Infective endocarditis (IE) represents a significant concern among hospital-acquired infections, frequently caused by the Gram-positive bacterium Staphylococcus aureus. Nuclear imaging is emerging as a noninvasive and precise diagnostic tool. However, the gold standard radiotracer [18F]-FDG cannot distinguish between infection and inflammation, resulting in false positives. Based on the presence of collagen-binding proteins in the cell wall of S. aureus, we propose the radiolabeling of collagen for its evaluation in IE animal models by single-photon emission computed tomography (SPECT) imaging. We radiolabeled rat tail collagen I using DTPA chelator and [99mTc]NaTcO4. Selectivity was evaluated in vitro using 3 Gram-positive bacteria, 1 Gram-negative bacteria and 1 yeast. In vivo SPECT/computed tomography (CT) imaging was conducted on 8 SD rat models of IE and 8 sterile sham model as controls. Ex vivo biodistribution and autoradiography were performed following imaging. Diagnosis of IE was confirmed through microbiological studies and H&E histopathology. [99mTc]-DTPA-Collagen was synthesized successfully with a yield of 42.86 ± 6.35%, a purity of 95.84 ± 1.85% and a stability higher than 90% after 50 h postincubation. In vitro uptake demonstrated the selectivity for Gram-positive bacteria (63.85 ± 15.15%). Ex vivo analysis confirmed hepato-splenic excretion. In vivo SPECT/CT imaging revealed highly localized uptake within the aortic valve with a sensitivity of 62.5% and specificity of 87.5%. We successfully synthesized and characterized a new SPECT radiotracer based on [99mTc]Tc-radiolabeled collagen. In vitro studies demonstrated the selectivity of the radiotracer for Gram-positive bacteria. In vivo SPECT/CT-based assessment in an IE model confirmed the potential of this approach to detect active IE.

Purpose. The Gram-positive Staphylococcus aureus bacterium is one of the leading causes of infection in humans. The lack of specific noninvasive techniques for diagnosis of staphylococcal infection together with the severity of its associated complications support the need for new specific and selective diagnostic tools. This work presents the successful synthesis of an immunotracer that targets the α-toxin released by S. aureus. Methods. [89Zr]Zr-DFO-ToxAb was synthesized based on radiolabeling an anti-α-toxin antibody with zirconium-89. The physicochemical characterization of the immunotracer was performed by high-performance liquid chromatography (HPLC), radio-thin layer chromatography (radio-TLC), and electrophoretic analysis. Its diagnostic ability was evaluated in vivo by positron emission tomography/computed tomography (PET/CT) imaging in an animal model of local infection-inflammation (active S. aureus vs. heat-killed S. aureus) and infective osteoarthritis. Results. Chemical characterization of the tracer established the high radiochemical yield and purity of the tracer while maintaining antibody integrity. In vivo PET/CT image confirmed the ability of the tracer to detect active foci of S. aureus. Those results were supported by ex vivo biodistribution studies, autoradiography, and histology, which confirmed the ability of [89Zr]Zr-DFO-ToxAb to detect staphylococcal infectious foci, avoiding false-positives derived from inflammatory processes. Conclusions. We have developed an immuno-PET tracer capable of detecting S. aureus infections based on a radiolabeled antibody specific for the staphylococcal alpha toxins. The in vivo assessment of [89Zr]Zr-DFO-ToxAb confirmed its ability to selectively detect staphylococcal infectious foci, allowing us to discern between infectious and inflammatory processes.

