Transient interruption of contrast on CT pulmonary angiography: effect of mid-inspiratory vs. end-inspiratory respiration command.

PURPOSE: To investigate the effects of mid-inspiratory respiration commands and other factors on transient interruption of contrast (TIC) incidence on CT pulmonary angiography. METHODS: In this retrospective study, 824 patients (mean age, 66.1 ± 15.3 years; 342 males) who had undergone CT pulmonary angiography between January 2021 and February 2023 were included. Among them, 545 and 279 patients were scanned at end- and mid-inspiratory levels, respectively. By placing a circular region of interest, CT attenuation of the main pulmonary artery (CTMPA) was recorded. Associations between several factors, including patient age, body weight, sex, respiratory command vs. TIC and severe TIC incidence (defined as CTMPA < 200 and 150 HU, respectively), were assessed using logistic regression analyses with stepwise regression selection based on Akaike's information criterion. RESULTS: Mid-inspiratory respiration command, in addition to patient age and lighter body weight, had negative association with the incidence of TIC. Only patient age, lighter body weight, female sex, and larger cardiothoracic ratio were negatively associated with severe TIC incidence. Mid-inspiratory respiration commands helped reduce TIC incidence among patients aged < 65 years (p = 0.039) and those with body weight ≥ 75 kg (p = 0.005) who were at high TIC risk. CONCLUSION: Changing the respiratory command from end- to mid-inspiratory levels, as well as patient age and body weight, was significantly associated with TIC incidence.

Effects of Intravenous Infusion of Iodine Contrast Media on the Tracheal Diameter and Lung Volume Measured with Deep Learning-Based Algorithm.

This study aimed to investigate the effects of intravenous injection of iodine contrast agent on the tracheal diameter and lung volume. In this retrospective study, a total of 221 patients (71.1 ± 12.4 years, 174 males) who underwent vascular dynamic CT examination including chest were included. Unenhanced, arterial phase, and delayed-phase images were scanned. The tracheal luminal diameters at the level of the thoracic inlet and both lung volumes were evaluated by a radiologist using a commercial software, which allows automatic airway and lung segmentation. The tracheal diameter and both lung volumes were compared between the unenhanced vs. arterial and delayed phase using a paired t-test. The Bonferroni correction was performed for multiple group comparisons. The tracheal diameter in the arterial phase (18.6 ± 2.4 mm) was statistically significantly smaller than those in the unenhanced CT (19.1 ± 2.5 mm) (p < 0.001). No statistically significant difference was found in the tracheal diameter between the delayed phase (19.0 ± 2.4 mm) and unenhanced CT (p = 0.077). Both lung volumes in the arterial phase were 4131 ± 1051 mL which was significantly smaller than those in the unenhanced CT (4332 ± 1076 mL) (p < 0.001). No statistically significant difference was found in both lung volumes between the delayed phase (4284 ± 1054 mL) and unenhanced CT (p = 0.068). In conclusion, intravenous infusion of iodine contrast agent transiently decreased the tracheal diameter and both lung volumes.

Deformed Popliteal Artery Due to Highly Flexed Knee Position Can Cause Kinks, Creating an Unfavorable Hemodynamic State.

BACKGROUND: Endovascular treatment devices of the femoropopliteal artery have evolved, improving clinical results. However, the effects of dynamic changes in the popliteal artery during knee flexion have not been sufficiently investigated. In this study we performed a 3-dimensional analysis to clarify the dynamic changes in the popliteal artery during knee flexion and their effects on hemodynamics.Methods and Results: To analyze dynamic changes in the popliteal artery in the knee flexion position, a computed tomography protocol was developed in the right-angled and maximum flexion knee positions. Thirty patients with lower extremity artery disease were recruited. V-Modeler software was used for anatomical and hemodynamic analyses. Various types of deformations of the popliteal artery were revealed, including hinge points and accessory flexions. Kinks can occur in the maximum flexion position; however, they rarely occur in the right-angled flexion position. In addition, hemodynamic analysis revealed a tendency for lower minimum wall shear stress and a higher maximum oscillatory shear index at the maximum curvature of the popliteal artery. CONCLUSIONS: Kinks in the maximum flexion position suggested that the outcome of endovascular treatment may change in areas such as Japan, where knee flexion is customary. Hemodynamics at the maximum curvature of the popliteal artery indicated that the luminal condition was unfavorable for endovascular treatment.

Clinical valve thrombosis and arterial embolism in a cancer patient after transcatheter aortic valve replacement.

The number of cancer patients with severe aortic stenosis and atrial fibrillation (AF) is increasing in the aging population. Transcatheter aortic valve replacement (TAVR) is an established treatment option for severe aortic stenosis with high surgical risk, including individuals with cancer. Antithrombotic therapy should be considered for post-TAVR or AF patients. However, antithrombotic management in cancer patients remains challenging due to the increased risk of both thromboembolism and bleeding. We present a case of clinical valve thrombosis and arterial embolism after transcatheter aortic valve replacement in an elderly patient with a history of metastatic pancreatic cancer and permanent atrial fibrillation under treatment of single antiplatelet therapy. Warfarin treatment after successful surgical thrombectomy to the occluded arteries improved clinical valve thrombosis, although the long-term outcome remains unclear. This case demonstrates that novel management algorithms for thromboembolism and bleeding in elderly cancer patients with AF and valvular heart disease are urgently needed.

