4pBA1 – Ultrasound Helps Detect Cancer Biomarkers – Tatiana Khokhlova

The clinical evaluation of solid tumors typically includes needle biopsies, which can provide diagnostic (benign vs. cancer) and molecular information (targetable mutations, drug resistance, etc). This procedure has several diagnostic limitations, most notably, the potential to miss the mutations only millimeters away. In response to these limitations, the concept of “liquid biopsy” has emerged in recent years: the detection of nucleic acid cancer biomarkers, such as tumor-derived microRNAs (miRNAs) and circulating tumor DNA (ctDNA). These biomarkers have shown high diagnostic value and could guide the selection of appropriate targeted therapies. However, the abundance of these biomarker classes in the circulation is often too low to be detectable even with the most sensitive techniques because of their low levels of release from the tumor.

How can we make tumor cells release these biomarkers into the blood? The most straightforward way would be to puncture the cell membrane so that its content is released. One technology that allows for just that is high intensity focused ultrasound (HIFU). HIFU uses powerful, controlled ultrasound waves that are focused inside human body to ablate the targeted tissue at the focus without affecting the surrounding organs. Alternatively, if HIFU waves are sent in short, infrequent but powerful bursts, they cause mechanical disruption of tissue at the focus without any thermal effects. The disruption is achieved by small gas bubbles in tissue that appear, grow and collapse in response to the ultrasound wave– a phenomenon known as cavitation. Depending on the pulsing protocol employed, the outcome can range from small holes in cell membranes and capillaries to complete liquefaction of a small region of tumor. Using this technology, we seek to release biomarkers from tumor cells into the circulation in the effort to detect them using a blood test and avoiding biopsy.
Figure caption: Experimental setup and the basic concept of “ultrasound-aided liquid biopsy”. Pulsed high intensity focused ultrasound (HIFU) waves create, grow and collapse bubbles in tissue, which leads to puncturing of cell membranes and capillary walls. Cancer-derived microRNAs are thus released from the cells into the circulation and can be detected in a blood sample.
To test this approach, we applied pulsed HIFU exposures to prostate cancer tumors implanted under the skin of laboratory rats, as illustrated in the image above. For image guidance and targeting we used conventional ultrasound imaging. Blood samples were collected immediately before and at periodic intervals after HIFU treatment and were tested for the presence of microRNAs that are associated with rat prostate cancer. The levels of these miRNAs were elevated up to 12-fold within minutes after the ultrasound procedure, and then declined over the course of several hours. The effects on tissue were evaluated in the resected tumors, and we found only micron-sized areas of hemorrhage scattered through otherwise intact tissue, suggesting damage to small capillaries. These data provided the proof of principle for the approach that we termed “ultrasound-aided liquid biopsy”. We are now working on identifying other classes of clinically valuable biomarkers, most notably tumor-derived DNA, that could be amplified using this methodology.


Tatiana Khokhlova – tdk7@uw.edu
George Schade – schade@uw.edu
Yak-Nam Wang – ynwang@uw.edu
Joo Ha Hwang – jooha@uw.edu
University of Washington
1013 NE 40th St
Seattle, WA 98105

John Chevillet – jchevill@systemsbiology.org
Institute for Systems Biology
401 Terry Ave N
Seattle, WA 98109

Maria Giraldez – mgiralde@med.umich.edu
Muneesh Tewari – mtewari@med.umich.edu
University of Michigan
109 Zina Pitcher Place 4029
Ann Arbor, MI 48109

Popular version of paper 4pBA1
Presented Thursday afternoon, October 30, 2014, at 1:30 pm
168th ASA Meeting, Indianapolis

Cervical Assessment with Quantitative Ultrasound – Timothy J Hall

The cervix, which is the opening into the uterus, is a remarkable organ. It is the only structure in the entire body that has diametrically opposed functions. The normal cervix stays stiff and closed throughout most of pregnancy while the baby develops and then completely softens and opens at just the right time so the full-grown baby can be born normally, through the vagina. This process of softening and opening involves remodeling, or breaking down, of the cervix’s collagen structure together with an increase in water, or hydration, of the cervix. When the process happens too soon, babies can be born prematurely, which can cause serious lifelong disability and even death. When it happens too late, mothers may need a cesarean delivery. [1,2]

Amazingly, even after 100 years of research, nobody understands how this happens. Specifically, it is unclear how the cervix knows when to soften, or what molecular signals initiate and control this process. As a result, obstetrical providers today evaluate cervical softness in exactly the same way as they did in the 1800s: they feel the cervix with their fingers and classify it as ‘soft’, ‘medium’ or ‘firm’. And, unsurprisingly, despite significant research effort, the preterm birth rate remains unacceptably high and more than 95% of preterm births are intractable to any available therapies.

