3aBA1 – Ultrasound-Mediated Drug Targeting to Tumors: Revision of Paradigms Through Intravital Imaging – Natalya Rapoport

3aBA1 – Ultrasound-Mediated Drug Targeting to Tumors: Revision of Paradigms Through Intravital Imaging – Natalya Rapoport

Ultrasound-Mediated Drug Targeting to Tumors: Revision of Paradigms Through Intravital Imaging


Natalya Rapoport – natasha.rapoport@utah.edu

Department of Bioengineering
University of Utah
36 S. Wasatch Dr., Room 3100
Salt Lake City, Utah 84112

Popular version of paper 3aBA1, “Ultrasound-mediated drug targeting to tumors: Revision of paradigms through intravital imaging”

Presented Wednesday morning, May 25, 2016, 8:15 AM in Salon H

171st ASA Meeting, Salt Lake City


More than a century ago, Nobel Prize laureate Paul Ehrlich formulated the idea of a “magic bullet”. This is a virtual drug that hits its target while bypassing healthy tissues. No field of medicine could benefit more from the development of a “magic bullet” than cancer chemotherapy, which is complicated by severe side effects. For decades, the prospects of developing “magic bullets” remained elusive. During the last decade, progress in nanomedicine has enabled tumor-targeted delivery of anticancer drugs via their encapsulation in tiny carriers called nanoparticles. Nanoparticle tumor targeting is based on the “Achilles’ heels” of cancerous tumors – their poorly organized and leaky microvasculature. Due to their size, nanoparticles are not capable to penetrate through a tight healthy tissue vasculature. In contrast, nanoparticles penetrate through a leaky tumor microvasculature thus providing for localized accumulation in tumor tissue.  After tumor accumulation of drug-loaded nanoparticles, a drug should be released from the carrier to allow penetration into a site of action (usually located in a cell cytoplasm or nucleus). A local release of an encapsulated drug may be triggered by tumor-directed ultrasound; application of ultrasound has additional benefits: ultrasound enhances nanoparticle penetration through blood vessel walls (extravasation) as well as drug uptake (internalization) by tumor cells.

For decades, ultrasound has been used only as an imaging modality; the development of microbubbles as ultrasound contrast agents in early 2000s has revolutionized imaging. Recently, microbubbles have attracted attention as drug carriers and enhancers of drug and gene delivery. Microbubbles could have been ideal carriers for the ultrasound-mediated delivery of anticancer drugs.  Unfortunately, their micron-scale size does not allow effective extravasation from the tumor microvasculature into tumor tissue. In Dr. Rapoport’s lab, this problem has been solved by the development of nanoscale microbubble precursors, namely drug-loaded nanodroplets that converted into microbubbles under the action of ultrasound[1-6]. Nanodroplets comprised a liquid core formed by a perfluorocarbon compound and a two-layered drug-containing polymeric shell (Figure 1.Schematic representation of a drug-loaded nanodroplet). An aqueous dispersion of nanodroplets is called nanoemulsion.

A suggested mechanism of therapeutic action of drug-loaded perfluorocarbon nanoemulsions is discussed below [3, 5, 6]. A nanoscale size of droplets (ca. 250 nm) provides for their extravasation into a tumor tissue while bypassing normal tissues, which is a basis of tumor targeting. Upon nanodroplet tumor accumulation, tumor-directed ultrasound triggers nanodroplet conversion into microbubbles, which in turn triggers release of a nanodroplet-encapsulated drug.  This is because in the process of the droplet-to-bubble conversion, particle volume increases about a hundred-fold, with a related decrease of a shell thickness. Microbubbles oscillate in the ultrasound field, resulting in a drug “ripping” off a thin microbubble shell (Figure 2. Schematic representation of the mechanism of drug release from perfluorocarbon nanodroplets triggered by ultrasound-induced droplet-to-bubble conversion; PFC – perfluorocarbon). In addition, oscillating microbubbles enhance internalization of released drug by tumor cells.

