Friday, July 27, 2007

Rounds in Different ICUs, and the Horrible Monster that Haunts My Dreams

Rounds in 3 ICUs
So far I have spent time in three different ICUs: neonatal, pediatric, and medical. The ways patients are handled in the NICU and PICU are different, though the underlying structure of each unit is very much the same. The kids in the PICU can potentially have a much wider range of problems than those in the NICU, such as developmental disabilities and cancer. One of the patients in isolation was thought to have tuberculosis, while a 1-year old girl was suffering from severe scoliosis. The way the units are organized, however, is quite similar. Going on rounds with Dr. Kutko and her team was reminiscent of Dr. Frayer's team: the morning was spent going to see each patient and occasionally meeting with a surgeon to discuss surgery.

The organization sort of fell apart when I went to the medical ICU. If I had to describe it in one word, it would be "chaotic."Prior to rounds, the residents and fellows meet to discuss each patient. I often heard talk about terminally ill patients, many of which have cancer. Once the rounds begin (which is usually never on schedule), we would meet Dr. Berlin. The conditions of the patients we would meet were generally much worse than anything I'd seen in the other ICUs, and each discussion would be more involved with much more data to consider. At times, Dr. Berlin had other obligations, so he would often leave us and let one of the fellows take charge. It was an interesting (and fast paced) experience, though somewhat depressing to think that some of the patients I saw may not have much longer.

Error Messages
I am trying to write a Matlab program that can generate a two-dimensional airway model of the lungs, turn it into a mesh, and then export it in a form that is readable by Fluent. Right now, the hard part is trying to make it readable. Trying to reverse engineering the Fluent .msh file format is proving to be the bane of my existence. Instead of showing results, I chose to show the error message that I keep getting and a picture of a monster. If the error message had a representative monster, this is what it would look like.

Thursday, July 26, 2007

Ladies and Gentlemen, the results are in...

Still no word from the movers. Well, there goes my entire apartment deposit. But, that affords me some more time to type out a blog entry on a cell phone dial pad! T9 makes every sentence seem so much more epic...

Unfortunately, I am unable to post the graphs from the preliminary data analysis, but it appears that the automatic segmentation algorithm lies somewhere between the phase contrast analysis and the manual segmentation. The manual segmentation tends to overestimate when compared to the other techniques, while the PC flow analysis tends to underestimate. Furthermore, the relation between all three is relatively linear, as indicated by a high correlation (0.95 or greater between any two of the three techniques) and a high level of confidence in the zero intercept inear regression.

And perhaps of the greatest importance, the technique demonstrates a "high degree of accuracy," as indicated by Dr. Weinsaft, when used to evaluate the cadiac metrics of subjects with Left Ventricle Disfunction (those who eject only a small portion of their blood in each cardiac cycle, on the order of 25% when compared to normal function of 50 or greater.) This has traditionally been one of the most time consuming
scenarios for a clinician to evaluate, so the time saving benefits from this automatic segmentation stand to be quite considerable.

Admittedly, the data set is still somewhat small (just 20 fully completed cases with an eventual target of 50 to 100). But the trends are already beginning to show. The next step, other than validation with more data sets, is to reconsider the design of the algorithm. As I mentioned before, which technique is more accurate? Phase contrast analysis or manual segmentation? Further, should the algorithm even emulate these techniques or should the design process be independent of other techniques? Perhaps a "true" measure should be experimentally derived using experimentation somehow?

The logistical hurdles of obtaining the truth are considerable. But for now, we are fairly convinced that the automatic segmenter operates consistly between the phase contrast measure and the magnitude measure, both of which are valid and widely used techniques in the clinical world.

Open Cholecystectomy

Over the past week I have observed many, many operations, some of which have been previously blogged before. One operation that hasn't been blogged is Cholecystectomy which is the surgical removal of a gallbladder. This procedure is typically necessary when there are gallstones occluding the gallbladder duct/cystic duct or severe inflammation of the gallbladder(cholecystitis). These gallstone could potentially cause the gallbladder to swell and ultimately rupture. Some of the symptoms including sharp abdominal pain and nausea. For the case that I observed, gallbladder was severely inflamed and was suspected to be cancerous which necessitated an open cholecystectomy instead of a laparoscopic cholecystectomy.

Laparascopic Cholecystectomy


So it turns out that a gallbladder can be removed and one can lead completely normal life without one, but under diets with less fat. This is because the primary function of a gallbladder is to store bile( for fat emulsification ) secreted in the liver. Having an inflamed gallbladder adds risks to liver inflammation and inflammation to other adjacent organs such as the pancreas.


