Abdomen and pelvis

CT ANATOMY

MAMDOUH MAHFOUZ MD

mamdouh.m5@gmail.com

www.ssregypt.com

Indications

Patient preparation

Patient position

Scanogram

• To assess equivocal imaging findings

• Staging of hepatic neoplasms

• Metastatic workup of primary malignancies

• Diagnosis of abdominal masses

• Assessment of biliary problems

• Diagnosis of vascular lesions

• Assessment of suspected post-traumatic complications

CT

ABDOMEN

Patient preparation

Oral contrast material to opacity the gastrointestinal tract [gastrographin 38% diluted by water to 4%]

- Timing?

Not indicated in Acute abdominal trauma

Acute renal colic

Dehydrated patients

Indications

Patient preparation

Patient position

Scanogram

CT

ABDOMEN

No required preparation unless the patient is going to be sedated

or injected with contrast material

FASTING FOR 4 - 6 HOURS

Scanogram Frontal

10mmscan intervals [ 5mm sections are necessary for pancreas, suprarenal glands, urinary bladder]

Window setting Soft tissue window

Lung window [scans at the lung bases]

Bone window [lesions in the spine or pelvic bones]

Patient preparation

IV contrast material [urographin,…] 60ml

• Fasting 4-6 hours ?!

• Pre contrast scans [ liver, kidney, urinary bladder]

• Triphasic scan for liver [ arterial, portal, delayed]

Detailed examination of the Superior Mesenteric Artery and Celiac Artery. Scan time = 9.4 seconds. 1mm slice thickness

Value of precontrast study

Hyper vascular deposits

Arterial phase

Value of arterial phase

images in hepatic

lesion detection

Male

pelvis

Female

pelvis

LS

MS

AS

PS

Hepatic segmental anatomy

LS MS

AS

PS

LS MS

AS

PS

No focal lesions

?!!

Contrast enhanced CT

or MRI

?!

Diffuse hepatic diseases?!!

Fatty liver

Cirrhosis

Storage diseases

No dilated biliary radicals ?!!

Intra

hepa

tic bi

le du

ct di

latati

on

Vessels in the

liver ?!! Hepatic artery

Hepatic veins

Portal veins

CT Portography

CT Portal venography in a

56Y Male with portal vein

thrombosis

CT Portal venography

showing portal

hypertension with GE

varicosities

Normal variants

Agenesis of the anterior segment of the right hepatic lobe

Porta-hepatis

Hepatic artery

Portal vein

cbd

Pancreas

Anatomy Anterior pararenal space,

retroperitonium Head (3cm) neck, body (2.5cm)

and tail (2cm) Pancreatic density is similar to

unopacified bowel and vessels 5mm sections Pancreas does not have a firm

capsule

Pancreatic atrophy with fatty infiltration, age related

Pancreatitis, acute Pancreas, normal

Pancreatic

anatomy

Pancreatic head, superior mesenteric artery and vein

Suprarenal glands

F 35Y

QUIZ

CASES

1

2

3

MRI Coil selection

Body coil

Phased – array multicoils

• Increases signal/ noise

ratio

• Allows smaller field of view

• High cost

• Very high signal of

subcutaneous fat

Examination protocol

• Coronal localizer

• Axial T1 and T2 WIs

• Coronal T1 and T2 WIs

• Axial T2 fat suppression

• Dynamic post contrast axial T1 WIs

[Arterial , portal and delayed phases with or without fat suppression ]

Normal liver is of similar or higher signal to muscles [T1] Normal liver shows intermediate signal [T2] Spleen shows increased signal compared to the liver [T2]

MRI normal spleen

Multiple Angiomyolipomas T1, T1 Fat sat, T1 fat sat +c

MR advantages

MR is more sensitive in detection

and characterization of hepatic hemangioma

[high signal on heavily T2 weighted sequences]

MR can differentiate focal fatty changes from deposits

In diffuse fatty infiltration hypo dense deposits may

be masked by the hypo dense background of fatty

liver on CT .On MR the background is relatively high

signal in T1 WIs while deposits are of low signal,

so increases the difference

MR is sensitive for detection of hemorrhage

Hemangio

mas

demonstrat

ed by

heavily

weighted

T2 MRI

Normal renal

MRI.

T

1

T1+

C T

2

Normal renal MRI.

[Fat suppression]

T1 weighted images

Normal liver is of similar or higher signal to muscles

• T1 spin echo sequences

• T1 breath hold gradient echo images SPGR/ FLASH

Short TE 5 msec TR> 100mesc

Flip angle 80-90 degrees

Magnetization prepared T1 weighted GRE images [STIR]

very short TR < 10mesc

flip angle 40 degrees

Inversion time 500

T2 weighted images

Normal liver shows intermediate signal

Spleen shows increased signal compared to the liver

• Conventional T2 spin echo sequences

• T2 with rapid acquisition and relaxtion enhancement FSE Difference from T2 SE

• Higher signal intensity of fat on FSE

• magnetic susceptibility artifacts of metals on FSE

• ↑ magnetization transfer effect in FSE→ signal of solid lesions

MRI Fat suppression

Advantages • Decrease motion artifacts

• Improve signal/ noise and

contrast/ noise ratios of focal hepatic lesions

نستغفرك و نتوب اليك @نشهد ان ال اله اال انت @سبحانك الهم و بحمدك

Thank you

Diaphragmatic attachment of the liver

Malignant Colonic polyp