mri nephrology 2017

BYMOHAMED ABOU EL-GHAR

UROLOGY & NEPHROLOGY CENTERMANSOURA UNIVERSITY

Basics of MRI in Nephrology

What is MRI

MRI is a machine creates a magnetic field, sends radio waves through your body, and then measures the response with a computer.

This creates an image or picture of the inside of your body that is much clearer than can be obtained with most other methods.

MRI

The potential advantages of MRI for evaluating urinary tract abnormalities are:

No ionizing radiation. Multiplanar capabilities. Excellent anatomic resolution

and soft tissue contrast.

Before MRI

Cardiac pacemaker or implantable defibrillator.

Catheter that has metal components.

Metallic prosthesis.A ferromagnetic metal

vascular clip.An implanted or external

medication pump.A cochlear implant.A neurostimulation system.

MRI EXAMINATION TECHNIQUES

• high magnetic field (1.5 – 3 Tesla)

• high performance gradients

• phased-array coil → high SNR & small FOV


T2 WEIGHTED IMAGING

• simple cysts• complicated cysts • angiomyolipoma (AML)• hematoma, aneurysm• infectious mass• renal cell carcinoma (RCC)

T2- weighted MRI

• SPIN ECHO SEQUENCE• IN PHASE AND OPPOSED PHASE SEQUENCE• 3D GRE SEQUENCE


T1 WEIGHTED IMAGING

• complicated cysts (hemorrhage, infections, septations)

• AML• melanin-containing lesions• proteinaceous mucin containing lesions• Adrenal mass characterization

T1-Weighted MRI

3D GRE sequence

HIGH SPATIAL RESOLUTIONHIGH TEMPORAL RESOLUTION


• Single shot or multishot• Full coverage of the kidney in one 18-23

s breathhold

3D GRE T1 SEQUENCE+

GADOLINIUM

DYNAMIC CONTRAST-ENHANCED MR IMAGING


MRU

MRU is the most important technique in uroradiology.

It has a good diagnostic value in virtually all kinds of urinary tract disorders.

MRU can reduce the need for radiation exposure and invasive procedure.

MRU Examination Techniques

T2-Weighted ( STATIC - FLUID) MR Urography.

* Multi-slice MRU * Single slice MRU T1-Weighted (EXCRETORY) MR

Urography.

T2-W(static –Fluid) MRU

In static- fluid MRU, Heavily T2w Turbo spin echo (TSE) sequences are used to obtain water images of the urinary tract.

It is used to image fluid filled cavities such as hydronephrosis.

• slice thickness: 6-10 cm• inclusion of the entire pelvicaliceal system and

the whole course of the ureters• coronal plane and sagittal plane

SINGLE SLICE PROJECTION IMAGE

Advantages:

• acquisition time: 3-8 s• no motion artifacts• no post-processing• ureterohydronephrosis and

location of obstruction

Disadvantages:

• no cause of obstruction• low spatial resolution• low signal to noise ratio

MRU EXAMINATION TECHNIQUES

MULTISLICE TECHNIQUE

• overlapping slices• section thickness: less than 5 mm• post-processing: MIP images

Advantages• reduced partial volume

averaging• small pathological details

Disadvantages• more time consuming• superimposing

extraurinary fluid

MRU EXAMINATION TECHNIQUES

T2-weighted MR urography

T1-w excretory MR Urography

Excretory MRU imitates the conventional IVU.

Gd-Enhanced urine is imaged with use of fast T1-w GRE sequences.

Low –molecular –weight Gd have demonstrated a good safety profile at standard clinical dose.

Diffusion-weighted imaging (DWI)• MR diffusion-weighted imaging (DWI) provides information on

the velocity and direction of movement of the water molecules in tissue under influence of a diffusion gradient

• The velocity and direction of the diffusion movement of the water molecules can be quantified by means of the apparent diffusion coefficient (ADC)

Koh DM et al, AJR (2007)


Diffusion-weighted imaging (DWI)Restricted diffusion: *Malignancy (increased number of cells ) *Ischemia (cytotoxic edema) *Abscess (increased viscosity)


Limitations

MOTION ARTIFACTS

• BREATHING• VESSEL AND CARDIAC PULSATILITY• BOWEL MOVEMENTS

Single shot EPI DWI



Diffusion sequence

Collecting system


Bladder


All In Approach

Preoperative assessment of potential live kidney donor.

