Five pearls and pitfalls in using head CT for diagnosis of traumatic brain injury. This was presented at the 51st Annual Scientific Meeting of the Royal College of Radiologists of Thailand (6 Aug 2014)
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Traumatic Brain Injury Pearls and Pitfalls (2014)
1. Rathachai Kaewlai, MD
Ramathibodi Hospital, Mahidol University
For the Annual Meeting of the Royal College of Radiologists of Thailand
6 September 2014, Centara Grand @CentralPlaza Ladprao, Bangkok
8. Leading cause of disability and mortality
from trauma
Young individuals, many life-year losses
80% presenting at Emergency Department
Timely diagnosis and management crucial
for patient outcome
9. What to report on a head trauma CT?
Primary injury
Secondary effects
Skull and skull base fractures
Quantification of injuries and prognostic/
management significance
10. Poor prognostic signs on CT
EDH > 150 mL1
SDH > 10 mm thick, midline shift > 20 mm 2,3
Temporal or bilateral IPH4
IPH + SDH4
DAI5
1Rivas JJ, et al. Neurosurgery 1988;23:44-51
2Servadei F, et al. Br J Neurosurg 2000;14:110-6
3Zumkeller M, et al. Neurosurgery 1996;39:708-12
4Wong GK, et al. Br J Neurosurg 2009;23:601-5
5Adams JH, et al. J Neurol Neurosurg Psychiatry 1991;54:481-3
11. Joseph B, et al. J Trauma Acute Care Surg 2014;76:965-9
12. Joseph B, et al. J Trauma Acute Care Surg 2014;76:965-9
Focal neurologic
examination,
abnormal pupil,
GCS < 12
Imaging findings
Imaging plan
13. Integration of patient’s history, neurologic
exam and initial CT results for Rx plan
Easy to assign category (in this paper, only 0.7% were
wrongly grouped)
Reduce use of repeat CT (28%)
Reduce number of neurosurgical consultation (35%)
Reduce number of admission (10%)
For radiologists, we now realize what are
significant and should be reported
14.
15.
16.
17. Skull encases the brain
Brain immersed in CSF
Cellular cohesiveness of brain
Skull surface and dural reflections
Blunt impact by moving object
Moving skull vs stationary object
Rotational translation and
deceleration
Coup injuries = superficial
Contrecoup = deep
Images from Wikipedia.org
22. Knowing biomechanics of closed TBI
important for detection of lesions and
forensic purpose
Minimal brain lesions might complete the
mosaic for reconstruction of
biomechanical condition
23.
24.
25. Wei SC, et al. AJNR 2010
213 NCCTs
▪ 32 cases with traumatic ICH = 104 foci on either
axial or coronal images
▪ 80 foci were true-positive lesions
▪ 15 true positives not detected on axial images
(15/104 = 14%, in 8 patients)
▪ 14 false-positive findings on axial but excluded on
coronal
26. Axial images are less accurate in areas
Parallel to axial image plane (esp immediately
adjacent to bony surfaces)
Common areas where false negatives occur
Floor of anterior cranial fossa
Floor of middle cranial fossa
32. Lesion detection
Floor of anterior and middle cranial fossae
Tentorial lesions
Horizontal skull fracture
Vertically oriented lesions
Enable us to be certain about diagnosis
33.
34.
35. To control elevated ICP in severe TBI
Removal of a large portion of frontal-temporal-parietal-
occipital skull bone (12x15 cm)
Underlying dura opened in stellate fashion to
bone edge. Scalp flap was closed without
duroplasty
Kolias, A. G. et al. (2013) Decompressive craniectomy: past, present and future
Nat. Rev. Neurol. doi:10.1038/nrneurol.2013.106
36. EDH after and remote to decompressive
craniectomy (DC)
Upon opening skull -- relief of tamponade
effect and hemorrhagic expansion of
injured meningeal artery, dural vein or
fractured diploe
Evolve during operation
May present during or after operation
Can be fatal. Often need 2nd operation
37. Su TM, et al. J Trauma 2008
Case series of 12 patients
Contralateral DEDH occurred after
decompressive craniectomy
10/12 found to have contralateral calvarial fx
on preoperative CT
12/12 found to have fx at surgery
38. Talbott JF, et al. AJNR 2014
Retrospective review of 203 patients who had
decompressive craniectomy for TBI
6% had DEDH
▪ Age 32 +/- 13 years, two thirds had severe TBI,
mostly high impact injuries
▪ Time from sx to postoperative CT = 13 h
▪ All had contralateral calvarial fx on preoperative CT
at site of DEDH
39. Talbott JF, et al. AJNR 2014
Large size (mean volume = 86 mL,
mean thickness = 2.5 cm)
Mean midline shift = 10 mm
Site of DEDH
▪ Contralateral to side of craniectomy
(10/12) and bilateral (2/12)
▪ All DEDH at site of calvarial fx
42. Incidence 4.5-6.8% in patients with TBI
undergoing DC
Predictor = contralateral calvarial fx
(esp. >2 bones involved)
Surgeon should be alerted to
Risks of intraoperative brain swelling
through craniectomy defect
Need for early postoperative CT
43. Head injury, repeat CT per protocol
Initial CT done 6 hours ago:
Right SDH (5 mm thick) and small cortical SAH.
Admission GCS = 13, now stable
Do we need to repeat CT again?
44.
45. CT is the first-line imaging study “rapidly
acquired” and “accurate for significant
intracranial hemorrhage”
First CT done as soon as possible after
ED arrival
When first CT shows ICH and the patients
is observed, do we need repeat (F/U) CT?
