Ante-natal doppler assesment

Quite frequently we need to make a doppler assesment of ante-natal patients, whenever abnormal biometry points towards IUGR. A quick check on umbilical artery, see if there is good diastolic flow, and confirm IUGR if you see a diastolic notch and high pulsatility. S/D ratios may be unreliable many a times. But, taking a ratio of MCA and umbilical artery is very sensitive and specific. I would suggest no panic if you only see low S/D ratio in MCA, while uterine and umbilical arteries are fine.

Checklist
1. Umbilical artery
2. MCA
3. Uterine arteries
4. Umbilical vein
5. Ductus venosus

1. S/D Ratio and PI of MCA/Umbilical artery less than 1 signifies IUGR.

2. Diastolic notch or absence of diastolic flow in umbilical arteries signifies adverse outcome.

3. Diastolic notch with high pulsatility index of Uterine arteries signifies uteroplacental insufficiency.

4. Smooth umbilical venous cord flow with peak velocity of 16 cm/sec signifies IUGR.

5. Decreased pulsatility in MCA signifies redistribution of blood flow.

6. Loss of 'M' Pattern in ductus venosus due to absent or reversed 'a' wave.

Mediastinal cystic masses

Cysts are forte of ultrasonologists but when it comes to mediastinum, confusions prevail. We can very well characterize the cyst but we keep manoevring our transducer through the limited intercostal window to see the relations with mediastinal structures. Chest X-Rays are definitely helpful to guide us but in my view, CT scan can clear all the clouds when it comes to mediastinal cyst.
Differential diagnosis
1. Congenital benign cysts - Bronchogenic cyst, Esophageal duplication cyst, Neurenteric cyst, Pericardial cyst, Thymic cyst.
2. Meningocele
3. Mature cystic teratoma
4. Lymphangioma
5. Tumors with cystic degeneration - Thymomas, Hodgkin's disease, Germ cell tumor, Mediastinal carcinomas, Metastases to lymph nodes, Nerve root tumors.
6. Mediastinal abscess
7. Pancreatic pseudocyst
8. Hydatid cyst
Benign cysts : Fundamentals are same for cysts anywhere else in body. A smoothly marginated cyst with thin enhancing walls and homogenous low attenuation non-enhancing contents, with no infiltration of adjacent mediastinum are usually benign. MR will show T2 hyperintensity within cyst.
1. Bronchogenic cyst: Mostly situated near carina in middle or posterior mediastinum, these cysts are mostly detected incidentally during imaging. If on a CXR, you see a subcarinal homogenous round opacity, often towards right side, think of bronchogenic cyst. Confirmation can be done by CT scan revealing a low attenuation cyst. But, again it depends on whether the cyst is infected or got hemorrhage, attenuation may vary and even be more than 100 HU. Sometimes, air-fluid or fluid-fluid levels may also be seen.
2. Duplication cyst: CT/MR imaging appearance are identical to bronchogenic cyst except that they have more intimate contact with esophagus and walls are little bit thicker.
3. Pericardial cyst: You see a cyst at cardiophrenic angle, mostly on right side and if you can demonstrate a communication with pericardial sac, you will hit the bull's eye! But, you get misguided right from the CXR. Some may ignore it as mediastinal fat pad. While the sceptic ones may evaluate for morgagnian hernia. CT does the trick most of the time. (I even got confused with loculated pleural effusion today!)
4. Meningocele: CXR looks similar to a neurogenic tumor radiograph, where you see paraspinal mass in posterior mediastinum, with enlarged intervertebral foramina. CT shows a cyst and you are done with diagnosis.
5. Thymic cyst: Very very rare cyst. Anterior mediastinal cystic mass lesion (just like any other thymic mass lesion) with CT characteristics of cyst should be a thymic cyst.
6. Mature cystic teratoma: Mostly in anterior mediastinum, with soft tissue, fat and calcification. within. Hardly any doubt remain in most of the cases.
7. Lymphangioma: A lobulated cystic lesion insinuating here and there in the mediastinum, even extending to neck sometimes. Seldom they cause any compressive symptom.
Recommended article: http://radiographics.rsna.org/content/22/suppl_1/S79.abstract