The cervix is like a cylinder with a canal in the middle that goes up into the uterus. This is where the sperm travels to fertilize the egg, which then nests in the uterus. Cervical collagen is roughly arranged in 3 layers. There is a thin layer on the inner part that where collagen is mostly aligned along the cervical canal, and similarly a thin layer that runs along the outside of the cervix. Between these layers, in the middle of the cervix is a thicker layer of collagen that is circumferential, aligned like a belt around the canal. Researchers theorize that the inner and outer layers stabilize the cervix from tearing off as it shortens and dilates for childbirth, while the middle circumferential layer is most important for the strength and stiffness of the cervix to prevent it from opening prematurely, but nobody is certain. This information is critical to understanding the process of normal, and abnormal, cervical remodeling, and that is why recently there is growing interest in developing technology that can non-invasively and thoroughly assess the collagen in the cervix and measure its softness and hydration status. The most promising approaches use regular clinical ultrasound systems that have special processing strategies to evaluate these tissue properties.

One approach to assessing tissue softness uses ultrasound pressure to induce a shear wave, which moves outward like rings in water after a stone is dropped. The speed of the shear wave provides a measurement of tissue stiffness because these waves travel slower in softer tissue. This method is used clinically in simple tissues without layers of collagen, such as the liver for staging fibrosis. Cervical tissue is very complex because of the collagen layers, but, after many years of research, we finally have adapted this method for the cervix. The first thing we did was compare shear wave speeds in hysterectomy specimens (surgically removed uterus and cervix) between two groups of women. The first group was given a medicine that softens the cervix in preparation for induction of labor, a process called “ripening”. The second group was not treated. We found that the shear wave speeds were slower in the women who had the medicine, indicating that our method could detect the cervices that had been softened with the medicine.[3] We also found that the cervix was even more complex than we’d thought, that shear wave speeds are different in different parts of the cervix. Fortunately, we learned we could easily control for that by measuring the same place on every woman’s cervix. We confirmed that our measurements were accurate by performing second harmonic generation microscopy on the cervix samples in which we measured shear wave speeds. This is a sophisticated way of looking at the tiny collagen structure of a tissue. It told us that indeed, when the collagen structure was more organized, the shear wave speeds were faster, indicating stiffer tissue, and when the collagen started breaking down, the shear wave speeds were slower, indicating softer tissue.
The next step was to see if our methods worked outside of the laboratory. So we studied pregnant women who were undergoing cervical ripening in preparation for induction of labor. We took measurements from each woman before they got the ripening medicine, and then afterwards. We found that the shear wave speeds were slower after the cervix had been ripened, indicating the tissue had softened.[4] This told us that we could obtain useful information about the cervix in pregnant women.
We also evaluated attenuation, which is loss of ultrasound signal as the wave propagates, because attenuation should increase as tissue hydration increases. This is a very complicated measurement, but we found that if we carefully control the angle of the ultrasound beams relative to the underlying cervical structure, attenuation estimates are sensitive to the difference between ripened and unripened tissue in hysterectomy specimens. This suggests the potential for an additional parameter to quantify and monitor the status of the cervix during pregnancy, and we are currently analyzing attenuation in the pregnant women before and after they received the ripening medicine.

This technology is exciting because it could change clinical practice. On a very basic level, obstetrical providers would be able to talk in objective terms about a woman’s cervix instead of the subject “soft, medium, or firm” designation they currently use, which would improve provider communication and thus patient care. More importantly, it could provide a means to thoroughly study normal and abnormal cervical remodeling, and associate structural changes in the cervix with molecular changes, which is the only way to discover new interventions for preterm birth.