Abstract Background and Aims Hyponatremia is the most common electrolyte disturbance in clinical care. Even mild presentations are associated with poor prognosis and increased mortality, in spite of which there is a trend to minimize the importance of small variations in natremia, that have historically been dismissed as not having negative consequences despite growing evidence against it. In this regard, it has not been studied to date whether an intermittent but recurrent hyponatremia is relevant. There are clinical scenarios where this condition could occur and be overlooked, such as cirrhosis or heart failure. Method Different rat models have been used to study the effects of different hypotonic situations on the electrolyte balance and central nervous system: intermittent recurrent hyponatremia (intraperitoneal (i.p.) daily dose of desmopressin acetate (ddAVP) and a water dose equivalent to 2.5% of the animal's body weight in hyposodic diet fed animals), acute on intermittent recurrent hyponatremia (i.p. water overload equivalent to 10% of the animal's body weight in animals subjected to intermittent recurrent hyponatremia) and acute hyponatremia (i.p. administration of a 10% of the animal's body weight water overload in chow fed animals). Apparent diffusion coefficient (ADC) obtained from diffusion weighted images (DWI) acquired through magnetic resonance (7T Bruker Biospec) was used to study content and distribution of brain water, and immunohistochemistry was used to examine glial fibrillary acidic-protein (GFAP), astrocyte marker, and myelin basic protein (MBP), oligodendrocyte and myelin marker. Results In the intermittent recurrent hyponatremia model, mild and transient hyponatremia was induced (baseline Nap 136.50±1.73mEq/L vs 4h post-medication 129.44±1.20mEq/L, p<0.001), which was recovered 24h after treatment (141.25±0.96mEq/L, NS compared to baseline). However, this situation was repeated over a 7 day period. This translated into a lower ADC value in the whole brain (WB) compared to chow fed animals (25.07±1.71 vs 26.71±2.40*10−3mm2/s, p = 0.05) after this 7 day period, suggesting an increase in total brain water in this situation. There was also an increase in GFAP expression in the gray matter (GM) compared to chow fed animals (33.22±5.25 vs 25.07±2.31au, p = 0.031), although no significant changes in MBP’s expression were seen. Acute on intermittent recurrent hyponatremia induced hypotonic hyponatremia (116.00±1.16mEq/L, p<0.001 compared to baseline). In this situation, a progressive decrease in ADC values in the WB was seen, and it was less pronounced compared to chow fed animals (slope -0.11±0.02 vs -0.26±0.006, p = 0.014). When GM and white matter (WM) were analysed separately, they both showed a progressive increase in ADC values, more evident in the WM (slope WM 0.19±0.04, p<0.05; slope GM 0.05±0.02, p = 0.002). The water overload increased GFAP and MBP’s expression in the WM (GFAP 23.17±6.37 vs 16.83±5.17au, p = 0.001; MBP 45.20±8.32 vs 28.76±7.03au, p<0.001), but no changes were seen in the GM, similarly to what had been observed in the acute hyponatremia model. Conclusion Intermittent recurrent hyponatremia is a novel animal model that suggests there can be significant water retention after only a few hours of hyponatremia a day, provided this situation is repeated over time. Such water retention translates into greater brain water accumulation and astroglial activation in the GM. These animals's response to an additional water overload does not show big variations compared to what is observed in acute hyponatremia. This study highlights the importance of slight fluctuations in natremia, which, if maintained over time, can translate underlying water retention with consequences at the central nervous system level.

Background and Purpose Reperfusion therapy is the standard of care for ischaemic stroke; however, there is a need to identify new therapeutic targets able to ameliorate cerebral damage. Neutrophil β 1 adrenoceptors (β1AR) have been linked to neutrophil migration during exacerbated inflammation. Given the central role of neutrophils in cerebral damage during stroke, we hypothesize that β1AR blockade will improve stroke outcomes. Experimental Approach Rats were subjected to middle cerebral artery occlusion–reperfusion to evaluate the effect on stroke of the selective β1AR blocker metoprolol (12.5 mg·kg −1 ) when injected i.v. 10 min before reperfusion. Key Results Magnetic resonance imaging and histopathology analysis showed that pre‐reperfusion i.v. metoprolol reduced infarct size. This effect was accompanied by reduced cytotoxic oedema at 24 h and vasogenic oedema at 7 days. Metoprolol‐treated rats showed reduced brain neutrophil infiltration and those which infiltrated displayed a high proportion of anti‐inflammatory phenotype (N2, YM1 + ). Additional inflammatory models demonstrated that metoprolol specifically blocked neutrophil migration via β1AR and excluded a significant effect on the glia compartment. Consistently, metoprolol did not protect the brain in neutrophil‐depleted rats upon stroke. In patients suffering an ischaemic stroke, β1AR blockade by metoprolol reduced circulating neutrophil–platelet co‐aggregates. Conclusions and Implications Our findings describe that β1AR blockade ameliorates cerebral damage by targeting neutrophils, identifying a novel therapeutic target to improve outcomes in patients with stroke. This therapeutic strategy is in the earliest stages of the translational pathway and should be further explored.

