Drop In Signal Intensity Research Articles

Biomarkers of systemic treatment response: MR images of intratumoral fat deposition in colorectal liver metastases (CRLM) after chemotherapy.

Colorectal cancer cells containing mobile lipids are said to be an early indicator of chemotherapy effects. The objective of the study was to examine the frequency and clinical relevance of intratumoral fat deposition in colorectal liver metastases (CRLM) post-chemotherapy using dual-echo chemical shift gradient-echo magnetic resonance imaging (MRI). A retrospective analysis of 98 patients with CRLM diagnosed between 2017 and 2022 (69M, mean age 62.87 ± 10.73years old) who had an MRI after chemotherapy was performed. On dual-echo chemical shift gradient-echo MRI, intratumoral fat deposition of CRLM was evaluated. A signal intensity drop of ≥ 12% in opposed-phase images vs. in-phase images indicated intratumoral fat. After chemotherapy, the presence of fat deposition was correlated with patients' overall survival. Before and after chemotherapy, 0 (0%) and 29 (29.59%) patients exhibited intratumoral fat. The number of CRLM ranged from 1 to 25 with a median of 3 and a mean size of 32.58 ± 22.95mm. The groups had statistically different survival times. Overall survival was shorter for patients with intratumoral fat deposition in CRLM (32months (24-60, 95% CI)) than for patients without fat deposition in CRLM (48months (36-NA, 95% CI)). In our group, nearly 30% of CRLM patients exhibited intratumoral fat after chemotherapy. Patients with intratumoral fat deposition in CRLM have a shorter overall survival time. The presence of fat in CRLM correlates with a poor long-term prognosis.

Machine Learning-Based Magnetic Resonance Radiomics Analysis for Predicting Low- and High-Grade Clear Cell Renal Cell Carcinoma.

To explore whether high- and low-grade clear cell renal cell carcinomas (ccRCC) can be distinguished using radiomics features extracted from magnetic resonance imaging. In this retrospective study, 154 patients with pathologically proven clear ccRCC underwent contrast-enhanced 3 T magnetic resonance imaging and were assigned to the development (n = 122) and test (n = 32) cohorts in a temporal-split setup. A total of 834 radiomics features were extracted from whole-tumor volumes using 3 sequences: T2-weighted imaging (T2WI), diffusion-weighted imaging, and contrast-enhanced T1-weighted imaging. A random forest regressor was used to extract important radiomics features that were subsequently used for model development using the random forest algorithm. Tumor size, apparent diffusion coefficient value, and percentage of tumor-to-renal parenchymal signal intensity drop in the tumors were recorded by 2 radiologists for quantitative analysis. The area under the receiver operating characteristic curve (AUC) was generated to predict ccRCC grade. In the development cohort, the T2WI-based radiomics model demonstrated the highest performance (AUC, 0.82). The T2WI-based radiomics and radiologic feature hybrid model showed AUCs of 0.79 and 0.83, respectively. In the test cohort, the T2WI-based radiomics model achieved an AUC of 0.82. The range of AUCs of the hybrid model of T2WI-based radiomics and radiologic features was 0.73 to 0.80. Magnetic resonance imaging-based classifier models using radiomics features and machine learning showed satisfactory diagnostic performance in distinguishing between high- and low-grade ccRCC, thereby serving as a helpful noninvasive tool for predicting ccRCC grade.

FAT-RICH VS FAT-POOR RENAL AML ON MULTIPARAMETRIC MRI.

