Instrumentation and methods for frequency-domain and multimodal near-infrared spectroscopy

In this thesis, instrumentation for a frequency-domain (FD) near-infrared spectroscopy (NIRS) device and for multimodal brain measurements was implemented. Different techniques were applied to human and newborn lamb brain studies. A method to detect light leakage in NIRS measurements was developed. The FD instrument, developed at the Helsinki University of Technology was extended, by implementing 16 pseudo-differential preamplifiers for the analog-to-digital converters with a low noise and excellent interchannel isolation. An instrumentation for a digital signal-processor based lock-in amplifier was also developed. Methods for increasing the number of wavelengths and source positions in the imaging instrument were studied. A second-generation source system with a fast fiber-optic switch and four high-power laser diodes with a low noise temperature-stabilizing electronics was implemented. The imaging device was placed into a cabinet to enable its portability. New detection and source fiber terminals were developed for multimodal brain studies. The different versions of the imaging instrument were applied to four human brain measurements. In a breath-holding and hyperventilation study, the effects of source-detector distance (SDD) and measurement wavelength on the contrast of NIRS responses and the frequency content of signals were studied. Hemodynamic changes in the human brain related to the changes in sleep stages were detected. The multimodal NIRS and electroencephalography measurement setup was implemented and used to study the effects of baseline blood flow changes on the visually evoked hemodynamic and neuronal responses. The feasibility of NIRS as a part of multimodal monitoring setup to detect cerebral hemodynamic changes induced by iloprost and nitric oxide in the preterm lamb brain was also demonstrated. The linearity of the FD measurement parameters as a function of SDD on the human forehead was studied. The regression of phase measurement was observed to be sensitive to light leakage from source to detectors, much more than the regression of modulation amplitude or average intensity measurement. Utilizing this observation, a method to detect light leakage based on the pathlength measurement was developed. The contrast and depth sensitivity of NIRS signals were shown to decrease in measurements where light leakage occurs

Deadlines and MOOCs : How Do Students Behave in MOOCs with and without Deadlines

Full research paper-Online education can be delivered in many ways. For example, some MOOCs let students to proceed with their own pace, while others rely on strict schedules. Although the variety of how MOOCs can be organized is generally well understood, less is known about how the different ways of organizing MOOCs affect retention. In this work, we compare self-paced and fixed-schedule MOOCs in terms of retention and work-load. Using data from over 8.000 students participating in two versions of a massive open online course in programming, we observe that drop-out rates at the beginning of the courses are greater than towards the end of the courses, with self-paced MOOC being more extreme in this respect. Mostly because of different starts, the fixed-schedule course has a better overall retention rate (45%) than its self-paced counterpart (13%). We hypothesize that students initial investment of time and effort contributes to their persistence in their course, meaning that they do not want to let their initial investment go to waste. At the same time, in both self-paced and fixed-schedule MOOCs, there are students who receive almost full points from one week but fail to continue to the next week. This suggests that the issue of dropouts in MOOCs may also be related to participants struggling to take up new tasks or schedule their work over a longer time period. Our results support scheduling student activities in open online courses and opens up new research directions in engaging students in self-paced courses.Peer reviewe

Predictive equations over-estimate the resting energy expenditure in amyotrophic lateral sclerosis patients who are dependent on invasive ventilation support

<p>Abstract</p> <p>Background</p> <p>Amyotrophic lateral sclerosis (ALS) is a form of degenerative motor neuron disease. At the end stage of the disease artificial feeding is often required. Nevertheless, very little is known about the energy demand of those ALS patients who are chronically dependent on tracheostomy intermittent positive pressure ventilation. The objective of our study was to clarify the resting energy expenditure (REE) in mechanically ventilated ALS patients.</p> <p>Methods</p> <p>We measured the REE of five ALS patients (four men, one female) twice during a 12 month-period using indirect calorimetry with two sampling flow settings (40 L/min and 80 L/min). The measured REEs (mREE) were compared with values calculated using five different predictive equations.</p> <p>Results</p> <p>The mean (± SD) of all mREEs was 1130 ± 170 kcal/d. The measurements with different flow settings and at different time instances provided similar results. The mean of mREEs was 33.6% lower, as compared to the mean calculated with five different predictive equations REE (p < 0.001). Each of the predictive equations over-estimated the REE.</p> <p>Conclusions</p> <p>The mREE values were significantly lower for every patient than all the predicted ones. Determination of daily nutrition with predictive equations may therefore lead in mis-estimation of energy requirements. Because ALS patients may live years with artificial ventilation their nutritional support should be based on individual measurements. However, further study is needed due to the small number of subjects.</p

