Δεδομένης και της χρήσης της τεχνικής SPECT, ο σκοπός της παρούσας διπλωματικής εργασίας είναι η διερεύνηση του κατά πόσο μπορούν, συνδυαστικά, οι 5 αυτές τεχνικές να δείξουν μία πιο σαφή εικόνα στη διαφορική διάγνωση όγκων του ΚΝΣ. Συνδυάζοντας τα δεδομένα που θα ληφθούν από τις μετρήσεις θα δημιουργηθεί μια μικρή βάση δεδομένων η οποία ως απώτερο στόχο θα έχει τη διεύρυνσή της στο μέλλον και συνεπώς την εξαγωγή ασφαλέστερων συμπερασμάτων. / Combination and evaluation of advanced MR techniques (MRS, DWI, DTI, PWI) and Scintigraphy in the differential diagnosis of Central Nervous System tumors.

Dynamic contrast enhanced (DCE) cardiac magnetic resonance imaging (MRI) is well-established as a non-invasive method for qualitatively detecting obstructive coronary artery disease (CAD) which can impair myocardial blood flow and may result in myocardial infarction. Mathematical modelling of cardiac DCE-MRI data can provide quantitative assessment of myocardial blood flow. Quantitative assessment of myocardial blood flow may have merit in further stratification of patients with obstructive CAD and to improve the diagnosis and prognostication of the disease in the clinical setting. This thesis investigates the development of a quantitative analysis protocol for cardiac DCE-MRI data. In the first study presented in this thesis, Fermi and distributed parameter (DP) modelling are compared in single bolus versus dual bolus analysis. For model-based myocardial blood flow quantification, the convolution of a model with the arterial input function (i.e. contrast agent concentration-time curve extracted from the left ventricular cavity) is fitted to the tissue contrast agent concentration-time curve. In contrast to dual bolus DCE-MRI protocols, single bolus protocols reduce patient discomfort and acquisition protocol duration/complexity but, are prone to arterial input function saturation caused in the left ventricular cavity by the high concentration of contrast agent during bolus passage. Saturation effects can degrade the accuracy of quantification using Fermi modelling. The analysis presented in this study showed that DP modelling is less dependent on arterial input function saturation than Fermi modelling in eight healthy volunteers. In a pilot cohort of five patients, DP modelling detected for the first time reduced myocardial blood flow in all stenotic vessels versus standard clinical assessments. In the second study, it was investigated whether first-pass DP modelling can give accurate myocardial blood flow, against ideal values generated by numerical simulations. Unlike Fermi modelling which is convolved with only the first-pass range of the arterial input function, DP modelling is convolved with the entire contrast agent concentration-time course. In noisy and/or dual bolus data, it can be particularly challenging to identify the end point of the first-pass in the arterial input function. This study demonstrated that contrary to Fermi modelling, myocardial blood flow analysis using DP modelling does not depend on the number of time points used for fitting. Furthermore, this data suggests that DP modelling can reduce the quantitative variability caused by subjectivity in selection of the first-pass range in cardiac MR data. This in turn may help to facilitate the development of more automated software algorithms for myocardial blood flow quantification. In the third study, Fermi and DP modelling were compared against invasive clinical assessments and visual MR estimates, to assess their diagnostic ability in detecting obstructive CAD. A single bolus DCE-MRI protocol was implemented in twentyfour patients. In per vessel analysis, DP modelling reached superior sensitivity and negative predictive value in detecting obstructive CAD compared to Fermi modelling and visual estimates. In per patient analysis, DP modelling reached the highest sensitivity and negative predictive value in detecting obstructive CAD. These studies show that DP modelling analysis of cardiac single bolus DCE-MRI data can provide important functional information and can establish haemodynamic biomarkers to non-invasively improve the diagnosis and prognostication of obstructive CAD.

