Deep learning of renal scans in children with antenatal hydronephrosis

INTRODUCTION

Antenatal hydronephrosis (ANH) is one of the most common anomalies identified on prenatal ultrasound, found in up to 4.5% of all pregnancies. Children with ANH are surveilled with repeated renal ultrasound and when there is high suspicion for a ureteropelvic junction obstruction on renal ultrasound, a mercaptuacetyltriglycerine (MAG3) Lasix renal scan is performed to evaluate for obstruction. However, the challenging interpretation of MAG3 renal scans places patients at risk of misdiagnosis.

OBJECTIVE

Our objective was to analyze MAG3 renal scans using machine learning to predict renal complications. We hypothesized that our deep learning model would extract features from MAG3 renal scans that can predict renal complications in children with ANH.

STUDY DESIGN

We performed a case-control study of MAG3 studies drawn from a population of children with ANH concerning for ureteropelvic junction obstruction evaluated at our institution from January 2009 until June of 2021. The outcome was renal complications that occur ≥6 months after an equivocal MAG-3 renal scan. We created two machine learning models: a deep learning model using the radiotracer concentration versus time data from the kidney of interest and a random forest model created using clinical data. The performance of the models was assessed using measures of diagnostic accuracy.

RESULTS

We identified 152 eligible patients with available images of which 62 were cases and 90 were controls. The deep learning model predicted future renal complications with an overall accuracy of 73% (95% confidence inteveral [CI] 68-76%) and an AUC of 0.78 (95% CI 0.7, 0.84). The random forest model had an accuracy of 62% (95% CI 60-66%) and an AUC of 0.67 (95% CI. 0 64, 0.72) DISCUSSION: Our deep learning model predicted patients at high risk of developing renal complications following an equivocal renal scan and discriminate those at low risk with moderately high accuracy (73%). The deep learning model outperformed the clinical model built from clinical features classically used by urologists for surgical decision making.

CONCLUSION

Our models have the potential to influence clinical decision making by providing supplemental analytical data from MAG3 scans that would not otherwise be available to urologists. Future multi-institutional retrospective and prospective trials are needed to validate our model.

HIV Care Outcomes in Relation to Racial Redlining and Structural Factors Affecting Medical Care Access Among Black and White Persons with Diagnosed HIV-United States, 2017

Black/African American (Black) versus White persons are unequally burdened by human immunodeficiency virus (HIV) in the United States. Structural factors can influence social determinants of health, key components in reducing HIV-related health inequality by race. This analysis examined HIV care outcomes among Black and White persons with diagnosed HIV (PWDH) in relation to three structural factors: racial redlining, Medicaid expansion, and Ryan White HIV/AIDS Program (RWHAP) use. Using National HIV Surveillance System, U.S. Census, and Home Mortgage Disclosure Act data, we examined linkage to HIV care and viral suppression (i.e., viral load < 200 copies/mL) in relation to the structural factors among 12,996 Black and White PWDH with HIV diagnosed in 2017/alive at year-end 2018, aged ≥ 18 years, and residing in 38 U.S. jurisdictions with complete laboratory data, geocoding, and census tract-level redlining indexes. Compared to White PWDH, a lower proportion of Black PWDH were linked to HIV care within 1 month after diagnosis and were virally suppressed in 2018. Redlining was not associated with the HIV care outcomes. A higher prevalence of PWDH residing (v. not residing) in states with Medicaid expansion were linked to HIV care ≤ 1 month after diagnosis. A higher prevalence of those residing (v. not residing) in states with > 50% of PWDH in RWHAP had viral suppression. Direct exposure to redlining was not associated with poor HIV care outcomes. Structural factors that reduce the financial burden of HIV care and improve care access like Medicaid expansion and RWHAP might improve HIV care outcomes of PWDH.

0840 Sleep Quality in Clinically Indicated In-Laboratory Polysomnography

Introduction

Few studies have explored how patients sleep or what characteristics might be predictive of poor sleep during clinically-indicated polysomnography (PSG) in an in-laboratory setting.

Methods

We reviewed clinically indicated diagnostic PSG studies completed over a 10-year period in a single academic sleep center. Total sleep time (TST) and sleep efficiency (SE) were used as proxies for sleep quality. Patients were categorized as normal or poor sleepers based on TST &lt;4 hours or SE &lt;50%. Multivariate linear and logistic regression analyses were performed to determine factors associated with sleep quality while controlling for demographics, medications, comorbidities and measures of sleep.

