Lingual Thyroid

Fig: Arrows point to the ectopic thyroid tissue at the tongue base, above the epiglottis (arrowhead) on this sagittal-reformatted CT image.

Facts

• Thyroid tissue at the tongue base
  
• Most common location for ectopic thyroid
• Only site of active functioning thyroid tissue in 70% of cases
• Uncommon clinical problem but seen in approximately 10% of autopsy cases
• Become symptomatic at any age but usually during puberty, menses or pregnancy (increased metabolic demand)
• Malignant transformation very rare, incidence less than 1%. Suspected when a known patient with lingual thyroid develops new symptoms or clinical evidence of enlargement
  

CT Findings

• Characteristic location = in midline, at the tongue base (other types of ectopic thyroid can be anywhere from tongue base to anterior to the heart)
• Characteristic attenuation and enhancement = similar to thyroid tissue (very enhanced, may contain calcifications or low attenuation areas)
• Absent thyroid tissue in the expected normal location
  

Reference:
Kennedy TL, et al. Lingual thyroid carcinoma with nodal metastasis. Laryngoscope 2007 (November)

Pulmonary Laceration

Fig. Axial CT image shows a 'hole' in the lung with air-fluid level (arrow), surrounded by ground glass opacity (arrowheads) in a trauma patient. Findings represent pulmonary laceration surrounded by contusion.

Facts

• Laceration in the lung tissue results in a 'hole' instead of a linear tear because of elastic recoil of the lungs stretching the tear.
• Most lacerations in an acute phase contain blood and air (hematopneumatocele).
• Most lacerations are surrounded by contusion.
• Four types of lung laceration include compression rupture (central location), compression shear (paravertebral), rib penetration tear (near rib fracture) and tear associated with underlying lung fibrosis.
• Most common type of pulmonary laceration is a compression rupture tear.
  

This patient had a compression-shear pulmonary laceration.

Reference:
Kaewlai et al. MDCT of blunt thoracic trauma. RadioGraphics 2008 (October)

Tsunami Sinusitis

Fig.1: Water's view of the skull shows air-fluid levels (arrows) in bilateral maxillary sinuses in a victim of tsunami trauma.
Fig.2: Direct coronal CT image performed 1 month after Fig.1 shows resolution of left maxillary sinusitis but persistent right sided sinusitis. There is a conglomerate mass of high attenuation (arrowheads) with air in the right maxillary sinus.

Facts

• Sinusitis may occur in patients with tsunami trauma
• Found in 10% of all cases in one series
  
• Usually polymicrobial
• Sand may be present in the sinus, which is hyperattenuating on CT (likely related to sand composition) and located in the dependent portion of the sinuses. Sand and seawater may enter sinuses through ostia and retain within.

Today, 4 years ago, was the day of one of the world's worst natural disasters -- tsunami. More than 200 000 people were killed and missing. More than a million people were displaced.

Reference:
1. Kaewlai, et al. Radiologic findings in tsunami trauma: experience with 225 patients injured in the 2004 tsunami. Emerg Radiol 2007;14:395
2. Limchawalit, et al. Images in clinical medicine. Tsunami sinusitis. N Engl J Med 2005

Imaging of Facial Trauma Part 3

Imaging Of Facial Trauma Part 3

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Distal Intestinal Obstruction Syndrome (DIOS)

Fig.1: Axial CT without IV contrast shows absence of pancreas (star), which is a feature of cystic fibrosis. The colon (arrow) is filled with fecal materials.
Fig.2: CT image at the lower cut reveals 'fecalization' of small bowel, and collapsed descending colon. This patient has known cystic fibrosis status post recent lung transplantation. He developed intermittent abdominal distension and diarrhea. He did not have peritoneal irritation sign on physical exam.