Background: The study aims to show the MRI imaging features of Fat-rich and Fat-poor AML using MULTIPARAMETRIC renal MRI protocol. Fat-poor angiomyolipomas (AMLs) are challenging to differentiate from other renal lesions on USG and CT and often necessitate biopsy or surgery for differentiation. The Methods: study group consisted of 9 patients with histologically proven AMLs who underwent MULTIPARAMETRIC renal MRI (T2WI, Chemical Shift imaging, DWI,) before the histopathology. The lesions were reviewed independently by a radiologist and a resident. On T2-weighted images, among Fat rich AML (n=2 i.e. 66%) showed heter Results: ogeneous hyperintense signal and (n=1 i.e. 33%) showed homogenous hyperintense signal as compared to renal cortex. Among Fat Poor AML (n=4 i.e. 66%) showed homogenous hypointense signal and (n=2 i.e. 33%) showed heterogeneous hypointense signal as compared to renal cortex. On Chemical Shift Imaging, among Fat rich AML, mean Signal Intensity drop (%) on out of phase imaging for Fat rich AML in our study was 27.07%±1.65%. Also Fat rich AML (n=3 i.e. 100%) showed Indian Ink Artifact within the mass or at its interface with the kidney. Among Fat Poor AML, mean Signal Intensity drop (%) on out of phase imaging for Fat poor AML in our study was 0.6%±6.7% (p value <0.001). On Diffusion Weighted Imaging, apparent diffusion coefcient (ADC) maps show low ADC values regardless of the types of AML, because fat signal intensity is suppressed. among Fat rich AML mean ADC values of lesion in our study was 0.86±0.09, Among Fat Poor AML, mean ADC values of lesion in our study was 0.96±0.01. Conclusion: Our study enables us to conrm consistent associations of MR imaging features with specic subtypes of AML. In our study, T2 signal intensity, T2 signal intensity ratio, signal drop on out of phase imaging, showed promising results differentiating between fat rich and fat poor AML

LBSAT65 Search For A Duplicitous Pheochromocytoma

Abstract Introduction Pheochromocytomas are discovered during work up of adrenal incidentalomas and can be biochemically and clinically silent. We present a case of a patient who presented with typical "adrenergic spells" suggestive of pheochromocytoma but negative biochemical testing and non-confirmatory imaging findings. Case Report 39-year-old male presented with 4 weeks history of episodes of throbbing headaches, palpitations, sweating. He was found to be hypertensive, blood pressure of 220/110 mm Hg. Losartan was initiated, but symptoms persisted. Work-up for endocrine causes of hypertension revealed normal plasma renin activity 1.123 ng/ml/hr (0.167 to 5.380) and undetectable aldosterone level <1 ng/dl (0. 0-3. 0), mildly elevated random plasma normetanephrine 270 pg/ml (0-210), normal plasma metanephrines 49 pg/ml (0-88). Low-dose dexamethasone suppression test showed unsuppressed morning cortisol of 2.1ug/dl, undetectable ACTH <5 pg/ml, dexamethasone level 486 ng/dl. 24 urinary cortisol and 2 midnight salivary cortisol samples failed to confirm the diagnosis. 24-hr urine studies showed mildly elevated 24-hr normetanephrine 735 ug/24 hr (156-729), normal 24-hr metanephrines 197 ug/L (58-276), normal 24 hr epinephrine and dopamine levels. Repeat testing revealed normal plasma metanephrines levels and mildly elevated plasma normetanephrine levels 287 pg/ml (less than twice above the upper limit of normal). Dopamine and Chromogranin A levels were undetectable. Abdominal CT showed 2 cm round soft tissue density 42HU in right adrenal gland. Left adrenal gland contained 3 nodules measuring 11, 15 and 16 mm–all with density <10HU. MRI findings for the 2.2 cm right adrenal nodule was without significant drop in signal intensity on the in and out of phase sequences appearing moderately T2 hyperintense and T1 hypointense. Differential included atypical/fat poor adenoma, pheochromocytoma, or metastasis. On GA 68 Dotatate PET-CT this 2.2cm adrenal nodule had minimal to low radiotracer uptake. Since a pheochromocytoma could not be ruled out, patient was started on alpha blockade. Preoperative genetic testing was negative for common mutations associated with pheochromocytoma/paraganglioma syndromes. Patient underwent laparoscopic right adrenalectomy. Histopathology report confirmed 2.8 cm pheochromocytoma with a low PASS (2/20) and low GAPP score. Conclusion and Discussion Patients with borderline nor metanephrine elevations represent a diagnostic and therapeutic dilemma. The patient presented with adrenergic paroxysms strongly suggestive of underlying pheochromocytoma. Labs and imaging were not typical for pheochromocytoma and were indeterminate. Given strong clinical suspicion for a pheochromocytoma, we decided to proceed with adrenalectomy after pre-treatment with alpha blockers. Final histopathologic report confirmed the diagnosis of pheochromocytoma. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.