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.


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.

Wednesday, July 25, 2007

Brain Lab

Vascular Surgery
Week 5

Neuro Detour cont’d
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.

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

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.

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.
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.

Tuesday, July 24, 2007

5th week in Plastics

This past week I was able to see quite a few interesting cases. Monday morning I listened to a lecture on hand trauma and then watched and residents discussed how to approach specific cases. This lecture turned out to be very useful because we had a hand trauma case this week. A garbage man was unlucky enough to get his hand caught in the garbage compactor. He was brought into the OR in the hopes of salvaging his index finger which had been almost completely crushed. The surgeons removed the debris from the finger (including the crushed bone) and tried to piece back together what they could. A microscope was used to attach nerves, veins, and arteries that had been severed. With all the effort, the surgeons were still very skeptical that the finger would be able to survive because there appeared to be no blood flow in the tip of the finger.

In addition to plastics cases, I also attended a couple Neuro cases. This was very interesting to watch. The surgeons entered the brain through the nasal cavity, removing the septum in order to have a clear view of the interior. Although miniaturized, the tools were the same basic tools used during many of the plastics cases. The patient had a pituitary tumor which was removed through the nasal cavity with a device that worked by simply pinching off a small portion at a time. Once the tumor had been excised, the septum was reconstructed from tissue taken from the abdomen of the patient.

On Friday, I decided to see something other than surgical intervention to help patients. I went on rounds in the NICU with Mike and Dr. Frayer. I found that in the NICU the doctors are very concerned with the overall patient . In my experience thus far, many surgeons are there to treat one main problem, which may even be the root of a lot of other problems, but in the NICU, the health of the patient overall seems much more important. The main discussion of each patient was that of overall function. With all the advancements in medicine to date, it is amazing to me how important simple bodily functions matter. Calorie intake, weight gain or loss, peeing, pooping, and all the basic functions of living are of utmost importance in the NICU. Spending one day to complete rounds in the NICU was a very worthwhile experience.

Additionally, I want to discuss one case that I have been able to see progress through my time here. When I first arrived, the patient was in the hospital awaiting surgery. He had previously had surgery on his neck to stabilize some of his vertebrae and hardware was used to complete the surgery. You can see the hardware in the first image (metal on either side of the spine). An infection set in at the site of the surgery, and the patient was transfered to Plastics. I didn't realize prior to my time here that Plastic Surgeons work a lot on wound care and thus often receive patients from other services once infections are found. In this case, Dr. Spector took the patient to the OR to irrigate and debride the wound. He then closed the wound in layers to provide more stability to the wound. To do this each layer must be separated from the above tissue and then closed over. You can see in the second image how this was completed. Additionally, Jackson Pratt (white plastic in wound) drains were left in the patient to allow for drainage of fluids from the wound site. This prevents pockets of fluid for forming underneath which must then be remove with a needle. An image of just the drain is also shown (from: The drains are cut to fit in the wound bed and then a small hole is made away from the incision and the drain is threaded through the hole. Once there is no longer large amount of fluid being drained, the JP is simply removed by pulling it through the insertion site. The ability to observe the fluid as it drains from the site is helpful because it can be an early indication of infection. Since the surgery the patient has been able to return home and the wound is nearly completely closed with minimal problems.

Monday, July 23, 2007

Of PC Flow and Moving Woes

Ok, I'll admit it. I'm not in New York City. Earlier this week I returned to Ithaca to catch up on the latest cow tipping action, and to move out of my apartment. Three days later, my entire life is in a series of carefully sealed and labeled boxes, my movers still haven't shown up ("Today! We promise. We promised yesterday? Well we mean it this time!"), and I'm sitting on a living room box typing a BME blog entry on my cell phone. That has to count for something, right?

Any ways, back to my project. We haven't fully worked out the automatic segmentation yet, as Noel is still tweaking a few things, but from the look of it, the comparisons between the Phase Contrast derived measurements and the manually segmented magnitude images are intriguing. It appears that while they have a somewhat high correlation (0.95 or greater), one always seems higher than another.

From these early results, it is easy to see that the two forms of "ground truth" may not even agree! How, then, can we ever judge the accuracy of te automatic segmention algorithm? Perhaps it will be similar to the PC flow analysis, but not the magnitude based measurement. And if so, is this more accurate than i it was the other way around?

An interesting question that, for me in any case, remains unsolved. Looks like this phone doesn't seem to get along with PubMed. Alas...

