February 28, 2009

Creutzfeldt-Jakob Disease on DWI MRI

Fig 1&2: Axial DWI MRI images of a 68-year-old man who presented with rapidly progressive dementia showed high signal intensity in the regions of cerebral cortex of the frontal and temporal lobes (arrowheads) and deep nuclei of basal ganglia (arrows). More subtle changes are also noted in the thalami. Findings are consistent with Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob Disease (CJD)

  • Progressive, fatal spongioform encephalopathy
  • Transmissable disease
  • Clinical: rapidly progressive dementia (<2>
  • Distribution of abnormality: usually symmetric, deep gray nuclei (caudate head, putamen, thalamus), cerebral cortex
  • Characters: high signal on T2 and FLAIR, restricted diffusion on DWI
  • DWI may be the most sensitive imaging method for the early clinical diagnosis of CJD
Shiga Y, et al. Diffusion-weighted MRI abnormalities as an early diagnostic marker for Creutzfeldt-Jakob disease. Neurology 2004;63:443-449.

February 25, 2009

Torus (Buckle) Fracture

Fig: Forearm radiograph shows a fracture as bulged cortex at the distal end of the radius. This is a classic torus (buckle) fracture.


  • Axial loading on extremity with/without other forces (i.e. varus, valgus, hyperextension or hyperflexion)
  • Failure of cortex on the compression side, resulting in fracture
  • Torus (buckle) fracture of distal radius and ulna is most common fracture in lower forearm of young children
  • Two appearances: 1) classic buckle fracture -- cortex bulges outward, 2) angled buckle fracture -- cortex angles inward (the second type is more difficult to appreciate)
Jadhav SP, Swischuk LE. Commonly missed subtle skeletal injuries in children: a pictorial review. Emerg Radiol 2008 (November)

February 22, 2009

Biological Effects of Radiation Used in Imaging (3): Risks

Excess Risks of Mortality from Solid Cancer in Human
  • Dose >100 mSv
  • Dose 50-100 mSv
  • Dose 10-50 mSv (i.e. to lung or breast in retrospective-ECG-gated cardiac CT, pediatric abdominal CT)
  • Unclear risk if dose <10>
Natural effective dose of radiation received by general population = 3-4 mSv per year

Radiation risks
  • Negligible (<0.1>
  • Extremely low (0.1 - 1 mSv) - abdomen radiograph, lumbar spine radiograph
  • Very low (1-10 mSv) - head CT, chest CT, abdomen CT (adult)
  • Low (10-100 mSv) - multiphase CT
  • Moderate (>100 mSv) - interventional procedures, repeat CT
Verdun FR. Radiation risk: what you should know to tell your patients. Radiographics 2008 (September).

February 19, 2009


Fig 1: Axial MR image (T2) of a 57-year-old man presenting with headache shows a large T2 hyperintense mass in the left cerebellar hemisphere. The mass compresses the adjacent fourth ventricle.
Fig 2: Sagittal MR image (T1 with gadolinium) shows a focus of nodular enhancement at the wall of the mass, which is predominantly T1 hypointense. There is hydrocephalus.


  • Rare, benign neoplasm of endothelial origin
  • Most are sporadic. Between 4 and 20% of patients with hemangioblastomas of the cerebellum or spinal cord have von Hippel-Lindau disease.
  • Usually in cerebellum (hemisphere > vermis > medulla near area postrema)
  • Most often have a firm mural nodule (near pial surface) associated with a glial-lined cyst. The cyst contains clear yellow fluid but hemorrhage can occur innto the cyst.

Imaging Appearance:
  • Peripherally located cerebellar mass with central cystic region with peripheral enhancing nodule.
  • Cystic portion of the hemangioma may be brighter than that of cerebral spinal fluid.
  • In some cases, hemangioblastomas can be solid, mixed solid/cystic.

Lee SR, Sanches J, Mark AS, et al. Posterior fossa hemangioblastomas: MR imaging. Radiology 1989; 171:463-468.

February 16, 2009

Subendocardial Fat in Myocardial Infarction

Fig: Axial contrast-enhanced CT image shows a curvilinear low attenuation in the subendocardial portion of the left anterior descending (LAD) coronary artery territory of the left ventricle. The patient had a history of remote myocardial infarction (MI).

Myocardial Fat

  • Common entity, found histologically in 68% of ischemic heart disease patients and 84% of patients with history of MI.
  • May result from inability of ischemic myocytes to metabolize fatty acids.
  • Can be shown on cardiac MRI and CT.
  • In one study, it was detected in 22% of cases and it was most commonly seen in LAD territory.

What does it mean?
  • It is associated with greater infarct age
  • Patients with myocardial fat had more severe regional wall motion abnormalities on echocardiography
Ahn SS, et al. CT detection of subendocardial fat in myocardial infarction. AJR 2009;192:532-537.

February 13, 2009

Mallet Finger

An oblique radiograph of the index finger of a young man who sustained trauma to the hand shows a flexion deformity of the distal interphalangeal (DIP) joint (outlined with yellow line).

