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Thứ Sáu, 17 tháng 6, 2022

Imaging shows A-Z COVID vaccine may trigger blood clots


June 15, 2022

MRI, CT, and ultrasound identify blood clots not found on clinical assessment in a majority of individuals who have COVID-19 vaccine-induced low blood platelets after their first dose of the AstraZeneca vaccine, according to a case study published June 14 in Radiology.

The findings could help clinicians better care for patients who have received the AstraZeneca inoculation and have developed what is called vaccine-induced immune thrombotic thrombocytopenia (VITT), wrote a team led by Priya Rogers of Addenbrooke's Hospital in Cambridge, U.K.

"Whole-body imaging can identify patients who require early referral to specialist vascular or hepatobiliary centers [due to VITT]," the group noted.

Images in a 64-year-old woman who presented with confusion and collapse and was diagnosed with intracranial hemorrhage associated with cerebral venous sinus thrombosis secondary to VITT
Images in a 64-year-old woman who presented with confusion and collapse and was diagnosed with intracranial hemorrhage associated with cerebral venous sinus thrombosis secondary to VITT. (A) Axial unenhanced head CT image demonstrates a large right parietal lobe intraparenchymal hemorrhage and (B) bilateral infarcts in the cerebellum confirmed on axial brain T2-weighted MRI. (D) CT pulmonary angiogram coronal reformatted image shows eccentric mural thrombus within the aorta (white arrow) and large central saddle embolus (red asterisks). Images and caption courtesy of the RSNA.

Experts recommend symptom-specific imaging for VITT, but its prevalence remains unclear, Rogers and colleagues noted. To clarify the question, the group conducted a study that included 40 patients who developed thrombocytopenia after receiving their first dose of the AstraZeneca vaccine. The patients were imaged with CT, ultrasound, and/or MRI depending on protocol in seven different centers across the U.K.

Of these 40 patients, 80% developed thrombosis symptoms within 14 days and 20% within 14 to 28 days. The investigators also found the following:

  • 75% of patients underwent additional imaging, primarily with CT pulmonary angiogram or CT of the abdomen or pelvis.
  • 83% of those patients who had additional imaging were found to have hidden blood clots.
  • 73% of the patient cohort presented with neurological symptoms (headache, blurred vision, seizure, collapse) and were confirmed by CT or MR venogram to have a cerebral venous sinus blood clot.
  • 30% had extension of their primary blood clot.
  • 20% of the total cohort died (eight of 40); those with confirmed progressive thrombosis (four patients) had a mortality rate of 50%.

Most patients underwent some form of CT imaging, the authors noted.

Imaging modality within 48 hours of admission for symptoms of blood clotting
Total patientsMRI abdomen with contrastUltrasound duplex abdomenUltrasound duplex peripheral veinsCT abdomen/pelvis with contrastCT pulmonary angiogramCT chest abdomen/pelvis with contrast/CT aortogramCT head and CT/MRI venogram

Imaging can play a key role in identifying and dealing with vaccine complications, according to Rogers and colleagues.

"[Our] findings emphasize that VITT is a multisystem disorder and suggest that whole-body contrast-enhanced imaging is likely to identify further thrombosis," they concluded.

Thứ Sáu, 10 tháng 6, 2022

Quantitative US can help detect hepatic steatosis


By Erik L. Ridley, AuntMinnie.com staff writer

June 8, 2022 -- A quantitative ultrasound technique can be highly sensitive for detecting hepatic steatosis, correlating highly with MRI measurements, according to research published June 8 in the American Journal of Roentgenology

In a prospective, cross-sectional study, researchers from Cincinnati Children's Hospital Medical Center found that ultrasound-derived fat projection (UDFF) yielded 94.1% sensitivity for detection of MRI proton-density fat fraction (PDFF) measurements exceeding a commonly used threshold for clinically significant hepatic steatosis.

"These results support a clinical role of UDFF in the detection of hepatic steatosis, with a UDFF > 5% having high sensitivity for detection of MRI PDFF ≥ 5.5%," wrote corresponding author Dr. Andrew Trout and colleagues.

Although increased hepatic echogenicity and associated decreased conspicuity of the portal triads on ultrasound has been utilized to identify hepatic steatosis, the modality has -- unlike MRI -- not traditionally been able to provide true quantification of liver fat. In their study, the researchers sought to evaluate the performance of UDFF, one of several new methods developed by ultrasound vendors for detecting and quantifying hepatic steatosis on ultrasound.

They included 56 overweight and obese adults and adolescents ≥ 16 years in the study. During a single visit between August and October 2020, all participants received investigational liver MRI on a Signa Architect 3-tesla MRI scanner (GE Healthcare), as well as an ultrasound exam with a DAX deep abdominal transducer on an Acuson Sequoia ultrasound scanner (Siemens Healthineers).

UDFF, a clinically available technique developed by Siemens, was measured on all patients. The method is derived from the measurement and combination of both attenuation effect and backscatter. After a median UDFF is calculated across five measurements on all three acquisitions, a final UDFF percentage is then produced based on the median of the three acquisitions, according to the researchers.

ultrasound-derived fat fraction images of a 23-year-old man with body mass index of 25
A 23-year-old man with body mass index of 25.1. (A) For ultrasound-derived fat fraction (UDFF) measurement, the operator places crossbar at liver capsule, with sample region of interest fixed 1.5 cm deep from crossbar, to ensure measurement obtained sufficiently deep to liver capsule. Overall UDFF was 3%. (B) Median MRI proton density fat fraction (PDFF) from three acquisitions was 3%, demonstrating agreement. Images courtesy of the American Roentgen Ray Society and the American Journal of Roentgenology.

In the study, three MRI PDFF acquisitions were also completed using GE's Ideal IQ whole-liver 3D axial confounder-corrected technique. An image analyst then calculated the PDFF measurements under the supervision of a pediatric radiologist with 10 years of post-training experience, according to the researchers.

The UDFF measurements had a positive association with MRI PDFF results, producing a rho of 0.82 and intraclass correlation coefficient of 0.84. The mean bias between UDFF and PDFF was 4%.

Overall, UDFF had an area under the curve of 0.9 for diagnosing MRI PDFF ≥ 5.5 -- the threshold considered to represent clinically significant hepatic steatosis. A UDFF overall cutoff of > 5% produced 94.1% sensitivity and 63.6% specificity for diagnosing MRI PDFF ≥ 5.5.

The researchers noted that liver UDFF is expressed as a percentage, analogous to MRI PDFF.

"Thus, not only is diagnostic performance for a specific threshold fat fraction clinically relevant, but the correspondence in measured fat fraction percentage between techniques is also relevant, particularly if the techniques are used to monitor for change in fat fraction over time or in response to therapy," they wrote.

Furthermore, the area under the receiver operating characteristic curve for UDFF did not differ significantly based on the number of measurements. As a result, the researchers concluded that three measurements are likely sufficient for determining UDFF in clinical practice, according to the researchers.

"Use of three UDFF measurements is anticipated to achieve similar results as obtained from a greater number of measurements while improving examination efficiency; we do not advise use of a single measurement given the possibility of obtaining a single erroneous value," they wrote.