Carotid doppler study

Carotid doppler evaluation is one of the easiest doppler to record and at the same time, quite difficult to interpret (and sometimes even identifying vessels!). Position the patient's head in slight hyperextension and rotate 45 degrees away from the side being examined. Perform a complete gray scale survey, which means a longutidinal and axial survey along neck, caudal angulation in supraclavicular region and cephalic angulation of transducer at level of mandible. Color doppler is done to look for any hemodynamic abnormality and then proceed to pulse wave doppler. Due to tortuous/non-linear course of vessels, correct angle is vital to the study. Don't align the angle with the vessel as we always tend to do, but align with the velocity vector. Avoid color aliasing artefact by setting an optimum color scale (not too low nor too high). Identification of vessels is done as
a) Common carotid artery is easily located, and then follow it superiorly to locate 2 vessels beyond bifurcation. Sometimes, bifurcation is pretty high-up and difficult to identify. ECA is identified by presence of its multiple branches in neck. Another method is tapping on superficial temporal artery and looking for reflected flow in ECA. Normally, ICA shows some color during diastole while ECA doesn't.
b) Identification of the vertebral artery is achieved by locating the CCA in sagittal view and sweeping the tranducer laterally to the transverse processes of cervical spine.

Checklist
1. Intima media thickness, plaque measurement and characterization
2. Area reduction
3. ICA PSV, ICA:CCA PSV ratio
4. Near complete/complete occlusion
5. Vertebral steal (Complete or partial)

1. Intima media thickness: Intima media thickness means measuring from inner wall (echogenic) till the hypoechoic media layer. It is normally less than 1 mm.
2. Plaque morphology: Check if plaque is homogenous or heterogenous, echogenic or hypoechoic. Hypoechoic and heterogenous plaques are more ominous.
3. Area reduction: Area reduction >50% is significant stenosis.
4. ICA PSV and ICA:CCA PSV ratio: ICA PSV is normally less than 125 cm/sec. More than 230 cm/sec PSV is very significant stenosis. ICA:CCA PSV ratio should be less than 2.0. If it is more than 4.0, its quite significant. Normal flow in CCA is 45-120 cm/sec.
A suggested format is given below.

Renal artery doppler

Renal doppler is one of the most frustrating doppler study where struggle begins right from the moment you start looking for renal artery, especially in a poorly prepared obese patient. 12 hour fasting and taking them as first patient in morning is advised. Adjust color doppler parameters like color gain, pulse repitition frequency and wall filter, by setting it on larger vessel like aorta. Try first anterior abdominal approach to locate renal vessels. If it fails, try an oblique or decubitus position with liver serving as acoustic window. Begin at celiac axis or SMA as they are easier to locate, and move slightly caudad, you may easily find atleast the origin of right renal artery. Then, you may follow the right renal artery till the hilum. Left renal artery is harder to follow all the way, so one may make the patient turn in right lateral decubitus position and scan from left posterolateral aspect (using left kidney as acoustic window). Similar approach may be used for right renal artery by turning patient to left decubitus.

Checklist
a. Kidney echotexture, parenchymal thickness, any focal lesion.
b. Longitudinal survey of aorta from ceilac artery origin till bifurcation, to look for plaques.
c. Measure PSV (peak systolic velocity) in aorta at the level of origin of renal artery.
d. Origin of renal arteries (atleast PSV)
e. Proximal, mid and distal segments of each renal artery (PSV)
f. Segmental arteries at upper, mid and lower poles.
Thus, capture 7 waveforms on each sides (Measure PSV, RI, Acceleration time). Look for areas of color shift, aliasing or any turbulence. Make sure to look at origin and proximal segment in elderly patients, where plaques are more likely to occur. Similarly, look for entire renal artery and segmental branches in younger patients to rule out Fibromuscular Dysplasia.
Normal renal artery waveform is low resistance flow pattern with good diastolic forward flow, with no spectral window.

