Medical Imaging of the Pediatric Trauma Pa5ent November 13, 2014
Thaddeus W. Herliczek, MD, MS
Objectives
• Describe the imaging modalities available to image the pediatric trauma patient.
• Describe the ALARA principle and the risks of CT in pediatric patients.
• Identify appropriate imaging algorithm for imaging pediatric cervical spine trauma.
Take Home Points • Every imaging modality has advantages and
disadvantages. • Plain radiography and CT are the modalities of
choice for the pediatric trauma patient. • Potential benefits of appropriate imaging in
pediatric trauma patient exceed the risks of radiation.
• Pedi C-spine: radiographs first, not CT. • When in doubt, talk to your radiologist.
Trauma
• 600,000 trauma-‐related pediatric hospital admissions annually in the U.S.
• Trauma5c injuries can be difficult to diagnose by physical exam alone.
• Prompt and appropriate imaging can prevent significant morbidity and mortality of pediatric trauma pa5ents.
Imaging Menu
• Radiography • Ultrasound • Fluoroscopy • Computed Tomography • Magne5c Resonance Imaging
Radiography
• Advantages; – Highest spa5al resolu5on. – Excellent evalua5on of osseous structures. – Fast. – Portable. – Inexpensive.
Radiography • Disadvantages; – Limited soft tissue contrast. – Ionizing radiation.
Ultrasonography
Two types in setting of trauma; 1. Diagnostic US 2. F.A.S.T.= Focused Abdominal Sonogram for
Trauma
-‐Assessment for intraperitoneal fluid. -‐Replaced peritoneal lavage.
Ultrasonography
• Advantages – Portable – No ionizing radiation – Less expensive than CT or MRI
Ultrasonography • Problems – Availability – Time – Low sensitivity and specificity for detecting visceral
injuries and hemoperitoneum. – US does not adequately evaluate osseous structures,
retroperitoneum, gas containing structures (bowel and lung) and mediastinum.
– Operator Dependent
Ultrasonography – Low sensitivity and specificity for detecting visceral
injuries and hemoperitoneum. – Missed 12/32 splenic injuries. – 1/3 of visceral injuries do not have hemoperitoneum
– Low sensitivity and low negative predictive value render a normal screening US insufficient to exclude abdominal injury.
– Presently, US is not recommended to exclude traumatic injury.*
* Minimal controversy and there is ongoing research esp. contrast enhanced US.
Fluoroscopy
• Real 5me “con5nuous” evalua5on with x-‐rays.
• Usually following inges5on or injec5on of contrast medium into an orifice or blood vessel.
• Rarely used in trauma pa5ents. • Men5oned only for completeness.
Computed Tomography (CT) • Advantages; – Excellent soft tissue contrast resolution. – Readily available. – Fast. – High sensitivity and specificity. – Multiplanar reformats. – Excellent evaluation of all tissues except spinal cord
and ligament/tendon trauma.
Computed Tomography
• Its advantages render it the imaging modality of choice to assess traumatic injury of the head, face, neck, abdomen and pelvis.****
• *** Could be on the “test”.
CT
• One of the keys to a successful chest or abdomen/pelvis trauma CT is infusion rate of IV contrast.
• This is dramatically influenced by the caliber of the IV in place. The ideal IV line for CT is an 18g in the right antecubital fossa.
• Please place larger catheters whenever possible. (Bernoulli’s Principle)
Magne5c Resonance Imaging (MRI)
• Uses non-‐ionizing radia5on. • No known deleterious effects. • Some studies suggest it is equivalent to CT for evalua5on of trauma5c injuries.
• Excellent so] 5ssue contrast. • Imaging modality of choice for spinal cord injury.
MRI
– Longer image acquisition time – Sedation (< 7 years, developmental delay, agitation) – High magnetic field limits supportive equipment and ability to monitor and resuscitate
patients – Limited availability – Expensive – Limited evaluation of cortical bone/fractures
Disadvantages
Ionizing Radia5on
• X-rays from plain radiography, CT, and fluoroscopy are a form of ionizing radiation.
• X-rays can have deleterious effects. – Burns - Cancer – Alopecia -Birth defects
ALARA= As Low As Reasonably Achievable
• Children are more sensi5ve to radia5on exposure than adults. – Inherently more radiosensi5ve. (esp. thyroid, breast 5ssue, gonads)
– Longer life expectancy over which to express the radia5on induced damage to genes.
– Girls are slightly more sensi5ve than boys.
ALARA= As Low As Reasonably Achievable
Radia5on Scale
• US, MRI and the decision not to obtain imaging expose the child to the same amount of ionizing radiation: None.
• Radiography exposes children to relatively low doses of ionizing radiation.
• CT exposes children to the greatest amount of ionizing radiation in medical imaging.
• The possibility of a deleterious effect from medical radiation is very small.
ALARA= As Low As Reasonably Achievable
Radia5on Scale
• One year of natural background radiation exposure is similar dose as 30 chest radiographs.
• Transcontinental flight on a commercial airliner exposes child to same dose of radiation as 2 chest radiographs.
• On our Hasbro CT scanner (iterative reconstruction
algorithm), CT of the chest is the same radiation dose as 6 chest radiographs.
ALARA= As Low As Reasonably Achievable
Important Principles
• ALARA • Risk vs. Benefit • The Bobom Line
ALARA= As Low As Reasonably Achievable
A.L.A.R.A. • As Low As Reasonably Achievable
– American College of Radiology tenet on radiation dose/exposure.