Taylorism on steroids or enabling autonomy? A systematic review of algorithmic management

The use of algorithmic management systems is rapidly changing organizational models and practices, as millions of workers in multiple sectors worldwide are managed by computer software. Despite receiving increasing academic interest, little summarizing literature exist on the ways algorithmic systems are used in management. This article aims to fill this gap by systematically reviewing and qualitatively analyzing 172 articles on the topic. Our research contributes to the existent algorithmic management literature in three ways. First, we provide a descriptive overview of algorithmic management as a field of research. Second, we identify and synthesize the discussion on the key concepts of the topic, namely how algorithmic management: (1) simultaneously restrains and enables workers’ autonomy—yet income dependency and other factors force inflexible work practices; (2) creates a complex, digital version of Taylorism; and (3) creates new and changes existing organizational power structures. Third, as our main theoretical contribution, we create the framework of Algorithmic Management Grid that demonstrates the ways in which organizations use algorithmic systems in management. The Algorithmic Management Grid illustrates how, in both novel and traditional organizational models, algorithmic management may be used with emphasis either on controlling or enabling workers. Based on the reviewed literature, we claim that so far, companies have mostly utilized algorithmic systems in a controlling manner, neglecting the technology’s enabling potential in organizing.publishedVersionPeer reviewe

Burden of non-motor symptoms in unclear parkinsonism and tremor : A study with [I-123]FP-CIT SPECT

Background: Non-motor symptoms (NMSs) are clearly more prevalent in Parkinson's disease (PD) patients compared to healthy individuals. However, NMSs are also common in the elderly and other neurological conditions, and thus, it is not known whether NMSs could be used to differentiate PD from parkinsonism/tremor without dopamine deficiency. Methods: We prospectively evaluated NMSs immediately before brain dopamine transporter (DAT) [I-123]FP-CIT SPECT scanning in 193 patients with unclear parkinsonism/tremor. According to the clinical follow-up and imaging results, 84 patients had PD. NMSs and their correlations with striatal DAT binding were investigated in PD patients and in parkinsonism/tremor patients with normal dopamine function. Results: Total NMS burden, anxiety or depression did not differ between PD patients and patients with normal DAT binding. DAT-normal patients reported more perception-related (p = 0.045) and attention/memory-related NMSs than PD patients (p <0.001). Total NMS score did not correlate with striatal DAT binding in either group. Conclusions: In clinically uncertain cases, the total NMS burden cannot be used as a tool in distinguishing PD patients from patients with non-dopaminergic parkinsonism/tremor. Clinical screening of NMSs appears equally important in all patients with parkinsonism.Peer reviewe

Bupropion Causes Misdiagnosis in Brain Dopamine Transporter Imaging for Parkinsonism

Objective: The objective of this study was to report long-lasting effects of bupropion on brain dopamine transporter (DAT) in a patient with depression and parkinsonism. Methods: The patient was a 52-year old man who had been treated with 150 mg/d of bupropion for depression. The patient developed cognitive problems, bradykinesia, and reduced stride length for which he was scanned with [123I]FP-CIT single photon emission computed tomography after the recommended 1-week discontinuation of bupropion. Levodopa treatment trial was initiated without a response. Eleven months later, the patient was scanned for a second time after a 1-month stoppage of bupropion. Results: The first scan was abnormal with left putamen specific binding ratio of 1.99 (SDs from the reference value mean, −2.40), right putamen of 2.27 (SD, −1.84), left caudate of 2.33 (SD, −2.26), and right caudate of 2.29 (SD, −2.18). The second scan (after 1-month discontinuation) was normal, and specific binding ratios had increased from 5.2% to 31.7% in all striatal regions as compared with the first scan. Brain magnetic resonance imaging and [18F]fluorodeoxyglucose positron emission tomography imaging were normal, and there was no levodopa response or other features supporting neurodegenerative parkinsonism. Conclusions: Bupropion has previously generally been discontinued 1 week prior DAT imaging, which meets the recommended, albeit arbitrary, time interval of 5 plasma clearance half-lives before the scan. One-week discontinuation of bupropion before DAT imaging may be insufficiently short. Our case shows that longer medication washout and rescan may be needed when there is contradiction between the imaging result and clinical outcome in patients with medications affecting DAT binding</p

