Ewing's Sarcoma- A review.

Hello everybody!

Let's review a few important points on Ewing's sarcoma.

Ewing sarcoma is one of the small, round cell lesions of bone

Second most common malignant bone tumor in children (after osteosarcoma)
Common in males than females.

Occurs between the ages of 5-30 years.

 Location:

Arise in medullary cavity, usually of long bones in the lower extremities. Commonly involves metadiaphysis of long bones.

Most commonly occurs in long bones and pelvis but they can occur in virtually any bone.

Clinical Findings:

Most common symptoms are localized pain and swelling.

Additional symptoms:

Fever

Weight loss

Anemia

Leukocytosis

Elevated erythrocyte sedimentation rate 

Imaging Findings:

Most lesions are visible on conventional radiographs

However, their degree of spread is better evaluated with MRI

Common manifestations on conventional radiography include

1)Poorly marginated, lytic, destructive lesion

2)Permeative (small holes) or moth-eaten (mottled) appearance

3)Rarely, they can be sclerotic,Soft tissue mass or infiltration is common

4)Soft tissue mass may occur without destruction of cortex.Soft tissue mass may produce saucerization (scalloped depression in cortex)

5)Periosteal reaction is common

6)Lamellated - onion-skinning due to successive layers of periosteal development

7)Sunburst or spiculated - hair-on-end appearance when new bone is laid down perpendicular to cortex along Sharpey’s fibers.

8)Codman’s triangle - formed between elevated periosteum with central destruction of cortex

9)Osteosclerosis may be present secondary to reactive bone formation

Prognosis:60-75% five-year survival.

Treatment:Systemic chemotherapy is the mainstay of treatment with surgery and/or radiotherapy playing a role depending of the location and size of the tumour.

Hope this was useful.

Let's Learn Together!

-Medha.

Types of barium-contrast imaging.

Hello everybody!

Let's quickly revise the types of Barium investigations.

So to enlist the investigations are: Barium swallow, barium meal, barium follow-through, and barium enema.

The barium swallow, barium meal, and barium follow-through are together also called an upper gastrointestinal series (study), whereas the barium enema is called a lower gastrointestinal series (study).

Procedure:

In upper gastrointestinal series examinations, the barium sulfate is mixed with water and swallowed orally, whereas in the lower gastrointestinal series (barium enema), the barium contrast agent is administered as an enema through a small tube inserted into the rectum.

Let's review individual examinations breifly:

Barium swallow X-ray examinations are used to study the pharynx and esophagus.

Barium meal examinations are used to study the lower esophagus, stomach and duodenum.

Barium follow through examinations are used to study the small intestine.

Enteroclysis also called small bowel enema is a Barium X-ray examination used to display individual loops of the small intestine by intubating the jejunum with a small tube and administering Barium sulfate followed by methylcellulose or air.

Barium enema examinations are used to study the large intestine and rectum.

Hope this was useful!

Let's learn Together!

-Medha.

CT scans and role of Contrast enhancement

Contrast enhancement and it's role in CT scan
The concept of Contrast enhancement in radiology is not new and it has been in practice even before the Advent of CT scans.
CT scan as a modality of imaging was invented by a British engineer Godfrey Hounsfield in the year 1972.

Purpose of Contrast enhancement

Contrast enhancement is a method of exaggerating  the visible difference between adjacent structures on scan by administrating contrast agents.The term Contrast enhancement in CT scan includes usage of radio opaque substances for better visualization of the anatomic structures as well as better localization and characterization of the pathologies, better differentiation of the pathology from the normal surrounding structures.

Principle of Contrast enhancement

The diffusion of contrast agents from the blood stream to the body tissue is physiologically limited. In pathologies such as cancer, blood vessels grow (angioneogenesis) with increased leaking of contrast agents resulting in lesions much more visible on Contrast enhanced scans.
In CNS, contrast diffusion is limited by Blood brain barrier. Disruption of BBB lead to enhancement after administration of contrast agents.

Indications of Non Contrast CT (NCCT )
For detection of
1.Stones in kidney,ureter, cbd
2.Calcification
3. Fat in various tumors
4. Head injury
5. Acute hemorrhage
6. Stroke
7. SAH


CECT

The pathologic lesions show enhancement or attenuation depending upon the phase of contrast enhancement. So if you are looking for a particular pathology,it is important to know in which phase of CECT to look for.
For that purpose,I've enumerated the phase in which CT scan is done and can be recorded.

1. Non enhanced phase (NECT)
Uses are same as those of Ncct. Many a times this scan is done before administration of the dye to compare pre and post contrast enhancement study.
Calcification, fat in tumors, inflammation and infarction can be seen in this phase well.

2. Early arterial phase (15-20 secs post injection)
When contrast is still in the arteries, it has not enhanced the organs.
This phase is useful to look for vascular abnormalities such as aneurysms, vascular stenosis, etc

3. Late arterial phase (35-40 secs post injection)
Sometimes known as arterial phase.
All the structures that get their blood supply from arteries will show optimal enhancement in this phase.

4. Hepatic or late portal phase (70-80 secs post injection)
Liver parenchyma enhance trough blood supply by portal vein and some enhancement of hepatic veins.

5. Nephrogenic phase (100 secs post injection)
This is when all of the renal parenchyma including medulla enhances. Particularly helpful for small renal cell carcinoma which are otherwise missed.

6. Delayed phase (6-10 mins post injection) called as wash out phase or equilibrium phase
Washout of contrast in all abdominal structures except for fibrotic tissues which become relatively more dense in this phase.