1. Feltovich H, Hall TJ, and Berghella V. Beyond cervical length: Emerging technologies for assessing the pregnant cervix. Am J Obst & Gyn, 207(5): 345-354, 2012.
2. Feltovich, H and Hall TJ. Quantitative Imaging of the Cervix: Setting the Bar. Ultrasound Obstet Gynecol. 42(2): 121-128, 2013.
3. Carlson LC, Feltovich H, Palmeri ML, Dahl JJ, Del Rio AM, Hall TJ, Estimation of shear wave speed in the human uterine cervix. Ultrasound Obstet Gynecol. 43( 4): 452–458, 2014.
4. Carlson LC, Romero ST, Palmeri ML, Munoz del Rio A, Esplin SM, Rotemberg VM, Hall TJ, Feltovich H. Changes in shear wave speed pre and post induction of labor: A feasibility study. Ultrasound Obstet Gynecol.published online ahead of print Sep.2014.


Unlocking the Mystery of the Cervix
Timothy J Hall, Helen Feltovich, Lindsey C. Carlson, Quinton W. Guerrero, Ivan M. Rosado-Mendez
University of Wisconsin, Madison, WI (tjhall@wisc.edu)

1aNS2 – How an acoustic metamaterial can make a better sound absorber – Matthew D. Guild

From listening to music to seeing an ultrasound of a baby in the womb, sounds are all around us and are an integral part of our daily life. Many of the sounds we want to hear – such as speaking with a friend at a restaurant – but other sounds (such as conversations at nearby tables) we want to block. This unwanted sound is referred to as noise, and for many years people have worked to make different types of passive devices (that is, does not require any power to operate) to reduce the noise level we hear, such as earplugs or sound absorbing panels.

These types of devices achieve their sound absorbing properties from the materials they are made of, which is traditionally a spongy material made from soft rubbers or fabrics. While effective at absorbing sound, these materials absorb sound equally from every direction, and the acoustic properties of such a material are referred to as isotropic. For applications where the source you are interested in (musicians on stage, friend seated across from you at dinner, etc.) is in one direction, and the source of the noise comes from another direction, these traditional sound absorbers will not discriminate between what you want to hear and what you don’t. Another limitation with traditional sound absorbers is the fact that these sound absorbing materials are visually opaque and cannot be used for transparent applications (which is why most indoor musical performance spaces or recording studios do not have windows).

Unfortunately, many of these qualities of sound absorbers are limited by the physical nature of the materials themselves. However, in recent years a new class of materials has been developed for acoustical applications referred to as acoustic metamaterials. Acoustic metamaterials use the acoustic motion of its carefully designed small-scale structure to create a composite material with extreme acoustic properties. These extreme properties are the focus of current research, and are being used to develop novel applications like acoustic cloaking and lenses with super-resolution (beyond the resolution which can be achieved with an ordinary lens). In these applications currently being investigated, acoustic metamaterials have typically been modeled using ideal materials with no losses (and therefore no absorption of sound), with the presence of losses seen as a hindrance to the design. In air, these losses arise from the friction of the air oscillating through the sound absorber. For sound absorber applications, however, accounting for these losses are necessary to absorb the acoustic energy.

Recently, there has been interest in using the losses within an acoustic metamaterial to make better sound absorbers using resonant structures. These resonant structures, like the ringing of a bell, are excited at a single frequency (tone), and only work over a very limited frequency range in the vicinity of that tone. An alternative approach is the use of sonic crystals, which are a periodic distribution of small, hard rods in air. Sonic crystals by themselves act like an ordinary sound absorber, but can be arranged and designed to create structures with extraordinary acoustic properties.

In this work, the use of densely packed sonic crystals was examined to demonstrate its applicability as a sound absorber. Sonic crystal samples were designed, modeled and then fabricated using a 3D printer to be acoustically tested. By varying the size and how densely packed the sonic crystals were, acoustic experimental measurements were made and compared with predicted values. Layered arrangements were designed and fabricated, which demonstrated different sound absorbing properties in different directions and are illustrated in Fig. 1.


Fig. 1 An acoustic metamaterial sound absorber made of alternating layers (shaded in gray) with each layer consisting of circular rods (black circles) that (a) absorbs sound in one direction, but (b) lets most of the sound through in the other direction. (c) A photo of a test sample (yellow) fabricated using a commercially available 3D printer.