Facts

• DIOS is short for 'distal intestinal obstruction syndrome'. Also known as meconium ileus equivalent (MIE)
  
• Unique to cystic fibrosis (CF)
  
• 10% - 15% of patients with CF
  
• Caused by accumulation of mucous and feces in small bowel and ascending colon
• Common in older child or young adult
• Predisposing factors: after transplantation (probably due to dehydration and medications), dehydration, pancreatic enzyme supplement cessation, unknown
  

Radiographic Features

• Fecal materials in terminal ileum, cecum and ascending colon
• Thickened mucosal fold of bowel
  

Reference:
1. Moody AR, et al. CT monitoring of therapy for meconium ileus. J Comput Assist Tomogr 1990 (November/December)
2. Agrons GA, et al. Gastrointestinal manifestations of cystic fibrosis: radiologic-pathologic correlation. Radiographics 1996 (July)

Hounsfield Unit

What is Hounsfield Unit?

• CT number
• Unit used to measure attenuation of tissue on CT
• A representative of relative attenuation coefficient of tissues, using water as a reference
  
• Water is defined as zero Hounsfield unit
• Matters with higher physical density (g/cm3), higher electron density (e/cm3) than water will have higher HU; and vice versa
• HU depends on kV peak (used in CT image acquisition) and filtration technique (used in CT image reconstruction)
• HU values on an image are only approximate (because it will change if kV changes)
  

Who is Hounsfield?

• Godfrey Hounsfield is a British electrical engineer
• He shared a 1979 Nobel Prize in physiology or medicine with Allan Cormack for the development of computed tomography (CT)

Reference:
Huda W, et al. Review of radiology physics. 2003
www.wikipedia.com

ARRS 2008 Registration Opens

Registration for the annual meeting of the American Roentgen Ray Society (ARRS) opens today (December 15, 2008)!
Information

A brief history of the ARRS as quoted on its website:
"The American Roentgen Ray Society, founded in 1900, is the first and oldest radiology society in the United States. The society has been a forum for progress in radiology since shortly after the discovery of the X-ray and is dedicated to the goal of the advancement of medicine through the science of radiology and its allied sciences. The goal of the ARRS is maintained through an annual scientific and educational meeting and through publication of the American Journal of Roentgenology."

Meniscal Bucket-Handle Tear

Fig: Coronal T2 image (with fat suppression) shows a displaced fragment (arrow) of medial meniscus into the intercondylar notch of the knee. Note intact ACL (arrowheads).

What is 'Bucket-Handle' Tear?

• Longitudinal, peripheral tear of the meniscus with displacement of fragment toward the intercondylar notch of the knee
• Leads to locked knee and surgery (debridement or repair) is necessary
• If occurs at the outer 1/3 (white/white zone), only debridement; if middle and peripheral third (white/red, red/red zones) require repair
  

How to Diagnose?

• Using MRI with coronal and sagittal planes
• Look for extra-structure in the intercondylar notch on coronal image!
• Double PCL (posterior cruciate ligament) on sagittal image
  
• Donor meniscus (usually medial) look smaller than usual (key to differentiate bucket-handle tear from normal oblique intermeniscal ligament)

Reference:
Stoller DW, et al. Diagnostic imaging: orthopedics. 2004

Crazy-Paving Pattern

Fig. Axial CT of the chest shows diffuse bilateral ground-glass opacities superimposed by interlobular septal thickening (arrowheads) and intralobular lines (blue arrows). Note a left chest tube used to treat left pneumothorax, which brought this patient to the hospital.

What is "Crazy-Paving" Pattern?

• Ground-glass opacity superimposed with interlobular septal thickening and intralobular lines
  
• Can be scattered or diffuse
  
• Can be caused by alveolar filling process, interstitial process, or a combination

What Can Cause "Crazy-Paving" Pattern?

• CLASSIC: Pulmonary alveolar proteinosis 
  
• COMMON: Pneumocystis jirovecii pneumonia (PCP), pulmonary edema (ARDS), pulmonary hemorrhage
  
• NOT COMMON: Bronchioloalveolar carcinoma, alveolar sarcoidosis, nonspecific interstitial pneumonitis (NSIP), Cryptogenic organizing pneumonia (COP), lipoid pneumonia
  

Our case is a patient with biopsy proven pulmonary alveolar proteinosis.

