved after 2 weeks and ^99mTc‐HMPAO SPECT of the brain showed a slight improvement of relatively decreased CBF in the regions. Conclusion: Nicergoline might have a therapeutic potential as an augmentation strategy for late onset depression.     

Alzheimer's disease and corticobasal degeneration presenting as corticobasal syndrome

The aim of this article is to compare patients with Alzheimer's disease (AD) pathology and corticobasal degeneration pathology (CBD) presenting as corticobasal syndrome (CBS). Clinicopathologic series was used. Five patients with AD and 11 patients with CBD were clinically diagnosed with CBS. Patients with AD pathology had an earlier age of onset than patients with CBD pathology (58 vs. 68 years, P = 0.004), but the two groups had similar disease duration and core features of CBS. Tremors were only present in CBD cases (73%, P = 0.026), but myoclonus was more common in AD than CBD (80 vs. 18%, P = 0.036). Neuropsychological testing showed similar degrees of memory impairment and attentional deficits. ^99mTc‐HMPAO SPECT imaging demonstrated parietal hypoperfusion in AD patients and frontotemporal hypoperfusion in CBD patients. AD patients with clinical CBS have similar characteristics to CBD patients. Functional brain imaging may have greater utility than the clinical and neuropsychological features in differentiating AD presenting as CBS from CBD. © 2009 Movement Disorder Society     

Juvenile parkinsonism with symmetrical hypoperfusion in the cerebellum--a case report]

We report a 24-year-old female presenting levodopa-responsive juvenile parkinsonism with symmetrical hypoperfusion in the cerebellum. At the age of 21, she noticed difficulty in brushing her teeth and writing with the right hand. She developed resting tremor in the right hand. These symptoms were dramatically relieved by levodopa. One year prior to the admission, she noticed dystonia and drug-induced motor fluctuations and her symptoms became worse. Neurological examinations disclosed resting and postural tremor in both hands and the right leg. Bradykinesia and cogwheel rigidity were noted on the right side. Deep tendon reflexes were slightly increased on the right side, while Babinski sign was negative. Slight lateropulsion was observed without retropulsion. Sensory, autonomic and cerebellar disturbances were not observed. No abnormalities were found in parkins gene or in the genes of spinocerebellar ataxia (SCA) 1,2,3,6,7,8 and alpha-synuclein. Cranial CT scan and brain MRI were normal, but technetium-99m ethyl cysteinate dimer (ECD) single photon emission computed tomography (SPECT) showed symmetrical hypoperfusion in the cerebellum. Other 5 patients presenting juvenile parkinsonism and 10 aged-matched normal controls in our hospital did not show hypoperfusion in the cerebellum on ECD SPECT. Cerebellar blood flow has not been measured in the previously reported cases of juvenile parkinsonism. These results suggested that etiopathogenesis in this patient was different from that in previously reported cases.     

短暂性脑缺血发作患者脑血流变化研究

目的 通过对脑血流(rCBF)SPECT检查，探讨短暂性脑缺血发作患者的局部脑血流变化。方法 对29例短暂性脑缺血发作患者在发病6～48h内同时行头部CT及SPECT检查，并于发病48～72h后再次复查头部CT。另外对30例健康志愿者进行头部CT及SPECT检查。结果 SPECT检出阳性率为72．4％(21／29)。且神经功能缺损越重，rCBF的灌注缺损就越低。结论 在患者尚未发生脑组织结构异常的代谢和功能性损伤时，SPECT可灵敏的探测到损伤局部的脑血流变化，对估计患者的预后，有一定的指导意义。     

Relationship between psychiatric symptoms and regional cerebral blood flow in patients with mild Alzheimer's disease