While only a proof of concept, this work shows that acoustic metamaterials (in this case made from sonic crystals) can be used to create sound absorbers that are not isotropic (letting sound through in one direction while absorbing it in another). At the same time, the sonic crystals can be arranged to allow some visual transparency through the arrangement of rods, and can be fabricated using commercially available techniques such as a 3D printer. More details about the modeling, design and testing of this acoustic metamaterial absorber can be found in our paper, which is available at http://arxiv.org/abs/1405.7200


Matthew D. Guild* – mdguild@utexas.edu
Victor M. García-Chocano – vicgarch@aaa.upv.es
Wave Phenomena Group
Dept. of Electronics Engineering,
Universitat Politècnica de València
Camino de vera s/n, E-46022 Valencia, Spain

Weiwei Kan – rdchkww@gmail.com
Department of Physics,
Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics
Nanjing University, Nanjing 210093, People’s Republic of China

José Sánchez-Dehesa – jsdehesa@upv.es
Wave Phenomena Group
Dept. of Electronics Engineering,
Universitat Politècnica de València
Camino de vera s/n, E-46022 Valencia, Spain

* Current address: Acoustics Division, U.S. Naval Research Laboratory, Washington DC 20375, USA

Popular version of paper 1aNS2
Presented Monday morning, October 27, 2014
168th ASA Meeting, Indianapolis

4pBA3 – Focusing Sound to Disrupt Microorganisms – Timothy A Bigelow

During the civil war, the risk of lethal infection drove surgeons to perform multiple amputations on wounded soldiers. The loss of life from the infection outweighed the loss of the limb. In modern medicine, the occurrence of amputations is much less due to the development of sterile surgical techniques, but a type of “amputation” is still the only treatment option for many patients battling infection.

In modern medicine, numerous implants have been developed to treat many different ailments ranging from basic hernia, to pacemakers, to neuronal implants to control seizures. These implants play a vital role in the restoration of function or quality of life for these patients. However, if an infection grows on the implant despite sterile surgical techniques, then the only treatment option is to remove and replace the infected implant with a new device. The bacteria responsible for the infection protect themselves by forming a biofilm on the surface of the implant. Bacteria in the biofilm are protected from antibiotics and the administration of antibiotics can even cause the formation of antibiotic resistant strains. Recently, however, we have shown that focused ultrasound can precisely target and destroy these biofilms (Figure 1). Therefore, in the future, we hope to develop a noninvasive therapy to treat infections on medical implants based on ultrasound.

bigelow disrupting biofilmsbigelow disrupting biofilms

Fig 1: The surface of graphite plates after growing Pseudomonas aeruginosa biofilms and exposing to high-intensity focused ultrasound. Green shows live cells while red shows dead cells. In the absence of treatment, a live biofilm is clearly visible. The ultrasound exposures resulted in almost complete biofilm destruction with few if any live cells remaining.


There are two primary types of therapy that can be performed with ultrasound. The first uses the energy in the sound to heat the tissue. The second uses the sound to excite microscopic bubbles in the tissue resulting in a mechanical change to the tissue structure. Our technology is based on the generation and subsequent excitation of the microscopic bubbles. The high-intensity of the sound causes the bubbles to violently collapse shredding cells adjacent to the bubbles. In addition to treating biofilm infections, we have also shown that the excitation of these microscopic bubbles can lyse microalgae for the release of lipids. These lipids can then be utilized in the formation of biofuels. The use of focused ultrasound was shown to be more energy efficient than other comparable methods of lysing the microalgae.


Timothy A Bigelow – bigelow@iastate.edu

Iowa State University
2113 Coover Hall
Ames, IA 50014


Popular version of paper 4pBA3
Presented Thursday afternoon, October 30, 2014
168th ASA Meeting, Indianapolis




Stone disease in the children is becoming more commonplace. Over the past 25 years the incidence has increased approximately 6-10% annually and is now 50 per 100,000 adolescents 1. The diagnosis of kidney stones in children, as in adults, relies primarily on diagnostic imaging. In adults, the most common imaging study performed in the United States for the initial diagnosis of kidney stones is a computed tomography (CT) scan, due to its superior sensitivity and specificity. This is not preferred for children as CT utilizes ionizing radiation and children have an increased sensitivity to radiation effects. In addition, stone formers often have recurrent stone episodes over their lifetime, which is especially relevant to younger stone formers. The repeated exposures of a CT scan could lead to an increased risks of secondary cancers2. As a result, ultrasound is often performed in children instead because there is no radiation associated with its use1. Ultrasound, however, is less sensitive and specific compared with CT, and is known to overestimate kidney stone size3-5, which is one of the primary determinants of how stones are managed.

