ABSTRACT
OBJECTIVES: To evaluate the effect of abolishing instructions to fast prior to contrast-enhanced CT on acute adverse reactions (AARs). METHODS: In our institution, we instructed patients to fast one meal before contrast-enhanced CT examinations. However, we abolished these instructions at the end of March 2019, and solid food intake was not restricted before contrast-enhanced CT after this date. The differences in the incidence of AARs before (December 2015-November 2018, n = 43,927) and after (April 2019-March 2020, n = 14,676) abolishing instructions to fast were compared. We allowed 4 months (December 2018-March 2019) for this policy change to fully permeate the CT referrals. The medical records of patients who vomited were retrospectively reviewed by one of the authors for notations of aspiration or aspiration pneumonia attributable to vomiting. RESULTS: The overall incidence of AARs before (1.60%, n = 705) and after abolition (1.40%, n = 205) did not change significantly. As the chemotoxic reactions, the incidence of nausea decreased significantly (0.31 to 0.18%, p = 0.006). The incidence of vomiting did not change (0.12 to 0.16%), and there were no cases of aspiration pneumonia attributable to vomiting during the study period. The incidence of severe hypersensitivity/allergy-like reactions did not change (0.06 to 0.05%). CONCLUSIONS: Abolishing instructions to fast decreased the incidence of nausea, but did not affect the incidence of vomiting. No cases of aspiration pneumonia attributable to vomiting were found. Our study confirmed that fasting is not required prior to contrast-enhanced CT.
ABSTRACT
The purpose of this study was to improve the contrast between the nerves and blood by reconsidering the imaging parameters of the sampling perfection with application-optimized contrasts using different flip angle evolutions (SPACE) method, and to compare it with conventional methods, including the constructive interference in steady state (CISS) and T2-weighted SPACE (T2-SPACE) methods. In the phantom study, the repetition time (TR), echo time (TE), flip angle (FA), and turbo factor (TF) of SPACE were varied using the restore pulse. The parameters for which the nerve-blood contrast (C1) and cerebrospinal fluid-nerve contrast (C2) were equal were selected. Though multiple conditions resulted in C1 and C2 equivalence, we determined/set the TR=500 ms, TE=21 ms, FA=120°, and TF=30, considering the acquisition time, specific absorption rate (SAR), and artifacts. This sequence was called "short TR and short TE SPACE with restore pulse (SSSR)". In the phantom and healthy volunteer studies, the contrast between the nerves and blood in the SSSR method was statistically superior in both the physical and visual assessments compared with conventional methods. In the healthy volunteer study, C1 improved from 0.08 for CISS and 0.18 for T2-SPACE to 0.43 for SSSR. This is because the nerve signals in conventional methods were low due to the heavy T2-weighted, while those in the SSSR method were high due to the short TE and effect of the restore pulse. In conclusion, the contrast between the nerves and blood was significantly higher in the SSSR method compared with conventional methods.
Subject(s)
Imaging, Three-Dimensional , Magnetic Resonance Imaging , Artifacts , Humans , Phantoms, ImagingABSTRACT
Diffusion kurtosis imaging (DKI) is a method of analyzing restricted diffusion. Mean kurtosis (MK) is obtained from DKI. It is not known how different MRI scanners and coil systems will change MK when the same imaging parameters are used. The purpose of this study is to identify tendencies in MK when using various MRI scanners and coil systems. A total of 27 healthy volunteers were enrolled in this study. DKI was performed on the brain for each volunteer on five MRI scanner/coil system combinations using the same scan parameters. MK of 10 anatomical areas of the brain were compared, and the signal-noise ratios (SNRs) of b-2000 s/mm2 images were measured in identical areas. There were no significant differences among MKs from multi transmit (MT) MRI systems, but MK was significantly lower on the single transmit MRI system because of pepper artifact caused by low SNR. In conclusion, we found no significant differences in MK among MT systems, and MK was significantly lower without MT.