– All medical professionals must strive toward this goal when caring for all patients, but especially
children. – Potential risks of unnecessary exposure to ionizing radiation warrant judicious patient
selection for CT scanning.
*** Could be on the “test”.
How do we keep radia5on exposure ALARA?
• Clinicians – Request imaging only when necessary.* • Area of ongoing research
– Request the appropriate exam.
– Communicate with your pediatric radiologist.
• Radiologists – Ensure imaging is
necessary. – Ensure that the appropriate
exam is requested. – Suggest appropriate
alterna5ve modali5es (ex. MRI for C-‐spine).
– Communicate with the reques5ng clinician.
– Adjust imaging parameters to keep radia5on exposure low, but maintain diagnos5c image quality.
ALARA= As Low As Reasonably Achievable
The Transferred Pa5ent
• Many children with trauma5c injuries arrive at Hasbro Children’s Hospital for treatment having already received diagnos5c imaging at an outside ins5tu5on.
• The CD’s or films that accompany them are crucially important. If these get lost, it can result it repeated diagnos5c imaging, unnecessary radia5on exposure and delayed diagnosis.
• Please help prevent misplacement of these exams.
Risk vs. Benefit
• While x-‐rays (plain radiography and CT) increase the risk of deleterious effects such as cancer, the poten>al benefit from the clinically necessary imaging study drama>cally outweighs this risk.
ALARA= As Low As Reasonably Achievable
The Bobom Line is…. • The possibility for traumatic injury must
dictate the need for radiation-based medical imaging as the risk from exposure to ionizing radiation associated with radiological examinations is low. Nevertheless, it is still advisable to avoid such exposure where possible.
ALARA= As Low As Reasonably Achievable
Resources • “Radiation Risks and Pediatric Computed
Tomography (CT): A Guide for Health Care Providers.” National Cancer Institute at U.S. National Institutes of Health. www.cancer.gov
• Frush et al. “Computed tomography and radiation risks: What pediatric health care providers should know.” Pediatrics 112; 4: 951-957.
• Brenner, D. and Hall, E. “Computed Tomography-An Increasing Source of Radiation Exposure.” NEJM 357;22: 2277-2284.
• ImageGently.com
Cervical Spine Imaging
• Controversial Topic.
• No accepted consensus.
Another problem
• Cervical spine trauma can involve osseous, ligamentous, capsular, vascular and neural structures.
• No one imaging modality can evaluate injury to all these tissues. – Radiographs and/or CT for osseous structures. – MRI for ligamentous, capsular and neural structures. – CTA/MRA for vascular injury.
Cervical Spine Imaging in Pediatric Trauma Pa5ents
• Imaging algorithm varies by age, institution, superstition, etc.
• Guidelines for imaging exist, but they vary by institution, association, etc.
• Literature on pediatric cervical spine imaging remains sparse.
Pediatric Cervical Spine Imaging
• Controversy in pediatric imaging is secondary to desire to exclude/identify cervical spine trauma versus maintaining radiation exposure (and cost) As Low As Reasonably Achievable (ALARA).
• Most recommendations are based on adults. • Given the controversy and variability, we’ll
review what the American College of Radiology recommends and what I think.
What do I propose?
Cervical Spine Injury Suspected
Plain radiographs first
Tailored cervical spine CT and/ or cervical spine MRI as needed
????: If abnormality present or questioned abnormality.
*** Could be on the “test”.
Take Home Points • Every imaging modality has advantages and
disadvantages. • Plain radiography and CT are the modalities of
choice for the pediatric trauma patient. • Potential benefits of appropriate imaging in
pediatric trauma patient exceed the risks of radiation.
• Pedi C-spine: radiographs first, not CT. • When in doubt, talk to your radiologist.
References
• American College of Radiology Appropriateness Criteria • Benya et al. “Abdominal sonography in examination of children with blunt abdominal
trauma.” AJR 2000; 174: 1613-1616. • Brenner et al. “Estimated risks of radiation induced fatal cancer from pediatric CT.”AJR 2001;
176: 289-296. • Brenner, D. and Hall, E. “Computed Tomography-An Increasing Source of Radiation
Exposure.” NEJM 357;22: 2277-2284. • Bushberg, J. The Essential Physics of Medical Imaging 2nd edition., “Radiation Biology”.
Lippincott Williams and Wilkins. New York. 2002. Pps. 853-60. • Children’s Hospital Boston Clinical Practice Guidelines • Keenan et al. “Using CT of the cervical spine for early evaluation of pediatric patients with
head trauma.” AJR 2001; 177: 1405-1409. • Kleinerman, Ruth A. “Cancer risks following diagnostic and therapeutic radiation exposure in
children.” Pediatric Radiology 2006; 36: 121-125. • Netter, Frank. Atlas of Human Anatomy 2nd Ed. Hoechstetter Printing Co. 1997. • Parry et al. “Typical Patient Radiation Doses in Diagnostic Radiology.” from The AAPM/
RSNA Physics Tutorial for Residents. Radiographics Vol. 19 No. 5. Pps. 1289-1302 • Richards et al. “Blunt abdominal trauma in children: Evaluation with emergency ultrasound.”
Radiology 2002; 222: 749-754. • Slovis, Thomas L. “The ALARA concept in pediatric CT: myth or reality?” Radiology 2002;
223: 5-6.
Medical Imaging of the Pediatric Trauma Pa5ent
November 13, 2014 Thaddeus W. Herliczek, MD, MS
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