Longitudinal Changes in Cerebral Perfusion, Perivascular Space Volume, and Ventricular Volume in a Healthy Cohort Undergoing a Spaceflight Analog.

BACKGROUND AND PURPOSE: A global decrease in brain perfusion has recently been reported during exposure to a ground-based spaceflight analog. Considering that CSF and glymphatic flow are hypothesized to be propelled by arterial pulsations, it is unknown whether a change in perfusion would impact these CSF compartments. The aim of the current study was to evaluate the relationship among changes in cerebral perfusion, ventricular volume, and perivascular space volume before, during, and after a spaceflight analog. MATERIALS AND METHODS: Eleven healthy participants underwent 30 days of bed rest at 6° head-down tilt with 0.5% atmospheric CO2 as a spaceflight analog. For each participant, 6 MR imaging brain scans, including perfusion and anatomic-weighted T1 sequences, were obtained before, during, and after the analog period. Global perfusion, ventricular volume, and perivascular space volume time courses were constructed and evaluated with repeated measures ANOVAs. RESULTS: Global perfusion followed a divergent time trajectory from ventricular and perivascular space volume, with perfusion decreasing during the analog, whereas ventricular and perivascular space volume increased (P < .001). These patterns subsequently reversed during the 2-week recovery period. CONCLUSIONS: The patterns of change in brain physiology observed in healthy participants suggest a relationship between cerebral perfusion and CSF homeostasis. Further study is warranted to determine whether a causal relationship exists and whether similar neurophysiologic responses occur during spaceflight.

A deep convolutional neural network ensemble for composite identification of pulmonary nodules and incidental findings on routine PET/CT.

AIM: To evaluate primary and secondary pathologies of interest using an artificial intelligence (AI) platform, AI-Rad Companion, on low-dose computed tomography (CT) series from integrated positron-emission tomography (PET)/CT to detect CT findings that might be overlooked. MATERIALS AND METHODS: One hundred and eighty-nine sequential patients who had undergone PET/CT were included. Images were evaluated using an ensemble of convolutional neural networks (AI-Rad Companion, Siemens Healthineers, Erlangen, Germany). The primary outcome was detection of pulmonary nodules for which the accuracy, identity, and intra-rater reliability was calculated. For secondary outcomes (binary detection of coronary artery calcium, aortic ectasia, vertebral height loss), accuracy and diagnostic performance were calculated. RESULTS: The overall per-nodule accuracy for detection of lung nodules was 0.847. The overall sensitivity and specificity for detection of lung nodules was 0.915 and 0.781. The overall per-patient accuracy for AI detection of coronary artery calcium, aortic ectasia, and vertebral height loss was 0.979, 0.966, and 0.840, respectively. The sensitivity and specificity for coronary artery calcium was 0.989 and 0.969. The sensitivity and specificity for aortic ectasia was 0.806 and 1. CONCLUSION: The neural network ensemble accurately assessed the number of pulmonary nodules and presence of coronary artery calcium and aortic ectasia on low-dose CT series of PET/CT. The neural network was highly specific for the diagnosis of vertebral height loss, but not sensitive. The use of the AI ensemble can help radiologists and nuclear medicine physicians to catch CT findings that might be overlooked.

Unusual management problems in the treatment of a long-standing destructive periapical cyst. Report of a case.

A case report is presented in which an orthognathically compromised patient presented with a destructive periapical lesion that caused resorption of first and second molar roots and buccal and palatal cortical plates. The initial diagnosis and treatment were influenced by the absence of pre-existing dental records and an unrecountable dental history. Unusual endodontic management problems were encountered when copious intracoronal fluid, determined to be saliva, continually flowed through the open canals via a periodontal defect. The pathology report described the rare finding of large portions of fibrous scar tissue, indicating that some healing had occurred prior to treatment.

Rationale for treatment and management of avulsed teeth.

Fifteen hours after the patient's tooth was avulsed in a bicycle accident, replantation procedures began. This case presents a process of replantation and its success. An avulsed tooth is a traumatic experience. Replantation is often of psychological value. Although the possibility of the eventual loss of the tooth should be explained to the patient, replantation reduces the traumatic effect of the accident. It also has clinical value. Successful replantation results in prolonged retention which will improve esthetic appearance, arch form, chewing, enunciation, and integrity of the arch. Use of calcium hydroxide in avulsed teeth has allowed the rate of replantation success to increase greatly. It is a practical technique that is scientifically sound, has many positive indications, and has provided an invaluable service to patients.