MRI

By | March 20, 2015

Despite its safety the very size of the machine is intimidating to many patients.  Some patients cannot go inside of a closed machine such as this.  These claustrophobic patients can be imaged in "open" machines, but the resolution of these machines is still inferior.

Despite its safety the very size of the machine is intimidating to many patients. Some patients cannot go inside of a closed machine such as this. These claustrophobic patients can be imaged in “open” machines, but the resolution of these machines is still inferior.

Magnetic resonance imaging (MRI) is an amazing technique where nuclear physics meets medicine. It is based on two of the three basic properties of atomic particles, mass (not important here), charge and spin. Classical electromagnetic theory states that any time an electrically charged particle is accelerated (here spinning) it produces a magnetic field. For our purposes here the single protons in a hydrogen atom all have charge and spin. Most of the time we do not appreciate any magnetic properties in living tissues because the protons are all spinning randomly in different directions. In an MRI the patient is placed in a strong uniform magnetic field, which forces the protons to align their spin axes. Next a smaller oscillating magnetic field is applied, which causes some of the protons to flip. This orientation is unstable because of the large fixed magnetic field. The protons then slowly flip back and when they do this they give of small amounts of energy in the radio frequency section of the electromagnetic spectrum. This emitted energy can be detected and manipulated mathematically just like the transmitted energy in a CAT scan. The source of this energy can in this way be localized and a three dimensional representation of the tissue in the scanner created. What makes the technique of MRI so powerful is that the hydrogen atoms contained in different molecules have slightly different patterns for these transitions. By changing the stimulating pattern or relaxation pattern of the varying magnetic field, one can look for protons in water (the T2 weighted scans we use so commonly in spine work show water as in spinal fluid as bright white), fats, proteins or carbohydrates. Finally we have an imaging modality that gives the physician to sort of “dial in” the structures that most interest him rather than presenting him with a fixed one size fits nobody examination. Another highly touted advantage of MRI over CT is the absence of ionizing radiation. At Schlesinger Pain Centers I am quick to warn the patients that we do not know what if any effects exposure to very strong magnetic fields may have on the body. It took more than a generation for the late effects of X-rays to become known and I would not be surprised if delayed effects emerge following repeated exposure to strong magnetic fields and the exciting pulses given to induce state changes in the protons.

CAT Scans

By | March 19, 2015

With image acquisition times of less than a second CAT scans can be used to image even the heart and great vessels.  This CT angiogram shows a saddle embolus (dark linear density at the bifurcation of the pulmonary artery (bright white).

With image acquisition times of less than a second CAT scans can be used to image even the heart and great vessels. This CT angiogram shows a saddle embolus (dark linear density at the bifurcation of the pulmonary artery (bright white).

CAT Scans are mathematically manipulated plain X-rays, sort of. The advantage and the disadvantage of plain X-rays is that every grain or pixel represents the sum of the effects of the absorption characteristics of the tissues on the beam as it travels through the body, not to mention the effects of scattered radiation. Conventional tomography was an attempt to see one area clearly while throwing the rest of the body out of focus. In this technique the X-ray tube and the film both move at the same speed but in opposite directions during a time exposure. Theoretically X-rays passing through the plane that is equidistant between the tube and the film will hit same spot on the film for the entire exposure while all other planes will spread over a larger and larger area, blurring them out. In practice these films were difficult and expensive to produce, exposed the patient to considerable radiation and were only somewhat clearer than regular films.

Computerized axial tomography again uses a moving tube and collector but this time uses a series of still shots to mathematically reconstruct the tissues being examined. In the original scanners, used only for imaging the brain, a single tube and collector rotated around the patient’s head making 180 different exposures at 1° increment. Each slice took 5 minutes to expose. By a series of linear transforms a mini computer was able to assign an X-ray density (a gray scale value) to each point within the skull. Computation time on the first experimental scanners was on the order of 2.5 hours on a large mainframe computer. Current scanners use multiple tubes and collectors and can complete a slice in less than a second.