Background: Behavioral and psychological symptoms of dementia (BPSD) are frequently observed in patients with dementia and often cause serious problems. However, the cause of BPSD has not yet been elucidated. Moreover, the precise evaluation of BPSD in mild dementia has not been studied in any great detail. In the present study, we investigated the relationship between psychiatric symptoms and regional cerebral blood flow (rCBF) in patients with mild Alzheimer's disease (AD). Methods: The present study included 47 patients (20 men and 27 women) who were diagnosed with mild AD. Mean patient age was 72.8 ± 8.2 years. Single photon emission computed tomography (SPECT) with ^99mTc‐ethyl cysteinate dimer (^99mTc‐ECD) was performed in all patients. The SPECT data were analyzed using a three‐dimensional stereotactic region of interest template, which evaluated CBF in 24 segments. Psychiatric symptoms were evaluated in patients using the Brief Psychiatric Rating Scale. Each psychiatric symptom was designated as ‘symptom present’ in cases in which the BPRS item score was more than 3. We compared 10 segments of rCBF in symptom‐present patients with those in symptom‐absent patients. Results: Motor retardation was the most common psychiatric symptom (36.2%), followed by depression (19.1%), anxiety (17.0%), emotional withdrawal (17.0%), and somatic concern (14.9%). Alzheimer's disease patients with motor retardation exhibited a tendency towards lower rCBF in seven segments (left callosomarginal, bilateral parietal, bilateral angular, and bilateral temporal). However, no specific tendency was observed in depression, anxiety, and somatic concern. Conclusions: In the present study, we observed a tendency for decreased brain perfusion in patients with motor retardation. Further studies are necessary to confirm that this trend contributes to the appearance of psychiatric symptoms in patients with mild AD.     

Statistical parametric mapping demonstrates asymmetric uptake with Tc-99m ECD and Tc-99m HMPAO SPECT in normal brain

Tc-99m ethyl cysteinate diethylester (ECD) and Tc-99m hexamethyl propylene amine oxime (HMPAO) are commonly used for single-photon emission computed tomography (SPECT) studies of a variety of neurologic disorders. Although these tracers have been very helpful in diagnosing and guiding treatment of neurologic disease, data describing the distribution and laterality of these tracers in normal resting brain are limited. Advances in quantitative functional imaging have demonstrated the value of using resting studies from control populations as a baseline to account for physiologic fluctuations in cerebral perfusion. Here, we report results from 30 resting Tc-99m ECD SPECT scans and 14 resting Tc-99m HMPAO scans of normal volunteers with no history of neurologic disease. Scans were analyzed with regions of interest and with statistical parametric mapping, with comparisons performed laterally (left vs. right), as well as for age, gender, and handedness. The results show regions of significant asymmetry in the normal controls affecting widespread areas in the cerebral hemispheres, but most marked in superior parietotemporal region and frontal lobes. The results have important implications for the use of normal control SPECT images in the evaluation of patients with neurologic disease.     

Feed‐forward hierarchical model of the ventral visual stream applied to functional brain image classification

Functional brain imaging is a common tool in monitoring the progression of neurodegenerative and neurological disorders. Identifying functional brain imaging derived features that can accurately detect neurological disease is of primary importance to the medical community. Research in computer vision techniques to identify objects in photographs have reported high accuracies in that domain, but their direct applicability to identifying disease in functional imaging is still under investigation in the medical community. In particular, Serre et al. ( 2005 : In: IEEE Conference on Computer Vision and Pattern Recognition (CVPR‐05). pp 994–1000) introduced a biophysically inspired filtering method emulating visual processing in striate cortex which they applied to perform object recognition in photographs. In this work, the model described by Serre et al. [2005] is extended to three‐dimensional volumetric images to perform signal detection in functional brain imaging (PET, SPECT). The filter outputs are used to train both neural network and logistic regression classifiers and tested on two distinct datasets: ADNI Alzheimer's disease 2‐deoxy‐D ‐glucose (FDG) PET and National Football League players Tc99m HMPAO SPECT. The filtering pipeline is analyzed to identify which steps are most important for classification accuracy. Our results compare favorably with other published classification results and outperform those of a blinded expert human rater, suggesting the utility of this approach. Hum Brain Mapp 35:38–52, 2014. © 2012 Wiley Periodicals, Inc.