Results

We included 4957 patients, who were mostly female (58.9%), middle-aged (52.9 y), Caucasian (69.3%), and overweight or obese (91.3%). 3682 patients (74.2%) were diagnosed with sleep apnea (Apnea Hypopnea Index(AHI)&gt;5/hr).

Average TST was 5.75±1.43 hours (Interquartile range [IQR] = 4.94 - 6.73) and average SE was 75.1%±16.1% (IQR=66.9 - 87.2). TST and SE were lower for males compared to females (5.48 vs 5.93 hr, p&lt;0.001; 73% vs 77%, p&lt;0.001). In multivariable analysis, older age (TST: OR = 1.04, 95% CI:[1.03,1.05]; SE: OR = 1.04, 95% CI:[1.04,1.05]), male sex (TST: 1.38,[1.14,1.68]; SE: 1.34,[1.07,1.68]), normal body habitus (TST: 1.47,[1.02,2.08]; SE: 1.51,[1.01,2.27]) and a higher AHI (TST: 1.02,[1.02,1.03]; SE: 1.02,[1.003,1.03]) were significantly associated with being a poor sleeper for both TST and SE. Antidepressant use was associated with poor sleep for TST (0.77, [0.59,1]), but not for SE (0.98, [0.73,1.3]).

Conclusion

Sleep quality during the in-laboratory PSG differed by sex, age and presence of sleep apnea. Sleep quality during in-lab PSG is thought to be compromised by obtrusive monitoring and an unfamiliar environment, but average sleep quality may be higher than expected for patients in the laboratory. Future studies should consider examining in-lab sleep quality in different patient populations.

Support

N/A

1052 Continuous Blood Pressure Monitoring In Sleep

Introduction

Abnormal nocturnal blood pressure(BP) such as non-dipping or nocturnal hypertension(reverse-dipping) represents a potent marker for cardiovascular risks. Standard cuff-based ambulatory nocturnal BP measurement yields limited data points potentially resulting in imprecise results, especially compared to continuously recorded BP. We hypothesized nocturnal BP based on periodic measurement would be different from true average beat-to-beat based BP.

Methods

We prospectively enrolled patients undergoing clinically indicated in-lab polysomnography, both CPAP and non-CPAP studies, for sleep apnea evaluation. Nocturnal BP was continuously monitored beat-to-beat by a noninvasive Caretaker™ device, which uses the Pulse Decomposition Analysis(PDA) algorithm. We compared BP recorded at 30-minute intervals with average BP continuously recorded over 30 minutes, both recorded by Caretaker™. We also looked at the differences between recording spot and continuous BP from an awake or sleeping state and BP variability(SD) based on continuously recorded BP. Using first 30 min as a reference, we determined dipping status (dipping: 10-20% reduction, level: 0-10% reduction, riser: any increase) by the two methods.

Results

A total of 18 patients were recruited(male:11, mean age:52.2). Among a total of 261 periodic BP measurements, 60 (30.0%) were obtained while awake. Mean nocturnal SBP by periodic BP measurement was higher compared with beat-to-beat-derived average BP(135.6mmHg[24.2] vs. 131.5[20.3], p&lt;0.0001). The difference between the two methods remained similar when continuous BP was derived from sleep vs. awake period(4.5mmHg[3.1] vs. 7.7[9.9], p=0.202). BP variability was more pronounced during awake compared with sleep period(6.7mmHg[8.1] versus 3.95[7.5], p=0.047). 8 patients were dippers by spot check measurement, but 11 were dippers by continuous BP.

Conclusion

Standard ambulatory periodic nocturnal BP recording may not yield true sleep BP patterns due to its spot-check nature and lack of sleep-awake information, which leads to inaccurate dipping measurements. Incorporation of beat-to-beat continuous BP measurement can provide more accurate and meaningful nocturnal BP information.