One problem, which has not yet been resolved is the dose of radiation to the patient. A typical exam of the abdomen or chest exposes the patient to about 13 mGy. As a comparison the average chest X-ray results in a dose of only 0.02 mGy and the annual background radiation from the sun for the average American is 2.4 mGy. At Schlesinger Pain Centers we do not hesitate to use CAT Scans when they are clearly indicated but most of the time we prefer MRIs not only because of the lack of exposure to ionizing radiation, but also because of the improved sensitivity and resolution of the structures in which we are most interested.

Ultrasound

By | March 18, 2015

While the breadth of applicability in pain management is not as great as that of fluoroscopy, modern ultrasonography is an exciting advance because the two techniques shares so little overlap and therefore compliment each other so well. Fluoroscopy is best at seeing and seeing through bone. For structures that have a close and reliable relationship to a boney structure such as the exiting nerve root in a transforaminal epidural steroid injection (TF ESI) shown in the last blog, fluoroscopy is an excellent imaging and guidance technique. Even there it is not perfect. As we spoke of yesterday, the structures that we are most interested in, the nerve, the radicular artery and vein cannot be seen. Their presence can be inferred by their ability to exclude or contain and conduct x-ray dye. High frequency sound waves as opposed to electromagnetic waves penetrate bone poorly, therefore bone hides all structures behind it, but ultrasound is excellent at resolving small differences in soft tissues. Nerves can be seen directly and more importantly they can be located in relation to a number of other structures such as fascia, muscle and blood vessels that are invisible on fluoroscopy. One of the most vivid illustrations of the power of ultrasound is in the conduct of stellate ganglion blocks. The stellate ganglion is a sympathetic ganglion formed by the fusion of the inferior cervical ganglion and the first thoracic ganglion. It controls autonomic functions such as blood flow and sweat production to head, neck, arm and the upper chest. It is also involved in the pathogenesis of a number of rare pain syndromes involving these same structures. It was always considered a difficult, dangerous and unreliable block largely because of the number of vital structures (carotid artery, jugular vein, vertebral artery, phrenic nerve, superior laryngeal nerve, trachea, esophagus, thyroid gland, etc.) found close to it, most of which cannot be see on fluoroscopy. Just as importantly the ganglion bear no reliable relationship to the nearest boney structures, which may be a centimeter or more away, but with ultrasound the ganglion is directly visible and it bears a constant relationship to the carotid artery anteriorly and the longus coli muscle posteriorly. With this better visualization we have been able to cut the volume of local anesthetic by 80% making the injection safer and more reliable. At Schlesinger Pain Centers we do about one stellate ganglion block per month, all of them with ultrasound guidance.

Saint Patrick’s Day 2015

By | March 17, 2015

On Saint Patrick's day, all the world is Irish.

On Saint Patrick’s day, all the world is Irish.

On Saint Patrick’s Day all the world is Irish. Some are ethnically Irish and the rest of us are wannabe Irish. Today it doesn’t really matter. In that spirit, the staff and I here at Schlesinger Pain Centers would like to wish all of Irish friends a very happy Saint Patrick’s Day.

Plain X-Ray and Fluoroscopy

By | March 16, 2015

We are so obsessed with safety that we view all transforaminal injections first in the subtracted and then in the positive as shown above to eliminate any possibility of mask artifacts.

We are so obsessed with safety that we view all transforaminal injections first in the subtracted and then in the positive as shown above to eliminate any possibility of mask artifacts.

Plain X-ray and fluoroscopy are both techniques that use the differential attenuation of gamma radiation by body tissues to produce clinically useful images. Conventional X-rays used silver halide film to produce single images while fluoroscopes used a fluorescent collector to capture moving images. Advances in electronics and digital photography have blurred the distinctions between the two techniques but the ability to capture live motion is still an important reason to use fluoroscopy in the pain clinic. While most of the work that we do at Schlesinger Pain Centers is done as single frames to cut down on the radiation exposure to our patients and staff, certain delicate transforaminal injections require fast frame cine-fluoroscopy techniques to rule out the possibility of a dangerous intravascular injection. So concerned with safety are we that I equipped our fluoroscope with a digital subtraction angiography package at an additional cost of $25,000, all for an injection that we do at most once a week. Was it worth it? Eight years with zero complications, yeah it’s worth it.