Stimuli-responsive nanomaterials are very attractive for biomedical applications. They can be activated through external stimuli or by the physico-chemical conditions present in cells or tissues. Here, we describe the preparation of hybrid iron oxide-manganese oxide core-satellite shell nanostructures that change their contrast mode in magnetic resonance imaging (MRI) from T2 to T1, after being internalized by cells. This occurs by the dissolution of the MnO2 of the shell, preserving intact the iron oxide at the core. First, we study the seeded-growth synthesis of iron oxide-manganese oxide nanoparticles studying the effect of varying the core size of the magnetic seeds and the concentration of the surfactant. This allows tuning the size and shape of the final hybrid nanostructure. Then, we show that the shell can be removed by a redox reaction with glutathione, which is naturally present inside the cells at much higher concentrations than outside the cells. Finally, the dissolution of the MnO2 shell and the change in the contrast mode is confirmed in cell cultures. After this process, the iron oxide nanoparticles at the core remain intact and are still active as heating mediators when an alternating magnetic field is applied.

Data generated in the SPM analysis described in the PlosOne paper "Effect of illumination level [18F]FDG-PET brain uptake in free moving mice"

In both clinical and preclinical scenarios, 2-deoxy-2[18F]fluoro-D-glucose ([18F]FDG) is the radiotracer most widely used to study brain glucose metabolism with positron emission tomography (PET). In clinical practice, there is a worldwide standardized protocol for preparing patients for [18F]FDG-PET studies, which specifies the room lighting. However, this standard is typically not observed in the preclinical field, although it is well known that animal handling affects the biodistribution of [18F]FDG. The present study aimed to evaluate the effect of ambient lighting on brain [18F]FDG uptake in mice. Two [18F]FDG-PET studies were performed on each animal, one in light and one in dark conditions. Thermal video recordings were acquired to analyse animal motor activity in both conditions. [18F]FDG-PET images were analysed with the Statistical Parametric Mapping method. The results showed that [18F]FDG uptake is higher in darkness than in light condition in mouse nucleus accumbens, hippocampus, midbrain, hindbrain, and cerebellum. The SPM analysis also showed an interaction between the illumination condition and the sex of the animal. Mouse activity was significantly different (p = 0.01) between light conditions (632 ± 215 s of movement) and dark conditions (989 ± 200 s), without significant effect of sex (p = 0.416). We concluded that room illumination conditions during [18F]FDG uptake in mice affected the brain [18F]FDG biodistribution. Therefore, we highlight the importance to control this factor to ensure more reliable and reproducible mouse brain [18F]FDG-PET results.

Gelatin-halloysite nanotubes (HNTs) nanocomposite scaffold capable of sustaining the SrR release were introduced for the first time by overcoming the limitations of SrR oral and systemic administration, and also enhancing the physicomechanical, osteogenic potential, and bone forming ability of gelatin-based scaffolds. The mean pore size, porosity, and water absorption, and mechanical properties of gelatin scaffolds increased by adding HNTs, especially after SrR incorporation. As revealed by X-ray diffraction analysis, the layer spaces in HNTs crystals remain unchanged after incorporation in gelatin. Moreover, SrR interacts at the molecular level with HNTs during the scaffold processing. The release profile in the in vitro conditions indicated the control of SrR release by Fickian diffusion and continuation within 21 days. Mesenchymal stem cells (MSCs) on the scaffolds showed that SrR effectively improved proliferation of the MSCs and accelerated osteogenic differentiation as revealed by Alizarin red staining and Real Time Quantitative Reverse transcription polymerase chain reaction (qRT-PCR). In vivo studies demonstrated that the SrR releasing from the Gel/HNTs scaffolds enhanced bone formation and vascularization. Our results suggest that HNTs could control the releasing of SrR and its localized delivery at the defect site, simultaneously with enhancing physicomechanical and bone regeneration ability of gelatin scaffolds.

