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)

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

4. www.ThaiRSC.com

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

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

19. One day later

20. FLAIR T2W

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

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

28.  Vertically oriented lesion easier to detect
on coronal reformation than axials

29.  Horizontal skull fracture

30.  Horizontal skull fracture

31.  Enable us to be certain about diagnosis

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

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

40. Contralateral skull fracture > 2 bones – 41 times to develop DEDH following DC
Talbott JF, et al. AJNR 2014

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?

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
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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

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

68.  Example: Effective Dose = DLPx0.0023 = 1.7 mSv
 Typical head CT DLP 1100 mGy.com or ~2.5 mSv
 Annual non-medical background radiation ~3 mSv

69. Before 2010
Dose (median,
range) n=490
2011-2013
Dose (median,
range) n=564
Median dose
reduction (%)
P
value
CTDIvol
(mGy)
109
(109-140)
51.5
(17-120)
-53% <0.01
Total DLP
(mGy-cm)
2232
(1482-6121)
943
(268-4323)
-57% <0.01
Effective dose
(mSv)
4.7
(3.1-12.8)
2
(0.6-9.1)
-57% <0.01

70.  Brain Injury Guidelines (BIG)
 Coup-contrecoup injury
 Value of coronal reformation
 Delayed EDH after decompressive
craniectomy
 Repeat head CT
 Radiation dose