A personalized deep learning denoising strategy for low-count PET images

Objective. Deep learning denoising networks are typically trained with images that are representative of the testing data. Due to the large variability of the noise levels in positron emission tomography (PET) images, it is challenging to develop a proper training set for general clinical use. Our work aims to develop a personalized denoising strategy for the low-count PET images at various noise levels.Approach.We first investigated the impact of the noise level in the training images on the model performance. Five 3D U-Net models were trained on five groups of images at different noise levels, and a one-size-fits-all model was trained on images covering a wider range of noise levels. We then developed a personalized weighting method by linearly blending the results from two models trained on 20%-count level images and 60%-count level images to balance the trade-off between noise reduction and spatial blurring. By adjusting the weighting factor, denoising can be conducted in a personalized and task-dependent way.Main results.The evaluation results of the six models showed that models trained on noisier images had better performance in denoising but introduced more spatial blurriness, and the one-size-fits-all model did not generalize well when deployed for testing images with a wide range of noise levels. The personalized denoising results showed that noisier images require higher weights on noise reduction to maximize the structural similarity and mean squared error. And model trained on 20%-count level images can produce the best liver lesion detectability.Significance.Our study demonstrated that in deep learning-based low dose PET denoising, noise levels in the training input images have a substantial impact on the model performance. The proposed personalized denoising strategy utilized two training sets to overcome the drawbacks introduced by each individual network and provided a series of denoised results for clinical reading.

Functional 4-D clustering for characterizing intratumor heterogeneity in dynamic imaging: evaluation in FDG PET as a prognostic biomarker for breast cancer

Purpose

Probe-based dynamic (4-D) imaging modalities capture breast intratumor heterogeneity both spatially and kinetically. Characterizing heterogeneity through tumor sub-populations with distinct functional behavior may elucidate tumor biology to improve targeted therapy specificity and enable precision clinical decision making.

Methods

We propose an unsupervised clustering algorithm for 4-D imaging that integrates Markov-Random Field (MRF) image segmentation with time-series analysis to characterize kinetic intratumor heterogeneity. We applied this to dynamic FDG PET scans by identifying distinct time-activity curve (TAC) profiles with spatial proximity constraints. We first evaluated algorithm performance using simulated dynamic data. We then applied our algorithm to a dataset of 50 women with locally advanced breast cancer imaged by dynamic FDG PET prior to treatment and followed to monitor for disease recurrence. A functional tumor heterogeneity (FTH) signature was then extracted from functionally distinct sub-regions within each tumor. Cross-validated time-to-event analysis was performed to assess the prognostic value of FTH signatures compared to established histopathological and kinetic prognostic markers.

Results

Adding FTH signatures to a baseline model of known predictors of disease recurrence and established FDG PET uptake and kinetic markers improved the concordance statistic (C-statistic) from 0.59 to 0.74 (p = 0.005). Unsupervised hierarchical clustering of the FTH signatures identified two significant (p < 0.001) phenotypes of tumor heterogeneity corresponding to high and low FTH. Distributions of FDG flux, or Ki, were significantly different (p = 0.04) across the two phenotypes.

Conclusions

Our findings suggest that imaging markers of FTH add independent value beyond standard PET imaging metrics in predicting recurrence-free survival in breast cancer and thus merit further study.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05265-8.

4D radiomic biomarker of functional tumor heterogeneity to predict breast cancer recurrence in pretreatment dynamic FDG-PET

