July 21, 2014

Fatty Liver

Axial "in-phase" MR image shows increased signal intensity of the liver.
Axial "opposed-phase" MR image shows decreased signal of the entire liver when compared with the same areas on in-phase image. 
Facts

  • Triglyceride accumulation within cytoplasm of hepatocytes
  • Can be due to alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, drugs
  • May progress to steatohepatitis and cirrhosis
  • Avoid the use of "fatty infiltration of the liver", which is misleading because fat deposition in Fatty Liver is in hepatocytes - rarely in other cell types
  • Sensitivity/specificity for detection:
    • Ultrasound = 60-100% / 77-95%
    • Non-contrast CT = 43-95% / 90%
    • Chemical-shift MRI = 81% / 100%

MR Imaging

  • Because protons in water and fatty acid molecules precess in different resonance frequency, proton chemical shift imaging can be utilized to image this difference
  • If images are obtained when fat and water protons are "in-phase", their signals are additive (brighter). If they are "out-of-phase", their signals cancel each other (structure becoming darker)
  • Amount of hepatic fat can be quantified by assessing the degree of signal loss
Reference
Hamer OW, Aguirre DA, Casola G, et al. Fatty liver: imaging patterns and pitfalls. Radiographics 2006; 26:1637-1653.

July 11, 2014

Focal Urinary Bladder Wall Thickening


Axial and sagittal-reformatted CT images show focal thickening of the posterior wall of the urinary bladder (arrows) with increased enhancement relative to normal bladder wall. 

Differential Diagnosis

  • Tumor (benign, malignant, metastasis)
  • Adherent clot
  • Infection/inflammation (TB, cystitis cystica/glandularis, malakoplakia, schistosomiasis)
  • Trauma (mural hematoma)
  • Extravesical pathologies (spread of extravesical inflammation or tumor, endometriosis)
Facts
  • Transitional cell carcinoma accounts for most focal bladder masses
  • Most of the time it is impossible to distinguish tumor from other causes of focal wall abnormality and cystoscopy is necessary
Our case: Transitional cell carcinoma in a 73-year-old female

Reference

Patel U. Imaging And Urodynamics Of The Lower Urinary Tract. Springer 2010.
Bhargava. Ultrasound Differential Diagnosis. Jaypee Brothers Publishers, 2005.

July 1, 2014

Krukenberg Tumors


Axial and coronal-reformatted CT images of a 41-year-old woman shows an enlarged, solid-appearing right ovarian mass (arrows). The left ovary (not shown) is normal. 

Facts:
  • Metastatic tumor to the ovary that contains mucin-secreting, signet ring cells
  • Usually originate from primary tumors of GI tract (most common = colon and stomach)
  • 10% of all ovarian tumors
  • Occur in reproductive age
Imaging:
  • Nonspecific appearance. Can be solid or mixed solid/cystic
  • High suspicion for ovarian metastasis if:
    • Bilateral 
    • Complex-appearing ovarian masses
    • Known GI tract tumor (esp. colon and stomach)
    • MRI showing T1/T2 hyper intensity due to mucin
Our case: Ovarian metastasis from primary gastric cancer.

Reference:
Jung SE, et al. CT and MR imaging of ovarian tumors with emphasis on differential diagnosis. Radiographics 2002; 22:1305.

June 13, 2014

Slideshow: Imaging of Facial Trauma

June 9, 2014

Slideshow: Imaging of Non-traumatic Intracranial Hemorrhages


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