Quantifying Gadolinium-Based, Theranostic Nanoparticle Uptake in MR Images of Pancreatic Cancer

<h3>Purpose/Objective(s)</h3> Nanomedicines are proving to be a viable option in improving radiotherapeutic benefits by amplifying the effects of radiotherapy. A recently developed, gadolinium (Gd) based theranostic agent has shown promise in the treatment of previously difficult to treat tumors. Here we examine, for the first time, uptake of this agent in patients with pancreatic cancer undergoing MR-guided adaptive radiotherapy. <h3>Materials/Methods</h3> Data have been acquired from four patients with pancreatic cancer enrolled in a stereotactic MR-guided adaptive radiotherapy clinical trial utilizing Gd-based nanoparticles (Nano-SMART). This trial has nanoparticles intravenously infused prior to MR simulation scanning (3T and 0.35T) and again prior to the first fraction (of five daily fractions). Physician-drawn contours were delineated on an MRI-guided real-time on-table adaptive radiotherapy 0.35T planning bSSFP scan. T1 maps of the abdomen were produced on a 3T scanner (a fully-body MRI scanner, from a technology company) before and after nanoparticle administration, using a prototype Look-Locker T1 mapping sequence with 28-30 slices (3 mm thickness, 1 mm spacing) and 244 × 244 pixels (1.56 × 1.56mm). Pre- and post- nanoparticle T1 maps were registered to the 0.35T planning images. Nanoparticle concentrations within contour defined volumes were calculated from T1 maps using the measured change in T1 values and a previously determined relaxivity constant (8.9 mM⁻¹s⁻¹). Average concentrations were compared across patients and anatomical structures. The use of an MR-Linac for adaptive radiotherapy enabled examination of nanoparticle uptake over time. MRI scans (bSSFP) were captured at each fraction, processed for bias field correction and normalized to spinal canal volumes; a region previously determined to not have significant uptake. Adapted contours defined fraction-specific volumes which were examined for patterns in signal intensity (SI) over time. <h3>Results</h3> Average T1 values for all targeted volumes (CTV, GTV) dropped after nanoparticle infusion. The amount of uptake varied significantly amongst patients but similarly amongst structures, with a notable initial concentration in the liver and kidneys. Fraction-specific MR scans indicated an approximate 20% drop in SI after the first fraction, followed by a more gradual loss of SI, suggesting a persistence of tumor uptake after initial administration. <h3>Conclusion</h3> We have demonstrated the ability to quantify nanoparticle uptake in patients with pancreatic cancer. Results indicate significant uptake of this new radiosensitizer agent in the pancreatic lesions as well as in the liver and kidneys. Follow-up scans and control subjects will inform tumor response due to nanoparticle-enhanced adaptive radiotherapy.

The critical role of mobile phase pH in the performance of oligonucleotide ion-pair liquid chromatography-mass spectrometry methods.

The critical role of mobile phase pH in the performance of oligonucleotide ion-pair liquid chromatography-mass spectrometry methods.

Experimental investigation of flame fluctuation reduction in distributed combustion

Analysis of dynamic combustor stability is essential for the development of practical devices that employ distributed reaction zones. The fluctuation of reaction zone (RZ) was studied to compare normal air combustion and distributed combustion at an equivalence ratio of 0.9 in a swirl-stabilized burner using methane fuel. Distributed combustion was fostered by diluting the inlet air stream with carbon dioxide that resulted in a gradual drop in the adiabatic flame temperature (Tad). High-speed broadband chemiluminescence at 3 kHz was used to study the global combustion dynamics. Vortex shedding observed along the shear layers influenced the oscillation of flame base in normal air combustion. However, relatively stable bases were observed in distributed combustion. Fast Fourier Transformation performed on RZ base fluctuation data supported the observations from chemiluminescence signatures. Proper orthogonal decomposition (POD) analysis indicated various vortex-shedding patterns as the dominant structures in conventional swirl flames. The power spectral density (PSD) of POD modes showed the rotational effect of RZ and weak von Karman vortex shedding to influence fluctuation in distributed combustion. The self-sustained flame oscillations in normal swirl flames were investigated from the acoustic and heat release fluctuation signals. Both acoustic and heat release fluctuations gradually reduced when approaching the distributed combustion. The PSD of these signals demonstrated a common peak at ~ 174 Hz (in normal swirl flames) with possible thermo-acoustic coupling. This peak was consistent with the peaks obtained from the base fluctuation and POD spectra. The peak gradually diminished when approaching the state of distributed combustion. A similar observation of gradually decreasing acoustic and heat release fluctuation was made with a constant Tad. However, the drop in chemiluminescence signal intensity with CO2 dilution was relatively low in case of constant Tad compared to the variable Tad case. The local and global Rayleigh index obtained for the variable Tad cases at different dilution levels showed positive values at O2 = 21 and 20%, which signified self-sustained instability. However, the distributed combustion possessed a negative Rayleigh index indicating dampening of instability. These results support the gradual decline of thermo-acoustic instability when approaching the distributed combustion condition.