With conventional oil reserves in decline, energy companies are increasingly turning to enhanced oil recovery (EOR) processes to extend the productive life of oilfield wells. Laboratory-scale core floods, in which one fluid displaces another from the pore space of a rock core, are widely used in petroleum research for oilfield evaluation and screening EOR processes. Achieving both macro- and pore-scale understandings of such fluid displacement processes is central to being able to optimise EOR strategies. Many of the mechanisms at play, however, are still poorly understood. In this thesis nuclear magnetic resonance (NMR) has been used for quantitatively, non-invasively and dynamically studying laboratory core floods at reservoir-representative conditions. Spatially-resolved relaxation time measurements (L-T1-T2) have been applied to studying a special core analysis laboratory (SCAL) protocol, used for simulating reservoir oil saturations following initial oil migration (primary drainage) and characterising core samples (capillary pressure curves). Axial heterogeneities in pore filling processes were revealed. It was demonstrated that upon approaching irreducible water saturation, brine saturation was reduced to a continuous water-wetting film throughout the pore space; further hydrocarbon injection resulted in pore pressure rise and wetting film thinning. L-T1-T2 techniques were also applied to a xanthan gum polymer-EOR flood in a sandstone core, providing a continuous measurement of core saturation and pore filling behaviours. A total recovery of 56.1% of the original oil in place (OOIP) was achieved, of which 4.9% was from xanthan. It was demonstrated that deposition of xanthan debris in small pores resulted in small-pore blocking, diverting brine to larger pores, enabling greater oil displacement therein. L-T1-T2, spectral and pulsed field gradient (PFG) approaches were applied to a hydrolysed polyacrylamide (HPAM)-EOR flood in a sandstone core. A total recovery of 62.4% of OOIP was achieved, of which 4.3% was from HPAM. Continued brine injection following conventional recovery (waterflooding) and EOR procedures demonstrated most moveable fluid saturation pertained to brine, with a small fraction to hydrocarbon. Increases in residual oil ganglia size was demonstrated following HPAM-EOR, suggesting HPAM encourages ganglia coalescence, supporting the "oil thread/column stabilisation" mechanism proposed in the literature. NMR relaxometry techniques used for assessing surface interaction strengths (T1/T¬2) were benchmarked against an industry-standard SCAL wettability measurement (Amott-Harvey) on a water-wet sandstone at magnetic field strengths comparable to reservoir well-logging tools (WLTs). At 2 MHz, T1/T2 was demonstrated to be weakly sensitive to the core wettability, although yielded wettability information at premature stages of the Amott-Harvey cycle. This suggests the potential for NMR to deliver faster wettability measurements, in SCAL applications or downhole WLT in situ reservoir characterisation.

abstract: With a growing number of adults with autism spectrum disorder (ASD), more and more research has been conducted on majority male cohorts with ASD from young, adolescence, and some older age. Currently, males make up the majority of individuals diagnosed with ASD, however, recent research states that the gender gap is closing due to more advanced screening and a better understanding of how females with ASD present their symptoms. Little research has been published on the neurocognitive differences that exist between older adults with ASD compared to neurotypical (NT) counterparts, and nothing has specifically addressed older women with ASD. This study utilized neuroimaging and neuropsychological tests to examine differences between diagnosis and sex of four distinct groups: older men with ASD, older women with ASD, older NT men, and older NT women. In each group, hippocampal size (via FreeSurfer) was analyzed for differences as well as correlations with neuropsychological tests. Participants (ASD Female, n = 12; NT Female, n = 14; ASD Male, n = 30; NT Male = 22), were similar according to age, IQ, and education. The results of the study indicated that the ASD Group as a whole performed worse on executive functioning tasks (Wisconsin Card Sorting Test, Trails Making Test) and memory-related tasks (Rey Auditory Verbal Learning Test, Weschler Memory Scale: Visual Reproduction) compared to the NT Group. Interactions of sex by diagnosis approached significance only within the WCST non-perseverative errors, with the women with ASD performing worse than NT women, but no