Explaining technique of synchronizing timing of intravenous contrast with respect to 4D CT to get perfect triple phase scan in 4D CT.

1. 4D CT Simulation with
Synchronized Intravenous Contrast
Injection in Hepatocellular
Carcinoma for Target Delineation
Dr Anil Gupta MD DNB*, Dr Rishabh Kumar MD, Dr Hanuman
Prasad Yadav MD
Institute of Liver and Biliary Sciences, New Delhi

2. BACKGROUND
 Stereotactic Body Radiotherapy (SBRT) has emerged as a promising option for the
treatment of Hepatocellular Carcinoma (HCC)
 SBRT Planning and Delivering is Challenging
 It becomes especially more challenging for HCC due to -
Adjoining healthy liver is radiosensitive
CT density is similar to that of the adjoining healthy liver
Tumor motion is nonlinear and has hysteresis
Senger et al al
HYSTERESIS IN
LIVER

3. PRESENT SOLUTIONS
 Tumor motion Breath hold/Compression planning OR 4 Dimensional CT (4D CT)
 HCC’s density problem  Characteristic appearance on contrast imaging with arterial
phase enhancement and delayed phase washout
 The quality of the contrast enhanced images is highly dependent on the exact timing of
the contrast injection and CT scan
 Due to long scanning time of 4DCT (~2-4min), timing contrast injection with 4DCT is
problematic
DIAGNOSTIC NON
CONTRAST SCAN
DIAGNOSTIC ARTERIAL
PHASE SCAN
DIAGNOSTIC DELAYED
PHASESCAN

4. Where Breath Hold Facility
Is Not Available Or Patient
Not Suitable For Breath
Hold
• One way- Non Contrast 4D CT merged with Diagnostic arterial/delayed CT = All respiratory
phases has to be merges= Inherent fusion error
• Second way- Delayed contrast 4D CT protocol (Beddar et al) =Lacks arterial phase, accurate
delineation of boundaries not possible
• Third way - Taking a smaller scan region of the arterial phase containing only the tumor
region (Helou et al) = Chances of missing tumor due to motion, organ at risk will not come
in scan
What if we are able to time the contrast with 4 D CT ??

5. OBJECTIVE
PRIMARY OBJECTIVE
1. To develop the protocol for 4D CT simulation with synchronized intravenous contrast
2. To test it’s feasibility
3. To test it’s safety
SECONDARY OBJECTIVE
1. To compare mean peak enhancement of diagnostic arterial with synchronized 4D CT
INCLUSION CRITERIA
1. Unresectable HCC who are not eligible for breath hold technique
2. Able to maintain uniform respiratory rate and rhythm
Patient sample size= 25

6. CONTRAST
KINETICS
• Time to Peak (Tpeak) is the time elapsed
from the start of the contrast injection
to the peak enhancement of the aorta
• Level of Interest(LOI) is the level at
which one desires the Tpeak
• TID is the injection duration
• CTT is the transit time for the contrast
from the antecubital vein to the aorta
Tpeak= TID + CTT
Bae KT et al 2010
L
0
Liver
Span=
18
cm
Ls
Load
sensor
LOI
In our study we followed a fixed contrast volume method and
gave 125ml of contrast at 3ml/s giving us a TID of 41.6s. We
assumed a transit time of 10s, and hence the general Tpeak for
all our cases was calculated to be 50s.
Bae KT et al 2010

7. CONTRAST
KINETICS
• Time to scan LOI (T0) It is the time taken by the
CT scanner to come at the LOI
T0 = L0 X Cine Duration
𝐃𝐞𝐭𝐞𝐜𝐭𝐨𝐫 𝑪𝒐𝒗𝒆𝒓𝒂𝒈𝒆
• L0 Is the length between the scan start position
and the LOI
• Detector coverage is the length scanned by the
CT scanner for a duration equal to the patients
cine time
• Cine Duration is the time required to image one
respiratory cycle = 60/Respiratory rate
L
0
Liver
Span=
18
cm
Ls
Load
sensor
LOI
In our study, detector coverage was 2 cm
and cine duration for our cases varied from
4 to 6 seconds. L0 was varying from 13 to
16. So, T0 was coming in range of 23 to 48s.
Bae KT et al 2010