Support

N/A

ZikaPLAN: Zika Preparedness Latin American Network

The ongoing Zika virus (ZIKV) outbreak in Latin America, the Caribbean, and the Pacific Islands has underlined the need for a coordinated research network across the whole region that can respond rapidly to address the current knowledge gaps in Zika and enhance research preparedness beyond Zika. The European Union under its Horizon 2020 Research and Innovation Programme awarded three research consortia to respond to this need. Here we present the ZikaPLAN (Zika Preparedness Latin American Network) consortium. ZikaPLAN combines the strengths of 25 partners in Latin America, North America, Africa, Asia, and various centers in Europe. We will conduct clinical studies to estimate the risk and further define the full spectrum and risk factors of congenital Zika virus syndrome (including neurodevelopmental milestones in the first 3 years of life), delineate neurological complications associated with ZIKV due to direct neuroinvasion and immune-mediated responses in older children and adults, and strengthen surveillance for birth defects and Guillain-Barré Syndrome. Laboratory-based research to unravel neurotropism and investigate the role of sexual transmission, determinants of severe disease, and viral fitness will underpin the clinical studies. Social messaging and engagement with affected communities, as well as development of wearable repellent technologies against Aedes mosquitoes will enhance the impact. Burden of disease studies, data-driven vector control, and vaccine modeling as well as risk assessments on geographic spread of ZIKV will form the foundation for evidence-informed policies. While addressing the research gaps around ZIKV, we will engage in capacity building in laboratory and clinical research, collaborate with existing and new networks to share knowledge, and work with international organizations to tackle regulatory and other bottlenecks and refine research priorities. In this way, we can leverage the ZIKV response toward building a long-term emerging infectious diseases response capacity in the region to address future challenges.

Acute and Chronic Risk Preceding Suicidal Crises Among Middle-Aged Men Without Known Mental Health and/or Substance Abuse Problems: An Exploratory Mixed-Methods Analysis

BACKGROUND

Suicides among men aged 35-64 years increased by 27% between 1999 and 2013, yet little research exists to examine the nature of the suicide risk within this population. Many men do not seek help if they have mental health problems and suicides may occur in reaction to stressful circumstances.

AIMS

We examined the precipitating circumstances of 600 suicides without known mental health or substance abuse (MH/SA) problems and with a recent crisis. Whether these suicides occurred within the context of an acute crisis only or in the context of chronic circumstances was observed.

METHOD

Using data from the National Violent Death Reporting System and employing mixed-methods analysis, we examined the circumstances and context of a census of middle-aged male suicides (n = 600) in seven states between 2005 and 2010.

RESULTS

Precipitating circumstances among this group involved intimate partner problems (IPP; 58.3%), criminal/legal problems (50.7%), job/financial problems (22.5%), and health problems (13.5%). Men with IPP and criminal/legal issues were more likely than men with health and/or job/financial issues to experience suicide in the context of an acute crisis only.

CONCLUSION

Suicides occurring in reaction to an acute crisis only or in the context of acute and chronic circumstances lend themselves to opportunities for intervention. Further implications are discussed.

Caffeine increases striatal dopamine D2/D3 receptor availability in the human brain

Caffeine, the most widely consumed psychoactive substance in the world, is used to promote wakefulness and enhance alertness. Like other wake-promoting drugs (stimulants and modafinil), caffeine enhances dopamine (DA) signaling in the brain, which it does predominantly by antagonizing adenosine A2A receptors (A2AR). However, it is unclear if caffeine, at the doses consumed by humans, increases DA release or whether it modulates the functions of postsynaptic DA receptors through its interaction with adenosine receptors, which modulate them. We used positron emission tomography and [(11)C]raclopride (DA D2/D3 receptor radioligand sensitive to endogenous DA) to assess if caffeine increased DA release in striatum in 20 healthy controls. Caffeine (300 mg p.o.) significantly increased the availability of D2/D3 receptors in putamen and ventral striatum, but not in caudate, when compared with placebo. In addition, caffeine-induced increases in D2/D3 receptor availability in the ventral striatum were associated with caffeine-induced increases in alertness. Our findings indicate that in the human brain, caffeine, at doses typically consumed, increases the availability of DA D2/D3 receptors, which indicates that caffeine does not increase DA in the striatum for this would have decreased D2/D3 receptor availability. Instead, we interpret our findings to reflect an increase in D2/D3 receptor levels in striatum with caffeine (or changes in affinity). The association between increases in D2/D3 receptor availability in ventral striatum and alertness suggests that caffeine might enhance arousal, in part, by upregulating D2/D3 receptors.