Di-carbonyl-o-semiquinonato rhodium complexes

Two novel dicarbonyl-semiquinonato rhodium complexes were synthesized and studied. Complexes are analogues of (CO)2Rh(3,6-DBSQ) (3,6-DBSQ-3,6-di-tert-butyl-o-benzosemiquinone) which thread-like crystals can bend reversibly under light or heat activation (G.A. Abakumov, V.I. Nevodchikov, Dokl. Acad. Nauk SSSR 1982, 266, 1407–1410). Complexes differ from (CO)2Rh(3,6-DBSQ) by substituents in 3,6-positions of quinonato ring (cyclohexyl (1) and isopropyl (2) instead of tert-butyl). Single crystal structural study indicates that both complexes are the derivatives of Rh(I) with o-semiquinonato anion-radical. Molecules form pairs due the short contacts in contrast to (CO)2Rh(3,6-DBSQ) and other similar compounds which form the endless alternated chains with direct Rh-Rh bond. At that, complex 1 molecules form isolated pairs, whereas molecules of 2 can be united in the chain. Both compounds 1 and 2 have the array of intensive bands in IR spectrum in the region 1350 cm−1 which is closer to bond stretch vibrations of C–O ordinary bond but not sesquilateral. EPR of solutions of complexes indicates presence of monomeric complex molecules where the single unpaired electron is localized in o-semiquinonato ligand. The drop of EPR signal intensity with cooling of solutions of 1 and 2 evidence that the association process takes place.

Comparison of in-phase and opposed-phase T1W gradient echo and T2W fast spin echo dixon chemical shift imaging for the assessment of non-neoplastic, benign neoplastic and malignant marrow lesions.

The objective of this study is to compare T1-weighted gradient echo (T1W GrE: control technique) chemical shift imaging (CSI) with T2-weighted fast spin echo (T2W FSE: experimental technique) CSI for differentiating non-neoplastic and neoplastic marrow lesions. Patients undergoing MRI for various marrow lesions were investigated with T1W GrE and T2W FSE Dixon CSI. Signal intensity (SI) change between in-phase (IP) and opposed-phase (OP) sequences was calculated, and SI drop > 20% considered to represent non-neoplastic lesions while SI drop < 20% considered to represent neoplastic lesions. Final diagnosis was based on imaging features (n = 42) or histology (n = 43) and classified as non-neoplastic, benign neoplastic, and malignant neoplastic. Inter-observer and inter-technique agreement between 2 readers was calculated. The study included 85 patients (44 males and 41 females; mean age 41.1years, range 2-83years). Final diagnosis included 19 (22.4%) non-neoplastic lesions, 27 (31.8%) benign neoplasms, and 39 (45.9%) malignant neoplasms. On T1W GrE CSI, 19-21 lesions were classed as non-neoplastic and 64-66 as neoplastic, while on T2W FSE Dixon CSI, 22-24 lesions were classed as non-neoplastic and 61-64 as neoplastic. Lesion classification matched between the 2 techniques in 91.8-96.5% of cases. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of T1W GrE CSI for differentiating non-neoplastic and neoplastic marrow lesions were 66.7-72.2%, 88.1-89.6%, 61.9-63.2%, 90.9-92.2%, and 84.7%, and of T2W FSE Dixon CSI were 72.2-77.8%, 85.1-86.6%, 58.3-59.1%, 92.1-93.4%, and 83.5%. T1W GrE CSI and T2W FSE Dixon CSI produce similar results in the assessment of non-neoplastic and neoplastic marrow lesions.

Focal nodular marrow hyperplasia: Imaging features of 53 cases.

