May 31, 2012

Acute Isodense Subdural Hematoma

Plain and contrast-enhanced axial CT images of the brain show an isodense subdural hematoma (SDH, arrows) in the left cerebral convexity, much better appreciated on post-contrast image. There is also a thinner right frontal convexity SDH. 

Facts: Isodense Subdural Hematoma (SDH)
  • Subdural blood collection that has similar attenuation with the gray matter
  • Acute SDH appears as a high density collection with declining density with time. It passes "isodense" state mostly in subacute phase (2-6 weeks after initial trauma)
  • Isodense SDH poses diagnostic dilemma because it is not apparently seen on CT
  • In acute setting this can be seen in anemic patients (acute isodense SDH). Experimental data showed that Hb 8-10 g/dl will be isodense to the adjacent brain

Smith, Jr., WP, Batnitzky S, Rengachary SS. Acute isodense subdural hematomas: a problem in anemic patients. AJR 1981; 136:543-546. 

May 21, 2012

USPSTF Recommends Against PSA-based Prostate Cancer Screening

In its newest Statement published yesterday in the Annals of Internal Medicine, the U.S. Preventive Services Task Force (USPSTF) recommends against PSA-based screening for prostate cancer. Read the full paper (free) here.

Prostate Cancer: Facts
  • Most commonly diagnosed non-skin cancer in men in USA, estimated lifetime risk 15.9%
  • Most cases have good prognosis even without treatment
  • Lifetime risk of dying of prostate cancer 2.8%
Screening with PSA
  • PSA-based screening programs detect many cases of asymptomatic prostate cancer but evidence suggests that many of them will not progress or will progress slowly that it would have remained asymptomatic for the lifetime
  • "Overdiagnosis" of prostate cancer based on PSA is between 17-50% 
  • Screening resulted in none or minimal reduction in prostate cancer mortality (0 to 1 prostate cancer deaths avoided per 1000 men screened)
  • "False positivity" near 80% (cutoffs value 2.5-4 ug/L)
  • Applies to men in general US population. Although older age is the strongest risk factor for development of prostate cancer, neither screening nor treatment trials show benefit in men older than 70 years
  • Decision to initiate or continue PSA screening should be understood by patients about possible benefits and harms of screening
Recommendations of Others
  • The American Urological Association, the American Academy of Family Physicians and the American College of Physicians: currently updating their guideline
  • The American Cancer Society: men at average risk beginning at age 50 years and black men or men with a family history of prostate cancer beginning at age 45 years
Annals of Internal Medicine May 21, 2012  LINK

May 11, 2012

ACR Appropriateness Criteria for Suspected Aortic Injury

Axial contrast-enhanced CT image shows a pseudoaneurysm (arrow), intimal flap and periaortic hematoma of the proximal descending thoracic aorta in a patient experienced severe blunt chest trauma.

A newly revised American College of Radiology (ACR)'s Appropriateness Criteria for blunt chest trauma - suspected aortic injury has been published in March 2012 in the journal Emergency Radiology, summary and useful points are provided below

  • Chest x-ray remains an initial screening examination in patients who has sustained blunt chest trauma
  • In the appropriate clinical setting and with a CXR demonstrating mediastinal widening or other signs of mediastinal hemorrhage, thoracic aortography or helical chest CT is indicated
  • CTA is emerging as a very sensitive and specific examination for aortic injury and has replaced aortography in many trauma centers
Useful Points
  • Mediastinal widening has been defined as a transverse diameter of 8 cm from the left side of aortic arch to the right margin of the mediastinum (even on AP portable CXR)
  • Mediastinal widening is 90% sensitive but 10% specific for aortic injury
  • Approx 7% of patients with aortic injury have normal initial CXR
  • If no mediastinal hematoma seen on CT, probability of significant aortic injury is very low
Demehri S, et al. ACR Appropriateness Criteria blunt chest trauma--suspected aortic injury. Emerg Radiol 2012 (published online: 18 Mar 2012)

May 1, 2012

Age-related White Matter Changes

MR FLAIR images show multiple FLAIR hyperintense foci in bilateral periventricular and deep white matter in a 77-year-old patient.

  • Several possible mechanisms but at present it is believed to be an incomplete ischemia mainly related to cerebral small vessel arteriolosclerosis
  • Pathology: partial loss of myelin, axons, oligodendroglial cells; mild reactive gliosis, astrocytic gliosis, stenosis of arterioles from hyaline fibrosis
  • Important substrates for cognitive impairment and functional loss in the elderly
  • Very common in elderly with hypertension, diabetes, hyperlipidemai
  • Ill-defined hypodensities on CT
  • T1 hypointensities, T2/PD/FLAIR hyperintensities. FLAIR best to demonstrate severity of disease
  • When the largest lesion is adjacent to ventricles, it's called periventricular white matter changes
  • On diffusion tensor MRI, there is elevation of diffusivity and reduced fractional anisotrophy (FA) meaning impaired white matter integrity

Xiong YY, Mok V. Age-related white matter changes. J Aging Res 2011