We have identified a new technique to improve the accuracy of US stone sizing. Traditionally, a kidney stone will show up as a bright, or hyperechoic, object on US, and radiologists measure the longest linear dimension of the bright area to represent the stone size. We believe that the dark, or hypoechoic, acoustic shadow that appears behind a kidney stone provides additional information for predicting stone size. The resolution of the stone is affected by the distortion of the waves traveling through the intervening tissues; the resolution of the shadow is only affected by the local stone obstruction.

We screened 660 stone diagnoses over an 11 year period (2004 – 2014) at Seattle Children’s Hospital, a tertiary care referral center serving the greater Pacific Northwest. Over the study period, there were 37 patients presenting with an initial diagnosis of a kidney stone, and who had both a US and CT within three months of each other. Two reviewers retrospectively measured both the stone size and the shadow width from the ultrasound image. We compared the results to the stone size measured from the CT scan. A total of 48 stones were included in the study with an average size based on CT imaging of 7.85 mm. The shadow width was present in 88% of the cases, and, on average, was more accurate than measuring the stone itself. Measuring the stone width on ultrasound tended to overestimate the size of the stone by 1.2 ± 2.5 mm (reviewer 1) and 2.0 ± 1.7 mm (reviewer 2), while measuring the shadow width on ultrasound underestimated the size of the stone by -0.6 ± 2.5 mm (reviewer 1) and overestimated the stone size by 0.3 ± 1.2 mm (reviewer 2). In both cases, the shadow was a better predictor of stone size and, for reviewer 2, there was less variability in the data. Stone sizes based on CT are typically considered within 1 mm, with low variability.

Our technique is simple and can be easily adopted by pediatricians, radiologists, and urologists. It improves the accuracy of US and gives physicians more confidence that the reported size is more representative of the true stone size, without having to expose children to the radiation of a CT scan. This also allows the physician to make more accurate decisions about when to perform a surgery for a large stone or continue to observe a small stone that may pass on its own. The findings from this study may also potentially be applicable to stones in adult patients. We believe that with continued advancements in US, we can reduce the number of CT scans for both adults and children. The results in part highlight one of the drawbacks of ultrasound, which is user dependence; two users can have very different results. It is anticipated that future work on automated stone and shadow sizing can reduce this along with standardizing the method in which the shadow measurement is taken.

1. Tasian G and Copelovitch L. Evaluation and Management of Kidney Stones in Children. J Urol. 2014: Epub ahead of print
2. Pearce MS, Salotti JA, Little MP, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. Lancet 2012; 380: 499-505.
3. Ray AA, Ghiculete D, Pace KT, Honey RJD. Limitations to ultrasound in the detection and measurement of urinary tract calculi. Urology 2010; 76(2):295-300.
4. Fowler KAB, Locken JA, Duchesne JH, Williamson MR. US for detecting renal calculi with nonehnanced CT as a reference standard. Radiology 2002; 222(1):109-113.
5. Dunmire B, Lee FC, Hsi RS, Cunitz BW, Paun M, Bailey MR, Sorensen MD, Harper JD. Tools to improve the accuracy of kidney stone sizing with ultrasound. Aug 2014; [Epub ahead of print].


Franklin C. Lee1 – franklee@uw.edu

Jonathan D. Harper 1 – jdharper@uw.edu
Thomas S. Lendvay1, 2 – Thomas.lendvay@seattlechildrens.org
Ziyue Liu3 – ziliu@iupui.edu
Barbrina Dunmire 4 – mrbean@uw.edu
Manjiri Dighe 5 – dighe@uw.edu
Michael Bailey – bailey@apl.washington.edu
Mathew D. Sorensen1, 6 – mathews@uw.edu

University of Washington
1 Department of Urology, Box 356510
5 Department of Radiology, Box 357115
1959 NE Pacific St, Seattle, WA 98195

2 Seattle Children’s Hospital
Urology, Developmental Pediatrics
4800 Sand Point WA NE, Seattle, WA 98105

3 Indiana University
Department of Biostatistics
410 W. Tenth St, Suite 3000, Indianapolis, IN 46202

4 University of Washington
Applied Physics Lab – Center for Industrial and Medical Ultrasound2
1013 NE 40th St, Seattle, WA 98105

