July 31, 2011


Lateral radiograph of the neck shows a very large, well-defined calcification with layered appearance overlying the inferior aspect of the mandible.

Axial CT image confirms the location of the stone in the left submandibular gland. Dilated submandibular duct is also present (not shown).

  • Stone disease (sialolithiasis) is the most common disease of the salivary gland; male more common than female; very rare in children
  • Submandibular gland is the most common location of stones in the salivary gland (80% of all)
  • Stone disease is a common cause of acute and chronic salivary gland infections
  • Stones consist of mainly calcium phosphate
  • 20% of submandibular stones, and 40% of parotid stones are non-opaque
  • Occlusal radiographs useful in showing radiopaque stones
  • Sialography is useful in patients suspected of having non-opaque stones but it is contraindicated in acute infection
  • CT and ultrasound can show stones with high accuracy
  • Gland may be diffusely or focally enlarged with a stone in the duct
  1. Siddiqui SJ. Sialolithiasis: an unusually large submandibular salivary stone. Br Dent J 2002;193:89-91.
  2. Yousem DM, et al. Major salivary gland imaging. Radiology 2000;216:19-29.

July 21, 2011

Nephrogenic Systemic Fibrosis Disappeared After Restrictive Use of Gadolinium?

According to a large (50 000+) retrospective cohort of patients who underwent contrast-enhanced MR examinations at a single academic institution pre- and post-adoption of strict gadolinium guidelines:-
  • No new cases of nephrogenic systemic fibrosis (NSF) were diagnosed
  • During the pre-guidelines adoption and transitional period, the incidence of NSF was 3 cases per 10,000 contrast-enhanced MRI
  • After the adoption of guidelines, the incidence was 0 per all examinations
The Guidelines for Imaging Adult Patients
  • Based on renal disease severity
  • eGFR 60 or greater - GBCA can be administered as indicated
  • eGFR 30-59 - weight-based dose of GBCA (0.2 mL/kg) can be administered with maximal dose of 20 mL allowed within 24 hours
  • eGFR less than 30 - GBCA cannot be administered except in cases of medical necessity; informed consent required; nephrology consultation required; hemodialysis should be considered
  • Very rarely that any patients with eGFR less than 30 would get contrast-enhanced MR exams (36 in 52 954 exams; 0.07%)
eGFR = estimated glomerular filtration rate; GBCA = gadolinium-based contrast agent

Wang Y, Alkasab TK, Narin O, et al. Incidence of nephrogenic systemic fibrosis after adoption of restrictive gadolinium-based contrast agent guidelines. Radiology 2011; 260:105-111.

July 15, 2011

The Price of Being a Doctor

How one patient makes a doctor question his decision to be a physician, while another does the opposite? Follow the link to the Insights on Residency Training blog by the Journal Watch.

July 11, 2011

Predictors of Cervical Spine Fractures and Fracture Risk

Flow diagram (originally published by Blackmore CC, et al, Radiology 1999) demonstrating a prediction rule for determination of risk of cervical spine fracture in blunt trauma patients. Percentages indicate the risk of fracture for each group with 95% CIs. Area under the ROC curve = 0.87

  • Three common options exist to "clear" cervical spine in trauma patients: clinical evaluation, radiography or CT
  • Canadian C-spine Rule (CCR) or NEXUS criteria are generally used by emergency physicians and trauma surgeons to determine which patients require imaging clearance
  • Among patients who, based on CCR or NEXUS, need imaging clearance: an issue exists whether to choose x-ray vs. CT
  • In general, CT is preferred for patients with moderate or high likelihood of having C-spine injury given its higher accuracy, cost-effectiveness and ease of performance. However, C-spine CT has not been tested as cost-effective among patients with low likelihood of C-spine injury - practice has been different from one place to another
According to Blackmore CC, et al
  • We can stratify patients into groups of different fracture probabilities by using 4 predictors: severe head injury, high-energy cause, age and focal neurologic deficit
  • Definition of severe head injury = intracranial hematoma, brain contusion, skull fracture or unconsciousness
  • Definition of high-energy cause = high-speed MVC (greater than 30 mph), pedestrian struck by car
  • Definition of moderate-energy cause = low-speed MVC, MVC at unknown speed, bicycle accident, motorcycle accident or fall
  • Definition of focal deficit = those that could be in a spinal cord or spinal nerve distribution

Blackmore CC, Emerson SS, Mann FA, Koepsell TD. Cervical spine imaging in patients with trauma: determination of fracture risk to optimize use. Radiology 1999; 211:759-765.

July 6, 2011

Child Abuse

A frontal radiograph of the femur demonstrates classic metaphyseal lesions of the distal femur and proximal tibia medially (arrows)

  • The two most common injuries in child abuse = soft tissue injuries and fractures
  • Failure to recognize child abuse may result in the child's return to hostile environment, leading to repeated injuries and possible death
  • Highly specific fractures = rib, spinous process, and sternal fractures and classic metaphyseal lesions
  • High suspicion = multiple fractures of differing ages
The Skeletal Survey
  • To evaluate children less than 2 years old for signs of physical abuse
  • American College of Radiology (ACR) recommends a single frontal view of each region of the appendicular skeleton (arms, forearms, thighs, legs, hands and feet), frontal and lateral views of the axial skeleton (skull, C-spine, LS spine and thorax) and a frontal view of the pelvis <=== these are a minimum of 20 radiographs
  • In a recent report of 930 abused children, prevalence of fractures was 34%. Skeletal survey added value in 13% of cases in which new fractures were discovered only at skeletal survey but not on prior imaging. Most fractures occur in long bones, ribs and skull. Pelvis, spine, hands and feet were much less common to be fractured (only 1% of all cases, which also had other fractures diagnostic of abuse). The authors called for eliminating x-rays of the pelvis, spine, hands and feet from skeletal survey performed for suspected child abuse
Karmazyn B, Lewis ME, Jennings SG, et al. Prevalence of uncommon fractures on skeletal surveys performed to evaluate for suspected abuse in 930 children: should practice guidelines change? AJR 2011; 197:W159-W163.

July 1, 2011

Obstructing Ureteric Stone on Ultrasound

Figure 1: A gray-scale ultrasound image of the right kidney shows right hydronephrosis and hydropelvis.
Figure 2: The scan in the right pelvis demonstrates an echogenic focus (arrow) with posterior acoustic shadowing (arrowheads) at the site where the ureter abruptly changes its caliber.

  • Imaging in patients presenting with renal colic is performed to 1) confirm the suspected renal colic, 2) diagnose cause and level of obstruction, 3) detect or rule out complications of renal colic (obstruction, infection), 4) detect alternative diagnoses
  • Non-contrast CT is current gold standard for diagnosis of urinary tract stone disease
  • Ultrasound may be an initial imaging done although its sensitivity is limited (37% - 64%) for detecting renal calculus (lower for ureteric calculus) and acute obstruction (74% - 85%)
Imaging Appearance
  • Stone (brightly echogenic focus with posterior acoustic shadowing). For renal stone less than 5 mm, ultrasound is of limited accuracy. Ureteric stone is uncommonly appreciated on US.
  • Hydronephrosis
  • Twinkling artifact behind the stone, and absent ureteral jet on color Doppler imaging
Scott LM, Sawyers SR, Bokhari J, Hamper UM. Ultrasound evaluation of the acute abdomen. Ultrasound Clin 2007;2:493-523.