Basal study of transplanted kidney.Pelviureteral junction obstruction.Nephron sparing surgery.

MR Urography

Obstructed or non-obstructed?Urothelial lesions.Cause of obstruction.Congenital Anomalies.

Congenital Anomalies

CROSSED ECTOPIA

Ectopic kidney

-Simple renal ectopy refers to a kidney that remains in the ipsilateral retroperitoneal space.

-The most common position is in the pelvis or sacral region below the aortic bifurcation.

-Crossed renal ectopia with fusion occurs in 85%, without fusion in less than 10%.

ANOMALIES OF POSITION

RENAL DYSPLASIA

In infancy the appearance is variable, from normal to few isolated cysts, rarely a kidney packed with cysts. There is preservation of the renal shape, echogenicity and cortico -medullary differentiation.

ADPCKD

ARPCKD

Kidneys: the dilated tubules are responsible for the appearance.- Kidneys enlargment.-Diffuse increase

echogenicity and hyperechoic foci on US.

-Low attenuation with striate pattern on CT.

-Diffuse increase signal intensity in T2 w Images on MRI.

-Macro cyst in varying patterns can be present.

Liver: dilatation of the bile ducts.

Vascular Lesions

Renal artery stenosis.Renal aneurysm.Renal AV malformation…..etc.

Inflammatory Lesions

Diagnosis of different inflammatory lesions.

Extension and other organ involvement.Follow up after management.

Kidney Transplant Complications

Urinary leakage.Urinary obstruction.Renal parenchyma.

NSF

Nephrogenic systemic fibrosis (NSF) is a relatively uncommon condition in which fibrous plaques develop in the dermis and, often, in deeper connective tissues.

Reported cases have occurred almost exclusively in patients with severe renal disease, and almost all have been associated with prior use of gadolinium-containing MRI contrast agents.

The disease is often disabling, no proven treatments exist.

Clinical features of NSF

Onset: From the day of exposure for up to 2–3 months Initially– Pain– Pruritus– Swelling– Erythema– Usually starts in the legs Later– Thickened skin and subcutaneous tissues — ‘woody’ texture and brawny

plaques– Fibrosis of internal organs, e.g. muscle, diaphragm, heart, liver, lungs Result– Contractures– Cachexia– Death, in a proportion of patients

Who is at RISK

Whilst cases have occurred in patients with either acute or chronic renal failure.

Most have been in patients with chronic and severe kidney disease (CKD Stage 4 & 5, glomerular filtration rate (GFR) < 30 ml/ min/1.73 m2); most have been on dialysis.

At lower risk Patients with CKD 3 (GFR 30-59ml/min)

Not at risk of NSF Patients with stable GFR > 60 ml/min

Take care

Children under one year of age, have a physiologically low GFR yet no case of NSF has been reported in a patient under the age of 6 years.

In lactating patients, the proportion entering the breast milk is very small (1% of the injected dose), and very little of this is actually absorbed. Hence the risk to the child would appear negligible.

Lactating women: Stop breastfeeding for 24 hours and discard the milk.

Pregnant women: Can be used to give essential diagnostic information.

High Risk Patients

The minimum adequate dose of gadolinium is used. Restrict dose to 0.1 mmol/kg and avoid repeat scans.

Consider immediate post-scan hemodialysis. A single conventional hemodialysis session will

remove 75% of the free Gadolinium – a 2nd treatment 93% and a 3rd treatment 98% of a dose.

If the patient has severe renal failure, but is not receiving hemodialysis, the possibility of commencing hemodialysis will need individual consideration.

ESUR Guidelines, 8.1 Contrast Media Guidelines

Never deny a patient a clinically well- indicated enhanced MRI examination.

In all patients use the smallest amount of contrast medium necessary for a diagnostic result.

Future prospective MRI Techniques

BOLD.ASLDTIDynamic MRI.

DCEMRI

THANK YOU

mri nephrology 2017

Health & Medicine