Background/Objective: A dynamic contrast-enhanced T1 technique has been applied for calculating cerebral blood flow (CBF) with MRI. Previous studies have shown that the CBF calculated from T1 techniques was lower than the expected CBF. One cause could be the change in MRI signal intensity due to blood flowing into the measurement slice. The aims of this paper were: 1. To quantify the effects of inflow on perfusion measurements using a phantom.2. To apply a simple inflow correction to perfusion measurements taken from 11 healthy subjects.Patients and Methods: A flow phantom was designed to produce different velocities covering the velocity range of small vessels and big arteries. The inflow effects were measured in the phantom. After the contrast administration for healthy subjects, CBF was calculated based on T1 technique.Results: The inflow correction factor for the common carotid artery velocity and capillary level was calculated by the phantom as 1.23 and 1, respectively. The average value of CBF on the middle cerebral artery (MCA) grey matter territory of 11 healthy volunteers without any correction was 43.0 mL/100 g/min.Conclusion: For measuring the absolute CBF, the inflow correction factor for the arterial input function and tissue should be known. After applying the inflow correction factors, the absolute CBF may be calculated as 52.9 mL/100 g/min. This value is in good agreement with those in the PET literature.

This paper examines the work of Immanuel Kant in the light of a new theory on the nature of truth, knowledge and falsehood (the Inversion Theory of Truth). Kant’s idea that knowledge could be absolutely certain, and that its truth must correspond with reality, is discredited by a dissection of the Correspondence Theory of Truth. This examination of the nature of truth, as well as knowledge and falsehood, is conducted with reference to Sir Karl Popper’s writings on regulative ideas, the criterion of demarcation and the principle of falsifiability. It is argued that if truth is to be regarded as certain, it should be used to describe objects and events in the objective (noumenal) state, and that subjective knowledge must contain (and is improved by) falsehood. Perceptions and knowledge are obtained by the biological and evolutionary process of Active Subjectivism. Ideas we have knowledge of can be metaphysical or scientific, according to Popper’s Criterion of Demarcation. Kant’s “Copernican revolution” claim that our intellect imposes absolutely true laws on nature could not allow for the possibility that ideas might be constructed from fallible perceptions, and hence that all knowledge is uncertain. Instead, he developed a Critique of Practical Reason in which religion, though not provable through logical reasoning, could be proved by our innate moral sense, giving us a Categorical Imperative that could lead to perverse results. By rejecting the absolute certainty of a priori knowledge, and admitting a degree of essential falsehood, we arrive at a more reasonable grounding for moral behavior.

ObjectiveSuitable magnetic resonance imaging (MRI) techniques from conventionalto new devices can help physicians in diagnosis and follow up of MultipleSclerosis (MS) patients. The aim of present research was to compareeffectiveness of Fluid Attenuation Inversion Recovery (FLAIR) sequence ofconventional MRI and Diffuse Weighted Imaging (DWI) sequence as a newtechnique in detection of brain MS plaques.Materials& MethodsIn this analytic cross sectional study, sample size was assessed as 40 people todetect any significant difference between two sequences with a level of 0.05.DWI and FLAIR sequences of without contrast brain MRI of consecutive MSpatients referred to MRI center of Shahid Sadoughi Hospital, Yazd, Iran fromJanuary to May 2012, were evaluated.ResultsThirty-two females and 8 males with mean age of 35.20±9.80 yr (range=11-66 yr) were evaluated and finally 340 plaques including 127 (37.2%) inT2WI, 127 (37.2%) in FLAIR, 63 (18.5%) in DWI and 24 (7.1%) in T1WI weredetected. FLAIR sequence was more efficient than DWI in detection of brainMS plaques, oval, round, amorphous plaque shapes, frontal and occipital lobes, periventricular, intracapsular, corpus callosum, centrum semiovale, subcortical, basal ganglia plaques and diameter of detected MS plaques in DWI sequencewas smaller than in FLAIR.ConclusionOld lesion can be detected by conventional MRI and new techniques might bemore useful in early inflammatory phase of MS and assessment of experimentaltreatments.