e12573

Background: Breast cancer heterogeneity is thought to be associated with adverse outcomes. Dynamic molecular imaging modalities, including PET, permit 4-D sampling of tumor biologic properties and can therefore capture functional heterogeneity revealed by the temporal dimension of the dynamic tracer uptake. With the goal of improved non-invasive characterization of in vivo tumor biology, we have developed and tested a novel radiomic biomarker that characterizes 4-D functional tumor heterogeneity (FTH). We hypothesize subclonal populations are spatially contiguous regions of shared physiologic behavior that drive breast cancer heterogeneity and can be quantified. We describe an initial application of this approach to FDG PET imaging of breast cancer. Methods: We retrospectively analyzed data from a study of 50 patients with locally advanced breast cancer. Patients underwent 60-minute dynamic FDG PET over the chest prior to neoadjuvant chemotherapy and breast surgery and were followed for disease recurrence (DFS). A 3-D region bounding each tumor was identified by a radiologist and a novel Markov Random Field based 4-D segmentation paradigm segmented each tumor into three spatially constrained sub-regions with distinct time activity curve dynamics. From each tumor, an FTH imaging signature was extracted characterizing cluster compactness and separation. FTH imaging signatures were z-score normalized across all patients. Time-to-event analysis was used to assess the prognostic value of the FTH imaging signatures in predicting DFS. Discriminatory capacity compared to a baseline model of established prognostic factors (age, hormone receptor status, baseline tumor size) and standard PET uptake and kinetics markers (SUV, K1, and Ki) shown to be predictive of DFS (Dunnwald, J Clin Oncol 26:4449, 2008) was evaluated using the c-statistic and the log-likelihood statistical test. Results: 17 of 50 women (34%) had recurrence events. Adding FTH imaging signatures to the baseline model of age, baseline tumor size, and hormone receptor status improved a cross validated c-statistic from 0.51 to 0.74 (p < 0.05), and demonstrated higher discriminatory capacity over a model of age, tumor size, hormone receptor status, and standard PET measures (c-statistic = 0.59). Conclusions: Imaging biomarkers of 4-D metabolic tumor heterogeneity may add prognostic value in predicting recurrence-free survival in breast cancer and merit further study.

Erratum: Measuring temporal stability of positron emission tomography standardized uptake value bias using long-lived sources in a multicenter network

[This corrects the article DOI: 10.1117/1.JMI.5.1.011016.].

Measuring temporal stability of positron emission tomography standardized uptake value bias using long-lived sources in a multicenter network

Positron emission tomography (PET) is a quantitative imaging modality, but the computation of standardized uptake values (SUVs) requires several instruments to be correctly calibrated. Variability in the calibration process may lead to unreliable quantitation. Sealed source kits containing traceable amounts of [Formula: see text] were used to measure signal stability for 19 PET scanners at nine hospitals in the National Cancer Institute's Quantitative Imaging Network. Repeated measurements of the sources were performed on PET scanners and in dose calibrators. The measured scanner and dose calibrator signal biases were used to compute the bias in SUVs at multiple time points for each site over a 14-month period. Estimation of absolute SUV accuracy was confounded by bias from the solid phantoms' physical properties. On average, the intrascanner coefficient of variation for SUV measurements was 3.5%. Over the entire length of the study, single-scanner SUV values varied over a range of 11%. Dose calibrator bias was not correlated with scanner bias. Calibration factors from the image metadata were nearly as variable as scanner signal, and were correlated with signal for many scanners. SUVs often showed low intrascanner variability between successive measurements but were also prone to shifts in apparent bias, possibly in part due to scanner recalibrations that are part of regular scanner quality control. Biases of key factors in the computation of SUVs were not correlated and their temporal variations did not cancel out of the computation. Long-lived sources and image metadata may provide a check on the recalibration process.

Synthesis and characterization of fluorinated derivatives of cresolsulfonphthalein

The reaction between dilute fluorine gas and cresolsufonphthalein in acetic acid was investigated. The mono-, di-, and trifluorinated cresolsufonphthalein derivatives were isolated and characterized. These compounds possessed the properties of pH indicators with biologically relevant pK_a values (6.4-7.5) and the absorption maxima of the basic forms at 582-592 nm. This method can be used for synthesis of positron-emitting ¹⁸F-labeled pH indicators with potential application for non-invasive in vivo pH measurement in biological objects.

Biodistribution and dosimetry of (18)F-EF5 in cancer patients with preliminary comparison of (18)F-EF5 uptake versus EF5 binding in human glioblastoma

PURPOSE

The primary purpose of this study was to assess the biodistribution and radiation dose resulting from administration of (18)F-EF5, a lipophilic 2-nitroimidazole hypoxia marker in ten cancer patients. For three of these patients (with glioblastoma) unlabeled EF5 was additionally administered to allow the comparative assessment of (18)F-EF5 tumor uptake with EF5 binding, the latter measured in tumor biopsies by fluorescent anti-EF5 monoclonal antibodies.

