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Showing posts with label Lecture Notes. Show all posts
Showing posts with label Lecture Notes. Show all posts


Introduction

• Monochorionic twin complication caused by intrauterine transfusion of blood from donor twin (D) to recipient twin (R) via arteriovenous (AV) placental anastomoses.
• Staging based on fluid volume, bladder size, Doppler findings, presence of hydrops.




Epidemiology

• This complication can occur in ~10% (range 15-25%) of monochorionic pregnancies giving an estimated prevalence of ~1:2000 of all pregnancies.

Pathology

• TTTS results from unbalanced vascular (arteriovenous and arterioarterial) anastomoses in the placenta - that is, placental circulation is directed predominantly towards one twin and away from the other.



Fig: Close-up view of the placenta from a case complicated by TTTS shows a large arteriovenous anastomosis from the donor artery to the recipient vein. These deep placental anastomoses manifest as "nose-to-nose" vessels on the placental surface.


Diagnostic Criteria

• Monochorionic (MC) twins.
• Oligohydramnios in one sac + polyhydramnios in other.
    - Seen only in MC diamniotic twins (MDT); diagnosis in monoamniotic twins is more challenging.




Ultrasound Findings

• The syndrome is usually first identified between 16 and 26 weeks’ gestation.
• Serial ultrasounds of all monochorionic gestations are recommended to monitor for the development of TTTS, with fluid and bladder checks every 2 weeks.

Donor

• Oligohydramnios defined as maximum vertical pocket (MVP) ≤ 2 cm.
• 'Stuck twin' describes severe oligohydramnios with smaller, donor twin in fixed position by uterine wall.
    – Variant 'cocoon' or intrauterine sling; D cocooned in membranes, sling reflects back to uterine wall.
    – D suspended by sling, floats in pool of R fluid.
    – Look for differing echogenicity of fluid; D urine more concentrated → fluid more echogenic.
• Echogenic bowel described as sign of hypoxia in donor.
• Doppler abnormalities in D usually involve umbilical artery (UA).
    – Absent (AEDF) or reversed end diastolic flow (REDF).


Fig: Cocoon




Fig: Stuck Twin


Recipient

• Polyhydramnios defined as MVP ≥ 8 cm at < 20 weeks, > 10 cm at > 20 weeks.
• Doppler abnormalities in R more likely to involve ductus venosus (DV) or umbilical vein (UV).
    – Look for increased pulsatility or reversed A wave in DV.
    – Look for pulsatile UV flow.
        □ Indicates imminent hydrops.
• Cardiomyopathy due to volume overload.
    – Cardiomegaly, tricuspid regurgitation, impaired ventricular function, biventricular hypertrophy.
• Pulmonary atresia, pulmonary stenosis (PS) incidence as high as 9.6%.
    – Isolated PS seen in 0.2% uncomplicated MDT, 2.9% of TTTS cases treated with laser.
    – 18% regressed after laser, 65% required neonatal valve dilation in series published in 2015.

Other Features

• Discordant twin growth not mandatory feature.
    ○ Only 20% of donor twins met criteria for selective growth restriction (sFGR) in one large series of TTTS.

• Umbilical cords may differ in size.
    ○ R larger than donor D.



Fig: Postnatal examination of the placenta demonstrating the discordant sizes of the donor (D) and recipient (R) cords.




Fig: Early Twin-Twin Transfusion Syndrome.
Stage I: Monochorionic twins at 16 weeks’ gestational age. A discrepancy in abdominal diameters is apparent. The smaller twin on the maternal left (L) has much less amniotic fluid than the larger twin on the maternal right (R).
The very thin separating amnion is visible between the twins (arrowhead).




Fig: Twin-Twin Transfusion; Stuck Twin.
Monochorionic twins at 16 weeks’ gestational age. One twin (O) is ‘stuck’ to the anterior uterine wall as a result of severe oligohydramnios. Its twin (P) is far posterior, freely moving in a large amount of amniotic fluid.
The membrane (arrowhead) is barely visible surrounding a tiny amount of echogenic amniotic fluid between the legs of the ‘stuck’ twin.



Fig: Continued shunting from donor to recipient causes volume overload, which can, as in this case, lead to hydrops. Note the skin thickening and ascites. The cord Doppler is also abnormal with absent end diastolic flow and pulsatile umbilical vein flow. This is stage 4 TTTS.



Fig: In another case, pulsed Doppler ultrasound shows tricuspid regurgitation in the recipient as well as thick myocardium and pericardial effusion. These are all signs of cardiac decompensation.