To describe the characteristic imaging features of focal nodular marrow hyperplasia (FNMH). Retrospective review of all patients with a diagnosis of FNMH between January 2007 and September 2019. The study included 53 patients, 7 males and 46 females with a mean age of 58 years (range 12-95 years). All had MRI with conventional spin echo sequences showing a poorly defined round/oval lesion with mild T1W iso/hyperintensity compared to skeletal muscle, low T2W turbo spin echo (TSE) signal intensity (SI) compared to marrow fat and variable SI on STIR, but never associated with reactive marrow oedema. All 53 patients had follow-up MRI, with all lesions remaining stable or partially resolving. In-phase (IP) and out-of-phase (OP) chemical shift imaging (CSI) was obtained in 31 of these, with 28 (90.3%) showing >20% SI drop on the OP sequence, while 3 (9.7%) demonstrated <20% SI drop. CT was available in 26 cases, 17 (65.4%) showing mild medullary sclerosis. Single-photon emission computed tomography CT (SPECT-CT) was available in four cases and Flourodeoxyglucose positron emission tomography CT (FDG PET-CT) in 2, all showing increased uptake. Focal uptake was also seen in three of eight patients who had undergone whole body bone scintigraphy. Only one lesion was biopsied, confirming FNMH. The imaging appearances of FNMH have been described on various modalities, particularly MRI with emphasis on the role of IP and OP CSI typically demonstrating >20% SI reduction. FNMH should be recognised and treated as a 'do not touch' lesion which does not require biopsy or prolonged follow-up. We describe and clarify the imaging characteristics of FNMH on MRI, including CSI, CT and various nuclear medicine modalities. An imaging algorithm is suggested for allowing a non-invasive diagnosis.

Subsuns and rainbows during solar eclipses.

A photographic observation sequence was obtained of a subsun before, during, and after the total phase of the 2016 solar eclipse. The time-resolved images were obtained from a high-altitude jet aircraft. The image sequence was searched for the possible presence of a solar corona-generated subsun during totality. Although the subsun-creating conditions apparently persisted during totality, the drop in signal intensity compared to the local background prevented its detection. Separately, we document a visual observation from the 1977 total solar eclipse of a rainbow that faded, in the last a few seconds before totality, from being normally multicolored to monochromatic red from water drops then predominantly illuminated by light from the solar chromosphere. A similar transition in the final seconds before, and after, totality is expected to occur for parhelia. The posited short-living monochromatic red parhelion resulting from the momentary illumination of ice crystals by the solar chromosphere is still waiting to be observed.

Anomalous signal intensity increase on out-of-phase chemical shift imaging: a manifestation of marrow mineralisation?

In-phase (IP) and out-of-phase (OOP) chemical shift imaging (CSI) is an established technique for clarifying the nature of indeterminate bone marrow lesions, a signal intensity (SI) drop of > 20% at 1.5 tesla (T) or > 25% on 3T on the OOP sequence being consistent with a non-neoplastic process. Occasionally, SI increase is seen on OOP sequences. The aim of this study is to determine if this is related to marrow sclerosis or matrix mineralisation. In 184 cases, the SI change on OOP was calculated. For patients in whom the SI on OOP increased compared with the IP sequence, available CT studies and radiographs were reviewed to look for marrow sclerosis and/or matrix mineralisation. Forty out of 184 patients (34.25%) showed an anomalous increase in SI on the OOP sequence. CT studies were available in 27 cases (67.5%), of which medullary sclerosis was seen in 20 (74.1%) while matrix mineralisation was seen in a further 2 cases. Review of radiographs demonstrated matrix mineralisation in 6 cases, while punctate signal void consistent with chondral calcification was seen on MRI in 2 more cases. Based on either typical imaging features (n = 22) or histology (n = 18), 7 lesions (17.5%) were classed as non-neoplastic, 18 (45%) as benign neoplasms and 15 (37.5%) as malignant neoplasms. When assessing focal marrow lesions with CSI, anomalous SI increase may be seen on the OOP sequence in approximately one-third of cases. In over 75% of such cases, CT or radiographs demonstrate either diffuse marrow sclerosis or matrix mineralisation.