Stimulant-induced dopamine increases are markedly blunted in active cocaine abusers

Dopamine signaling in nucleus accumbens is essential for cocaine reward. Interestingly, imaging studies have reported blunted dopamine increases in striatum (assessed as reduced binding of [(11)C]raclopride to D2/D3 receptors) in detoxified cocaine abusers. Here, we evaluate whether the blunted dopamine response reflected the effects of detoxification and the lack of cocaine-cues during stimulant exposure. For this purpose we studied 62 participants (43 non-detoxified cocaine abusers and 19 controls) using positron emission tomography and [(11)C]raclopride (radioligand sensitive to endogenous dopamine) to measure dopamine increases induced by intravenous methylphenidate and in 24 of the cocaine abusers, we also compared dopamine increases when methylphenidate was administered concomitantly with a cocaine cue-video versus a neutral-video. In controls, methylphenidate increased dopamine in dorsal (effect size 1.4; P<0.001) and ventral striatum (location of accumbens) (effect size 0.89; P<0.001), but in cocaine abusers methylphenidate's effects did not differ from placebo and were similar whether cocaine-cues were present or not. In cocaine abusers despite the markedly attenuated dopaminergic effects, the methylphenidate-induced changes in ventral striatum were associated with intense drug craving. Our findings are consistent with markedly reduced signaling through D2 receptors during intoxication in active cocaine abusers regardless of cues exposure, which might contribute to compulsive drug use.

Recent outbreaks of infectious syphilis, United Kingdom, January 2012 to April 2014

Six outbreaks of infectious syphilis in the United Kingdom, ongoing since 2012, have been investigated among men who have sex with men (MSM) and heterosexual men and women aged under 25 years. Interventions included case finding and raising awareness among healthcare professionals and the public. Targeting at-risk populations was complicated as many sexual encounters involved anonymous partners. Outbreaks among MSM were influenced by the use of geospatial real-time networking applications that allow users to locate other MSM within close proximity.

Precipitating circumstances of suicide among youth aged 10-17 years by sex: data from the National Violent Death Reporting System, 16 states, 2005-2008

We examined the circumstances that precipitated suicide among 1,046 youth aged 10-17 years in 16 U.S. states from 2005 to 2008. The majority of deaths were among male subjects (75.2%), non-Hispanic whites (69.3%), those aged 16-17 years (58.1%), those who died by hanging/strangulation/suffocation (50.2%) and those who died in a house or an apartment (82.5%). Relationship problems, recent crises, mental health problems, and intimate partner and school problems were the most common precipitating factors and many differed by sex. School problems were reported for 25% of decedents, of which 30.3% were a drop in grades and 12.4% were bullying related. Prevention strategies directed toward relationship-building, problem-solving, and increasing access to treatment may be beneficial for this population.

Decreased dopamine activity predicts relapse in methamphetamine abusers

Studies in methamphetamine (METH) abusers showed that the decreases in brain dopamine (DA) function might recover with protracted detoxification. However, the extent to which striatal DA function in METH predicts recovery has not been evaluated. Here we assessed whether striatal DA activity in METH abusers is associated with clinical outcomes. Brain DA D2 receptor (D2R) availability was measured with positron emission tomography and [(11)C]raclopride in 16 METH abusers, both after placebo and after challenge with 60 mg oral methylphenidate (MPH) (to measure DA release) to assess whether it predicted clinical outcomes. For this purpose, METH abusers were tested within 6 months of last METH use and then followed up for 9 months of abstinence. In parallel, 15 healthy controls were tested. METH abusers had lower D2R availability in caudate than in controls. Both METH abusers and controls showed decreased striatal D2R availability after MPH and these decreases were smaller in METH than in controls in left putamen. The six METH abusers who relapsed during the follow-up period had lower D2R availability in dorsal striatum than in controls, and had no D2R changes after MPH challenge. The 10 METH abusers who completed detoxification did not differ from controls neither in striatal D2R availability nor in MPH-induced striatal DA changes. These results provide preliminary evidence that low striatal DA function in METH abusers is associated with a greater likelihood of relapse during treatment. Detection of the extent of DA dysfunction may be helpful in predicting therapeutic outcomes.