This tumor treatment modality has been tested in mice bearing breast, ovarian, or pancreatic cancerous tumors and has been proved very effective. Dramatic tumor regression and sometimes complete resolution was observed when optimal nanodroplet composition and ultrasound parameters were applied

Rapoport 3A


Rapoport 3B


Rapoport 3C


(Figure 3. A – Photographs of a mouse bearing a subcutaneously grown breast cancer tumor xenograft treated by four systemic injections of the nanodroplet-encapsulated anticancer drug paclitaxel (PTX) at a dose of 40 mg/kg as PTX. B – Photographs of a mouse bearing two ovarian carcinoma tumors (a) – immediately before and (b) – three weeks after the end of treatment; mouse was treated by four systemic injections of the nanodroplet-encapsulated PTX at a dose of 20 mg/kg as PTX; only the right tumor was sonicated. C – Photographs (a, c) and fluorescence images (b, d) of a mouse bearing fluorescent pancreatic tumor taken before (a, b) and three weeks after the one-time treatment with PTX-loaded nanodroplets at a dose of 40 mg/kg as PTX (c,d). The tumor was completely resolved and never recurred) [3, 4, 6].

In the current presentation, the proposed mechanism of a therapeutic action of drug-loaded, ultrasound-activated perfluorocarbon nanoemulsions has been tested using intravital laser fluorescence microscopy performed in collaboration with Dr. Brian O’Neill (then with Houston Methodist Research Institute, Houston, Texas) [2]. Fluorescently labeled nanocarrier particles (or a fluorescently labeled drug) were systemically injected though the tail vein to anesthetized live mice bearing subcutaneously grown pancreatic tumors. Nanocarrier and drug arrival and extravasation in the region of interest (i.e. normal or tumor tissue) were quantitatively monitored. Various drug nanocarriers in the following size hierarchy were tested: individual polymeric molecules; tiny micelles formed by a self-assembly of these molecules; nanodroplets formed from micelles. The results obtained confirmed the mechanism discussed above.

  • As expected, dramatic differences in the extravasation rates of nanoparticles were observed.
  • The extravsation of individual polymer molecules was extremely fast even in the normal (thigh muscle) tissue; In contrast, the extravasation of nanodroplets into the normal tissue was very slow. (Figure 4. A – Bright field image of the adipose and thigh muscle tissue. B,C – extravasation of individual molecules (B – 0 min; C – 10 min after injection); vasculature lost fluorescence while tissue fluorescence increased. D,E – extravasation of nanodroplets; blood vessel fluorescence was retained for an hour of observation (D – 30 min; E – 60 min after injection).
  • Nanodroplet extravasation into the tumor tissue was substantially faster than that into the normal tissue thus providing for effective nanodroplet tumor targeting.
  • Tumor-directed ultrasound significantly enhanced extravasation and tumor accumulation of both, micelles and nanodroplets (Figure 5. Effect of ultrasound on the extravasation of Fluorescence of blood vessels dropped while that of the tumor tissue increased after ultrasound). Also, pay attention to a very irregular tumor microvasculature, to be compared with that of a normal tissue shown in Figure 4.
  • The ultrasound effect on nanodroplets was 3-fold stronger than that on micelles thus making nanodroplets a better drug carriers for ultrasound-mediated drug delivery.
  • On a negative side, some premature drug release into the circulation that preceded tumor accumulation was observed. This proposes directions for a further improvement of nanoemulsion formulations.
Rapoport 1



Rapoport 2



Rapoport 5


2aBAa7 – Ultrasonic “Soft Touch” for Breast Cancer Diagnosis – Mahdi Bayat

2aBAa7 – Ultrasonic “Soft Touch” for Breast Cancer Diagnosis – Mahdi Bayat

Ultrasonic “Soft Touch” for Breast Cancer Diagnosis


Mahdi Bayat – bayat.mahdi@mayo.edu

Alireza Nabavizadeh- nabavizadehrafsanjani.alireza@mayo.edu

Viksit Kumar- kumar.viksit@mayo.edu

Adriana Gregory- gregory.adriana@mayo.edu

Azra Aliza- alizad.azra@mayo.edu

Mostafa Fatemi- Fatemi.mostafa@mayo.edu


Mayo Clinic College of Medicine
200 First St SW
Rochester, MN 55905


Michael Insana- mfi@illinois.edu

University of Illinois at Urbana-Champaign
Department of Bioengineering
1270 DCL, MC-278
1304 Springfield Avenue
Urbana, IL 61801