Abstract WP269: Automatic Segmentation of Cerebral Arteries in MRA TOF Using Deep Learning

Purpose: Time-of-Flight (TOF) MRA is commonly used for grading cerebrovascular diseases. Analysis of cerebral arteries in MRA TOF is a challenging and time consuming task that would benefit from automation. Established image processing methods for automatic segmentation of cerebral arteries suffer from common artefacts such as kissing vessels (when two nearby vessels touch) and signal intensity drop (especially in the presence of pathology). Artificial intelligence models are promising candidates for resolving such artefacts. Here, we propose and assess the performance of a deep learning model for automatic segmentation of cerebral arteries in MRA TOF which is robust to common MRI artefacts. Methods: A 3D convolutional neural network (CNN) is proposed for automatic segmentation of intracranial arteries in MRA TOF. The neural network is trained with a custom loss function and residual blocks to penalize the occurrence of common artefacts such as kissing vessels. The model is trained and tested on a dataset consisting of 82 subjects (50 healthy volunteers and 32 patients with intracranial stenosis) following a 3-fold cross-validation method, i.e. 3 models are trained where each model is blind to one-third of the data in the training process to avoid bias. Manual segmentation of the arteries done by an expert reader are used as ground-truth for training and testing the model. Results: The proposed deep learning model achieved excellent accuracy compared against the ground truth (Dice score 0.89). Our proposed deep learning model outperformed a state-of-the-art neural network for image segmentation (3DU-Net, Dice score 0.85) and resulted in considerably less occurences of artefacts such as kissing vessels (9% of cases had segmentation artefacts for our model vs 16% for 3D U-Net). The proposed deep learning model was fast, taking only 2 seconds to produce a 3D model of the arteries on a laptop with a dedicated GPU. Conclusion: The proposed deep learning model accurately segments intracranial arteries in MRA TOF and is robust to common artefacts of MR imaging thanks to implementation of a custom loss function. The model can potentially increase the accuracy and speed of grading cerebrovascular diseases.

Development and validation of a TTR-specific copy number screening tool, and application to potentially relevant patient cohorts

TTR amyloidosis (ATTR) is a fatal condition caused by extracellular deposits of misfolded transthyretin. Patients often present with cardiac disease, but manifestations may also involve other organs including the peripheral nervous system. ATTR is considered familial when heterozygous mutations in the TTR gene are present (ATTRmutant or ATTRm), or acquired when no TTR aberrations are detected (ATTRwildtype or ATTRwt). We hypothesized that TTR copy number variants (CNVs), which would escape the standard diagnostic approaches, contribute to ATTR-related phenotypes, and developed a multiplex ligation-dependent probe amplification-based (MLPA-based), TTR-specific copy number screening tool. High inter-sample and intra-sample homogeneity of MLPA signals and the expected drop in signal intensity for restriction digest-based positive controls validated this tool. Subsequent application to 13 patients diagnosed with ATTRwt, and to 93 patients presenting with late onset and presumably inherited polyneuropathy did not identify TTR CNVs. We discuss insufficient sensitivity of the assay as well as non-existence and non-pathogenicity of TTR CNVs as potentially underlying our negative finding, but suggest size and composition of our cohorts as more likely explanations. Our CNV-screening tool will be made available to initiatives interested in screening additional and potentially more appropriate patient samples.

In Vivo Tracking of Mesenchymal Stem Cell in Rat Genitalia with Erectile Dysfunction Labeled by Superparamagnetic Iron Oxide Using Magnetic Resonance Imaging and Its Therapeutic Effect

Background: Molecular imaging with nanoparticles makes non-invasive monitoring of target cells without sacrifice of subjects and repeated evaluation possible. Objectives: To evaluate the imaging feasibility of a rat animal model with erectile dysfunction (ED) by bilateral cavernosal nerve injury using human mesenchymal stem cells (MSCs) labeled with superparamagnetic iron oxide (SPIO) and simultaneously to evaluate the beneficial effect of MSCs on ED. Materials and Methods: Thirty-six rats were injected with MSCs labeled with SPIO particle into the corpus cavernosum after bilateral cavernosal nerve injury. In vivo MR imaging was serially performed up to 16 weeks using 1.5 T clinical scanner. After MR imaging, the penile specimens were evaluated for the expression of transforming growth factor-β1 (TGF-β1) by polymerase chain reaction. Results: MR imaging showed a drop in signal intensity at the injection site in the stem cell-injected group. The size of hypointensity was decreased in MSC-injected group in a time-dependent manner; whereas, signal void was not detected at the injection site in the control group. In addition, polymeric chain reaction (PCR) analyses of penile tissues from both groups revealed that the mRNA expression of TGF-β1 was significantly decreased in MSC-injected groups after 4 weeks of injection compared to the control group. Conclusion: MSCs’ beneficial effects on ED was monitored with MR imaging, which might be a valuable tool for tracking and therapeutic monitoring in the future clinical study of stem cell therapy in ED.