group differences between men. Effect sizes between the female groups (ASD female vs. NT female) showed more than double that of the male groups (ASD male vs. NT male) for all WCST and AVLT measures. Participants with ASD had significantly smaller right hippocampal volumes than NT participants. In addition, all older women showed larger hippocampal volumes when corrected for total intracranial volume (TIV) compared to all older men. Overall, NT Females had significant correlations across all neuropsychological tests and their hippocampal volumes whereas no other group had significant correlations. These results suggest a tighter coupling between hippocampal size and cognition in NT Females than NT Males and both sexes with ASD. This study promotes further understanding of the neuropsychological differences between older men and women, both with and without ASD. Further research is needed on a larger sample of older women with and without ASD. / Dissertation/Thesis / Masters Thesis Speech and Hearing Science 2019

The body motion of patients, during magnetic resonance (MR) imaging causes significant artifacts in the reconstructed image. Artifacts are manifested as a motion induced blur and ghost repetitions of the moving structures. which obscure vital anatomical and pathological detail. The techniques that have been proposed for suppressing motion artifacts fall into two major categories. Real-time techniques attempt to prevent the motion from corrupting the data by restricting the data acquisition times or motion of the patients, whereas the post-processing techniques use the information embedded in the corrupted data to restore the image. Most methods currently in widespread use belong to the real-time techniques, however with the advent of fast computing platforms and sophisticated signal processing algorithms, the emergence of post-processing techniques is clearly evident. The post-processing techniques usually demand an appropriate model of the motion. The restoration of the image requires that the motion parameters be determined in order to invert the data degradation process. Methods for the correction of translational motion have been studied extensively in the past. The subject of this thesis encompasses the rotational motion model and the effect of rotational motion on the collected MR data in the spatial frequency space (k-space), which is in general, more complicated than the translational model. Rotational motion artifacts are notably prevalent in MR images of head, brain and limbs. Post-processing techniques for the correction of rotational motion artifacts often involve interpolation and re-gridding of the acquired data in the k-space. These methods create significant data overlap and void regions. Therefore, in the past, proposed corrective techniques have been limited to suppression of artifacts caused by small angle rotations. This thesis presents a method of managing overlap regions, using weighted averaging of redundant data, in order to correct for large angle rotations. An iterative estimation technique for filling the data void regions has also been developed by the use of iterated application of projection operators onto constraint sets. These constraint sets are derived from the k-space data generated by the MR imager, and available a priori knowledge. It is shown that the iterative algorithm diverges at times from the required image, due to inconsistency among the constraint sets. It is also shown that this can be overcome by using soft. constraint sets and fuzzy projections. One of the constraints applied in the iterative algorithm is the finite support of the imaged object, marked by the outer boundary of the region of interest (ROI). However, object boundary extraction directly from the motion affected MR image can be difficult, specially if the motion function of the object is unknown. This thesis presents a new ROI extraction scheme based on entropy minimization in the image background. The object rotation function is usually unknown or unable to be measured with sufficient accuracy. The motion estimation algorithm proposed in this thesis is based on maximizing the similarity among the k-space data subjected to angular overlap. This method is different to the typically applied parameter estimation technique based on minimization of pixel energy outside the ROI, and has higher efficiency and ability to estimate rotational motion parameters in the midst of concurrent translational motion. The algorithms for ROI extraction, rotation estimation and data correction have been tested with both phantom images and spin echo MR images producing encouraging results.