Background: Precise detection and classification of intracortical (IC) lesions in multiple sclerosis (MS) patients are very important for understanding their role in disease progression and determining their effects on the clinical presentations of the disease. Objectives: This study aimed to evaluate the efficacy of phase-sensitive inversion recovery (PSIR) in delineation of cortical lesions in MS patients. Patients and Methods: This cross-sectional, single-center study was performed among 38 patients with the mean age of 31 years, who were recruited from December 2018 to August 2020. All MS patients underwent magnetic resonance imaging (MRI), using a 1. 5-Tesla scanner. Two expert neuroradiologists interpreted the fluid-attenuated inversion recovery (FLAIR), T2-weighted turbo spin echo (T2W-TSE), and PSIR images. The lesions were classified as purely IC, mixed gray/white matter (WM) [leukocortical (LC)], and juxtacortical (JC). The number of lesions in each region was compared between the FLAIR, T2W-TSE, and PSIR sequences. Results: The number of cortical lesions (IC and LC) was significantly higher in PSIR compared to T2W-TSE and Fluid attenuated inversion recovery (FLAIR) (P < 0. 001), while the number of JC lesions was lower; in other words, the mean number of plaques was higher in T2W-TSE and FLAIR as compared to PSIR. Conclusion: The PSIR sequence significantly improved the delineation of cortical lesions and could be useful in monitoring cortical injuries and disease progression in MS patients.

Background: It is needed to minimize the effect of flow direction on the desired area, such as arterial input function (AIF) in magnetic resonance imaging (MRI). Objective: The current study aimed to investigate the effect of flow direction on different velocities (0–, 80. 39 cm/s) for the strength of the signal intensity (SI) at the linear phase-encoding (LPE) and the center out phase-encoding (COPE) schemes and to recommend the best flow direction in a selected slice and scheme for absolute perfusion measurement by inversion recovery T1-weighted turbo fast low-angle shot (TurboFLASH) MR images. Material and Methods: In this experimental study, the flow rates were measured using a flow phantom, and the signal intensity (SI) was measured at the two opposite flow directions in the Z-axis perpendicular to the coronal image at a concentration of 0. 8 mmol/L of gadolinium-diethylenetriaminepantaacetic acid (Gd-DTPA) by using the LPE and COPE schemes. Results: The increase in velocity along with the growth in SI and inflow affected the use of LPE and COPE acquisitions in both directions. The velocity of the arterial input function is needed to calculate the inflow correction factor by using two schemes in two opposite flow directions to investigate perfusion. Conclusion: The COPE scheme was better than the LPE scheme in measuring perfusion since the velocity and direction of blood flow affect SI less.

Background: There is no gold standard diagnostic test for endolymphatic hydrops (EH). Three-dimensional fl, uid-attenuated inversion recovery (3D-FLAIR) imaging has been reported to depict EH with administration of gadolinium-based contrast media (GBCM). However, the optimal scan interval and angulation remain unknown in 3D-FLAIR labyrinthine imaging following double-dose injections of a gadolinium-based contrast agent in patients with vertigo and sensorineural hearing loss. Objectives: This study aimed to determine the optimal parameters of 3D-FLAIR labyrinthine imaging, including the optimal scan angulation and scan interval, for patients with sensorineural hearing loss and vertigo. Patients and Methods: In this cross-sectional clinical study, following the double-dose administration of a gadolinium contrast agent, 3D-FLAIR labyrinthine images were acquired from 22 patients with unilateral vertigo and sensorineural hearing loss at different intervals after injection. The corresponding contrast-to-noise ratios (CNRs) and signal-intensity ratios (SIRs) of these images, acquired at diff, erent intervals, were measured. Moreover, separate visualization of endolymphatic and perilymphatic spaces was scored, and angulation of the anterior skull base scan was investigated in the sagittal position. Results: The 3D-FLAIR images showed the strongest image contrast in the cochlea with a double-dose gadolinium-based contrast injection at six hours post-injection. Signifi, cantly higher SIR and CNR values were reported at six hours post-injection in both unaff, ected and aff, ected ears compared to other intervals (4 h vs. 6 h in the aff, ected side, SIR: 1. 65 ,0. 24 vs. 2. 09 ,0. 47, CNR: 13. 88 ,5. 54 vs. 19. 17 ,6. 81,in the unaff, ected side, SIR: 1. 58 ,0. 27 vs. 1. 82 ,0. 34, CNR: 12. 20 ,3. 88 vs. 15. 42 ,4. 58, P < 0. 001 for all,6 h vs. 8 h in the aff, ected side: SIR: 2. 09 ,0. 47 vs. 1. 72 ,0. 43, CNR: 19. 17 ,6. 81 vs. 12. 22 ,4. 96,in the unaff, ected side, SIR: 1. 82 ,0. 34 vs. 1. 57 ,0. 30, CNR: 15. 42 ,4. 58 vs. 10. 61 ,3. 87, P < 0. 001 for all). Visualization of the endo-and perilymphatic spaces for both the cochlea and vestibule was signifi, cantly better at six hours post-injection compared to four hours post-injection in both aff, ected sides (P < 0. 05 for both). The optimal angulation ranged from 6. 20°,to 13. 6°,(P < 0. 001). Conclusion: By using an optimal scan interval, together with an optimal scan angulation, 3D-FLAIR imaging can reliably visualize the endolymphatic space and sensitively indicate cochlear blood-labyrinth barrier disruptions without requiring extra image reconstruction.