Influence of a degraded triple-junction solar cell on the CPV system performances

A concentrating photovoltaic (CPV) plant is a complex system that integrates different technologies as single or multi-junction photovoltaic cells and optical devices. The CPV system performance analysis should take into account the malfunctions that can occur during the working, especially when the system operates with high values of sunlight concentration. A critical analysis of the solar cells is necessary to define the CPV system potential. In this paper a specific configuration of a CPV system is considered, and the experimental analysis of a system with a degraded triple-junction InGaP/GaAs/Ge solar cell is investigated. In particular, the triple-junction solar cell is stressed in an accelerated aging process of about 500 operating hours with a concentration of 310 suns without using a cooling system. After this process, for another 100 working hours the system has been monitored in order to compare, corresponding to different light concentration factors, the solar cell electric characteristics, the energy production and the power conversion efficiency in the pristine and degraded states. The results show the effect of the overheating of the triple-junction solar cell caused by the excessive increase of the light intensity. Under the same irradiance of 930 W/m2 the short circuit current, open circuit voltage and fill factor values of the aged solar cell, compared to the pristine device, result to be strongly reduced, while the extracted value of the series resistance increases and the values of the shunt resistances decrease. The increased value of the diode ideality factor m after the thermal stress indicates a non-negligible contribution of non-radiative recombination within the solar cell. Similar findings are deduced comparing the electroluminescence spectra of the pristine and degraded solar cell. The thermal stress induces a marked drop of electroluminescence signal intensity in the whole investigated wavelength range. It should be note that high electroluminescence efficiency is a good indicator in solar cells for high power conversion efficiencies. In particular, the power conversion efficiency is reduced by 50% referring to a CPV system with a degraded cell, while the electric output power is decreased by 30%. Hence, it is clear that the triple-junction cell inefficiencies, principally caused by a strong thermal stress, lead to a drastic drop of the CPV system performances. Finally, an active cooling system is absolutely necessary when high values of light concentration are reached.

Imaging of Nonmalignant Adrenal Lesions in Children.

The adrenal glands in children can be affected by a variety of benign lesions. The diagnosis of adrenal lesions can be challenging, but assessment of morphologic changes in correlation with the clinical presentation can lead to an accurate diagnosis. These lesions can be classified by their cause: congenital (eg, discoid adrenal gland, horseshoe adrenal gland, and epithelial cysts), vascular and/or traumatic (eg, adrenal hemorrhage), infectious (eg, granulomatous diseases), enzyme deficiency disorders (eg, congenital adrenal hyperplasia [CAH] and Wolman disease), benign neoplasms (eg, pheochromocytomas, ganglioneuromas, adrenal adenomas, and myelolipomas), and adrenal mass mimics (eg, extralobar sequestration and extramedullary hematopoiesis). Multimodality cross-sectional imaging helps to define the origin, extent, and relationship of these lesions to adjacent structures, as well as to guide treatment management. The anatomic and functional imaging modalities used to evaluate pediatric adrenal lesions include ultrasonography, computed tomography (CT), magnetic resonance imaging, and iodine 123 metaiodobenzylguanidine scintigraphy. Identifying the imaging features of nonmalignant adrenal lesions is helpful to distinguish these lesions from malignant adrenal neoplasms. Identifying characteristic imaging findings (eg, enlarged adrenal glands, with cerebriform surface, and stippled echogenicity in CAH; a T2-hyperintense mass with avid contrast enhancement in pheochromocytoma; low CT attenuation [<10 HU] and signal intensity drop on opposed-phase chemical shift images in adenoma; and enhancing suprarenal mass supplied by a systemic feeding artery in extralobar sequestration) can aid in making the correct diagnosis. In addition, clinical features (eg, ambiguous genitalia in CAH and hypertension in pheochromocytoma) can also guide the radiologist toward the correct diagnosis. ©RSNA, 2017.

Chromatin decondensation is accompanied by a transient increase in transcriptional output.