Factors affecting CECT
The timings depend on
1. Organs to be scanned and focussed
2. Type of CT machine available, number of slice
3. Amount of contrast given depending upon the body weight of the patient
4. Injection rate of the contrast
5. Route by which contrast given. (Mainly IV but can be oral,rectal too)

Lesions / pathologies visualized on CECT
1. Liver tumors
Due to it's dual blood supply, 80% by portal vein and 20% by hepatic artery normal parenchymal enhancement maximally in hepatic phase . On the contrary, all all liver tumors are supplied 100% by hepatic artery. So hyper vascular tumors are best seen in late arterial phase. Hypovascular tumors on the other hand are better seen in hepatic phase.
2. Fibrotic lesions
Fibrotic lesions like cholangiocarcinoma and fibrotic mets hold contrast much longer than normal parenchyma hence best seen in delayed phase.
3. Pancreatic tumors most of them being hypovascular are seen best in late arterial phase. In cases of acute pancreatitis, late arterial phase best detects necrosis. Remember chronic pancreatitis can be very well appreciated on NCCT due to calcification.
4. Anastomosis leakage 
CECT done in post op patients to check anastomosis leakage. Oral contrast play a role here for check scans done in post op bowel anastomosis.

5. Pulmonary embolism - 
Good quality scans are required to delineate the emboli in the pulmonary vasculature.
6.CT angiography 
For vascular studies.

Dr. Shil Pill

Chest x-ray - Left Lung.

Hello everybody!

Let's see the image correlations of the left lung today.

The left lung has an apical lobe ,lingula and a basal lobe.

Apical lobe has 2 segments: Anterior and posterior.
Lingula : The tongue like extension and the alleged counterpart of the middle lobe has 2 parts to it : Superior and Inferior.
Basal lobe has 4 segments namely : Superior, Posterior, Medial, Lateral.

Carefully observe how the identification of these segments differs while seeing an X-ray.

Apical lobe:

Basal Lobe:

So that's it with the interpretation of lung fields on X-rays!

Hope this is helpful!

-Medha.

Chest X-ray - Right Lung!

Hello everybody!
So today let's go through the Right lung segments as seen on a Chest x-ray with the help of images.

This will help us identify the exact location of the pathology and the possible etiology for the same.

So the Right lung has 3 lobes.
Upper
Middle
Lower.

Let's start with the right UPPER LOBE.
It has 3 segments.

Now moving to the MIDDLE LOBE .
It has 2 segments Medial and Lateral.

Moving to the LOWER LOBES.

It has 5 segments.

Superior Basal

Lateral Basal

Antero Basal

Medial Basal

Posterior Basal.

(3D CT Images courtesy - CU medicine Hong Kong)

So well I hope this helps to correlate the various Bronchopulmonary segments while interpreting a Chest x-ray!

Let's Learn Together!

-Medha.

Brain Function Imaging.

Hello everybody!
Today we shall breifly learn as to how we can study the brain function using imaging techniques.

Positron Emission Tomography (PET)made debut in 1980s; two more imaging techniques came in the 1990s: functional magnetic resonance imaging (fMRI) and magnetoencepalography (MEG).

1) Positron Emission Tomography:

This technique makes it possible to see in an image which part of the brain is active during a particular task.
As we also know that although brain as a whole does not consume significantally more energy when it is active than when it is idle, metabolic activity does increase in circumscribed regions of the brain when these regions are functionally active.
This increased metabolic activity in the brain is the basis of PET.

In this technique a positron-emitting isotope is tagged to a molecule of biological interest such as glucose or a neurotransmitter.

For example, the positron-emitting isotope of fluorine (18F) is tagged to deoxyglucose and it is injected intravenously.
Deoxyglucose is taken up by neurons in the same way as glucose, but it can neither be fully metabolised nor can it come out of the neurons.
Since functionally active neurons take up more glucose, active regions of the brain accumulate more deoxyglucose.
So , following visual stimulation, 18F-deoxyglucose accumulation can be seen in the visual cortex. This signifies increased glucose metabolism in the visual cortex. Thus we have evidence for involvement of specific regions of the brain in specific functions

Positron emission is detected by appropriate detectors which construct a series of computerised images of the brain similar to those seen in computerised tomography (CT).

2) Functional MRI :
It is based on the principle that increased neuronal activity leads to a local increase in blood flow through the active part of the brain.

The increase in blood flow is somewhat greater than is warranted by the increase in oxygen consumption.
Therefore, blood flowing through the active, hyperemic region of the brain has more oxygenated haemoglobin than the blood flowing through less active regions of the brain.
The magnetic properties of oxygenated and deoxygenated haemoglobin are different, the magnetic resonance signals from the active region of the brain increase.

Functional MRI systems currently in common use give a spatial resolution of about 1 mm, but a resolution of 0.5 mm has been achieved in experimental settings. This is an important breakthrough because cortical columns also have a width of about 0.5 mm.

3)Magnetoencephalography (MEG):

It can complement the information obtained from the conventional electroencephalography (EEG). MEG is based on the principle that neuronal activity in the cerebral cortex generates not only fluctuations in electrical potential (detected by EEG) but also magnetic fields. Unlike EEG signals, MEG signals are not distorted by the intervening tissues. These technical advances have given hope for rapid progress in localization of functions in the human brain.

So I hope ,this helps you guys to have a better picture on Brain Imaging.

Let's Learn Together!
-Medha.