Biological tissues are generally conductive and knowing the current distribution in these tissues is of great importance in many biomedical applications. Radio frequency current density imaging (RF-CDI) is a technology that measures current density distributions at the Larmor frequency utilizing magnetic resonance imaging (MRI). RF-CDI computes the applied current density, J, from the non-invasively measured magnetic field, H, produced by J. The previously implemented RF-CDI techniques could only image a single slice at a time. The previous method for RF current density reconstruction only computed one component of J. Moreover, this reconstruction required an assumption about H, which may be easily violated. These technical constraints have limited the potential biomedical applications of RF-CDI. In this thesis, we address the limitations of RF-CDI mentioned above. First, we implement a multi-slice RF-CDI sequence with a clinical MRI system and characterize its sensitivity to MRI random noise. Second, we present a novel method to fully reconstruct all three components of J without relying on any assumption of H. The central idea of our approach is to rotate the sample by 180 degrees in the horizontal plane to collect adequate MR data from two opposite sample orientations to compute one component of J. Furthermore, this approach can be extended to reconstruct the other two components of J by adding one additional sample orientation in the horizontal plane. This method has been verified by simulations and electrolytic phantom experiments. We have therefore demonstrated for the first time the feasibility of imaging the magnitude and phase of all components of the RF current density vector. The work presented in this thesis is expected to significantly enhance RF-CDI to image biological subjects. The current density vector J or any component of J can be measured over multiple slices without the compromise of motions of organs and tissues caused by gravitational force, thanks to the method of horizontal rotations. In addition, the reconstruction of the complex conductivity of biological tissues becomes possible due to the current advance in RF-CDI presented here.

Biological tissues are generally conductive and knowing the current distribution in these tissues is of great importance in many biomedical applications. Radio frequency current density imaging (RF-CDI) is a technology that measures current density distributions at the Larmor frequency utilizing magnetic resonance imaging (MRI). RF-CDI computes the applied current density, J, from the non-invasively measured magnetic field, H, produced by J. The previously implemented RF-CDI techniques could only image a single slice at a time. The previous method for RF current density reconstruction only computed one component of J. Moreover, this reconstruction required an assumption about H, which may be easily violated. These technical constraints have limited the potential biomedical applications of RF-CDI. In this thesis, we address the limitations of RF-CDI mentioned above. First, we implement a multi-slice RF-CDI sequence with a clinical MRI system and characterize its sensitivity to MRI random noise. Second, we present a novel method to fully reconstruct all three components of J without relying on any assumption of H. The central idea of our approach is to rotate the sample by 180 degrees in the horizontal plane to collect adequate MR data from two opposite sample orientations to compute one component of J. Furthermore, this approach can be extended to reconstruct the other two components of J by adding one additional sample orientation in the horizontal plane. This method has been verified by simulations and electrolytic phantom experiments. We have therefore demonstrated for the first time the feasibility of imaging the magnitude and phase of all components of the RF current density vector. The work presented in this thesis is expected to significantly enhance RF-CDI to image biological subjects. The current density vector J or any component of J can be measured over multiple slices without the compromise of motions of organs and tissues caused by gravitational force, thanks to the method of horizontal rotations. In addition, the reconstruction of the complex conductivity of biological tissues becomes possible due to the current advance in RF-CDI presented here.