Repeat variation in the human PER2 gene as a new genetic marker associated with cocaine addiction and brain dopamine D2 receptor availability

Low dopamine D2 receptor (D2R) levels in the striatum are consistently reported in cocaine abusers; inter-individual variations in the degree of the decrease suggest a modulating effect of genetic makeup on vulnerability to addiction. The PER2 (Period 2) gene belongs to the clock genes family of circadian regulators; circadian oscillations of PER2 expression in the striatum was modulated by dopamine through D2Rs. Aberrant periodicity of PER2 contributes to the incidence and severity of various brain disorders, including drug addiction. Here we report a newly identified variable number tandem repeat (VNTR) polymorphism in the human PER2 gene (VNTR in the third intron). We found significant differences in the VNTR alleles prevalence across ethnic groups so that the major allele (4 repeats (4R)) is over-represented in non-African population (4R homozygosity is 88%), but not in African Americans (homozygosity 51%). We also detected a biased PER2 genotype distribution among healthy controls and cocaine-addicted individuals. In African Americans, the proportion of 4R/three repeat (3R) carriers in healthy controls is much lower than that in cocaine abusers (23% vs 39%, P=0.004), whereas among non-Africans most 3R/4R heterozygotes are healthy controls (10.5% vs 2.5%, P=0.04). Analysis of striatal D2R availability measured with positron emission tomography and [(11)C]raclopride revealed higher levels of D2R in carriers of 4R/4R genotype (P<0.01). Taken together, these results provide preliminary evidence for the role of the PER2 gene in regulating striatal D2R availability in the human brain and in vulnerability for cocaine addiction.

Characteristics of perpetrators in homicide-followed-by-suicide incidents: National Violent Death Reporting System--17 US States, 2003-2005

Homicide-followed-by-suicide (referred to as "homicide-suicide") incidents are rare events but can have a profound impact on families and communities. A better understanding of perpetrator characteristics and how they compare with those of other homicide suspects and suicide decedents might provide insight into the nature of these violent acts. This report is based on 2003-2005 data from 17 US states participating in the National Violent Death Reporting System, a unique, incident-based, active surveillance system that integrates data on violent deaths from multiple sources. Of the 408 homicide-suicide incidents identified, most incidents were committed with a firearm (88.2%) and perpetrated by males (91.4%), those over 19 years of age (97.6%), and those of white race (77.0%); however, just over half of filicide (killing of children)-suicides (51.5%) were perpetrated by females. Over 55% of male homicide-suicide perpetrators versus 26.4% of other male suicide decedents had prior intimate partner conflicts (P < 0.001). In fact, having a history of intimate partner conflicts was even common among homicide-suicide perpetrators who did not victimize their intimate partners. Recognition of the link between intimate partner conflicts and homicide-suicide incidents and strategies involving collaboration among the court/legal and mental health systems might prevent these incidents.

Limits on gravitational-wave emission from selected pulsars using LIGO data

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.

Therapeutic doses of amphetamine or methylphenidate differentially increase synaptic and extracellular dopamine

Methylphenidate (MP) and amphetamine (AMP) are first-line treatments for attention-deficit hyperactivity disorder. Although both drugs have similar therapeutic potencies, the stimulatory effect of AMP on extracellular dopamine (ECF DA) is greater than that of MP. We compared extracellular effects directly against synaptic changes. ECF DA was assessed by microdialysis in freely moving rodents and synaptic dopamine (DA) was measured using PET and [11C]-raclopride displacement in rodents and baboons. Microdialysis data demonstrated that MP (5.0 mg/kg, i.p.) increased ECF DA 360% +/- 31% in striatum, which was significantly less than that by AMP (2.5 mg/kg, i.p.; 1398% +/- 272%). This fourfold difference was not reflected by changes in synaptic DA. In fact, rodent PET studies showed no difference in striatal [11C]-raclopride binding induced by AMP (2.5 mg/kg, i.p.; 25% +/- 4% reduction) compared with that by MP (5.0 mg/kg, i.p.; 21% +/- 4% reduction). Primate PET experiments also showed no differences between AMP (0.5 mg/kg, i.v.; 24% +/- 4% reduction) and MP (1.0 mg/kg, i.v.; 25% +/- 7% reduction) induced changes in [11C]-raclopride binding potential. The similar potencies of MP and AMP to alter synaptic DA, despite their different potencies in raising ECF DA, could reflect their different molecular mechanisms.