METHODS

(18)F-EF5 was synthesized by electrophilic addition of (18)F(2) gas, made by deuteron bombardment of a neon/fluorine mixture in a high-pressure gas target, to an allyl precursor in trifluoroacetic acid at 0° then purified and administered by intravenous bolus. Three whole-body images were collected for each of ten patients using an Allegro (Philips) scanner. Gamma counts were determined in blood, drawn during each image, and urine, pooled as a single sample. PET images were analyzed to determine radiotracer uptake in several tissues and the resulting radiation dose calculated using OLINDA software and standard phantom. For three patients, 21 mg/kg unlabeled EF5 was administered after the PET scans, and tissue samples obtained the next day at surgery to determine EF5 binding using immunohistochemistry techniques (IHC).

RESULTS

EF5 distributes evenly throughout soft tissue within minutes of injection. Its concentration in blood over the typical time frame of the study (∼3.5 h) was nearly constant, consistent with a previously determined EF5 plasma half-life of ∼13 h. Elimination was primarily via urine and bile. Radiation exposure from labeled EF5 is similar to other (18)F-labeled imaging agents (e.g., FDG and FMISO). In a de novo glioblastoma multiforme patient, focal uptake of (18)F-EF5 was confirmed by IHC.

CONCLUSION

These results confirm predictions of biodistribution and safety based on EF5's characteristics (high biological stability, high lipophilicity). EF5 is a novel hypoxia marker with unique pharmacological characteristics allowing both noninvasive and invasive measurements.

Phase I dose escalation trial of sorafenib as a single agent for adults with relapsed and refractory acute leukemias

7065

Background: Sorafenib is a multikinase inhibitor with activity against B-raf, VEGF, and FLT3. Based on preclinical activity in FLT3 mutant AML, sorafenib was studied in refractory acute leukemia. Methods: The primary objective was to determine the safety and tolerability of sorafenib in refractory acute leukemias. Secondary objectives included pharmacokinetics (PK) and pharmacodynamic (PD) effects of sorafenib on FLT3 phosphorylation. Dose escalation began at 400 mg BIDx14days per month, and proceeded through 600 mg BID x 21 days per month. Plasma concentration of sorafenib and its primary metabolite sorafenib N-oxide were measured by LC/MS//MS method. The plasma inhibitory assay was used to measure target inhibition of phosphorylated FLT3 and phosphorylated Erk. Results: Fifteen patients (13 = AML, 2 = ALL) were enrolled (ages 37–85) and treated on three dosing schedules (400 mg BID x 14 d, 400 mg BID x 21 days, 600 mg BID x 21days) of single agent sorafenib. The maximally tolerated dose was 400 mg BID x 21 days per month. Grade 3 or greater toxicities were experienced in 55% of cycles, most common grade 3 or greater toxicities being fatigue (16%) and hypokalemia (13%). No patients met criteria for complete or partial response, but 11 of 15 (73%) patients experienced stable disease as best response, with 6 showing a reduction in bone marrow blasts after only one cycle, half of who experienced a >50% reduction in bone marrow blasts. Interestingly, 2 pts with FLT3-ITD mutations both showed marrow blast response (1 pt >50%). Sorafenib resulted in sustained complete inhibition of FLT3 and Erk as demonstrated in all patients assessed (n = 11). Importantly, this inhibition was maintained throughout treatment cycle and 3/5 pts had FLT3 inhibitory activity 7 days post their last dose. Correlative studies suggest sorafenib N-oxide is an active metabolite. Conclusions: Sorafenib is a potent inhibitor of FLT3 with favorable PK and PD properties. Clinical activity as a single agent was limited to transient reductions in bone marrow blast counts and dose escalation was limited due to toxicities. Based on PK data in conjunction with standard curves for inhibition of FLT3 by sorafenib in plasma, the minimum FLT3 inhibitory dose of sorafenib is likely less than 400 mg BID.

No significant financial relationships to disclose.