Η γνωστική έκπτωση εμφανίζεται στο 40-70% των ασθενών με ΠΣ, επηρεάζει σημαντικά την ποιότητα ζωής τους και έχει συσχετισθεί τόσο με τη σωματική αναπηρία, όσο και με διάφορες απεικονιστικές παραμέτρους, όπως ο συνολικός όγκος βλαβών και δείκτες ατροφίας του εγκεφάλου. Μέθοδοι: Στην παρούσα μελέτη συμμετείχαν 80 ασθενείς με ΠΣ (50 με υποτροπιάζουσα-RRMS, 30 με δευτεροπαθώς προϊούσα-SPMS). Κατεγράφησαν δημογραφικά δεδομένα και η κλίμακα αναπηρίας EDSS. Παράλληλα, έγινε νευροψυχολογική εκτίμηση με το υπολογιστικό πρόγραμμα CNS-VS καθώς και με τη δοκιμασία οπτικονοητικής ιχνηλάτησης (TMT A και Β) και λεκτικής ροής. Μελετήθηκε η επίδραση στην καθημερινή λειτουργικότητα των ασθενών (κλίμακα IADL, ικανότητα για εργασία) και υπολογίσθηκε ο συνολικός όγκος βλαβών, η ατροφία μεσολοβίου, ατροφία θαλάμων και η διάταση της 3ης κοιλίας. Χρησιμοποιήθηκε επίσης ομάδα 31 υγιών μαρτύρων για τις νευροψυχολογικές δοκιμασίες και ξεχωριστή ομάδα 51 υγιών μαρτύρων για τα απεικονιστικά δεδομένα. Αποτελέσματα: Παρατηρήθηκε έκπτωση των γνωστικών λειτουργιών στο 38% των ασθενών με RRMS και στο 80% των ασθενών με SPMS. Οι ασθενείς μας, εμφάνισαν συχνότερα χαμηλές επιδόσεις στο χρόνο αντίδρασης (83,33% SPMS/ 58% RRMS), στη δοκιμασία TMT Β (76,67% SPMS/ 34% RRMS), στην ψυχοκινητική ταχύτητα (66,67% SPMS/ 20% RRMS), στη δοκιμασία TMT Α (63,33% SPMS/ 34% RRMS), στη δοκιμασία φωνολογικής λεκτικής ροής (50% SPMS/ 30% RRMS) και στη μνήμη (40% SPMS/ 16% RRMS). Στους ασθενείς με RRMS, η γνωστική έκπτωση εμφάνισε ασθενή συσχέτιση τόσο με τη σωματική αναπηρία, όσο και με τη διάρκεια της νόσου και το συνολικό όγκο βλαβών (p<.05). Αντίθετα, ισχυρή συσχέτιση παρατηρήθηκε μεταξύ της γνωστικής έκπτωσης και των δεικτών ατροφίας του εγκεφάλου (p<.001) Παράλληλα, η κλίμακα IADL εμφάνισε ισχυρή συσχέτιση με τη μνήμη, την ψυχοκινητική ταχύτητα, την ταχύτητα επεξεργασίας και με όλους τους δείκτες ατροφίας (p<.001). Στους ασθενείς με SPMS ανευρέθη ασθενή συσχέτιση μεταξύ γνωστικής έκπτωσης και πάχους 3ης κοιλίας (p<.05). Στο σύνολο των ασθενών με ΠΣ, συνυπολογίζοντας ως συμμεταβλητές την ηλικία, το φύλο, τα έτη εκπαίδευσης και τη διάρκεια της νόσου, η χαμηλή ψυχοκινητική ταχύτητα και οι χαμηλές επιδόσεις στη δοκιμασία TMT B αποτελούν τους πλέον ευαίσθητους δείκτες πρόβλεψης αυξημένης σωματικής αναπηρίας (p=.004 για ψυχοκινητική ταχύτητα και p=.007 για TMTB) και έκπτωσης καθημερινής λειτουργικότητας (p=.001 για ψυχοκινητική ταχύτητα), ενώ η έκπτωση της σύνθετης μνήμης (p=.002) και η χαμηλή επίδοση στη δοκιμασία TMT Β (p=.004) αποτελούν τους πλέον ευαίσθητους προγνωστικούς δείκτες της ανικανότητας των ασθενών για εργασία. Στο σύνολο των ασθενών με ΠΣ, η ατροφία των θαλάμων αποτελεί τον καλύτερο προγνωστικό δείκτη χαμηλής επίδοσης στη δοκιμασία TMT Β (p=.000) και έκπτωσης της σύνθετης μνήμης (p=.000), ενώ η ατροφία τοu μεσολοβίου αποτελεί τον πλέον ευαίσθητο δείκτη πρόβλεψης μειωμένης ψυχοκινητικής ταχύτητας (p=.000). Συμπεράσματα: Παρόλο που η έκπτωση των γνωστικών λειτουργιών είναι παρούσα από τα αρχικά στάδια της νόσου, είναι συχνότερη, πλέον έκδηλη και βαρύτερη στη χρόνια προιούσα ΠΣ. Δεν ανευρέθη διαφορετικό πρότυπο έκπτωσης γνωστικών λειτουργιών μεταξύ ασθενών με RRMS και ασθενών με SPMS. Το σφαιρικό αυτό πρότυπο, χαρακτηρίζεται από έκπτωση στην ταχύτητα επεξεργασίας πληροφοριών, ακολουθούμενο από ελλειμματικές εκτελεστικές λειτουργίες και έκπτωση της σύνθετης μνήμης. Η έκπτωση των καθημερινών δραστηριοτήτων είναι πολύ βαρύτερη στην SPMS, σε σύγκριση με την RRMS . Η επιφάνεια του μεσολοβίου και των θαλάμων αναδείχθηκαν οι πλέον ευαίσθητοι δείκτες στο διαχωρισμό των ασθενών με RRMS από SPMS. Παρατηρούμε δηλαδή, ότι παρόλο που η ατροφία είναι παρούσα από τα αρχικά στάδια της νόσου, με την πάροδο των ετών αυξάνεται