traumatic brain injury pearls and pitfalls (2014)

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

www.ThaiRSC.com

  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

  What to report on a head trauma CT?   Primary injury   Secondary effects   Skull and skull base fractures

  Quantification of injuries and prognostic/management significance

  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

Joseph B, et al. J Trauma Acute Care Surg 2014;76:965-9

Joseph B, et al. J Trauma Acute Care Surg 2014;76:965-9

Imaging findings

Focal neurologic examination,

abnormal pupil, GCS < 12

Imaging plan

  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

  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

One day later

FLAIR T2W

  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

  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

  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

  Vertically oriented lesion easier to detect on coronal reformation than axials

  Horizontal skull fracture

  Enable us to be certain about diagnosis

  Lesion detection   Floor of anterior and middle cranial fossae   Tentorial lesions   Horizontal skull fracture   Vertically oriented lesions

  Enable us to be certain about diagnosis

  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

  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

  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

  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

  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

Talbott JF, et al. AJNR 2014

Contralateral skull fracture > 2 bones – 41 times to develop DEDH following DC

  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

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?

  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

  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

  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

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

  Mild HI

Prospective Retrospective Change in management

2.3% 3.9%

Change in ICP monitoring

- 1.2%

Neurosurgical intervention

1.5% 2.4%


  Moderate HI


15.3% 18.4%


- 0%


- 8.2%


  Severe HI


25.3% 19.9%


- 13.8%


- 8%


  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%


CTDIvol 46, DLP 738 CTDIvol 71, DLP 1188

Good images can be achieved even with lower radiation dose!

There is no safe dose of radiation. -  Edward P Radford, MD

Scholar of the Risks from Radiation

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

Most sensitive

Least 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

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

Imaging exam ordered by referring physician

Vetting/protocoling by radiologist

Scanning

Post-processing

Monitoring of quality

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Scanning

Post-processing


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)

Medicineworld.org

  Tube current (mA)   Tube voltage (kVp)   Scan length   Detector collimation   Table speed   Pitch   Gantry rotation time   Automatic exposure control   Use of shielding

  Reduce mAs decreases radiation dose

  mA: effects noise only

0

10

20

30

40

50

60

0 200 400 600

Changes in Dose (CTDIw) as a Function of mAs

CTDIw Head (mGy) CTDIw Body (mGy)

Fixed kVp

mG

y

mAs

  Reduce kVp decreases radiation dose BUT has effect on both noise and attenuation

0

10

20

30

40

50

60

0 50 100 150

Changes in CTDIw as a Function of kVp

CTDIw Head (mGy) CTDIw Body (mGy)

Fixed mAs

Nakayama Y, et al. Radiology 2005 McNitt-Gray MF. Radiographics 2002

  Radiation dose is directly proportional to scan volume

Extra volume due to lack of gantry adjustment at time of scanning



Scanning

Post-processing


Some methods to reduce image noise (make a better-looking study)   Use smooth kernels   View thicker slices   Use iterative reconstruction (IR)

Jenkinsclinic.org

  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



Scanning

Post-processing


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

Blog.vpi-corp.com

CTDIvol -  Dose indicator for CT -  Accounted for dose gradient, helical pitch, single tube rotation DLP

-  CTDIvol x scan length -  Estimation of effective dose

  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

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

  Brain Injury Guidelines (BIG)   Coup-contrecoup injury   Value of coronal reformation   Delayed EDH after decompressive

craniectomy   Repeat head CT   Radiation dose

traumatic brain injury pearls and pitfalls (2014)

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