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
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%
Reljic T, et al. J Neurotrauma 2014
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
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
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
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
?????????????????????
Imaging exam ordered by referring physician
Vetting/protocoling by radiologist
Scanning
Post-processing
Monitoring of quality
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
Imaging exam ordered by referring physician
Vetting/protocoling by radiologist
Scanning
Post-processing
Monitoring of quality
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
Imaging exam ordered by referring physician
Vetting/protocoling by radiologist
Scanning
Post-processing
Monitoring of quality
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