σημαντικά. Η ψυχοκινητική ταχύτητα, η μνήμη και η δοκιμασία ΤΜΤ Β έχουν τη μεγαλύτερη προβλεπτική ικανότητα για την εξέλιξη της νόσου, τόσο σε επίπεδο σωματικής αναπηρίας, όσο και καθημερινής λειτουργικότητας. Οι δείκτες ατροφίας παρουσίασαν την ισχυρότερη συσχέτιση με τη γνωστική έκπτωση και την έκπτωση στην καθημερινή λειτουργικότητα. Από τους δείκτες αυτούς, η ατροφία των θαλάμων και του μεσολοβίου φαίνεται να έχουν την ικανότητα να προβλέψουν τη γνωστική έκπτωση στο σύνολο των ασθενών με ΠΣ. / Cognitive decline is present in 40%-70% of patients with MS and affects their quality of life. It has been significantly correlated with physical disability as well as with total lesion load and atrophy measures on MRI. Methods: In the present study, we evaluated 80 patients with MS (50 with RRMS, 30 with SPMS). We studied their demographic characteristics and assessed them clinically with EDSS. All patients underwent thorough Neuropsychological assessment with a computerized cognitive screening battery (CNS-VS) as well as with Trail Making Test A and B and verbal fluency task. We evaluated their everyday activities with the Instrumental Activities of Daily Living Scale, and we calculated the total lesion volume, thalamic atrophy, corpus callosum atrophy and 3rd ventricle width as apeared on the MRI. In addition, 31 healthy individuals underwent the same Neuropsychological assessment and 51 healthy individuals had brain MRI scans for comparison with our patients. Results: We found 38% of our RRMS patients and 80% of our SPMS patients to have cognitive deficits. More frequently affected measures were reaction time (83,33% SPMS/ 58% RRMS), TMT B(76,67% SPMS/ 34% RRMS), psychomotor speed (66,67% SPMS/ 20% RRMS), TMT A (63,33% SPMS/ 34% RRMS), phonological verbal fluency task (50% SPMS/ 30% RRMS) and memory (40% SPMS/ 16% RRMS). In our RRMS patients, cognitive impairment had a weak correlation with physical disability and total MR lesion load (p<.05) and a strong correlation with all atrophy measures (p<.001). Moreover, IADL were highly correlated with psychomotor speed, processing speed, memory and all MR atrophy measures (p<.001). On the other hand, our SPMS cognitively impaired patients had only a weak correlation with 3rd ventricle width (p<.05). When taking our MS patients as a single group and using as covariates age, sex, years of education and disease duration, we found that low psychomotor speed (p=.004) and poor performance on TMT B (p=.007) were the most sensitive predictors of increased physical disability, whereas psychomotor speed predicted impaired every day activities (p=.001). Employment status was predicted by impaired composite memory (p=.002) and poor performance on TMT B (p=.004). Thalamic atrophy was the most sensitive indicator for poor performance on TMT B (p=.000) and impaired memory (p=.000), while corpus callosum atrophy was the best indicator for slow psychomotor speed (p=.000). Conclusions: Although cognitive impairment is present from the early stages of MS, it is much commoner, more pronounced and severe at the progressive stage of MS. In the present study, we were not able to find a different pattern of cognitive decline between RRMS and SPMS patients. We observed a global pattern, consisting of impairment in information processing speed, followed by executive dysfunction and memory deficits. As disease progresses, everyday activities are affected more severely. Comparison of RRMS and SPMS patients revealed statistical significant difference in the surface of corpus callosum and thalami, indicating that although atrophy is present form the early stages of the disease, it is more prominent in the progressive stage. Psychomotor speed, composite memory and TMT B are the best predictors of EDSS and every day activities impairment (IADL). All of our MR atrophy measures had a strong correlation with cognitive decline and impaired every day activities. It seems that thalamic atrophy and corpus callosum atrophy are the best predictors of cognitive decline in our MS patients.

