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- 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.. -[r]

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 pathology g 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

radiation dose and dose

- The purpose of contrast-enhanced CT (CECT) is to find pathology

by enhancing the contrast between a lesion and the normal

CONTRAST

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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• Detection of stones in kidney, ureter.

• Detection of calcifications in liver,

Timing:

• 35-40 sec p.i or 15-20 sec after

LATE ARTERIAL PHASE

• 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

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

Timing:

DELAYED PHASE

• After 6-10 minutes p.i

Purpose:

• Enhancement of fibrotic lesions

• Enhancement of kidney and urinary

TIMING

OF SERIES

CT-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

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

TIMING OF SERIES

CT- 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

 Arterial phase (35 sec)

 Hepatic phase (70 sec)

 Delayed phase (3 - 4 mins)

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LIVER

LIVER

https://www.acr.org/‐/media/ACR/Files/RADS/LI‐RADS/LI‐RADS‐2018‐Core.pdf?la=en

PANCREAS

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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

• Split-Bolus MDCT Urography with Synchronous Nephrographic and

Excretory Phase Enhancement

•

https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/LI-RADS-2018-Core.pdf?la=enp

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THANK YOU !