Popular version of paper 2aBAa7, “Differentiation of breast lesions based on viscoelasticity response at sub-Hertz frequencies”

Presented Tuesday Morning, May 24, 2016, 9:30 AM, Snowbird/Brighton room

171st ASA Meeting, Salt Lake City



Breast cancer remains the first cause of death among American women under the age of 60. Although modern imaging technologies, such as enhanced mammography (tomosynthesis), MRI and ultrasound, can visualize a suspicious mass in breast, it often remains unclear whether the detected mass is cancerous or non-cancerous until a biopsy is performed.

Despite high sensitivity for detecting lesions, no imaging modality alone has yet been able to determine the type of all abnormalities with high confidence. For this reason most patients with suspicious masses, even those with very small likelihood of a cancer, opt in to undergo a costly and painful biopsy.

It is long believed that cancerous tumors grow in the form of stiff masses that, if found to be superficial enough, can be identified by palpation. The feeling of hardness under palpation is directly related to the tissue’s tendency to deform upon compression.  Elastography, which has emerged as a branch of ultrasound, aims at capturing tissue stiffness by relating the amount of tissue deformation under a compression to its stiffness. While this technique has shown promising results in identifying some types of breast lesions, the diversity of breast cancer types leaves doubt whether stiffness alone is the best discriminator for diagnostic purposes.

Studies have shown that tissues subjected to a sudden external force do not deform instantly, rather they deform gradually over a period of time. Tissue deformation rate reveals another important aspect of its mechanical property known as viscoelasticity. This is the main material feature that, for example, makes a piece of memory foam to feel differently from a block of rubber under the touch. Similar material feature can be used to explore mechanical properties of different types of tissue. In breast masses, studies have shown that biological pathways leading to different breast masses are quite different. While in benign lesions an increase in a protein-based component can potentially increase its viscosity, hence a slower deformation rate compared to normal tissue, the opposite trend occurs in malignant tumors.

In this study, we report on using an ultrasound technique that enables capturing the deformation rate in breast tissue. We studied 43 breast masses in 42 patients and observed that a factor based on the deformation rate was significantly different in benign and malignant lesions (Fig. 1).

The results of this study promise a new imaging biomarker for diagnosis of the breast masses. If such technique proves to be of high accuracy in a large pool of patients, then this technology can be integrated into breast examination procedures to improve the accuracy of diagnosis, reduce unnecessary biopsies, and help detecting cancerous tumors early on


Figure 1 Error bar chart for benign and malignant

Figure1- Distribution of relative deformation rates for malignant and benign breast lesions. A significantly different relative deformation rates can be observed in the two groups, thus allowing differentiation of such lesions.


2aBAa5 – Sound Waves Helps Assess Bone Condition – Max Denis

2aBAa5 – Sound Waves Helps Assess Bone Condition – Max Denis

Sound Waves Helps Assess Bone Condition


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

Leighton Wan – wan.leighton@mayo.edu

Matthew Cheong – cheong.matthew@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 2aBAa5, “Bone demineralization assessment using acoustic radiation force”

Presented Tuesday morning, May 24, 2016, 9:00 AM in Snowbird/Brighton room

171st ASA Meeting, Salt Lake City, Utah


The assessment of the human skeletal health condition is of great importance ranging from newborn infants to the elderly. Annually, approximately fifty percent of the 550,000 premature newborn infants in the United States suffer from bone metabolism related disorders such as osteopenia, which affect the bone development process into childhood. As we age through adulthood, reductions in our bone mass increases due an unbalance activity in the bone reformation process leading to bone diseases such as osteoporosis; putting a person at risk for fractures in the neck, hip and forearm areas.

Currently bone assessment tools include dual-energy X-ray absorptiometry (DEXA), and quantitative ultrasound (QUS). DEXA is the leading clinical bone quality assessment tool, detecting small changes in bone mineral content and density. However, DEXA uses ionizing radiation for imaging thus exposing patients to very low radiation doses. This can be problematic for frequent clinical visits to monitor the efficacy of prescribed medications and therapies.