Structural Characterization of 6-Thioguanosine and Its Monohydrate in the Gas Phase.

Detailed structural analysis of 6-thioguanosine (6TGs) in relation to its tautomerization and sugar conformation is performed in the gas phase using UV and IR spectroscopy combined with ab initio calculations. We have observed a thiol tautomer of 6TGs with its sugar moiety in the syn conformation that is stabilized by a strong intramolecular H-bonding between O5'H of the sugar and N3 atom of the guanine moiety. This observation is consistent with previous results for guanosine (Gs) in which the corresponding enol form is solely detected. We have also identified a monohydrate of 6TGs consisting of a thiol tautomer with the water linking guanine moiety and sugar OH group. It is demonstrated that hydration behavior of 6TGs is significantly different from that of Gs as a result of a weaker H-bonding ability of the thiol group.

Effective Strategy for Conformer-Selective Detection of Short-Lived Excited State Species: Application to the IR Spectroscopy of the N1H Keto Tautomer of Guanine.

The ultrafast deactivation processes in the excited state of biomolecules, such as the most stable tautomers of guanine, forbid any state-of-the-art gas phase spectroscopic studies on these species with nanosecond lasers. This drawback can be overcome by grafting a chromophore having a long-lived excited state to the molecule of interest, allowing thus a mass-selective detection by nanosecond R2PI and therefore double resonance IR/UV conformer-selective spectroscopic studies. The principle is presently demonstrated on the keto form of a modified 9-methylguanine, for which the IR/UV double resonance spectrum in the C═O stretch region, reported for the first time, provides evidence for extensive vibrational couplings within the guanine moiety. Such a successful strategy opens up a route to mass-selective IR/UV spectroscopic investigations on molecules exhibiting natural chromophores having ultrashort-lived excited states, such as DNA bases, their complexes as well as peptides containing short-lived aromatic residues.

Hydrogen-bonding interactions of uric acid complexes with water/melamine by mid-infrared spectroscopy.

Hydrogen (H)-bonding interactions of uric acid (UA) with water have been investigated via IR-UV double resonance measurements in the mid-IR region. Comparison of the present results with those obtained previously in the near-IR region enables us to examine microscopic hydration effects that are specific to the H-bonding acceptor sites of UA. It is shown that hydration of the C8O site promotes the mode coupling of this stretch with the C2O stretch. The occurrence of this coupling is manifested in the IR intensity pattern, in which the transition associated with the in-phase contribution C8O + C2O is significantly suppressed, whereas the corresponding out-of-phase contribution gives rise to a strong peak. We also measured the mid-IR spectra of the 1 : 1 complex formed between UA and melamine (MEL) and carried out a structural analysis using the spectroscopic signature of the H-bonding derived from the result of the monohydrated cluster. It is shown that the complex possesses a triple H-bonding structure with the C2O acceptor site of UA H-bonded to MEL. Furthermore, the IR-depleted UV spectroscopy technique was employed in order to ascertain whether other structural isomers are present in the probe UV spectra.

Multiple hydrogen-bonding interactions of uric acid/9-methyluric acid with melamine identified by infrared spectroscopy.

Hydrogen-bonded complexes of uric acid/9-methyluric acid (UA/9MUA) with melamine (MEL) are prepared by the combined technique of laser desorption and supersonic-jet expansion, and their stable structures are investigated by infrared spectroscopy and theoretical calculations. It is shown that the 1:1 complex formed between UA and MEL is of nonplanar type, in which the two chromophore planes are significantly folded and thus allow for triple hydrogen-bonding interactions. An anomalously broad IR band is observed in the low-frequency range 2500-2800 cm(-1), which is taken as evidence for the formation of a strong hydrogen bond between one of the NH sites of UA and MEL. In the case of 9MUA, in which hydrogen bonding to the N9H site of UA is blocked by the methyl group, two planar pairs formed of 9MUA and MEL are found to coexist. The nature of the multiple hydrogen-bonding interactions in these complexes is discussed based on the natural bond orbital analysis and compared with those of the guanine-cytosine base pair. The results are expected to provide important information on the structural characterization of urinary stones developed in infants after ingesting MEL-contaminated formula.

Ab initio studies on the photophysics of uric acid and its monohydrates: role of the water molecule.

The photophysical behavior of three lowest-energy tautomers of uric acid and seven most stable isomers of uric acid monohydrate is comprehensively studied by ab initio calculations. Ground-state energies are calculated with the CCSD(T) method, while excitation and ionization energies as well as excited-state potential energy profiles of photoinduced processes are calculated with the CC2 method. For the (1)ππ* state, it is found that the excitation energy of the monohydrate cluster is significantly lower than that of isolated uric acid when the water molecule is hydrogen-bonded at a specific carbonyl group. The calculated excited-state potential energy profiles suggest that some monohydrate isomers can undergo a migration of the water molecule from one site to another site in the (1)ππ* state with a small energy barrier. It is also found for both uric acid and its monohydrate that nonradiative decay via the NH bond dissociation in the (1)πσ* state is likely to occur at higher excitation energies. On the basis of the computational results, possible mechanisms for the absence of specific isomers of uric acid monohydrate from the resonant two-photon ionization spectrum are discussed.

