Catheter's in X-ray

Today I am going to talk about the research I have done in determining catheter tip locations from chest radiographs and a little of the future work we have planned.

As I mentioned previously, a lot of time is spent by radiologists doing intensive care unit imaging to make sure that every tube, line, and catheter is where it is supposed be. This is because if they aren't, complications and even death can occur. For example, its very important that feeding tubes end up in the stomach and not down one of the bronchi before you try to feed someone. But these reads are very time consuming, both in per scan rate and number of scans to read. So my research is focused on developing a method of computer aided detection of the tips, so that we at the very least can reduce the workload of the radiologists, which would further result in an increase in efficiency and throughput.

The first thing we looked at was that catheters were synthetic objects. They are basically tube with the ends cut off (kind of like a straw). This means that
1) The profile is consistent along its length
2) The profile of the object can known a priori
3) Intensity variations can be explained by
But we needed to verify the assumption so we took sample profiles along the length and got the graph below.



The profiles had roughly the same added attenuation at each point, the baseline is what mainly changed. So we are good to go on that front.

Taking into account the synthetic nature of the catheters, we developed a way to generate profiles automatically. These profiles are then matched from points outside the body to the tip, until no more evidence is found. We used normalized cross-correlation because it allowed for matching to occur regardless of intensity variations. Doing this progressive matching gave us results like the image below.



Not bad for proof of concept, right?

Luckily, I got to see many of the steps in how the images I am working with were acquired. This is actually quite helpful in knowing all the potential problems that the algorithm might need to deal with. I also spent time gathering data so that I have a larger set to work with. We are also planning on generating synthetic dataset next week to try out other methods of more direct detection.

CFD in Coronay Arteries: Part 1

For the past few weeks, I've been trying to develop a software that will be able to quantify the vulnerability of a plaque to rupture. As I mentioned before, no software in the market today is capable of extracting such information from CTA - this is my motivation. Nevertheless, no matter how motivated I am, it is not possible for me to develop such a software in a month; this is far beyond my capabilities. As a result, I broke the project up into four parts: Part 1, segment the lumen of the coronary arteries using CTA data; Part 2, discretize the boundaries into small cells to form a volume mesh or grid; Part 3, apply Navier-Stokes equations to solve the equations of motion; and finally, Part 4, validate simulation and develop a turbulence index to quantify the vulnerability of a particular lesion or plaque.

Part 1: Segmentation

Thus far, I've only been able to complete part 1 (figure). Basically, I have created an interface that allows one to load CTA data, preprocess the data through numerous filters, and finally, segment the arteries of interest using a region growing algorithm and/or simple thresholding. The software is far from perfect since it performs the segmenation in 2D. That is, it segments the arteries slice by slice, causing the whole process of segmentation to be slightly tedious. Nevertheless, one can use it to reconstruct arteries of interest.

Part 2: Tessellation

Pending... I'm trying to tessellate the segmented volume with rectangles. The following depicts the grid for a straight pipe. Although it seems simple, it is really not for odd geometries.
Part 3: Computational Fluid Dynamics

If I get lazy, which I probably will, I plan to use a CFD software package like FLUENT. This sophisticated software package will allow me to simulate blood flow in reconstructed arteries of interest. The following is a simulation by some company (I can't find there link so if anyone knows where this is from, post it in the comments).

Part 4: Validation and Index Development

I will validate the simulation by comparing theoretical fractional flow reserve values to practical ones (fraction of pressure about a lesion). And if the simulation proves to be incorrect, I will change the parameters of the mesh; otherwise, I will work on an index that decodes vulnerability.

J-Pouch

After an entire colectomy, the large intestine and rectum are removed. About a decade ago, it was necessary to divert a piece of small intestine to an artificial opening on the abdominal wall as the exit for the output. I’ve seen patients with this operation in China. The quality of life is significantly sacrificed after the operation. I always wondered if there is another way to make the exit. This week, I saw such an operation that makes a J-pouch to give a normal life to patients.

The operation was done laparoscopicly. The first part was as usual. Small holes were drilled on the abdominal wall and a 7cm incision was also made below the belly button. Large intestine and rectum were removed and taken out from the incision. However, the control muscle was kept, and this is the key point of the surgery.


After the removal of colon and rectum, the ileum was folded to form a reservoir. Later on, the bottom of the reservoir was connected to the control muscle. Sometimes, the second step requires two separate operations. After the reservoir is made, a temporary exit on abdomen is made so that the newly created reservoir isn’t in use immediately and may heal. 2 or 3 months after the first surgery, another operation closes the exit on abdomen.

The benefit of making a J-pouch is significant. The reservoir may store the waste until the need to have a bowel movement. The patient may have a pretty good control as normal people. It doesn’t need an external bag to store. Overall, the quality of life is enhanced.

Advanced Breast Reconstruction

So this past week I got to see one of the other, less common breast reconstruction procedures. As I mentioned in an earlier post, after a breast mastectomy, tissue expanders followed by implants are usually used to reconstruct the breast. However, a less common, way cooler, method is to use some type of flap, such as, the latissimus dorsi muscle, TRAM (transverse rectus abdominis myocutaneous), SIEP/DIEP (superficial/deep inferior epigastric perforator) flap. The free TRAM and SIEP/DIEP flaps are the most advanced procedures because they involve microsurgery to anastomose the tissue’s blood supply. Some flaps do not require this as the blood supply is left intact and the vessels are tunneled underneath the skin, as is the case for the latissimus dorsi muscle flap (on your back and tunneled under your armpit). Anyway, the cool one I got to see was the DIEP flap.