Background: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system that causes demyelination or loss of myelin in the white and gray matter of the brain and spinal cord. Objectives: In the current study, the phase sensitive inversion recovery (PSIR) sequence was compared with the other sequences (T2-weighted (T2W), short tau inversion recovery (STIR)) to represent the number and conspicuity of the lesions. Patients and Methods: In this study, 35 MS patients were referred to the imaging center for MRI of the cervical spine. In the sagittal view, T2 weighted turbo spin echo (T2TSE), STIR, and PSIR and in the axial view, T2 TSE, and PSIR sequences were compared. The sequences were compared regarding the number of lesions and conspicuity. P value < 0. 05 was considered statistically significant. Results: In sagittal view MRIs, mean plaque number in T2TSE, STIR and PSIR were 1. 7  1. 1, 3. 5  1. 4, and 3. 4  1. 4, respectively (P < 0. 001; PSIR and STIR were greater than T2TSE but their difference was not statistically significant). Regarding comparison of imaging conspicuity, most of the plaques in PSIR showed good resolution (75%). In fact, the highest conspicuity of plaques was detected in PSIR (P < 0. 001). In axial view MRIs, comparing mean plaque count and conspicuity of lesions, PSIR showed better results than T2TSE (P < 0. 001). Conclusion: PSIR sequence showed high sensitivity and precision in the detection of plaques in the cervical spine. PSIR sequence is efficient as a complementary sequence in evaluating the cervical lesions of MS patients. It could increase the diagnostic accuracy in these patients.

Background: Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are used as blood pool contrast agent for magnetic resonance angiography and perfusion imaging. Our aim in this study was to investigate the effect of the two coating types of iron oxide nanoparticles on the relationship between nanoparticles concentration and signal intensity (SI) in T1-weighted MR images.Methods: Different concentrations of the polyethylene glycol (PEG), and carboxydextran-coated iron oxide nanoparticles were imaged using inversion recovery Turbo-FLASH (Turbo fast low-angle shot) pulse sequence with inversion times (TIs) of 300-900 ms (interval of 100 ms). The maximum non-linear and linear relationship between the corrected SI (after non-uniformity correction) and the concentration of the two coated nanoparticles were calculated in T1-weighted images.Results: The maximum non-linear relationship between the corrected SI and the concentration of the PEG, and carboxydextran-coated nanoparticles were obtained at concentrations of 400 and 200mmol Fe/L at a TI of 900 ms, respectively. In addition, the maximum linear relationship between the corrected SI and the concentration of the PEG, and carboxydextran-coated nanoparticles (R2=0.99) appeared at 228.184 and 205.654 mmolFe/L with a TI of 300 ms, respectively.Conclusion: The maximum non-linear corrected SI of the carboxydextran-coated nanoparticles was slightly higher than that of the PEG-coated nanoparticles at similar TIs. However, the PEG-coated nanoparticles were better than the carboxydextran-coated nanoparticles as a T1 contrast agent for perfusion measurements.