Reference:

1. Rossi SE, et al. "Crazy-Paving" Pattern at Thin-Section CT of the Lungs: Radiologic-Pathologic Overview. Radiographics 2003;23:1509.

2. Johkoh T, et al. Crazy-paving Appearance at Thin-Section CT: Spectrum of Disease and Pathologic Findings. Radiology 1999;211:155.

Who is Aunt Minnie?

Beside 'Aunt Minnie' as a popular radiology website, do you know who really is Aunt Minnie?

A few communications in Radiology and AJR provided the answer.

Aunt Minnie

• Constellation of observations virtually pathognomonic of an entity (usually of an unusual or unexpected disease)
• Subliminal or subconscious pattern recognition of disease (similar to recognizing Aunt Minnie among a large group of similar women)
• The term attributed to two figures in radiology history: Ed Neuhauser (previous Chief at Children Hospital Boston) and Ben Felson (neither had an aunt named Minnie)

Reference:
Hall, et al. Gestalt: Radiology's Aunt Minnie. AJR 2008 (October)

Image source: www.auntminnie.com

Traumatic Aortic Injury (TAI)

Fig.1: Portable chest radiograph shows widening of the superior mediastinum (two-sided arrow), deviation of the NG tube (arrowheads) and trachea to the right.
Fig.2: Axial CT with IV contrast shows a large periaortic hematoma (stars) displacing the NG tube (arrowhead) to the right.
Fig.3: Axial CT at the level below the arch demonstrates a pseudoaneurysm (red arrow) anterior to the true lumen (red arrowhead). Hematoma (stars) and NG tube (yellow arrowhead)

Radiographic Findings

• Widening of superior mediastinum (subjective 'eyeball' estimation)
• Blurring of aortic contour
• Deviation of nasogastric tube to the right
• Normal - not common but x-ray can be normal if there is no or minimal periaortic hematoma (Normal chest radiograph does not exclude TAI in a trauma patient with suspicious mechanism)
  

CT Findings

• Direct signs: Pseudoaneurysm, intimal flap, irregularity of aortic wall, pseudocoarctation, thrombus with in the wall
• Indirect sign: Periaortic hematoma (not isolated anterior mediastinal hematoma)

Do We Need Aortography?

• Studies of MDCT (16- and 64-MDCT) showed accuracy of near 100% using surgery or follow-up CT as standard references
• When a direct sign is present, TAI can be diagnosed confidently without aortography
• Aortography can be reserved for equivocal cases, evaluation of aortic branch vessels and endovascular therapy
  

Reference:
1. Kaewlai, et al. MDCT of blunt thoracic trauma. Radiographics 2008 (October)
2. Steenburg, et al. Acute traumatic thoracic aortic injuries: experience with 64-MDCT. AJR 2008 (November)

Chest Wall Fat Mimicking Tumor

Fig.1: Chest radiograph shows abnormal opacity in the periphery of the right upper lobe, which is broad-based to the pleura and partially well defined on the side opposing the lung. Based on this appearance, pleural location is likely. Differential diagnosis is broad and may include pleural effusion (loculated), thickening, plaque, or mass.
Fig.2: Axial CT shows an extrapleural fat (arrowheads) deep to the costal margin.

Facts

• Extrapleural costal fat can be mistaken for pleural lesions including plaque and tumor
• Thickening of the extrapleural costal fat can be associated with lung scarring
• CT is an easy tool to use differentiate between fat and soft tissue mass
• Fat can be drawn into fissures (as seen on Fig.1). It looks as if it is in the pleural space, but it is covered by parietal pleura - therefore is extrapleural
  

Reference:
Fisher ER, et al. Extrapleural fat collections: pseudotumors and other confusing manifestations. AJR 1993 (July)