The DIEP flap procedure essentially combines two procedures in one. The tissue harvested to reconstruct the breast comes from the patient’s belly fat. So the patient basically gets an abdominoplasty (tummy tuck) at the same time. No muscle is taken with this flap, just fat. The novelty of this procedure is that the blood vessels perforating through the rectus muscle (the deep inferior epigastric vessels) are clipped and subsequently microsurgically anastomosed to the internal mammary vessels to feed the transplanted tissue in a quasi-Frankenstein kind of way.

Figure 1. The deep inferior epigastric perforator vessels.

Figure 2. The internal mammary vessels.

It was really amazing to watch the microsurgery. Blood vessels were sutured together with these tiny needles and very thin thread…I couldn’t even see where the needle was…just an occasional flare of light as the shiny metal reflected the light from the microscope. The surgeons performing this operation were very skilled; it was amazing to watch them work.

So the end result looked something like this. Pretty cool.

Figure 3. Final result showing the anastomosis of the DIEP and internal mammary blood vessels.

Brain Lab

Vascular Surgery
Week 5

Neuro Detour cont’d

http://www.brainlab.com/download/pdf/BrainLAB_Neurosurgery_Solutions.pdf

This is the VectorVision by BrainLAB. It integrates functional magnetic resonance imaging (fMRI) data to help a surgeon localize the removal of brain lesions while preserving surrounding brain tissue. The fMRI uses blood oxygen level-dependent (BOLD) contrast imaging to localize brain areas such as the motor cortex or language areas in response to task performance—the MR signal is slightly different depending on the level of blood oxygenation due to the diamagnetic when oxygenated, paramagnetic when deoxygenated, nature of hemoglobin.

http://www.brainlab.com

The surgeon uses the fMRI interfacial data to ensure the tumor is removed completely. The above image shows some of the brain anatomy highlighted. This is a fantastic technology, and I think it’s important to point out that innovation can stem from existing technology that is applied in a novel way.

Hernia repair

My doctor performs surgeries twice a week. By far the most common surgery she performs are hernia repairs. There are at least 1-2 cases per day, so I have seen over a dozen different hernia repairs.

A hernia occurs when the contents of a body cavity bulges out into another area of the body. Sometimes they contain portions of intestines or body fat that are naturally lined to inside the cavity. Hernias are usually harmless, but they can potentially be dangerous if they cut off the blood supply.

There are many types hernias and can occur in different stages of your life. Some form during birth, others during fetal development, existing openings in the abdominal cavity or weakening in the lining, and conditions that cause added pressure on cavities. Some of these conditions are obesity, heavy lifting, coughing, fluid in the cavity, straining during bowel movements, and chronic lung disease.

The signs of a hernia can range from a painless lump or a painful, tender protrusion in the abdomen. The doctor can examine the area of pain by adding pressure to that area. From this the doctor will be able to determine if you do have a hernia.

If the hernia can cause the blood supply to be reduced, the hernia may need to be operated on. If the hernia is irreducible, emergency surgery may be needed. But if the attempt to reduce the hernia succeeds, surgery can be scheduled later.

In a hernia repair surgery, the surgeon makes a cut over the area of the hernia. The bulging tissue or organ is placed back inside the muscle wall, the muscle tissue is repaired, and the skin is closed. In many inguinal hernia repairs, a small piece of plastic mesh is used to repair the defect in the muscle tissue.

Laparoscopic Myotomy

Overview
Laparoscopy describes a group of operations performed with the aid of a camera placed in the abdomen. The laparoscope was first combined with a video camera in the 1980s, an accomplishment that helped free up the surgeons' hands, so they could better work with their instruments. The laparoscope also allows doctors to perform minor surgeries with just a small cut in the abdomen. This technique is known as laparoscopic-assisted surgery.
Laparoscopic myotomy refers to a laparoscopic-assisted surgical procedure in which a muscle is cut. The case that I observed in the OR involved the cutting of the muscle from the esophagus to the stomach (a disorder called esophageal achalasia). Achalasia is a disorder of the esophagus. The esophagus is less able to move food toward the stomach, and the muscle from the esophagus to the stomach does not relax as much as it needs to during swallowing. This relaxation is needed to allow food to enter the stomach.

Diagnosis
Barium Swallow - Patients are asked to swallow a liquid which will be visible on an X-ray. A series of X-rays are then taken. Achalasia patients will often demonstrate abnormal valve relaxation and an absence of normal contractions.
Esophageal Manometry - Pressure recordings are assessed in this exam through a small catheter placed into the esophagus. Characteristic findings in patients with achalasia include an elevated lower valve pressure and failure of the valve to relax with swallowing.
Endoscopy - This is a procedure in which a small, flexible telescope is passed through the mouth into the esophagus. The lining of the esophagus can then be examined and biopsied.
Treatment
Medical therapy for achalasia with drugs that relieve the spasm of the sphincter (the muscle between esophagus and stomach) has largely been unsuccessful and associated with numerous side effects. The classical method for treatment remains endoscopic balloon dilatation and surgery. While dilatation can achieve a good result in up to 60% of patients, the results are frequently not durable. Also, dilatation carries the risk of esophageal perforation which would require emergency surgery.
Historically, definitive surgical treatment for patients with achalasia included a formal rib spreading incision to perform an esophageal myotomy or splitting of the abnormally thickened esophageal muscle at the lower sphincter. Recent improvements in laparoscopy have allowed for significant advances in the treatment of achalasia. NYP is currently performing a laparoscopic myotomy for most of the achalasia patients. This approach requires small abdominal incisions for the placement of a camera and telescopic instruments. The abnormally thickened muscle surrounding the esophagus is incised to allow for improved swallowing. After completion of this myotomy a loose stomach wrap is created around the esophagus to minimize reflux.
Length of stay has been reduced to two days with minimal post-operative discomfort. Also, patients are tolerating regular food at the time of discharge.