Nowadays, biomaterials have become a crucial element in numerous biomedical, preclinical, and clinical applications. The use of nanoparticles entails a great potential in these fields mainly because of the high ratio of surface atoms that modify the physicochemical properties and increases the chemical reactivity. Among them, carbon nanotubes (CNTs) have emerged as a powerful tool to improve biomedical approaches in the management of numerous diseases. CNTs have an excellent ability to penetrate cell membranes, and the sp2 hybridization of all carbons enables their functionalization with almost every biomolecule or compound, allowing them to target cells and deliver drugs under the appropriate environmental stimuli. Besides, in the new promising field of artificial biomaterial generation, nanotubes are studied as the load in nanocomposite materials, improving their mechanical and electrical properties, or even for direct use as scaffolds in body tissue manufacturing. Nevertheless, despite their beneficial contributions, some major concerns need to be solved to boost the clinical development of CNTs, including poor solubility in water, low biodegradability and dispersivity, and toxicity problems associated with CNTs' interaction with biomolecules in tissues and organs, including the possible effects in the proteome and genome. This review performs a wide literature analysis to present the main and latest advances in the optimal design and characterization of carbon nanotubes with biomedical applications, and their capacities in different areas of preclinical research.

Mutations in the EPM2A and EPM2B genes, encoding laforin and malin proteins respectively, are responsible for Lafora disease, a fatal form of progressive myoclonus epilepsy with autosomal recessive inheritance. Neuroimaging studies of patients with Lafora disease have shown different degrees of brain atrophy, decreased glucose brain uptake and alterations on different brain metabolites mainly in the frontal cortex, basal ganglia and cerebellum. Mice deficient for laforin and malin present many features similar to those observed in patients, including cognitive, motor, histological and epileptic hallmarks. We describe the neuroimaging features found in two mouse models of Lafora disease. We found altered volumetric values in the cerebral cortex, hippocampus, basal ganglia and cerebellum using magnetic resonance imaging (MRI). Positron emission tomography (PET) of the cerebral cortex, hippocampus and cerebellum of Epm2a−/− mice revealed abnormal glucose uptake, although no alterations in Epm2b−/− mice were observed. Magnetic resonance spectroscopy (MRS) revealed significant changes in the concentration of several brain metabolites, including N-acetylaspartate (NAA), in agreement with previously described findings in patients. These data may provide new insights into disease mechanisms that may be of value for developing new biomarkers for diagnosis, prevention and treatment of Lafora disease using animal models.

Aims Human influenza A virus (hIAV) infection is associated with important cardiovascular complications, although cardiac infection pathophysiology is poorly understood. We aimed to study the ability of hIAV of different pathogenicity to infect the mouse heart, and establish the relationship between the infective capacity and the associated in vivo, cellular and molecular alterations. Methods and results We evaluated lung and heart viral titres in mice infected with either one of several hIAV strains inoculated intranasally. 3D reconstructions of infected cardiac tissue were used to identify viral proteins inside mouse cardiomyocytes, Purkinje cells, and cardiac vessels. Viral replication was measured in mouse cultured cardiomyocytes. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to confirm infection and study underlying molecular alterations associated with the in vivo electrophysiological phenotype. Pathogenic and attenuated hIAV strains infected and replicated in cardiomyocytes, Purkinje cells, and hiPSC-CMs. The infection was also present in cardiac endothelial cells. Remarkably, lung viral titres did not statistically correlate with viral titres in the mouse heart. The highly pathogenic human recombinant virus PAmut showed faster replication, higher level of inflammatory cytokines in cardiac tissue and higher viral titres in cardiac HL-1 mouse cells and hiPSC-CMs compared with PB2mut-attenuated virus. Correspondingly, cardiac conduction alterations were especially pronounced in PAmut-infected mice, associated with high mortality rates, compared with PB2mutinfected animals. Consistently, connexin43 and Na(V)1.5 expression decreased acutely in hiPSC-CMs infected with PAmut virus. YEM1 L protease also decreased more rapidly and to lower levels in PAmut-infected hiPSC-CMs compared with PB2mut-infected cells, consistent with mitochondrial dysfunction. Human IAV infection did not increase myocardial fibrosis at 4-day post-infection, although PAmut-infected mice showed an early increase in mRNAs expression of lysyl oxidase. Conclusion Human IAV can infect the heart and cardiac-specific conduction system, which may contribute to cardiac complications and premature death. [GRAPHICS] .

The front cover artwork is provided by Universidad Autónoma de Madrid, Spain, the Jožef Stefan Institute Ljubljana, Slovenia, and the university hospitals Gregorio Marañon and La Princesa in Madrid, Spain. The image shows an occlusion in an artery which is marked by bimodal nanoparticles and detected by optical coherence tomography, while being exposed to a magnetic field, thereby improving the signal. Read the full text of the Article at 10.1002/cptc.201900071 .