Phase Ib/II pharmacokinetic/pharmacodynamic (PK/PD) study of combination voreloxin and cytarabine in relapsed or refractory AML patients

7005

Background: Voreloxin is a naphthyridine analog that intercalates DNA and inhibits topoisomerase II, inducing apoptosis. Clinical activity is observed in ovarian cancer and AML. Voreloxin combined with cytarabine (Ara-C) show supra-additive activity preclinically. Interim results from a phase Ib/II study in relapsed or refractory AML are reported. Methods: Dose-escalation in relapsed/refractory AML patients (pts) with ≤ 3 prior induction regimens; phase II expansion in first-relapse pts (CR1 ≥ 3 months) at MTD. Voreloxin given d1 and d4, combined with: A) continuous infusion 400 mg/m2/d x 5d Ara-C (CIV), or B) bolus 1 g/m2/d IV x 5d Ara-C. Voreloxin starting dose: A) 10 mg/m2/dose; B) 70 mg/m2/dose. Treatment: induction, reinduction if needed, and up to 2 courses for consolidation. DLT, PK, and PD were assessed in cycle 1. Pts’ PBMC were evaluated for induction of DNA damage response markers. Ex vivo sensitivity of pt BMA to voreloxin and Ara-C were evaluated by CellTiter-Glo proliferation assay. Results: 52 pts treated to date (A: 41 pts, dose-escalation; 5 pts Phase 2; B: 6 pts dose-escalation). A) MTD is 80 mg/m2/dose voreloxin. Infections are the most common G3 or higher toxicity. Voreloxin PK were dose proportional to 50 mg/m2, then plateaued. Evaluation of PBMC pre- and posttreatment suggests modulation of pDNA-PKcs and pChk2 may reflect response. Ex vivo BMA assay results suggest that voreloxin is the primary contributor to the majority of CRs observed. Phase Ib: 9 CRs + CRp were observed in multiply relapsed or 1° refractory pts. B) 70 mg/m2/dose voreloxin, no DLT; too early to evaluate activity. Conclusions: Voreloxin in combination with CIV Ara-C is generally well-tolerated, with CR in relapsed/refractory pts. Enrollment continues: A) phase II; B) phase Ib. Ex vivo activity assay results suggest that voreloxin is the primary contributor to the majority of CR. Induction of pDNA-PKcs and pChk2 in PBMCs from treated pts may reflect response.

[Table: see text]

Poor risk assessment in the elderly receiving cloretazine induction for AML or MDS

18562

Background: Elderly patients (pts) ≥60 years with acute myelogenous leukemia (AML) have lower response rates, and higher morbidity and mortality than younger pts when treated with cytotoxic induction therapy. Common disease-related factors that predict poor response in the elderly are adverse cytogenetics and secondary leukemia (following antecedent hematologic disorder or exposure to chemotherapy). Pt-related factors such as ECOG performance status (PS) and organ dysfunction affect treatment decisions due to poor tolerability and early death. Cloretazine, a novel alkylating agent has significant activity in AML and MDS with a favorable safety profile. A Phase II study of monotherapy induction was conducted in elderly pts with AML or high risk MDS (N = 105, median age 72, range 60–88), with a 31% complete response rate and minimal non-hematologic toxicity. To describe the pts in this study considered “unfit” for 7+3 induction, disease-related and pt-related information was obtained. The Hematopoietic Cell Transplantation Comorbidity Index (Sorrer et al, 2005) (HCT-CI) is a modification of the Charlson Comorbidity Index (Charlson et al.1987), for pts considered for stem cell transplant. Seventeen medical conditions are included with weighted values predicting non-relapse mortality (NRM). Methods: Baseline demographic and pt-related data was obtained from case report forms. In addition to disease-related prognostic indicators, pt-related data was scored by the HCT-CI. Pts were grouped in risk categories for NRM by HCT-CI scores (low = 0, intermediate = 1 or 2; high ≥3). Results: Either or both disease-related poor risk factors were present in 68 pts (65%): 42 pts (40%) had unfavorable cytogenetics and 45 pts (43%) had secondary AML. No pt had favorable cytogenetics. Ninety-four (89%) pts had at least one HCT-CI comorbidity. The most common were cardiac (46%), psychiatric (28%); hepatic (25%) and controlled infection (24%). By HCT-CI, the risk for NRM was low in 10%, intermediate in 32%, and high in 57% of pts. Conclusions: The majority of these elderly pts were poor-risk by disease-related criteria or comorbidities measured by the HCT-CI. This index warrants further testing for determining NRM risk of induction regimens for elderly pts with AML.