The feasibility of [F-18]EF5-PET/CT to image hypoxia in ovarian tumors: a clinical study

Rationale Evaluation of the feasibility of [F-18]EF5-PET/CT scan in identifying hypoxic lesions in ovarian tumors in prospective clinical setting. Methods Fifteen patients with a suspected malignant ovarian tumor were scanned with [F-18]EF5 and [F-18]FDG-PET/CT preoperatively. The distribution of [F-18]EF5-uptake, total intraabdominal metabolic tumor volume (TMTV), and hypoxic subvolume (HSV) were assessed. Results [F-18]EF5-PET/CT suggested hypoxia in 47% (7/15) patients. The median HSV was 87 cm(3)(31% of TMTV). The [F-18]EF5-uptake was detected in primary tumors and in four patients also in intra-abdominal metastases. The [F-18]EF5-uptake in cancer tissue was low compared to physiological excretory pathways, complicating the interpretation of PET/CT images. Conclusions [F-18]EF5-PET/CT is not feasible in ovarian cancer imaging in clinical setting due to physiological intra-abdominal [F-18]EF5-accumulation. However, it may be useful when used complementarily to FDG-PET/CT.</div

Spontaneous Hemodynamic Oscillations during Human Sleep and Sleep Stage Transitions Characterized with Near-Infrared Spectroscopy

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Progressive dopaminergic defect in a patient with primary progressive multiple sclerosis

Dopamine has a modulatory role in a number of autoimmune diseases, but there are no published cases of longitudinal dopaminergic imaging in multiple sclerosis (MS). Here we report a patient with primary progressive multiple sclerosis (PPMS) who was scanned twice with brain dopamine transporter single photon emission computed tomography (SPECT) with an interval of four years. The results showed a loss of tracer binding that corresponded to a 4–7 fold steeper decline than in normal ageing. The finding points to a relevant role of nigrostriatal dopaminergic degeneration in the pathological process of PPMS.</p

Individual parkinsonian motor signs and striatal dopamine transporter deficiency: a study with [I-123]FP-CIT SPECT

IntroductionTotal parkinsonian motor symptom severity correlates with presynaptic striatal dopamine function in patients with Parkinson's disease. There is a lack of studies that have investigated the associations between parkinsonian motor signs and striatal dopaminergic deficiency in patients with parkinsonism of an unknown origin. Identification of specific motor signs associated with the highest likelihood of striatal dopamine deficiency could aid the differential diagnostics of parkinsonian and tremor syndromes.MethodsIn this cross-sectional clinical and imaging study, detailed motor examinations were performed for 221 patients with parkinsonism or tremor of an unknown origin immediately before dopamine transporter (DAT) [I-123]FP-CIT SPECT imaging. Region-of-interest and voxel-based methods were used to investigate striatal DAT deficiency in relation to individual motor signs.ResultsUpper extremity rigidity and facial expression were the only motor signs that differentiated patients with normal and abnormal striatal DAT function. The presence of any upper extremity rigidity showed the highest likelihood of DAT deficiency (OR 4.79, 95% CI 1.56-14.75, P=0.006) followed by reduced facial expression (OR 2.14, 95% CI 1.14-4.00, P=0.018). In patients with DAT deficits, reduced facial expression was associated with DAT deficiency specifically in the caudate nucleus, and increased upper extremity rigidity was associated with DAT loss in the dorsal putamen (FWE-corrected PPeer reviewe