Neurological Surgery

Deep Brain Stimulation for Parkinson’s treatment

One particularly interesting surgery I was able to observe this week was a deep brain stimulation procedure to treat a Parkinson's patient. Parkinson’s disease results from a lack of dopamine being produced in the substantia nigra, and results in four possible symptoms – tremor of a limb, slowness of movement, rigidity, and poor balance. The patient I observed seemed to exhibit all of these symptoms, with bilateral tremors and rigidity in her arms and legs.

Since no treatment is currently able to prevent or slow the progression of Parkinson’s disease, all treatments aim to treat the symptoms to make life easier. The current options include medication, surgical lesioning, or deep brain stimulation. One common medication is L-dopa, which is converted into dopamine in the brain. Surgical lesioning involves removal of part of the brain that is abnormally active, such as the globus pallidus (pallidotomy). Deep brain stimulation (DBS) can involve the thalamus, subthalamic nucleus, or globus pallidus, all of which are important in the pathway for movement control. It is thought that DBS helps by pacing abnormally firing cells in these regions.

Dopaminergic pathways. Left side is for a normal brain, and right side is for a Parkinson's patient. Red arrows indicate an inhibitory effect and blue arrows indicate an excitatory effect.

Prior to the surgery, Dr. Kaplitt had determined the location of the subthalamic nucleus in the brain by taking an MRI, and had mapped the stereotactic coordinates of this structure. He drilled two holes in the skull and inserted electrodes in the locations indicated by the coordinates. Electrical activity was recorded for a depth range of approximately 20 mm using a 7 micron electrode tip. Using the recordings, the doctors were able to distinguish approximate borders between different areas in the brain - thalamus, subthalamic nucleus (STN), and substantia nigra. It was clearly visible that certain cells in the STN corresponded temporally with the tremors exhibited by the patient. Dr. Kaplitt inserted stimulating electrodes and applied a voltage across these and observed the physiological response of the patient. In certain locations, the applied stimulus was able to visibly decrease tremor and reduce rigidity in the patient's arms and hands. Two days after this procedure, the patient would have a permanent system implanted, much like the one shown in the figure below. The doctor suggested that the deep brain stimulation system in combination with medications would be able to better control the patient's symptoms in the future.

Deep brain stimulator.

The use of focused ultrasound for theraputics in medicine

This is my last week here at Weill, and over the immersion thus far I have gotten to see many, many... many different types of surgeries and medical-clinical procedures. With my little blue note book and cell-phone camera I have been taking notes and jotting down ideas.

At first I was going to focus my research project on neurological drug delivery using ultrasound. This was related very closely to my Ph.D. research and fit with my mentor Dr. Riina, but after seeing all that was available to be here at the hospital and the willingness of clinicians to work with me, I have been able to broaden my view and study.

I also admit that after seeing laproscopic bladder and prostate surgeries, and the tools the doctors use I was inspired to think up some new applications of ultrasound in the treatment of diseases.


Acoustical techniques have been used in a variety of situations to enhance medical treatments. For example, high intensity focused ultrasound (HIFU) has been used to ablate and liquefy tissues, and past and current studies are being conducted to assess the use of HIFU as a more complete surgical tool for minimally invasive therapy. Focused ultrasound is beginning to be assessed as a feasible way to deliver drugs to neurological tissues via selective disruption and permeablization of the blood brain barrier (BBB). Drugs that once could not cross the BBB because of molecular weight and hydrodynamic radius are now able to permeate into the neurological tissue with the application of ultrasound. Ultrasound has also been used in other applications such as gene therapy and drug activation, and for further information on therapeutic ultrasound one can read the Nature Drug Discovery Article "Healing sound: the use of ultrasound in drug delivery and other therapeutic applications.

The above image shows the enhancing effects of ultrasound on non-invasive drug delivery into tissue. Shown in yellow is the drug perfusion by diffusion mechanisms alone, shown in green is the enhanced delivery of drug with ultrasound The image x-axis is distance into the tissue and y-axis is the amount of drug potentially delivered.


My experience from watching surgeries, talking with clinicians, and reviewing literature on PubMed, has created many potential uses for enhanced drug delivery using ultrasound in the clinical setting.

1. Neurosurgery:

a.) After tumor removal drugs are delivered locally, or the space is filled with a gliadel BCNU wafer. The application of ultrasound may potentially enhance drug diffusion from the locally delivered chemotherapy, thus increasing the chemo's effectiveness.

b.) In trying to fix neural aneurysms the most common techniques are either to pinch it off, or filling it with a coil. The use of ultrasound may be able to activate a locally delivered filling agent, or it may be used to target drugs to reduce the growth and shrink the aneurysm.