[Table: see text]

In vivo imaging of serotonin transporters with [99mTc]TRODAT-1 in nonhuman primates

[99mTc]TRODAT-1 was the first 99mTc-labeled imaging agent to show specific binding to dopamine transporters (DAT) in the striatum (STR) of human brain. Additionally, in vitro binding and autoradiographic experiments demonstrated that this tracer also binds to serotonin transporters (SERT) in the midbrain/hypothalamus (MB) area. In this study, [99mTc]TRODAT-1 was investigated as a potentially useful ligand to image SERT in the MB of living brain. A total of eight single-photon emission tomography (SPET) scans were performed in two baboons (Papio anubis) after intravenous (i.v.) injection of 740 MBq (20 mCi) of [99mTc]TRODAT-1 using a triple-head gamma camera equipped with ultra-high-resolution fan-beam collimators (scan time: 0-210 min). In four blocking studies, baboons were pretreated with (+)McN5652 (1 mg/kg, i.v.) or methylphenidate (1 mg/kg, i.v.) to specifically block SERT or DAT, respectively. After co-registration with magnetic resonance images of the same baboon, a region of interest analysis was performed using predefined templates to calculate specific uptake in the midbrain area and the striatum, with the cerebellum as the background region [(MB-CB)/CB, (STR-CB)/CB]. Additionally, two PET scans of the same baboons were performed after i.v. injections of 74-111 MBq (2-3 mCi) of [11C](+)McN5652 to identify the SERT sites. In [99mTc]TRODAT-1/SPET scans, the SERT sites in the MB region were clearly visualized. Semiquantitative analysis revealed a specific uptake in MB ([MB-CB]/CB) of 0.30+/-0.02, which was decreased to 0. 040+/-0.005 after pretreatment with nonradioactive (+)McN5652, a selective SERT ligand. Pretreatment with methylphenidate reduced the specific binding of [99mTc]TRODAT-1 to DAT sites [(STR-CB)/CB] from 2.45+/-0.13 to 0.32+/-0.04 without any effect on its binding to SERT sites [(MB-CB)/CB], which was confirmed by the co-registration of the [11C](+)McN5652/PET scans. This preliminary study suggests that specific binding of [99mTc]TRODAT-1 to SERT sites can be detected by in vivo SPET imaging despite the low target to background ratio. These findings provide impetus for further development of similar compounds with improved binding affinity and selectivity to SERT sites.

Anxiety sensitivity and self-reported reasons for drug use

Two studies examined the relationships between anxiety sensitivity (AS), drug use, and reasons for drug use. In Study 1, 229 university students (57% F) completed the Anxiety Sensitivity Index (ASI) and a drug use survey, assessing use of a variety of drugs within the last month, and coping reasons for drug use. Consistent with a modified tension-reduction hypothesis, ASI scores were positively correlated with the number of both anxiety- and depression-related reasons for drug use endorsed. In Study 2, 219 university students (74% F) completed the ASI and a drug use survey, assessing use of several drugs (e.g., alcohol, cigarettes, caffeine, and marijuana/hashish) within the last year, and primary reasons (coping, affiliative, or enhancement) for the use of each drug. Marijuana/hashish users reported lower ASI scores than non-users supporting a negative relation between AS and the use of cannabis. ASI scores were positively correlated with the use of alcohol primarily to cope, and negatively correlated with the use of alcohol primarily to affiliate, among both gender groups, and ASI scores were positively correlated with the use of nicotine primarily to cope among the females. Implications of these findings for understanding risk for abuse of stress-response-dampening drugs by high AS individuals are discussed.

