TÀI LIỆU HỘI NGHỊ KỸ THUẬT ĐIỆN QUANG VÀ Y HỌC HẠT NHÂN VIỆT NAM LẦN 7 (2019) Nguồn: https://hinhanhykhoa.com/

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THE TECHNICAL FACTORS AFFECTING THE
QUALITY OF DIAGNOSIS IN ABDOMEN OF
CONTRAST – ENHANCED CT
CN: Phạm Văn Điệp
CN: Nguyễn Quang Trung
Radiology Department–Hanoi Medical University Hospital
OVERVIEW
• CT scan of the abdomen with an injection of contrast is a
method of high diagnostic value in abdominal pathologyg g p gy
• The diagnostic value after the visit depends on the image
quality obtained after the scan
• Requirements: Optimal image quality and ensure the lowest
di ti d d dradiation dose and dose

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- The purpose of contrast-enhanced CT (CECT) is to find pathology
by enhancing the contrast between a lesion and the normal
CONTRAST
y g
surrounding structures.
- Sometimes a lesion will be hypovascular compared to the normal
tissue and in some cases a lesion will be hypervascular to the
surrounding tissue in a certain phase of enhancement.
- So it is important to know in which phase a CT should be
performed depending on the pathology of patient
THE PHASES OF CECT
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Purpose:
NON- ENHANCED CT
(NECT)
Purpose:
• Detection of stones in kidney, ureter.
• Detection of calcifications in liver,
pancreas
• Fat in livertumors
• Fat in adrenal adenoma
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct-contrast-injection-and-protocols.html
NON- ENHANCED CT
(NECT)

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Timing:
EARLY ARTERIAL
PHASE
15-20 sec pre injection or immediately after
bolustracking
Purpose:
• Detection of dissection of aorta, arterial
bleeding
• Insulinoma
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct‐contrast‐injection‐and‐protocols.html
EARLY ARTERIAL
PHASE

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Timing:
• 35-40 sec p.i. or 15-20 sec after
LATE ARTERIAL
PHASE
p
bolustracking
Purpose:
Detection of
• Liver: HCC-FNH-Adenoma
• Pancreas : Adenocarcinoma, insulinoma
• Bowel ischemia
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct‐contrast‐injection‐and‐protocols.html
LATE ARTERIAL PHASE

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Timing:
HEPATIC PHASE
• 70-80 sec p.i. or 50-60 sec after
bolustracking
Purpose:
• Enhancement of the hepatic parenchyma
• Detection of hypovascular liver lesions:
cysts, abscess, most metastases
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct‐contrast‐injection‐and‐protocols.html
HEPATIC PHASE

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Timing:
NEPHROGENIC
PHASE
Timing:
• 100 sec p.i. or 80 sec after bolustracking
Purpose :
• Enhancement of all renal parenchyma
• Detection of renal cell carcinoma.
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct‐contrast‐injection‐and‐protocols.html
NEPHROGENIC PHASE

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Timing:
DELAYED
PHASE
• After 6-10 minutes p.i
Purpose:
• Enhancement of fibrotic lesions
• Enhancement of kidney and urinary
collecting system
• Detection of cholangiocarcinoma, transitional
cell carcinomacell carcinoma
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct‐contrast‐injection‐and‐protocols.html
DELAYED
PHASE

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TIMING
OF CT-
SERIES
THE
FACTORS
TOTAL
AMOUNT
OF
CONTRAST
INJECTION
RATE
ANOTHER
FACTORS
- In many protocols a standard dose is given related to the weight of
Total amount of
contrast
the patient:
Weight < 75kg : 100cc
Weight 75-90kg: 120cc
Weight > 90kg : 150cc
In some protocols we always want to give the maximum dose of- In some protocols we always want to give the maximum dose of
150cc, like when you are looking for a pancreatic carcinoma or liver
metastases
http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct‐contrast‐injection‐and‐protocols.html

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CREATININE CLEARANCE
https://www.mdcalc.com/creatinine‐clearance‐cockcroft‐gault‐equation
• Recommended injection rate of 5cc/sec using G18 I.V
h l ti th ki ti f l i
INJECTION RATE
when evaluating the kinetics of lesions
• Unneccessary in case just focus at hepatic phase or
having problem with machine, line,...
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INJECTION RATE
Patient with liver cirrhosis and
multifocal HCC injected at 2.5
ml/sec and at 5ml/sec
INJECTION RATE
Food and Drug Administration (FDA)-approved devices for
power/pressure injection as below:
 Injection rates for 24G catheters up to 2 ml/s
 Injection rates for 22G catheters up to 4 ml/s
 Injection rates for 20G catheter up to 5 ml/s
 Injection rates for 18G catheter up to 7 ml/s
https://doi.org/10.1016/j.crad.2014.08.004

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TIMING OF CT-
SERIES
 Timing of CT-series is important in order to grab the right moment of maximal
contrast differences between a lesion and the normal parenchyma.
 The protocol we choose to visit depends very much on the clinical diagnosis.
 CT generation
 Supply of heart and body condition of patients
LIVER
The phases :
 NECT (non-enhanced CT)
 Arterial phase (35 sec)
 Hepatic phase (70 sec)
 Delayed phase (3 - 4 mins)
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LIVER
LIVER

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https://www.acr.org/‐/media/ACR/Files/RADS/LI‐RADS/LI‐RADS‐2018‐Core.pdf?la=en
PANCREAS
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PANCREAS
a: pre- contrast b: 35s c: 55s d: 80s
PANCREAS
a: pre- contrast b: 35s c: 80s

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URINARY
URINARY
Kidney injury with delayed phase
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INJURY
Spleen injury with arterial phase
HEMORRHAGIC
hemorrhagic gastrointestinal

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BLOOD VESSEL
Dissection of superior mesenteric artery
 Depending on machines, equipment, medical facility.
ANOTHER FACTORS
 Factors of age, weight, heart disease, vascular.
 Experience of doctor and technicians.
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The delay time of post injection should be determined by
ANOTHER FACTORS
considering three factors:
● Time of contrast injection.
● Arrival time of contrast medicine.
● Scanning time (depending on the type of CT machine).
 CECT is a valuable diagnostic method, especially in emergency
medical conditions.
CONCLUDE
 For good diagnostic results, the image quality after scan is very
important.
 Equipment and experience of technicians is very important.
 Collaboration between doctors and technicians
 The selection of a protocol that is appropriate for each condition
and clinical diagnosis must also be noticed

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• http://www.radiologyassistant.nl/en/p52c04470dbd5c/ct-contrast-
i j ti d t l ht l
References
injection-and-protocols.html
• https://www.radiologyinfo.org/en/info.cfm?pg=safety-radiation
• Split-Bolus MDCT Urography with Synchronous Nephrographic and
Excretory Phase Enhancement
• How Much Dose Can Be Saved in Three-Phase CT Urography?
• https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/LI-RADS-
2018-Core.pdf?la=enp
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THANK YOU !THANK YOU !