Imaging Techniques

By | March 15, 2015

Mammography is one of the most difficult disciplines within radiology due in large part to the fact that the breast is an extremely heterogeneous organ as can be seen in the normal exam on the left.  Not all cancers are as easy to identify as the dense round mass distorting the normal breast architecture in the image on the right.

Mammography is one of the most difficult disciplines within radiology due in large part to the fact that the breast is an extremely heterogeneous organ as can be seen in the normal exam on the left. Not all cancers are as easy to identify as the dense round mass distorting the normal breast architecture in the image on the right.

The growth in the number and quality of imaging modalities over the last 40 years has been astounding. As before the best use of these techniques is correlative, but now not limited to surface anatomy and palpation. A common example from tumor board discussions is a small or questionable breast mass. The first step in evaluating such a mass might be mammography, a form of plain X-rays, but it might also be ultrasonography in the breast surgeon’s office. In complex cases an MRI of the breast might also be ordered. It is not a question of which is better, but how they compliment each other in terms of the type of information that they can add to the diagnostic investigation. In the next several blogs we will look and the individual modalities, their strengths, weaknesses and uses in clinical practice, here at Schlesinger Pain Centers.

Radiologic Anatomy

By | March 14, 2015

Compare the appearance of the second vertebra in this lateral X-ray of the cervical spine with...

Compare the appearance of the second vertebra, the trabecular pattern and the varying thickness of the cortical bone in this lateral X-ray of the cervical spine with…

its appearance in this drawing.  Be careful, the X-ray of the spine is looking left while the single bone is looking right.

its appearance in this drawing. Be careful, the X-ray of the spine is looking left while the single bone is looking right.

Radiologic anatomy is not a subject often covered in medical school. It is either viewed as childishly simple, such as finding the heart or a large area of consolidation on a chest X-Ray or it is viewed as a clinical specialty best studied as an elective during the fourth year of medical school. Neither of these points of view take into account the fact that at its best anatomy is a correlative endeavor, integrating the information gained from physical examination, microscopic anatomy with the information of how different forms of energy are absorbed, reflected or emitted from different tissues, under different conditions and from different points of view. For example a plain X-ray shows the kind of shadow that a tissue will cast when illuminated by gamma radiation. Compare the drawing of the axis, the second cervical vertebra above with the shadow that it cast on the accompanying X-ray. The X-ray clearly shows the differences in thickness of the bone in different places along with the trabecular pattern, both of which indicate the functions of and the stresses to which the substructures are exposed. Look at the thickness of the dentate process, the superior articular surfaces and the spinous process as compare to the laminae. The first two structures bear weight of the head as transmitted downward by the atlas and the third is a major site of muscular insertion. The laminae on the other hand serve primarily to complete the ring structure of the axis and therefore have a light and feathery appearance on X-ray. At Schlesinger Pain Centers we use only the best X-ray equipment with careful attention to technique, because if I am going to expose my patients to even a tiny dose of radiation, not to mention myself and the staff, I want to get the maximum information possible back.

Microscopic Anatomy

By | March 13, 2015

The adenomatous (precancerous) colonic cells on the left show subtle derangements in cell architecture as compared to the normal cells on the right.

The adenomatous (precancerous) colonic cells on the left show subtle derangements in cell architecture as compared to the normal cells on the right.

I have to admit that histology was one of my least favorite courses during the first year of medical school. The endless list of hard to see and hard to remember microscopic structures were bewildering in and of themselves, but I was especially annoyed by the demands of the instructors that I identify the tissue of origin from only a single microscopic slide. What I didn’t understand then, when it was simply an academic exercise, but what I began to appreciate as a senior and took an elective course in surgical pathology was that first of all you can find a metastatic deposit of tissue anywhere in the body, often far from the site of origin and secondly and far more importantly is that subtle disruptions of the tissue architecture and cellular anatomy are often the first signs of malignancy. Over the years as I have attended tumor board conferences both at Providence Saint Joseph Medical Center and at Glendale Adventist Medical Center I have learned that health is an orderly process and that every loss of microscopic structure was likely to be associated with a corresponding loss of physiologic control. In general the more disordered the microscopic slide appears the more aggressively the tumor is likely to behave. This is the reason why the better oncologists will always want to review the microscopic slides on their patients just as I always want to review the X-Rays and MRIs on my patients here at Schlesinger Pain Centers.