Acute leukemia

The acute leukemias continue to present a formidable challenge for which there is not yet a reliably curative 'standard approach' for the majority of adults with this family of diseases. In order to make progress in terms of curing these devastating diseases, we must understand leukemia biology on the clinical, cellular and molecular levels, with exploitation of the leukemia-associated molecular targets in designing strategies aimed at eradicating the leukemic clone. In this review, we will discuss a few key mechanisms of leukemogenesis that represent convergent pathways of malignant transformation and, as such, present pivotal molecular targets for therapy. Specifically, we focus on normal and leukemic hematopoietic cell cycle regulation, issues surrounding DNA damage and repair, programmed cell death (apoptosis) and drug responsiveness, and multidrug resistance as a marker for stem cell involvement and as a novel target for intervention. When functioning normally, such mechanisms determine a cell's ability to respond to DNA damage, traverse the cell cycle and maintain genomic integrity. And in addition to the target cell itself, there are crucial extracellular determinants of hematopoietic cell proliferation and differentiation that modulate net signalling activity and gene expression, cell-cell contact and growth-modulating factors for instance. The molecular dissection of these intersecting pathways, from the extracellular milieu to the genes themselves, in both the normal and transformed states will elucidate the means by which cells escape treatment-induced death. Such understanding should, in turn, lead to the development of targeted therapeutic strategies that exploit differences between normal and malignant cells, overcome the mechanisms by which leukemic cells acquire drug resistance, and enhance the curability of these devastating diseases.

Carcinoma of the lung in HIV-positive patients: findings on chest radiographs and CT scans

OBJECTIVE

Several recent clinical studies have described an association between HIV seropositivity and lung cancer. The purpose of this study was to describe the spectrum of imaging findings in HIV-positive patients who had proved carcinoma of the lung. In particular, we attempted to define the role of CT in diagnosing HIV-associated lung cancer.

MATERIALS AND METHODS

The study population consisted of 23 HIV-positive patients from two institutions who had lung cancer diagnosed between 1989 and 1993. All patients had both chest radiographs and CT scans. The group included 19 men and four women with a mean age of 42 years. The diagnosis of lung cancer was confirmed by bronchoscopy in eight patients, by pleural fluid aspiration or pleural biopsy in seven, by percutaneous needle biopsy of a lung lesion in three, by biopsy of an extrathoracic site in four, and by thoracotomy in one. Two thoracic radiologists retrospectively evaluated the chest radiographs and CT scans to identify parenchymal masses, lymphadenopathy, pleural disease, chest wall or mediastinal invasion, and metastatic lesions.

RESULTS

Fifteen (65%) of the 23 patients had a central or peripheral mass or nodule. Eight (35%) had extensive pleural disease, either as an isolated finding or in combination with other abnormalities. CT scans showed the malignant lesion underlying the extensive pleural disease in all but one case. All patients with extensive pleural disease had adenocarcinoma. No patient in the study was considered a candidate for resection on the basis of clinical and radiologic evaluation.

CONCLUSION

Lung cancer in HIV-positive patients manifested most often on chest radiographs as a central or peripheral mass or nodule. Extensive pleural disease in the absence of an apparent primary lesion was the second most common major manifestation. Lung cancer therefore merits serious consideration in the differential diagnosis of extensive pleural disease in HIV-positive patients. CT was most useful in evaluating malignant lesions associated with extensive pleural disease.

Bone densitometry observations of osteopetrosis in response to bone marrow transplantation

Spinal bone density was measured in eight patients with osteopetrosis to assess the natural history of the disease and to monitor the response to therapy. Quantitative computed tomographic scans of the lumbar vertebra were obtained in seven patients, and dual photon absorptiometric scans were obtained when the technique became available. Six children were afflicted with the infantile malignant recessive condition and two with the less severe dominant condition. In all cases, bone densitometry values ranged from four to five times higher than the mean for normal age and gender-matched controls. In four children with recessive osteopetrosis, quantitative computed tomographic and dual photon absorptiometric scans showed an excellent correlation (R = 0.93) between the methods. Quantitative computed tomographic values ranged from 597 to 730 mg/cm3 (mean = 655 mg/cm3) in children with osteopetrorickets and from 901 to 1000 mg/cm3 (mean = 980 mg/cm3) in the same children when the rickets was cured. In two children treated with bone marrow transplantation, bone densitometry values returned to normal within three years. Bone densitometry provides a safe and noninvasive method for observing the natural history and therapeutic response of the osteopetrotic syndromes.

