Rapid method for correction of CSF partial volume in quantitative proton MR spectroscopic imaging.

Partial volume effects with cerebrospinal fluid (CSF), if uncorrected, can lead to underestimation of metabolite concentrations in quantitative proton magnetic resonance spectroscopic imaging (MRSI) of the brain. A rapid method for the correction of CSF partial volume effects is described based on selective CSF imaging using long echo time (TE) fast spin echo (FSE) magnetic resonance imaging (MRI). In order to achieve maximum suppression of signal from brain parenchyma, the FSE sequence is coupled with an inversion recovery (IR) pulse. Scan time is minimized using single shot (SS) IR-FSE. The method is validated against a current "gold standard" for the determination of CSF volumes, namely, segmented 3D spoiled gradient-echo (SPGR) scans. Excellent agreement in CSF percentage determined by the two methods was found (linear regression analysis: slope = 0.99 +/- 0.02, intercept = 2.08 +/- 0.45; mean +/- standard errors, R = 0.93) in pooled data from four healthy subjects. An example of the use of SS-IR-FSE for partial volume correction in a leukodystrophy patient with T(2) hyperintense lesions is demonstrated. SS-IR-FSE is a simple and rapid method for applying partial volume corrections in quantitative proton MRSI, which may be of particular value in the clinical environment when time constraints do not allow longer, perhaps more accurate segmentation methods to be used.

Sensory and affective dimensions of phasic pain are indistinguishable in the self-report and psychophysiology of normal laboratory subjects.

This study evaluated the discriminant validity of subjects differentially scaling the sensory and affective dimensions of pain. It sought to determine (1) whether subjects can differentially scale sensory and affective aspects of phasic laboratory pain in the absence of task demand bias that fosters apparent differential scaling; (2) whether psychophysiologic responses to painful stimuli can predict pain report (PR); and (3) whether such responses contribute more to affective than to sensory judgments. Fifty-six men and 44 women repeatedly experienced varied painful electrical fingertip stimuli at low, medium, and high intensities. On half of the trial blocks, subjects made sensory judgments; on the remainder they made affective judgments. Response measures included PR, pupil dilation, heart rate, respiration rate, skin conductance response (SCR), and late near field evoked potentials. Subjects did not rate the stimuli differently when making sensory versus affective judgments. The psychophysiologic variables, principally the SCR, accounted for 44% of the variance in the PR. Psychophysiologic response patterns did not differentiate affective and sensory judgment conditions. Noteworthy sources of individual differences included baseline PR levels and the linear effects of SCR on PR.

Phasic pupil dilation response to noxious stimulation in normal volunteers: relationship to brain evoked potentials and pain report.

Pupillary response to noxious stimulation was investigated in men (n = 11) and women (n = 9). Subjects experienced repeated trials of noxious electrical fingertip stimulation at four intensities, ranging from faint to barely tolerable pain. Measures included pupil dilation response (PDR), pain report (PR), and brain evoked potentials (EPs). The PDR began at 0.33 s and peaked at 1.25 s after the stimulus. Multivariate mixed-effects analyses revealed that (a) the PDR increased significantly in peak amplitude as stimulus intensity increased, (b) EP peaks at 150 and 250 ms differed significantly in both amplitude and latency across stimulus intensity, and (c) PR increased significantly with increasing stimulus intensity. Men demonstrated a significantly greater EP peak amplitude and peak latency at 150 ms than did women. With sex and stimulus intensity effects partialled out, the EP peak latency at 150 ms significantly predicted PR, and EP peak amplitude at 150 ms significantly predicted the PDR peak amplitude.

Use of hospital services by AIDS patients with psychiatric illness.

The purpose of this study was to assess the effect of psychiatric illness on length of stay and patterns of admission among AIDS patients hospitalized for medical illnesses. Medical records were abstracted for AIDS patients admitted to hospitals in Washington State from 1990 through 1992. Psychiatric comorbidity was defined by the presence of an International Classification of Disease-9 code reflecting psychiatric illness. Medical morbidity was addressed using CD4 count and AIDS-defining illnesses as markers of disease severity. Of 2834 admissions, 15% included one or more psychiatric diagnoses. Psychiatric illness (F 39.1; df 1,2830; p < 0.001) and discharge disposition (F 81.2; df 2,2830; p < 0.001) contributed significantly to the model, explaining increased length of stay (F 67.2; df 3,2830; p < 0.001). Future research needs to address the possible etiology of psychiatric comorbidity's contribution to length of stay and the effect on quality and cost of care.

Psychiatric comorbidity and length of stay in hospitalized AIDS patients.

OBJECTIVE: The purpose of this study was to assess the effect of psychiatric comorbidity on specific measures of hospital utilization, including length of stay, among hospitalized AIDS patients. METHOD: Data collection involved medical record abstraction for AIDS patients admitted to any one of 19 hospitals in Washington State during 1990. Psychiatric comorbidity was defined by the presence of an ICD-9 code reflecting psychiatric illness. Medical/surgical admissions of AIDS patients with psychiatric diagnoses were compared to those of AIDS patients without psychiatric diagnoses on measures of mean length of stay for the first admission in 1990, total number of hospitalizations in 1990, and total number of hospital days in 1990. Medical morbidity was addressed using CD4+ cell count and current and previous AIDS-defining illnesses as markers of disease severity. RESULTS: Of 357 patients hospitalized with AIDS, 49 (14%) had at least one psychiatric diagnosis. Patients with psychiatric illness were hospitalized an average of 6.6 days longer than AIDS patients without such illnesses. Differences in medical morbidity did not account for the longer length of stay. CONCLUSIONS: Psychiatric comorbidity increased the average length of stay among hospitalized AIDS patients. Future research needs to address the possible effects of this phenomenon on quality and cost of care received by AIDS patients.