Evidence of biased immunoglobulin variable gene usage in highly stable B-cell chronic lymphocytic leukemia

Recognition of biased immunoglobulin variable (IgV) gene usage in B-cell chronic lymphocytic leukemia (B-CLL) may yield insight into leukemogenesis and may help to refine prognostic categories. We explored Ig variable heavy (VH) and light (VL) chain gene usage in highly stable and indolent B-CLL (n=25) who never required treatment over 10 or more years. We observed an unexpectedly high usage of mutated VH3-72 (6/25; 24.0%), a gene that was otherwise rare in B-CLL (7/805; 0.87%; P<0.01), including mutated cases (6/432; 1.39%; P<0.01) and was exceptional among indolent (1/230, 0.435%; P<0.01), and aggressive B-cell lymphomas (0/105; P<0.01). Three of six VH3-72 B-CLL cases utilized the same VL Vkappa4-1 gene. Two V(H)3-72 B-CLL cases had highly homologous VH complementarity determining regions 3 (CDR3s), encoding Cys-XXXX-Cys domains, and utilized Vkappa4-1 genes with homologous IgVL CDR3s. An identical threonine to isoleucine change at codon 84 of V(H)3-72 framework region 3 (FR3) recurred in four cases of highly stable VH3-72 B-CLL. This mutation is expected to cause a conformational change of FR3 proximal to CDR3 that might critically affect high-affinity antigen binding. B-cell receptors encoded by VH3-72 may identify a specific B-CLL group and be implicated in leukemogenesis through an antigen-driven expansion of B cells.

Effect of margins of excision on recurrence after local excision of ductal carcinoma in situ of the breast

AIMS

To determine important factors influencing recurrence after local excision of duct carcinoma in situ (DCIS) of the breast.

MATERIALS AND METHODS

The extent (size) in millimetres, classification (by cytonuclear grade (NHSBSP system), by extent of necrosis, and by the Van Nuys system), and excision margins of 115 cases of screen detected DCIS treated by local excision were measured. A prognostic index was calculated by the addition of the Van Nuys classification (low grade, 1; moderate grade, 2; high grade, 3), margin score (> or = 10 mm, 1; 1-9 mm, 2; < 1 mm, 3), and size score (< or = 15 mm, 1; 16-40 mm, 2; and > or = 41 mm, 3), giving a total score of 3-9.

RESULTS

Classification using cytonuclear grade, extent of necrosis, or the Van Nuys system did not correlate significantly with recurrence. The excision margin (in millimetres) was associated with recurrence (p = 0.027) and if excision margin status was simplified using the scoring system (> or = 10 mm, 1; 1-9 mm, 2; < 1 mm, 3), the margin score was significantly associated with recurrence (p = 0.03). A prognostic index based on the Van Nuys score, margin status, and size was significantly associated with recurrence (p = 0.003).

CONCLUSION

The results support the hypothesis that the margin of excision is the most important factor predicting the recurrence of DCIS after local excision.

Study of brain uptake and biodistribution of [11C]toluene in non-human primates and mice

Inhalant abuse is a rapidly growing health problem particularly among adolescents. Yet we know little about the neural mechanisms underlying the abuse liability of inhalants, particularly when compared to other addictive drugs. Specifically, our understanding of the relationship between the regional brain phamacokinetics and features classically associated with drug reinforcement is lacking. Under the hypothesis that the abuse liability of toluene can be related to its pharmacokinetic properties and the pattern of regional brain uptake, we developed the methodology for radiolabeling and purifying [11C]toluene for use in PET studies. Here we report the regional brain distribution and kinetics of the widely abused solvent toluene in non-human primates and the whole body biodistribution in mice. To our knowledge, this is the first reported study of the in vivo brain pharmacokinetics of labeled toluene in non-human primates. Rapid uptake of radioactivity into striatal and frontal regions was followed by rapid clearance from the brain. Concurrent findings in rodents indicate similar radio-tracer kinetics, with excretion through kidneys and liver. Taken together, our data provides insight into pharmacokinetic features possibly associated with the abuse liability of toluene.