Gross Anatomy

By | March 12, 2015

When we finished gross anatomy our clothing reeked so of formaldehyde that there was nothing to do but burn it.

When we finished gross anatomy our clothing reeked so of formaldehyde that there was nothing to do but burn it.

When we finished our last day in the gross anatomy lab my dissection partners and I burned the clothing that we had worn to lab every day[1] and had a drink back Bard Hall, the medical student dormitory, celebrating the end of an unpleasant experience, which we were certain would not be repeated. How wrong we were. I have made innumerable trips back to the gross anatomy lab, although none of them were for as long as in medical school and luckily the bodies we use now are frozen and thawed, rather than being preserved with formaldehyde. At least in the surgical specialties, new advances in treatment are best learned in the anatomy lab. All of the advanced pain control techniques I use at Schlesinger Pain Centers have been learned and have been practiced first in one of a handful of privately owned surgery and anatomy facilities throughout the country, such as the Medical Education & Research Institute (MERI) in Memphis Tennessee, run expressly for that purpose. Another difference between the gross anatomy that I study now as opposed to the survey course I took in medical school is the depth and the detail. Our goal is to learn every minute detail of the normal anatomy as well as all of the normal anatomical variants as well as the many ways that this normal anatomy can be distorted by age and disease. The growth of minimally invasive surgery and advanced injection techniques have made this kind of detailed anatomical knowledge more important than every before because these techniques while limiting the pain to the patient also limit the field of view of the operator. One interesting example that we see frequently at Schlesinger Pain Centers is the patient with degenerative scoliosis in the setting of prior surgery. Here we have a gross distortion of the relationship of one bone to the next and at the same time some of the structures that we use to judge these relationships have been removed. Only a detailed knowledge of the anatomy of the structures that remain allow us to safely place the needles that will allow us to diagnose and treat our patients.

[1] We had been warned by the upper classmen that the smell of formaldehyde in the lab was so strong that once it got into our clothing it would be impossible to wash it out. We were told to pick our oldest and rattiest pair of jeans and an equally unattractive shirt and wear it every day to the anatomy lab and to simply dispose of the clothing at the end of the course. We did all of this and stood in line for the showers everyday when we returned to the dormitory from the lab. Even so every one knew which group of freshmen had gone to lab that day and needless to say they ate alone.

Anatomy

By | March 11, 2015

Sometimes it is the simpler technological advances that change practice most, such as the development of smaller less expensive fluoroscopy equipment.  This turns diagnostic palpation into an exercise in correlative anatomy.

Sometimes it is the simpler technological advances that change practice most, such as the development of smaller less expensive fluoroscopy equipment. This turns diagnostic palpation into an exercise in correlative anatomy.

Anatomy in addition to being the first course I took in medical school at Columbia University College of Physicians and Surgeons is a constant part of my medical practice, precisely because as they taught me function usually follows form. This is so important that if I can I can define the anatomy I am usually more than half way to the diagnosis. The mantra about form and function is important even when it appears not to be the case, because it allows me to dismiss the large list of diagnoses where the rule is true and concentrate on the less common conditions where it appears to be false. One thing that has changed since my medical school days is the way that we define the anatomy. When I was in medical school CAT Scans were a research tool that was just beginning to become available in clinical practice and these machines housed in ivory towers were crude, large and expensive compared to what you can get for $500 today anywhere in Los Angeles. When I was in medical school magnetic resonance imaging (MRI) did not even exist. Today they provide noninvasively a level of detail unimaginable even with the best myelograms of the day. Just as importantly advances in technologies, such as fluoroscopy and ultrasound that were available when I was in medical school has made them available in the community, not just the ivory towers. Yes, I still use surface anatomy and palpation in my clinical practice, but it is now as a form of correlative anatomy. If I feel something or detect an area of significant tenderness on physical exam, here at the Burbank office of Schlesinger Pain Centers I am able to take the patient back to the procedure room and use fluoroscopy or ultrasound to better define the structure that I am feeling. In the next several blogs I will examine a variety of different types of anatomy and discuss how they shape the medical mindset.