Research in lab-on-a-chip (LOC) technology involving microfluidics is a growing field aiming at the development of miniaturized biomedical systems with rich functionality. In order to design effective LOC microfluidic systems, the flow fields and the fluids inside LOC devices need to be carefully characterized. High-resolution magnetic resonance imaging (MRI) offers a powerful non-intrusive technology for this application. In this thesis, the design and implementation of a prototype for a desktop high-resolution MRI instrument, consisting of a magnet, gradient coils, gradient amplifiers, and radio frequency (RF) electronics, is presented. To reduce the size and cost of this MRI instrument, a permanent magnetic configuration with a magnetic flux density of 0.6 T is designed with off-the-shelf NdFeB permanent magnets. The coils of the triaxial gradient module are developed using a novel lithography technique. This gradient module is capable of generating gradient fields as high as 2.83 T/m with custom made current amplifiers. The radio frequency (RF) probe is integrated with the gradient module and is connected to the RF electronics which are made using off-the-shelf components. Pulse sequences and signal processing for acquiring static images and velocity profiles are described. The performance of this instrument in terms of static and dynamic image resolution are presented. As a preliminary test, the velocity profile of water flowing inside a small tube was measured with a nominal resolution of 40 μm. The instrument is designed for a static resolution of better than 30 μm and a velocity resolution better than 50 μm/s. Improvements to the current instrument in addition to theoretical limitations are also detailed.

High signal-to-noise ratio (SNR) is typically required for higher resolution and faster speed in magnetic resonance imaging (MRI). Planar microcoils as receiver probes in MRI systems offer the potential to be configured into array elements for fast imaging as well as to enable the imaging of extremely small objects. Microcoils, however, are thermal noise dominant and suffer limited SNR. Cryo-cooling for the microcoils can reduce the thermal noise, however conventional cryostats are not optimum for the microcoils because they typically use a thick vacuum gap to keep samples to be imaged to near room temperature during cryo-cooling. This vacuum gap is typically larger than the most sensitive region of the microcoils that defines the imaging depth, which is approximately the same as the diameters of the microcoils. Here microfluidic technology is utilized to locally cryo-cool the microcoils and minimize the thermal isolation gap so that the imaging surface is within the imaging depth of the microcoils. The first system consists of a planar microcoil with microfluidically cryo-cooling channels, a thin N2 gap and an imaging. The microcoil was locally cryo-cooled while maintaining the sample above 8°C. MR images using a 4.7 Tesla MRI system shows an average SNR enhancement of 1.47 fold. Second, the system has been further developed into a cryo-cooled microcoil system with inductive coupling to cryo-cool both the microcoil and the on-chip microfabricated resonating capacitor to further improve the Q improvement. Here inductive coupling was used to eliminate the physical connection between the microcoil and the tuning network so that a single cryocooling microfluidic channel could enclose both the microcoil and the capacitor with minimum loss in cooling capacity. Q improvement was 2.6 fold compared to a conventional microcoil with high-Q varactors and transmission line connection. Microfluidically tunable capacitors with the 653% tunability and Q of 1.3 fold higher compared to a conventional varactor have been developed and demonstrated as matching/tuning networks as a proof of concept. These developed microfluidically cryo-cooling system and tunable capacitors for improving SNR will potentially allow MR microcoils to have high-resolution images over small samples.