Controlling Glycosyl Bond Conformation of Guanine Nucleosides: Stabilization of the anti Conformer in 5'-O-Ethylguanosine.

Nucleosides that consist of base and sugar moieties can adopt two main conformations, syn and anti, about the glycosidic bond. We have investigated the conformational properties of guanine nucleosides in the gas phase by using laser desorption combined with IR-UV double resonance spectroscopy. In guanosine, syn conformation is preferred as a result of internal hydrogen bonding between the 5'-OH group of the sugar and the N3 site of the guanine moiety. We have therefore employed a chemically modified nucleoside 5'-O-ethylguanosine, in which possible glycosyl bond conformations are restricted upon ethylation of the 5'-OH group. The result shows that anti conformer is stabilized by the formation of hydrogen bonding involving the 2'-OH group.

Structural identification of uric acid and its monohydrates by IR-UV double resonance spectroscopy.

We have employed IR-UV double resonance spectroscopy to identify the tautomeric and isomeric structures of uric acid and its monohydrated clusters which are produced by the techniques of laser-desorption and supersonic-jet cooling. The IR spectrum obtained for bare uric acid exhibits four distinct NH stretching transitions assignable to those of the most stable triketo form. We have also observed the two most stable monohydrated clusters, each with uric acid in the triketo form and water bonded to either the N3H or N9H site. It is demonstrated that the R2PI spectra of these monohydrates can be separated by using the IR-purified spectroscopic method.

Gas-phase isolation of diethyl guanosine 5'-monophosphate and its conformational assignment.

We show that intact neutral molecules of guanosine 5'-monophosphate can be vaporized by laser desorption when its phosphate group is esterified. The UV and IR spectroscopic measurements of this nucleotide reveal the existence of a novel internal hydrogen-bonding conformation of the phosphate group and guanine moiety.

Microhydration of the guanine-guanine and guanine-cytosine base pairs.

Monohydration structures of the guanine-guanine and guanine-cytosine base pairs have been elucidated by IR-UV double resonance spectroscopy combined with ab initio calculations. The systems studied consist of the homodimer of 9-methylguanine and the heterodimer of 9-methylguanine and 1-methylcytosine in which the methyl group is introduced to mimic the presence of the sugar-phosphate backbone and to block specific tautomerization. The monohydrate of the homodimer is identified as that of the most stable symmetric structure formed by the keto tautomers of guanine, which demonstrates that the base pair structure is not influenced by the hydration. It is also shown that at least two structural isomers, one of which retains the Watson-Crick GC pair structure, contribute the monohydrated cluster of the heterodimer. Although stacked base pairs are suggested to be significantly stabilized by the addition of water, the result shows no clear indication for the presence of stacked monohydrates in either homodimer or heterodimer case.

Hydration structures of 2'-deoxyguanosine studied by IR-UV double resonance spectroscopy: comparison with guanosine.

Infrared spectra of mono- and dihydrated clusters of 2'-deoxyguanosine (2'-dGs), which are formed by laser desorption combined with supersonic jet-cooling, have been measured by the technique of IR-UV double resonance spectroscopy. The structures of these hydrates are compared with those reported for guanosine (Gs) to elucidate the importance of the 2'-hydroxy group in the hydration. It is shown that monohydrated structures observed for 2'-dGs are similar to those of Gs, indicating no significant influence by the absence of 2'-OH group. For the dihydrated cluster, two structural isomers are identified and assigned to the dihydrates with the guanine moiety is in the keto form, which are consistent with the lowest-energy structures derived from theoretical calculations. Comparison with the results for Gs suggests that the presence of 2'-OH group leads to the stabilization of specific dihydrate structures involving the sugar group.

IR-UV double resonance spectroscopy of the hydrated clusters of guanosine and 9-methylguanine: evidence for hydration structures involving the sugar group.

Infrared spectra of mono- and dihydrated clusters of guanosine (Gs) formed by laser desorption combined with supersonic jet cooling have been measured by the technique of IR-UV double resonance spectroscopy. The results are compared with those of 9-methylguanine (9MG), in which the sugar group of Gs is replaced with a methyl group, to elucidate the importance of the sugar group in the hydration structures. It is shown that the UV spectrum observed for the monohydrated cluster of Gs is composed of multiple structural isomers of larger stabilities. One of the monohydrates is identified to possess a hydration structure involving the 5'-OH group of the sugar and the amino group of the guanine moiety. The IR spectrum of the dihydrated clusters reveals that the 2'-OH group is significantly influenced by the addition of the second water, which suggests the possibility of specific dihydrate structures for Gs.