The Front Cover shows an occlusion in an artery which is marked by bimodal nanoparticles and detected by optical coherence tomography, while being exposed to a magnetic field, thereby improving the signal. More information can be found in the Article by J. Hu et al. on page 529 in Issue 7, 2019 (DOI: 10.1002/cptc.201900071).

BACKGROUND Colorectal cancer (CRC) is the second most common cause of cancer death worldwide. It is broadly described that cyclooxygenase-2 (COX-2) is mainly overexpressed in CRC but less is known regarding post-translational modifications of this enzyme that may regulate its activity, intracellular localization and stability. Since metabolic and proteomic profile analysis is essential for cancer prognosis and diagnosis, our hypothesis is that the analysis of correlations between these specific parameters and COX-2 state in tumors of a high number of CRC patients could be useful for the understanding of the basis of this cancer in humans. AIM To analyze COX-2 regulation in colorectal cancer and to perform a detailed analysis of their metabolic and proteomic profile. METHODS Biopsies from both healthy and pathological colorectal tissues were taken under informed consent from patients during standard colonoscopy procedure in the University Hospital of Bellvitge (Barcelona, Spain) and Germans Trias i Pujol University Hospital (Campus Can Ruti) (Barcelona, Spain). Western blot analysis was used to determine COX-2 levels. Deglycosylation assays were performed in both cells and tumor samples incubating each sample with peptide N-glycosidase F (PNGase F). Prostaglandin E2 (PGE2) levels were determined using a specific ELISA. 1H high resolution magic angle spinning (HRMAS) analysis was performed using a Bruker AVIII 500 MHz spectrometer and proteomic analysis was performed in a nano-liquid chromatography-tandem mass spectrometer (nano LC-MS/MS) using a QExactive HF orbitrap MS. RESULTS Our data show that COX-2 has a differential expression profile in tumor tissue of CRC patients vs the adjacent non-tumor area, which correspond to a glycosylated and less active state of the protein. This fact was associated to a lesser PGE2 production in tumors. These results were corroborated in vitro performing deglycosylation assays in HT29 cell line where COX-2 protein profile was modified after PNGase F incubation, showing higher PGE2 levels. Moreover, HRMAS analysis indicated that tumor tissue has altered metabolic features vs non-tumor counterparts, presenting increased levels of certain metabolites such as taurine and phosphocholine and lower levels of lactate. In proteomic experiments, we detected an enlarged number of proteins in tumors that are mainly implicated in basic biological functions like mitochondrial activity, DNA/RNA processing, vesicular trafficking, metabolism, cytoskeleton and splicing. CONCLUSION In our colorectal cancer cohort, tumor tissue presents a differential COX-2 expression pattern with lower enzymatic activity that can be related to an altered metabolic and proteomic profile.

The front cover artwork is provided by Universidad Autónoma de Madrid, Spain, the Jožef Stefan Institute Ljubljana, Slovenia, and the university hospitals Gregorio Marañon and La Princesa in Madrid, Spain. The image shows an occlusion in an artery which is marked by bimodal nanoparticles and detected by optical coherence tomography, while being exposed to a magnetic field, thereby improving the signal. Read the full text of the Article at 10.1002/cptc.201900071 .

We report on the magnetic properties of stable suspensions from oxidized Multiwalled Carbon Nanotubes (MWCNT) functionalized with aminopyrene (AP). MWCNT form π−π stacking adducts with AP (AP-MWCNT), originating homogenous, stable, suspensions in N,N-dimethylformamide (DMF) or melted agarose. First, we investigated the magneto-optical properties of these adducts. When applying series of pulsed magnetic fields to nanotube suspensions in DMF, the pattern of light dispersed increased during the magnetic pulse and decreased in the intervals, a behavior consistent with magnetic field induced orientation of the adducts. When adducts were suspended in a melted agarose gel under an external magnetic field, the extinction coefficient of polarized light through the gel, was larger when the polarization plane was parallel to the magnetic field direction. Based on the magneto-optical responses observed, we further investigated the magnetic properties of AP-MWCNT implementing measurements with Superconducting Quantum Interference Device, Zero Field Cooling and Field Cooling, Thermogravimetric and Differential Scanning Calorimetry. Pre-oriented AP-MWCNT suspensions depicted a clear superparamagnetic character with hysteresis loops revealing larger magnetic susceptibility values along their longitudinal axis. In summary, magneto-optical and SQUID measurements revealed that nanotube adducts in suspension, behave as nanoscale compass needles aligning their long axis parallel to externally applied magnetic fields.

