Archive | September 2012

QUIZ: Unwell neonate. What is this sign called? And why are we…

QUIZ: Unwell neonate. What is this sign called? And why are we asking today of all days? Click for ANSWER

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Football sign – of massive pneumoperitoneum on a supine…

Football sign – of massive pneumoperitoneum on a supine abdominal radiograph. Normally the margins of the abdominal cavity are only faintly visible due to the density difference between intraperitoneal fat and the abdominal wall. However in the setting of pneumoperitoneum, air makes the outline of the distended abdominal cavity extremely distinct and somewhat football-shaped. Sometimes the falciform ligament is outlined centrally like the football’s seam. The sign is most frequently seen in infants with advanced necrotising enterocolitis (as was the case above) but may be seen with any cause of free gas. 

Update: Aussie rules football Grand Final 29 September 2012. GO HAWKS!

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Absent bow tie sign – a sagittal MRI knee sign of a displaced…

Absent bow tie sign – a sagittal MRI knee sign of a displaced meniscal tear (often bucket handle type). Normally the second (or even third) image through a meniscus ressembles the appearance of a bow tie with the central portion thinning out towards the inner free edge (left image, third slice of meniscus). When a bow tie is not seen on the second image then the absent bow tie sign is positive (right image) and a search for a displaced meniscus should ensue – by looking for a fragment-in-notch sign or double PCL sign.   

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Subacute subdural haematoma – can be difficult to identify on…

Subacute subdural haematoma – can be difficult to identify on non-contrast CT as the blood is isodense to brain parenchyma (the same density). When the subdural haemorrhage is unilateral then midline shift will be the major clue as to its presence. The above case shows bilateral symmetric subdural haematomas with isodense blood peripherally (*) causing inward displacement of the grey-white matter junction (blue line). This is better appreciated following contrast administration as the cortex becomes more dense and cortical vessels are seen (red arrows). 

This is just 1 of 20 great cases from the new “CT Brain” pack available for in-app purchase via our FREE iPhone / iPad App – DOWNLOAD OUR APP HERE!

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QUIZ: Suddenly unconscious. What important diagnosis should be…

QUIZ: Suddenly unconscious. What important diagnosis should be suspected on this non-contrast CT brain? Click for ANSWER

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Unilateral hyperlucent hemithorax – when one side of the chest…

Unilateral hyperlucent hemithorax – when one side of the chest is more lucent (black) than the other on a frontal chest radiograph. There are many potential causes including a few tricky ones. Some important things to consider:

  • rotated patient – can create a dramatic density difference
  • chest wall soft-tissue differences – particularly mastectomy (left image)
  • pneumothorax – always important! (right image)
  • air-trapping – particularly inhaled foreign bodies (check valve effect)
  • reduced lung vascularity – eg. pulmonary embolism (Wetermark’s sign)
  • contralateral increased density – eg. pleural effusion on other side

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Codman triangle – a distinctive triangular form of periosteal…

Codman triangle – a distinctive triangular form of periosteal reaction seen when an aggressive bone lesion grows faster than new periosteum can be ossified. Only the periosteum at the very margin of the lesion has time to ossify creating a triangular lip of new bone. The most common causes of a Codman triangle include osteosarcomaEwing sarcoma and osteomyelitis. This patient had osteosarcoma which was further characterised with MRI.

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QUIZ: What name is often given to these T2 hyperintense brain…

QUIZ: What name is often given to these T2 hyperintense brain lesions? Diagnosis? Click for ANSWER

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Radiology request: “Fishing accident. Bait still…

Radiology request:

  • “Fishing accident. Bait still attached.” 

Radiology report:

  • “There is a barbed fish hook lodged within the right pinna (external ear). Prawn-shaped soft tissue density surrounds the hook with radiodense material faintly visible within the crustacean’s gastrointestinal tract (prawn poo).” 

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