Things that must be considered to apply this technique are the following: getting the acoustic energy to the specific location, not damaging the tissue in its pathway and developing a re-usable minimally invasive mechanism.

Possible solutions are:

I. To produce an array that attaches to the head and is able to target the specific location (Like the acoustic version of the gamma knife). Existing mapping technology with MRI/image guided procedures could be used to simplify development

II. Use a high-power catheter based acoustic probe e.g. intravenous ultrasound, that may be guided to the place of interest. This however requires the development of new piezoelectric materials, that can produce large acoustic outputs with small surface area.

The above image is a potential acoustic therapeutic helmet.

2. Prostate Surgery:

Removal of the prostate may be

Sunday, July 22, 2007

A stapler device

It’s a good opportunity to see different type of medical devices in the OR. I thought a needle was a must when closing a wound, but I was wrong. A surgical stapler makes the anastomosis easy and fast.

A Transverse Anastomosis stapler (TA) is such a device that closes the bowel lumen while the dissection and excision of the specimen are in progress. The underneath picture is a sample of TA.

It’s very easy to use this devise. Basically, the doctor first puts the jaw of stapler gun at the right position. Of course this is the most important step. Fully squeeze the handle to load the staples, and fully squeeze the handle again to fire the staples. I think even myself can conduct these three steps as long as I know where to put the jaw.

Actually, the jaw is the magic part. It contains one double staggered row of titanium staples. After the staples are fired, the hook up area will look like this.

There are also some other features of this stapler gun. The staple unit can be replaced. It can be reloaded 7 times for a total of 8 firings. Safety Lockout prevents an unloaded or improper loaded stapler gun to be used. For me, it is really amazing to see how the mechanics can be applied to facilitate the surgical operation.

Calcium Score: Part 1

Everyone has heard of atherosclerosis; it is the term for the cardiovascular disease that is the outcome of atherogenesis (the accumulation of plaque in the arteries). An atheromatous plaque forms due to atheroma or the accumulation of lipoproteins (cholesterol) and connective tissue inside the arterial wall. Shear stress and other factors that thin the arterial wall can sometimes cause the wall containing the ‘vulnerable’ plaques (or soft plaques) to rupture. If the rupture clogs the coronary arteries, this can result in ischemia or even a heart attack (infarction of cardiac tissue).

With age, if the soft plaques do not rupture, the layer between them and the vessel wall near the lumen can undergo microcalcification, and in general, create calcium deposits in the arterial wall. As a result, the amount of calcium in the coronary arteries is an established number for identifying the severity of coronary artery disease. The number is commonly referred to as ones calcium score and anyone who gets a CTA (CT angiography) done can obtain their calcium score from their physician. However, one should be cautious since the distribution of the calcium in the coronary arteries (whether the calcium is diffused or focused) also plays an important role. Furthermore, the number does account for the number of soft plaques or vulnerable plaques, which in fact pose a greater risk since they have the potential to rupture. Evidently, there is no index out there that quantifies the vulnerability of plaques since they are difficult to identify using most imaging modalities or software. In fact, the software that I’ve been using only quantifies calcium in the coronary arteries.

In particular, I’ve been using software developed by GE called Smart Score (figure) to assign patients a calcium score. That is, I’ve been highlighting the calcium in the arteries using CTA and differentiating the calcium for the left anterior descending artery (LAD), left circumflex (LCX), and the right coronary arteries (RCA). Doing this is pretty straight-forward. I just click on a button labeled LAD if I want to highlight the calcium deposits in the LAD, RCA for calcium deposits in the right coronary artery, and LCX for deposits in the left circumflex. The software automatically segments the calcium deposits within the region I highlight using a simple thresholding algorithm. When I do this for all of the transverse slices of the heart, I record 8 numbers. One number corresponds to the overall volumetric score or the total volume of calcium in the coronary arteries, and three other numbers for the volume in the LAD, LCX and RCA. Similarly, an older and more commonly used number for calcium scoring, known as the agatson number, is recorded. The agatson number, unlike the volumetric score, scales the area of segmented calcium in each slice by the average Hounsfield value/ brightness of the segmented region. I believe this older method was developed to account for partial volume effect in CT images. In fact, even though the volumetric score is more accurate, the agatson score is still used due to legacy. I guess it doesn’t really matter. I have looked at both numbers for 200+ patients, and I can say that they don’t differ by a concerning amount.

I guess some of you might be wondering why I’m collecting this data in the first place. I’ll discuss the details of that later this week.