8. CONTRAST
KINETICS
• Time of Scan Delay (TSCAN DELAY) It is the
delay given from the start of the contrast
injection to the start of scan
TSCAN DELAY = Tpeak – T0
• The delay in scan with respect to start of
intravenous contrast injection makes the
the 4D CT synchronize with intravenous
contrast
L
0
Liver
Span=
18
cm
Ls
Load
sensor
LOI
In our study, TSCAN DELAY was varying
from 2 to 27s.
Bae KT et al 2010
After 5 minutes of delay
another 4D CT scan taken
in same setting- Delayed
4D CT scan

9. 4D CT Simulation with Synchronized
Intravenous Contrast Arterial Phase

10. 4D CT Average Intensity Projection showing various GTVs and OAR
After 5 mins delay in same setting

11. RESULTS
 Feasibility
- It is feasible, with good contrast enhancement
 Safety
- Only 2/25 patients had vomiting post scan
- No patients had Contrast induced Nephropathy
 Mean Peak
- Diagnostic arterial phase CT vs Synchronized 4DCT ( p-value = 0.58) – N.S
- Non-contrast diagnostic CT vs Synchronized 4DCT (p value=.0003)- Significant

12. Patient 1. HCC (a) Synchronized 4D CT contrast showing peak HU of 138
in average intensity projection (AIP). (b) Diagnostic 3D CT contrast of
same slide showing peak HU 0f 141. (c) Synchronized 4D CT delayed
showing washout. (d) Diagnostic non contrast scan. (e) DRR showing
Synchronized 4D CT scan length. L0, Ls, TSCANDELAY and corresponding
aortic enhancement at 4D CT scan length and LOI.
(c) (d) L
0
Liver
Span=
18
cm
Ls
Load
sensor
LOI
(a) (b)

13. (a) (b)
(c) (d) (e)
Patient 2. HCC post TACE (a) Synchronized 4D CT contrast showing peak
HU of 136 in average intensity projection (AIP). (b) Diagnostic 3D CT
contrast of same slide showing peak HU 0f 154. (c) Synchronized 4D CT
delayed showing washout. (d) Diagnostic non contrast scan showing
lipiodol and poor demarcation between liver parenchyma and HCC. (e)
DRR showing Synchronized 4D CT scan length. L0, Ls, TSCANDELAY and
corresponding aortic enhancement at 4D CT scan length and LOI.
L
0
=
13
cm
Ls
=
6cm
Liver
Span=
14
cm
Load
sensor
LOI

14. Patient 3. Hypodense HCC (a) Synchronized 4D CT contrast (AIP). (b)
Diagnostic 3D CT contrast of same slide. (c) Synchronized 4D CT delayed
showing washout. (d) Diagnostic non contrast scan. (e) DRR showing
Synchronized 4D CT scan length. L0, Ls, TSCANDELAY and corresponding
aortic enhancement at 4D CT scan length and LOI.
(a) (b)
(c) (d) L
0
Liver
Span=
20
cm
Ls
Load
sensor
LOI

15. Patient 4 HCC with Transient hepatic attenuation difference (THAD) (a)
Synchronized 4D CT contrast showing primary lesion with tumoral
thrombosis in portal vein along with Transient hepatic attenuation
difference (THAD) in average intensity projection (AIP). (b) Synchronized
4D CT delayed showing washout.
HCC Lesion
Tumoral thrombosis in Portal vein
THAD
(a) (b)

16. (a) (b)
(c) (d)
Patient 5. Infiltrative HCC (a) Synchronized 4D CT contrast showing no
enhancement in arterial phase (hypoenhancing HCC) (b) Diagnostic 3D
CT contrast of same slide showing no contrast enhancement. (c)
Synchronized 4D CT delayed showing washout but no washout in the
THAD component. (d) Diagnostic non contrast scan- difficult to appreciate
the tumor

17. CONCLUSION
A synchronized intravenous contrast 4D CT –
 Feasible
 Safe
 Good contrast enhancement and image quality
 More studies required

18. THANK YOU