6 Department of Veteran Affairs Medical Center
Division of Urology
1660 South Columbian Way, Seattle, WA 98108

2pBA14 – Waves by Ultrasound help better Breast Cancer Diagnosis – Max Denis

Currently, a large number of patients with suspicious breast masses undergo biopsy, more than half of which turn out to be benign. The huge number false positive cases results in an enormous unnecessary cost plus psychological and physical trauma to patients. To avoid such biopsies, one needs to use a modality that can better differentiate between the benign and malignant lesions.

Palpation, the examination of tissue through the use of touch, remains one of the simplest yet effective methods for detecting breast tumors. However, the sense of touch is not sensitive enough to detect small or very deep lesions. It is well known that breast tumors are often much harder than the normal tissue, and cancerous masses are harder than the benign ones [1]. Therefore, scientists have been trying to develop new imaging tools that are sensitive to tissue stiffness. Elasticity medical imaging is an emerging field that provides information about a tissue’s stiffness property [2].

This paper presents application of a new tool called “Comb Push ultrasound elastography (CUSE)”, developed in our ultrasound laboratory at Mayo Clinic Rochester [3,4,5] for accurate measurement and imaging of breast mass stiffness. This new tool will help improving detection and differentiation of breast masses, which will eventually help physicians in better diagnosis of breast cancer. We attempt to assess a tissue’s stiffness property noninvasively by applying ultrasound to tap on breast mass and determine its stiffness by measuring the speed of the resulting waves. These waves are called shear waves. Thereafter, a two-dimensional shear wave speed map is reconstructed. Having already identified the region of interest from the ultrasound, the shear wave speed map is overlaid onto the ultrasound image. Therefore, the shear wave speed within the breast mass can be measured which allows us to determine the stiffness of the mass.



Figure 1. Examples of CUSE evaluations of (a) benign and (b) cancerous breast masses.


Hence, the CUSE imaging technique may be useful as a noninvasive method as an adjunct to breast ultrasound for differentiating benign and malignant breast masses, and may help in reducing the number of unnecessary biopsies. This ongoing project is being done under an approved protocol by Mayo Institutional Review Board and funded by grants and R01CA148994- R01CA148994-04S1 from National Institute of Health and is led by Dr. Azra Alizad.



  1. Sewell CW (1995) Pathology of benign and malignant breast disorders. Radiologic Clinics of North America 33: 1067-1080.
  2. Sarvazyan A, Hall TJ, Urban MW, Fatemi M, Aglyamov SR, et al. (2011) An overview of elastography–an emerging branch of medical imaging. Current medical imaging reviews 7: 255.
  3. Song P, Manduca A, Zhao H, Urban MW, Greenleaf JF, et al. (2014) Fast Shear Compounding Using Robust 2-D Shear Wave Speed Calculation and Multi-directional Filtering. Ultrasound in medicine & biology 40: 1343-1355.
  4. Song P, Urban MW, Manduca A, Zhao H, Greenleaf JF, et al. (2013) Comb-push Ultrasound Shear Elastography (CUSE) with Various Ultrasound Push Beams.
  5. Song P, Zhao H, Manduca A, Urban MW, Greenleaf JF, et al. (2012) Comb-push ultrasound shear elastography (CUSE): a novel method for two-dimensional shear elasticity imaging of soft tissues. Medical Imaging, IEEE Transactions on 31: 1821-1832.


Max Denis – denis.max@mayo.edu     507-266-7449

Mohammad Mehrmohammadi – mehr@wayne.edu

Pengfei Song – song.pengfei@mayo.edu

Duane D. Meixner – meixner.duane@mayo.edu

Robert T. Fazzio – fazzio.robert@mayo.edu

Sandhya Pruthi – pruthi.sandhya@mayo.edu

Shigao Chen – chen.shigao@mayo.edu

Mostafa Fatemi – fatemi.mostafa@mayo.edu

Azra Alizad – alizad.azra@mayo.edu   507-254-5970


Mayo Clinic College of Medicine

200 1st St SW

Rochester, MN 55905


Popular version of paper 2pBA14

Presented Monday morning, October 28, 2014

168th ASA Meeting, Indianapolis