ACR Appropriateness Criteria for Suspected Aortic Injury

Axial contrast-enhanced CT image shows a pseudoaneurysm (arrow), intimal flap and periaortic hematoma of the proximal descending thoracic aorta in a patient experienced severe blunt chest trauma.

A newly revised American College of Radiology (ACR)'s Appropriateness Criteria for blunt chest trauma - suspected aortic injury has been published in March 2012 in the journal Emergency Radiology, summary and useful points are provided below

• Chest x-ray remains an initial screening examination in patients who has sustained blunt chest trauma
• In the appropriate clinical setting and with a CXR demonstrating mediastinal widening or other signs of mediastinal hemorrhage, thoracic aortography or helical chest CT is indicated
• CTA is emerging as a very sensitive and specific examination for aortic injury and has replaced aortography in many trauma centers

Useful Points

• Mediastinal widening has been defined as a transverse diameter of 8 cm from the left side of aortic arch to the right margin of the mediastinum (even on AP portable CXR)
• Mediastinal widening is 90% sensitive but 10% specific for aortic injury
• Approx 7% of patients with aortic injury have normal initial CXR
• If no mediastinal hematoma seen on CT, probability of significant aortic injury is very low

Reference

Demehri S, et al. ACR Appropriateness Criteria blunt chest trauma--suspected aortic injury. Emerg Radiol 2012 (published online: 18 Mar 2012)

Age-related White Matter Changes

MR FLAIR images show multiple FLAIR hyperintense foci in bilateral periventricular and deep white matter in a 77-year-old patient.

Facts:

• Several possible mechanisms but at present it is believed to be an incomplete ischemia mainly related to cerebral small vessel arteriolosclerosis
• Pathology: partial loss of myelin, axons, oligodendroglial cells; mild reactive gliosis, astrocytic gliosis, stenosis of arterioles from hyaline fibrosis
• Important substrates for cognitive impairment and functional loss in the elderly
• Very common in elderly with hypertension, diabetes, hyperlipidemai

Imaging

• Ill-defined hypodensities on CT
• T1 hypointensities, T2/PD/FLAIR hyperintensities. FLAIR best to demonstrate severity of disease
• When the largest lesion is adjacent to ventricles, it's called periventricular white matter changes
• On diffusion tensor MRI, there is elevation of diffusivity and reduced fractional anisotrophy (FA) meaning impaired white matter integrity

Reference:
Xiong YY, Mok V. Age-related white matter changes. J Aging Res 2011

Sternal Foramen

Axial, sagittal-reformatted and 3D CT images of the sternum shows a small round defect in the lower third of the sternum (arrows)

Facts: Sternal Foramen

• Small round/oval defect in the lower third of the sternum
• Incomplete fusion of multiple ossification centers
• Usually asymptomatic and of no clinical significance
• Prevalence 6.7% in autopsy population

Imaging

• Mostly incidentally found on chest CT
• Usually solitary
• Mostly in the body of the sternum. Rare in the manubrium

Reference:

Yekeler E, et al. Frequency of sternal variations and anomalies evaluated by MDCT. AJR 2006;186:956-960

Osteoid Osteoma

A frontal view of the right femur of a teenage boy demonstrates an ill-defined sclerotic area (arrows) in the proximal diaphysis with thickened cortex.

A coronal-reformatted CT image shows a well-defined lucency (arrow) within the central portion of sclerotic medulla. Within that lucency, a tiny calcific nidus is seen. Thickened cortex is also observed.

Facts: Osteoid Osteoma

• Self-limited benign osteogenic tumor consisting of a vascular mass (nidus) surrounded by reactive bone sclerosis
• Male predominance (male:female = 2:1). Teenagers and young adults (90% of cases between 5-30 years old)
• Characteristic pain referring to the nearest joint, worse at night. Pain is relieved by aspirin or NSAIDs
• Treatment options: surgical excision, CT-guided percutaneous resection or destruction of the nidus

Imaging Appearance

• Location: cortex, medulla or periosteum (anywhere but cortex most common)
• Long bones of lower extremity (esp femoral neck) most commonly affected. Almost never seen in flat bones and craniofacial bones
• Central lucent area (nidus) surrounded by sclerotic bone (nidus may be subtle and has variable degree of calcification)
• CT is helpful to identify the nidus (as in our case)
• MRI can be misleading because reactive bone marrow edema and soft tissue involvement may mimic malignancy

Our case: osteoid osteoma centered in the medullary cavity. The diagnosis was confirmed by CT (showing a lucent nidus with calcification) and clinical picture.

Reference:

Kadir S. Teaching Atlas of Interventional Radiology, 2005.

Vioria VJ, et al. Orthopaedic Pathology,

Cesarean Section Scar Diverticulum

A sagittal US scan of the uterus shows a cystic lesion in the anterior wall of the lower uterine segment. The patient reported prior cesarean section

Facts:

• Defect within the lower uterine cavity in patients with history of cesarean section in expected location of a hysterectomy incision
• Based on a study utilizing hysterosalpingograms, 60% of women with prior C-section had this anatomic defect
• Knowledge of this anatomic defect avoids misdiagnosing it as other pathology
• Often benign clinical significance. Some reports of ectopic scar pregnancy and abnormal uterine bleeding associated with this pathology

Imaging Appearance

• Focal outpouching (most common feature) and thin linear defect
• Location: lower uterine segment (most common) > uterine isthmus, upper endocervical canal

Imaging Mimics

• Prominent cervical glands (tubular, symmetric structure from both walls of endocervical canal)
• Postmyomectomy diverticula (unilateral, from site of resection, correlated with surgical history and location of diverticula)
• Gartner's duct cyst (long, tubular structure parallel to uterine cavity)
• Adenomyosis (location of defect anywhere along uterine cavity)

Reference

Surapaneni K, Silberzweig JE. Cesarean section scar diverticulum: appearance on hysterosalpingography. AJR 2008;190:870-4