February 25, 2011

Swirl Sign

An axial CT image of the brain in a trauma patient shows a hyperdense epidural hematoma (arrowheads) with a small rounded area of low attenuation (arrow) internally.

Facts: The Swirl Sign
  • An area of low attenuation within the extra-axial hematoma, usually in epidural hematoma, seen on nonenhanced CT scan
  • Represents an actively extravasating unclotted blood
  • The area is surrounded by clotted blood (50-70 Hounsfield Units). Clotted blood is hyperdense on CT because of protein component of hemoglobin

Al-Nakshabandi NA. The swirl sign. Radiology 2001; 218:433.

February 20, 2011

Pulmonary Embolism Caused by Acrylic Cement

An axial CT image shows hyperdense structures within the segmental branch of the right middle lobe pulmonary artery (arrow), and in the perivertebral venous plexus (arrowheads). The patient had recent vertebroplasty performed for lumbar back pain.

Facts: Vertebroplasty
  • Injection of acrylic cement (polymethylmethacrylate; PMMA) into the diseased vertebral body for partial remodeling and lumbar pain relief
  • Infrequent complications such as infection, cement leakage
Facts: Leakage from Vertebroplasty
  • Can be into the spinal canal, or perivertebral venous plexuses
  • Perivertebral venous leakage can be into the internal venous plexuses (potentially resulting in cord/nerve root compression) or external venous plexuses
  • More often if inadequate preparation of PMMA (acrylic cement must be mixed to consistency of paste before injection to ensure advanced polymerization)
  • More often if vertebroplasty is performed for vascular lesions (metastasis from thyroid cancer, renal cell carcinoma, vertebral angiomas)
Imaging Findings
  • Hyperdense material in the branches of pulmonary arteries with or without evidence of pulmonary infarction
  • Hyperdense materials in the perivertebral veins


Padovani B, et al. Pulmonary embolism caused by acrylic cement: a rare complication of percutaneous vertebroplasty. AJNR 1999; 20:375-377.

February 15, 2011

ACR-Proposed Premedication Regimen to Reduce Contrast Reactions

According to the version #7 (2010) ACR Manual on Contrast Media, the following regimens are recommended for premedication of patients at risk for developing contrast reaction.

Elective Premedication
  1. Prednisolone: 50 mg PO at 13 hours, 7 hours and 1 hour before contrast media injection, PLUS Diphenhydramine 50 mg IV, IM or PO 1 hour before contrast medium OR
  2. Methylprednisolone 32 mg PO 12 hours and 2 hours before contrast media injection. An anti-histamine (as in option 1) can be added. If unable to take oral medication, use hydrocortisone 200 mg IV instead
Emergency Premedication
  1. Methylprednisolone 40 mg or hydrocortisone 200 mg IV every 4 hours until contrast study required PLUS Diphenhydramine 50 mg IV 1 hour prior to contrast injection OR
  2. Dexamethasone 7.5 mg or betamethasone 6 mg IV every 4 hours until contrast study PLUS diphenhydramine 50 mg IV 1 hour prior to contrast injection OR
  3. Omit steroid entirely and give diphenhydramine 50 mg IV
"IV steroids have not been shown to be effective when administered less than 4 to 6 hours prior to contrast injection."

ACR Manual on Contrast Media (7th version, 2010)

February 12, 2011

Small Bowel Ischemia

An axial CT image shows a segment of decreased enhancement of the small bowel wall (arrows) as compared to the more normally enhancing loops (arrowheads).

Diminished Enhancement of Small Bowel Wall
  • Better to appreciate when the bowel is filled with neutral contrast agent
  • Pathognomonic for intestinal ischemia in a correct clinical setting
  • To detect, it is important to compare the loops that show decreased enhancement with the more normally enhancing loops
Causes of Small Bowel Ischemia
  • Strangulation
  • Low-flow states (arrhythemia, sepsis, shock)
  • Embolus or thrombosis of superior mesenteric artery (SMA)
  • Superior mesenteric vein (SMV) thrombosis
Our case: small bowel ischemia due to strangulated obstruction.

Macari et al. A pattern approach to abnormal small bowel: observation at MDCT and CT enterography. AJR 2007; 188:1344-1355.

February 9, 2011

MDCT of Active Extravasation

An axial CT image shows a laceration of the spleen (arrowhead), hemoperitoneum and localized area of high attenuation (arrow) in the perisplenic space, which had faced away on subsequent delayed images indicating active extravasation.

  • Area of hyperattenuation (mostly greater than 100 HU) within a hematoma on initial images that fades into an enlarged, enhanced hematoma on delayed images
  • Active extravasation is an uncommon but important finding in trauma patients
  • Indicates significant bleeding that may require surgical or endovascular treatment
Differential Diagnosis of High-Attenuation Area Within a Hematoma in Trauma Patients
  • Active extravasation
  • Pseudoaneurysm: adjacent to a vessel, no enlargement or increased attenuation on delayed images
  • Bone fragment: no change on delayed images
  • Foreign body
Hamilton JD, Kumaravel M, Censullo ML, et al. Multidetector CT evaluation of active extravasation in blunt abdominal and pelvic trauma patients. Radiographics 2008; 28:1603-1616.

February 3, 2011

Rolando Fracture

PA radiograph of the thumb demonstrates an intra-articular fracture of the base of the metacarpal with mild displacement.

Facts: Rolando Fracture
  • Originally described by Dr. Rolando as Y-shaped intraarticular fracture that extends to the carpometacarpal joint surface
  • Now, the eponym is widely used for any comminuted intraarticular fracture at the base of the thumb
  • Secondary to axial loading crusing the articular surface of the first metacarpal
  • Usually require operative reduction because of high association with post-traumatic arthritis if incongruity present at the articular surface
Peterson JJ, Bancroft LW. Injuries of the fingers and thumb in the athlete. Clin Sports Med 2006; 25:527-542.