Lung cancer in patients with immunodeficiency syndrome

We report adenocarcinoma of the lung in seven patients with human immunodeficiency virus (HIV) infection. We compared age, clinical findings and survival data with a sex-matched control group of HIV-negative patients with adenocarcinoma of the lung. Median age of HIV-infected patients with lung cancer was lower than in control patients with lung cancer. The HIV-infected patients had more systemic symptoms and abnormal physical findings than control subjects. Both groups had smoking histories. Laboratory data were similar but control subjects had lower blood oxygen tensions than did HIV patients; HIV patients had more abnormalities on chest roentgenograms and computed tomography scans than did control subjects. All HIV-infected patients were stage IV. Median survival was 4 weeks. For control patients, 50 percent had stage IV disease; median survival was 25.5 weeks. Thus, patients with HIV infection develop lung cancer at a younger age than sex-matched control subjects and undergo a more fulminant course with shortened survivals.

Occlusion of the melatonin-free interval blocks the short day gonadal response of the male Syrian hamster to programmed melatonin infusions of necessary duration and amplitude

Abstract Photoperiodic control of the neuroendocrine axis is mediated by changes in the duration of the nocturnal melatonin signal. This study tested the hypothesis that reading of the signal depends upon the presence of a period free of melatonin between successive signals. Adult male Syrian hamsters were pinealectomized and received chronic subcutaneous infusions of melatonin or saline for 6 weeks. Animals which received saline had large testes. Those which received a single daily infusion which lasted for 10 h (50 ng/h) followed by 14 h without infusion underwent gonadal atrophy. Other animals received a compound melatonin signal in which the melatonin-free interval was occluded by a continuous infusion (25 ng/h). Superimposed upon this was a 10 h phasic increase in infusion rate such that the maximum rate of infusion was equivalent to that observed in controls (25 ng/h increase, 50 ng/h peak rate), or the increase in rate over the baseline was the same as in controls (50 ng/h increase, 75 ng/h peak rate). In neither group did the animals undergo gonadal regression. Analysis of iodomelatonin binding sites by in vitro autoradiography failed to reveal any systematic difference between animals which did and did not respond to melatonin and so the absence of a response could not be attributed to loss of receptors. These data demonstrate that the photoperiodic system cannot identify the melatonin signal solely upon the features of nocturnal peak height or amplitude of the peak over baseline. They are consistent with the hypothesis that the melatonin-free interval plays a significant role in photoperiodic time measurement.

Magnetic resonance imaging of experimental demyelinating lesions

An animal model of central nervous system demyelination was created by injecting rat internal capsules with lysophosphatidylcholine (LPC). The resulting chemically induced demyelinating lesions were readily visible in T1-weighted spin-echo, T2 weighted spin-echo, and inversion-recovery magnetic resonance imaging (MRI) sequences. Changes in lesions were followed over 8 weeks and correlated with histopathology. Histologically, lesions were characterized initially by an acute, inflammatory phase with edema and blood-brain barrier breakdown, followed by macrophage-mediated removal of myelin debris and finally by remyelination after 3 to 4 weeks. MRI can differentiate lesion stages in the LPC model and may be useful in investigating mechanistic aspects of the demyelinating process. In addition the well-localized lesions may be amenable to study by techniques of volume-localized NMR spectroscopy.

Blood lead, calcium status, and behavior in preschool children

To determine if calcium status is associated with blood lead levels and behavior, 64 black urban children aged 18 to 47 months were studied. Twenty-seven controls (blood lead levels, less than 1.45 mumol/L) were compared with 37 cases (blood lead levels, greater than or equal to 1.45 mumol/L) with respect to four calcium measures (calcium intake, serum calcium level, 1,25-dihydroxyvitamin D level, and bone densitometric findings) and three behavioral scores. Levels of 25-hydroxyvitamin D provided a measure of vitamin D sufficiency. As expected, blood lead level was associated with pica scores. However, none of the calcium measures differed between cases and controls. Controlling for four confounders (season, pica score, maternal education, and sex), yielded no significant differences between the two groups in the mean values of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D level. There was no interaction between blood lead level and the four covariates. No relationship could be demonstrated between calcium status and the pica scores.