Diagnosis: Mallet Finger

  • It is a deformity caused by loss of extensor-tendon continuity to the DIP joint.
  • It is a misnomer - mallet = a hammer with a large wooden head, which does not look like this type of deformity.
  • There are many causes of mallet finger: the common one is laceration of extensor tendon but it may not leave a residual deformity. Other causes are intra-articular fracture of distal phalanx, tendon rupture or avulsion. Therefore, it may or may not be associated with a fracture
Stark HH, et al. Mallet finger. J Bone J Surg 1962;44:1061-1068.

February 10, 2009

Suspected Acute Appendicitis (5) - US Techniques

Ultrasound in patients with acute abdomen requires a 'graded compression' technique

Why Graded Compression Technique Required?

  • To displace fat and bowel away from transducer (so there is less distance from transducer to organ of interest, i.e. appendix)
  • To test reaction of that structure to compression
How to Perform Graded Compression?
  • Use a linear, high-frequency transducer
  • Use thin liquid ultrasound gel
  • Slow and gentle compression (similar to palpation)
  • Perform to the entire abdomen"mowing the lawn" to screen for bowel pathology "pathologic bowel usually readily stands out"
How Good Is It?
  • To confirm appendicitis (as high as 90%) (Ref #1)
  • To exclude appendicitis by 1) visualization of normal appendix (50%), 2) demonstration of an alternative condition (20%) (Ref #1)
  • To alter clinical management (decision to operate change from no to yes, and vice versa) in 28%-32% (Ref #2)

1. Puylaert J. Ultrasonography of the acute abdomen: gastrointestinal conditions. Radiol Clin N Am 2003;41:1227.
2. Gracey D, McClure M. The impact of ultrasound in suspected acute appendicitis. Clin Radiol 2007;62:573.

Related Posts:

Suspected acute appendicitis (1)
Suspected acute appendicitis (2)
Suspected acute appendicitis (3) - when and why doing imaging studies?
Suspected acute appendicitis (4) - CT techniques

February 7, 2009

Thickened Gallbladder Wall

Fig. 1: Transverse ultrasound image of the gallbladder in a 79-year-old afebrile woman with RUQ pain. There is diffuse gallbladder wall thickening (6 mm) and a hyperechoic material (arrow) in the gallbladder lumen. The gallbladder is distended.
Fig. 2: Longitudinal US image shows acoustic shadowing casted from hyperechoic material, representing a gallstone.

Differential Diagnosis of Thickened Gallbladder Wall

  1. Gallbladder disease - cholecystitis (acute or chronic)
  2. Liver disease - hepatitis, cirrhosis
  3. Diffuse disease - hypoalbuminemia, heart failure, renal failure
Our case was a surgically proven acute calculous cholecystitis.

Chapman S and Nakielny R. Aid to radiological differential diagnosis. 4th ed.

February 6, 2009

Annual Meeting of the Royal College of Radiologists of Thailand

Key Speakers:

  • Robert Novelline, MD (Massachusetts General Hospital and Harvard Medical School)
  • Theresa McLoud, MD (Massachusetts General Hospital and Harvard Medical School)
  • Chusilp Charnsangavej, MD (MD Anderson Cancer Center)
More Information HERE

February 4, 2009

Evolution of Pulmonary Laceration

Fig. 1: Axial CT image of a trauma patient shows a pulmonary laceration (arrow) surrounded by contusion (arrowheads) in the superior segment of the left lower lobe near the paravertebral region.

Fig. 2: Follow-up chest CT at 11 days after trauma, at the same level as in Fig. 1, reveals a complete resolution of pulmonary contusion (absence of ground glass opacity), and interval evolution of a laceration (hematopneumatocele) into a hematoma (arrow).


  • Evolution: laceration --> hematoma --> complete resolution
  • Most lacerations/hematomas disappear within weeks or months.
  • Pulmonary hematoma has a similar appearance to other lung nodule, therefore can be mistaken as malignancy. A history of recent trauma, previous CT for comparison, and close follow up CT is helpful.
Kaewlai et al. MDCT of thoracic trauma. RadioGraphics 2008 (October)

February 1, 2009

FDG-PET and Solitary Pulmonary Nodule Assessment (1)

Fig. 1: Axial CT image of a 70-year-old woman shows a well-defined, lobulated nodule in the left upper lobe.
Fig. 2: Axial FDG-PET image at the corresponding level to CT shows increased uptake of the nodule (relative to normal mediastinal uptake). The nodule was found to be adenocarcinoma.


  • PET has sensitivity of 97% and specificity of 78% for the diagnosis of malignant solitary pulmonary nodule (this conclusion was drawn from a meta-analysis of nodules of any size but predominantly >1 cm)
  • Pulmonary nodules negative on PET most likely benign, but further evaluation should be based on CT appearance (likelihood of cancer such as bronchioloalveolar carcinoma, carcinoid that are usually negative on PET) and clinical scenario.
  • Dual time point PET (scan at 70 and 120 minutes after FDG injection) increases sensitivity, specificity and accuracy of PET for the detection of malignant nodule.
  • Ability of PET to detect malignant nodule depends on the size of lesion and degree of uptake. Small lesions with high uptake may be shown on PET.
1. Gilman MD, Aquino S. State-of-the-art FDG-PET imaging of lung cancer. Sem Roentgenol 2005;40:144.
2. Gould MK, et al. Accuracy of positron emission tomography for diagnosis of pulmonary nodules and mass lesions. JAMA 2001;285:914.