Fig: Abnormal Doppler findings are used to stage TTTS. In this case, the donor (A) Umb A shows either absent or reversed end diastolic flow and pulsatile Umb V flow. 
The recipient (B) has normal cord flow. This is stage III-D TTTS.

Staging

Cardiovascular Profile Scoring (CVPS)

    ○ Points based on hydrops, DV/UV/UA Doppler, cardiothoracic ratio, cardiac function based on ventricular systolic function and atrioventricular valve regurgitation

Children's Hospital of Philadelphia (CHOP)

    ○ Points based on 4 Doppler and 9 echo parameters (including heart size, ventricular and valve function, venous Doppler, great artery size, pulmonary insufficiency)

Quintero System 

• Most established
    Stage I: oligohydramnios/polyhydramnios
    Stage II: bladder not visible in donor twin
    Stage III: abnormal Dopplers in either twin
    Stage IV: hydrops fetalis in either twin (almost always in the recipient; rarely in the donor)
    Stage V: in-utero demise of either twin




Complications

• Donor
    - Oligohydramnios, may be “stuck”
    - IUGR, small size
    - Small/nonvisualized bladder
    - If live born, has better outcome

• Recipient
    - Polyhydramnios
    - Possible hydrops
    - Dilated bladder ± dilated renal pelves
    - Large size
    - Cardiomegaly
    - Struggles postnatally


Treatment

• Fetoscopic laser surgery performed at specialized centers worldwide; a less invasive alternative is serial amniocentesis to equalize luid volumes and decrease the risk of preterm labor.



Fig: Graphic illustrates endoscopic laser coagulation of the chorionic anastomoses that cause TTTS. Access to the placenta is via the large amount of fluid in the recipient's sac. The "stuck" donor twin is seen on the left.



Laser was performed for TTTS 16 weeks prior to delivery in this case. The vascular equator is devoid of intertwin communications as a result of "dichorionization." All intertwin vascular connections along the equator are lasered with this technique.



• Other management options include:
    - Conservative management with surveillance for Quintero stage 1 TTT.
    - Serial amnioreduction, where laser treatment is not available .


Courtesy

• Diagnostic Ultrasound, 5th Ed; Carol M. Rumack
• Diagnostic Imaging: Obstetrics, 3rd Ed; Paula J. Woodward, Anne Kennedy, Roya Sohaey
• https://radiopaedia.org/articles/twin-to-twin-transfusion-syndrome-1
• Case courtesy of Dr Matt Skalski, Radiopaedia.org, rID: 68846
• Ultrasound Obstet Gynecol 2005; 25: 307–311
• Radiology Channel (Youtube)
• Wiley InterScience (www.interscience.wiley.com) DOI:10.1002/uog.5233

 

Mammography

 

Introduction

This technique uses a low-energy X-ray beam to maximize differences in soft-tissue density and demonstrates the internal architecture of the breast.

Compression of the breast, a short exposure time and the use of high-quality screen-film equipment improve image quality. 


Anatomy 


 

Radiological Anatomy

  


 

 Common Views

A. Mediolateral oblique view (MLO)

B. Craniocaudal view (CC)

 


1. Pectoralis muscle

2. Retroglandular fat

3. Glandular breast tissue

4. Nipple

5. Cooper’s ligaments

 

Why Compression Is Used

To decrease the thickness of the breast and make it more uniform.

To bring the breast structures as close to the image receptor (IR) as possible.

To decrease the dose needed and the amount of scattered radiation.

To decrease motion and geometric unsharpness.

To increase contrast by allowing a decrease in exposure factors.

To separate breast structures that may be superimposed.


Physics

X-ray beams with low penetrating characteristics must be used to produce visible images

Because the normal composition of the breast and the usual signs of cancer are in soft tissue with very little difference or physical contrast.

If very high kVp x-rays are used, very little absorption by tissues and consequently the contrast will be very poor.

Usually 25-30kVp is used.

This results in higher exposure.

The imaging receptors necessary for their visibility require a higher exposure than receptors for other radiographic procedures.





Criteria

Low kVp x-ray beam

Minimum filtration of the beam

Small focal point

Fine grain mammographic films

 

Breast Types



 

Fibroglandular Breast (Younger or Pregnancy)

 



 

Fibrofatty Breast (30-50 Years)

  


  Fatty Breast

 


 

Ultrasound

 



Why Ultrasound

Safe – No radiation hazard

Can differentiate between solid and cystic lesion

Real time evaluation

Can check the vascularity

Almost exact identification of location


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