Clinical imaging modalities have reached a prominent role in medical diagnosis and patient management in the last decades. Different image methodologies as Positron Emission Tomography, Single Photon Emission Tomography, X-Rays, or Magnetic Resonance Imaging are in continuous evolution to satisfy the increasing demands of current medical diagnosis. Progress in these methodologies has been favored by the parallel development of increasingly more powerful contrast agents. These are molecules that enhance the intrinsic contrast of the images in the tissues where they accumulate, revealing noninvasively the presence of characteristic molecular targets or differential physiopathological microenvironments. The contrast agent field is currently moving to improve the performance of these molecules by incorporating the advantages that modern nanotechnology offers. These include, mainly, the possibilities to combine imaging and therapeutic capabilities over the same theranostic platform or improve the targeting efficiency in vivo by molecular engineering of the nanostructures. In this review, we provide an introduction to multimodal imaging methods in biomedicine, the sub-nanometric imaging agents previously used and the development of advanced multimodal and theranostic imaging agents based in nanotechnology. We conclude providing some illustrative examples from our own laboratories, including recent progress in theranostic formulations of magnetoliposomes containing ω-3 poly-unsaturated fatty acids to treat inflammatory diseases, or the use of stealth liposomes engineered with a pH-sensitive nanovalve to release their cargo specifically in the acidic extracellular pH microenvironment of tumors.

Magnetic resonance imaging (MRI) is a technique based on the contents and relaxation features of water in tissues. In basic MRI sequences, diffusion phenomenon of water molecules is not taken into account although it has a notable influence in the relaxation times, and therefore in the signal intensity of images. In fact, MRI techniques that take advantage of water diffusion have experienced a huge development in last years. Diffusion-weighted imaging (DWI) has spectacularly evolved reaching nowadays a great impact both in clinical and preclinical imaging-especially in the neuroimaging field-and in basic research. We present here a protocol to perform DWI studies in a high-field preclinical setup.

We report on the magnetic properties of stable suspensions from oxidized 19 Multiwalled Carbon Nanotubes (MWCNT) functionalized with aminopyrene (AP). MWCNT form 20  stacking adducts with AP (AP-MWCNT), originating homogenous, stable, suspensions in 21 N,N-dimethylformamide (DMF) or melted agarose. First, we investigated the magneto-optical 22 properties of these adducts. When applying series of pulsed magnetic fields to nanotube 23 suspensions in DMF, the pattern of light dispersed increased during the magnetic pulse and 24 decreased in the intervals, a behavior consistent with magnetic field induced orientation of the 25 adducts. When adducts were suspended in a melted agarose gel under an external magnetic field, 26 the extinction coefficient of polarized light through the gel, was larger when the polarization plane 27 was parallel to the magnetic field direction. Based on the magneto-optical responses observed, we 28 further investigated the magnetic properties of AP-MWCNT implementing Superconducting 29 Quantum Interference Device (SQUID), Zero Field Cooling (ZFC) and Field Cooling (FC), and 30 Thermogravimetric (TGA) and Differential Scaning Calorimetry (DSC) measurements. Pre31 oriented AP-MWCNT suspensions depicted a clear superparamagnetic character with hysteresis 32 loops revealing larger magnetic susceptibility values along their longitudinal axis. ZFC, FC and 33 TGA/DSC revealed that these magnetic properties were preserved after thermal removal of 34 aminopyrene from the AP-MWCNT adduct, suggesting that the nanotubular structure dominates 35 the magnetic contributions. In summary, magneto-optical and SQUID measurements revealed that 36 nanotube adducts in suspension, behave as nanoscale compass needles aligning their long axis 37 paralell to externally applied magnetic fields. 38

Magnetic resonance images are obtained by a combination of different radiofrequency pulses and gradient waveforms applied to the subject inside a magnetic field. There are multiple pulse sequences used in clinical and preclinical studies adjusted to whatever physician or researches want to analyze, from basic anatomic images to accurate diagnostic techniques as diffusion, perfusion, or functional imaging. In this chapter, we present the most used radiofrequency pulse combinations of the two groups of sequences available in magnetic resonance imaging: spin-echo and gradient-echo sequences.