The levels of chromatin condensation usually correlate inversely with the levels of transcription. The mechanistic links between chromatin condensation and RNA polymerase II activity remain to be elucidated. In the present work, we sought to experimentally determine whether manipulation of chromatin condensation levels can have a direct effect on transcriptional activity. We generated a U-2-OS cell line in which the nascent transcription of a reporter gene could be imaged alongside chromatin compaction levels in living cells. The transcripts were tagged at their 5' end with PP7 stem loops, which can be detected upon expression of a PP7 capsid protein fused to green fluorescent protein. Cycles of global chromatin hypercondensation and decondensation were performed by perfusing culture media of different osmolarities during imaging. We used the fluorescence recovery after photobleaching technique to analyse the transcriptional dynamics in both conditions. Surprisingly, we found that, despite a drop in signal intensity, nascent transcription appeared to continue at the same rate in hypercondensed chromatin. Furthermore, quantification of transcriptional profiles revealed that chromatin decondensation was accompanied by a brief and transient spike in transcriptional output. We propose a model whereby the initiation of transcription is not impaired in condensed chromatin, but inefficient elongation in these conditions leads to the accumulation of RNA polymerase II at the transcription site. Upon chromatin decondensation, release of the RNA polymerase II halt triggers a wave of transcription, which we detect as a transient spike in activity. The results presented here shed light on the activity of RNA polymerase II during chromatin condensation and decondensation. As such, they point to a new level of transcriptional regulation.

Optical coherence tomography of actinic keratoses and basal cell carcinomas - differentiation by quantification of signal intensity and layer thickness.

Previous studies have shown that actinic keratoses (AKs) and basal cell carcinomas (BCCs) can be diagnosed by optical coherence tomography (OCT) based on morphological characteristics. There is a lack of systematic studies that give standardized information on signal intensity and layer thickness of AKs and BCCs. The aim of this study was to find out if AKs and BCCs can be objectively diagnosed through standardized measurement of signal intensity and layer thickness and to use OCT as a non-invasive objective method for the diagnosis and evaluation of AKs and BCCs. Additionally, tumour and skin layer thickness were investigated in correlation with histology. In this experimental study, 301 lesions (188 BCCs and 113 AKs) of 125 patients were clinically as well as dermoscopically diagnosed and investigated with OCT before therapy. Normal perilesional skin served as control. It is possible to differentiate BCCs and AKs from normal skin in OCT due to the decrease of local signal intensity in affected skin layers in relation to adjacent healthy skin. In AKs, a strong thickness increase of the stratum corneum and epidermis compared to normal skin were observed. For the distinction between AKs and BCCs, a drop of signal intensity in the dermis of AKs towards BCCs and a thicker epidermis of AKs in contrast to BCCs were registered. All results are statistically highly significant (P<0.0001). Besides, a strong correlation of tumour and skin layer thickness of BCCs and AKs in OCT with histology was found. Through standardized measurement of signal intensity and layer thickness, BCCs and AKs can be objectively diagnosed and distinguished from each other with OCT. This will further improve the use of OCT as a non-invasive objective method for the diagnosis and treatment monitoring of these diseases.

Ferrohydrodynamic modeling of magnetic nanoparticle harmonic spectra for magnetic particle imaging.

Magnetic Particle Imaging (MPI) is an emerging imaging technique that uses magnetic nanoparticles as tracers. In order to analyze the quality of nanoparticles developed for MPI, a Magnetic Particle Spectrometer (MPS) is often employed. In this paper, we describe results for predictions of the nanoparticle harmonic spectra obtained in a MPS using three models: the first uses the Langevin function, which does not take into account finite magnetic relaxation; the second model uses the magnetization equation by Shliomis (Sh), which takes into account finite magnetic relaxation using a constant characteristic time scale; and the third model uses the magnetization equation derived by Martsenyuk, Raikher, and Shliomis (MRSh), which takes into account the effect of magnetic field magnitude on the magnetic relaxation time. We make comparisons between these models and with experiments in order to illustrate the effects of field-dependent relaxation in the MPS. The models results suggest that finite relaxation results in a significant drop in signal intensity (magnitude of individual harmonics) and in faster spectral decay. Interestingly, when field dependence of the magnetic relaxation time was taken into account, through the MRSh model, the simulations predict a significant improvement in the performance of the nanoparticles, as compared to the performance predicted by the Sh equation. The comparison between the predictions from models and experimental measurements showed excellent qualitative as well as quantitative agreement up to the 19th harmonic using the Sh and MRSh equations, highlighting the potential of ferrohydrodynamic modeling in MPI.