1. Raised Peak systolic velocities: Normal PSV in renal arteries is 74-127 cm/s. PSV >180 cm/s and renal artery:aorta ratio >3.5 signifies significant stenosis.
2. Damping of intrarenal vessels: Tardus parvus waveform in segmental arteries with slow rise peak and rounded contour signifies stenosis. (Acceleration time >0.07)

Resistivity index (RI) is usually less than 0.7 in renal arteries. Raised RI is seen in many medical renal diseases and is quite non-specific.

Doppler assessment of spleno-portal axis

Checklist
a. Liver echotexture
b. Portal vein
c. Spleen size
d. Splenic and Superior mesenteric veins
e. Portosystemic collaterals
f. Hepatic artery
g. Hepatic veins

1. Liver echotexture: Coarsened echotexture (doesn’t mean increased echogenicity) with irregular nodular surface is characteristic of cirrhosis. Portal and hepatic veins are less visualized. Right lobe may shrink in size, with enlarged caudate and left lobe. “Caudate:Right lobe ratio exceeds 0.65.” (measured by comparing maximum transverse dimensions at axial image just below portal bifurcation).
2. Portal vein diameter: It should be less than 13 mm, measured where portal vein crosses the IVC, during quiet respiration, in supine position. “Diameter more than 13 mm indicates portal hypertension with high specificity.”
3. Response of the portal, splenic and superior mesenteric vein to respiration: Diameter of these veins should increase by more than 70% from quite to deep respiration. “Less than 70% increase in diameter indicates portal hypertension.”
4. Portal flow direction, velocity and waveforms: Normal flow is hepatopedal, with mean flow velocity (TAM) of 15-18 cm/s and shows respiratory variation. “Loss of respiratory variation, to-and-fro biphasic flow or reversal/hepatofugal flow signifies portal hypertension.” *
5. Spleen size: Spleen size more than 13 cm, measured in cephalocaudad direction in coronal plane.
6. Presence of portosystemic collaterals: These can be identified by following these simple steps:
• Start from left side, see if flow reversal is there in splenic vein, look for splenorenal and splenogastric collaterals (adjacent to upper and lower poles of spleen respectively).
• Evaluate blood flow direction in main portal vein. Flow reversal indicates collateralization
• Return to left portal vein and follow it till falciform ligament, where umbilical vein collateral may be visible.
• Look for a cephalad directed vessel arising from portal vein just at superior mesenteric vein-portal vein junction.
• Look for GB wall collaterals.
• Gastric and gastro-epiploic collaterals may be seen adjacent to posterior surface of liver towards left lobe.
• Look for collaterals at GE junction.
7. Hepatic artery: Due to decrease in portal flow, flow in hepatic artery is increased to maintain hepatic blood supply,

* Flow reversal in portal and splenic vein is a variable finding depending on collateral development. If splenorenal collaterals are predominant, flow may reverse in portal vein. However, if large umbilical vein collateral is predominant, flow may be hepatopedal in portal and splenic veins because diverting collateral (umbilical vein) arises in left portal system.

Eyes only see what it knows

We don't need to understand a photograph. Do we? Just because, our eyes are conditioned for this image reconstruction algorithm. But, a mysterical aura surrounds a radiograph and many a time we are not able to understand it. As a patient enters a diagnostic station, his body runs through a chain of imaging modalities, hundreds of imaging sequences and innumerable views to get a million of images. Radiologists scan through them, twist and storm their mind, rote the old books and images to produce a brilliant superfluous piece of paper called "report". This site aims at bridging a huge existing chasm between clinicians and radiologists. Lets condition our eyes to every possible thing, so that we look a radiograph with same complacency as a photograph.