Value of repeat (2nd) CT - controversial
46. Unexpected changes
or findings can be
beneficial in
management of TBI
patients
Increase of patient
exposure to ionizing
radiation
Misallocation of
resources
Elevation of
healthcare cost
Cartoons from buildingmbrand.wordpress.com
47. Well, it depends....
Reljic T, et al. J Neurotrauma 2014
110 references in PubMed thru 2012 reviewed
Meta-analysis of 41 studies = 13 prospective +
28 retrospective = 10,501 patients with TBI
48. Prospective
studies
Retrospective
studies
Progression of injury 31%
(15-50)
28%
(24-33)
Change in management 11.4%
(5.9-18.4)
9.6%
(6.5-13.2)
Change in ICP monitoring - 5.6%
(2.2-10.5)
Change in neurosurgical intervention 10.7%
(6.5-15.8)
5.2%
(3.3-7.5)
Significant heterogeneity of data led to subgroup analysis
Reljic T, et al. J Neurotrauma 2014
49. Mild HI
Prospective Retrospective
Change in
management
2.3% 3.9%
Change in ICP
monitoring
- 1.2%
Neurosurgical
intervention
1.5% 2.4%
Reljic T, et al. J Neurotrauma 2014
50. Moderate HI
Prospective Retrospective
Change in
management
15.3% 18.4%
Change in ICP
monitoring
- 0%
Neurosurgical
intervention
- 8.2%
Reljic T, et al. J Neurotrauma 2014
51. Severe HI
Prospective Retrospective
Change in
management
25.3% 19.9%
Change in ICP
monitoring
- 13.8%
Neurosurgical
intervention
- 8%
Reljic T, et al. J Neurotrauma 2014
52. Change in management mostly in moderate-severe
head injury
Prospective Retrospective
Mild HI 2.3% 3.9%
Moderate HI 15.3% 18.4%
Severe HI 25.3% 19.9%
AVERAGE 11.4% 9.6%
Reljic T, et al. J Neurotrauma 2014
53. Good images can be achieved even with
lower radiation dose!
CTDIvol 46, DLP 738 CTDIvol 71, DLP 1188
54.
55. There is no safe dose of radiation.
- Edward P Radford, MD
Scholar of the Risks from Radiation
56. Procedures Effective
Dose (mSv)
Risks
CXR (PA), extremity XR <0.1 Negligible
Abdomen XR, LS spine XR 0.1-1 Extremely low “death from flying
7200 km”
Brain CT, single-phase
abdomen CT, single-phase
chest CT
1-10 Very low “death from driving
3200 km)
Multiphase CT 10-100 Low
Interventions, repeated CT >100 Moderate
57. Most sensitive
Lymphoid tissue, bone marrow, GI epithelium,
gonads, embryonic tissues
Skin, vascular endothelium, lung, kidney, liver,
lens (eye)
CNS, muscle, bone and cartilage, connective
tissue
Least sensitive
Ref: ICRP 2007
Tissue Sensitivity
~ rate of cell proliferation
Inversely ~ to age
Inversely ~ to degree of cell
differentiation
Higher dose = more damage
Young = more damage
58. Imaging exam ordered
by referring physician
Vetting/protocoling by
radiologist
Scanning
Post-processing
Monitoring of quality
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59. Imaging exam ordered
by referring physician
Vetting/protocoling by
radiologist
Scanning
Post-processing
Monitoring of quality
Medicineworld.org
Technical parameter change
Avoid Z-creep (unnecessary coverage
and scan phases)
Make standard protocols available in CT
workstations for every techs to use
Reduce mAs
Use automatic tube current modulation
Reduce kVP (esp for CTA, stone protocol)
Incorporate patient size, age and
indication into making a protocol (work
with your physicists)
60. Tube current (mA)
Tube voltage (kVp)
Scan length
Detector collimation
Table speed
Pitch
Gantry rotation time
Automatic exposure control
Use of shielding
61. Reduce mAs decreases
radiation dose
mA: effects noise only
60
50
40
30
20
10
0
Changes in Dose (CTDIw)
as a Function of mAs
Fixed kVp
0 200 400 600
CTDIw Head (mGy) CTDIw Body (mGy)
mGy
mAs
62. Reduce kVp decreases
radiation dose BUT has
effect on both noise and
attenuation
60
50
40
30
20
10
0
Changes in CTDIw as a
Function of kVp
Fixed mAs
0 50 100 150
CTDIw Head (mGy)
CTDIw Body (mGy)
Nakayama Y, et al. Radiology 2005
McNitt-Gray MF. Radiographics 2002
63. Radiation dose is directly
proportional to scan volume
Extra volume due to lack of gantry adjustment at time of scanning
64. Imaging exam ordered
by referring physician
Vetting/protocoling by
radiologist
Scanning
Post-processing
Monitoring of quality
Jenkinsclinic.org
Some methods to reduce image noise
(make a better-looking study)
Use smooth kernels
View thicker slices
Use iterative reconstruction (IR)
65. Current CT reconstructs images from raw data
using filtered back projection (FBP). Faster
processing time traded with image noise
Iterative reconstruction (IR) allows less noisy
images but with longer processing
Same raw data processed with…
FBP may look noisy
IR appears less noisy
Korn A et al. AJNR 2012
FBP IR, 30% dose reduction
66. Imaging exam ordered
by referring physician
Vetting/protocoling by
radiologist
Scanning
Post-processing
Monitoring of quality
Blog.vpi-corp.com
Monitoring of study quality and dose by
imaging team (techs, physicists and
radiologists)
Send “Dose Report” into PACS
Educate radiologists and trainees about
dose parameters and standards
Regular updates of CT protocols
67. CTDIvol
- Dose indicator for CT
- Accounted for dose gradient,
helical pitch, single tube rotation DLP
- CTDIvol x scan length
- Estimation of effective dose