QUS has been sought as a nonionizing and noninvasive alternative to DEXA. QUS utilizes measurements of ultrasonic waves between a transmitting and a receiving transducer aligned in parallel along bone surface. Speed of sound (SOS) measurements of the received ultrasonic signal is used to characterize the bone material properties. The determination of the SOS parameter is susceptible to the amount of soft tissue between the skin surface and the bone. Thus, we propose utilizing a high intensity ultrasonic wave known as a “push beam” to exert a force on the bone surface thereby generating vibrations. This will minimize the effects of the soft tissue. The radiate sound wave due to these vibrations are captured and used to analyze the bone mechanical properties.

This work demonstrates the feasibility of evaluating bone mechanical properties from sound waves due to bone vibrations. Under an approved protocol by the Mayo Clinic Institutional Review Board (IRB), human volunteers were recruited to undergo our noninvasive bone assessment technique. Our cohort consisted of clinically confirmed osteopenia and osteoporosis patients, as well as normal volunteers without a history of bone fractures. An ultrasound probe and hydrophone were placed along the volunteers’ tibia bone (Figure 1a). A B-mode ultrasound was used to guide the placement of our push beam focal point onto the bone surface underneath the skin layer (Figure 1b). The SOS was obtained from the measurements.


Figure 1. (a) Probe and hydrophone alignment along the tibia bone. (b) Diagram of an image-guided push beam focal point excitation on the bone surface.

In total 14 volunteers were recruited in our ongoing study. A boxplot comparison of SOS between normal and bone diseased (osteopenia and osteoporotic) volunteers in Figure 2, shows that typically sound travels faster in healthy bones than osteoporotic and osteopenia bones with SOS median values (red line) of 3733 m/s and 2566 m/s, respectively. Hence, our technique may be useful as a noninvasive method for monitoring the skeletal health status of the premature and aging population.


Figure 2. Normal and bone diseased volunteers sound of speed comparisons.


This ongoing project is being done under an approved protocol by Mayo Institutional Review Board.


3aBA5 – Fabricating Blood Vessels with Ultrasound – Diane Dalecki, Ph.D., Eric S. Comeau, M.S., Denise C. Hocking, Ph.D.

3aBA5 – Fabricating Blood Vessels with Ultrasound – Diane Dalecki, Ph.D., Eric S. Comeau, M.S., Denise C. Hocking, Ph.D.

Fabricating Blood Vessels with Ultrasound

Diane Dalecki, Ph.D.
Eric S. Comeau, M.S.
Denise C. Hocking, Ph.D.
Rochester Center for Biomedical Ultrasound
University of Rochester
Rochester, NY 14627

Popular version of paper 3aBA5, “Applications of acoustic radiation force for microvascular tissue engineering”
Presented Wednesday morning May 20, 9:25 AM, in room Kings 2
169th ASA Meeting, Pittsburgh

Tissue engineering is the field of science dedicated to fabricating artificial tissues and organs that can be made available for patients in need of organ transplantation or tissue reconstructive surgery. Tissue engineers have successfully fabricated relatively thin tissues, such as skin substitutes, that can receive nutrients and oxygen by simple diffusion. However, recreating larger and/or more complex tissues and organs will require developing methods to fabricate functional microvascular networks to bring nutrients to all areas of the tissue for survival.

In the laboratories of Diane Dalecki, Ph.D. and Denise C. Hocking, Ph.D., research is underway to develop new ultrasound technologies to control and enhance the fabrication of artificial tissues1. Ultrasound fields are sound fields at frequencies higher than humans can hear (i.e., > 20 kHz). Dalecki and Hocking have developed a technology that uses a particular type of ultrasound field, called an ultrasound standing wave field, as a tool to non-invasively engineer complex spatial patterns of cells2 and fabricate microvessel networks3,4 within artificial tissue constructs.

When a solution of collagen and cells is exposed to an ultrasound standing wave field, the forces associated with the field lead to the alignment of the cells into planar bands (Figure 1). The distance between the bands of cells is controlled by the ultrasound frequency, and the density of cells within each band is controlled by the intensity of the sound field. The collagen polymerizes into a solid gel during the ultrasound exposure, thereby maintaining the spatial organization of the cells after the ultrasound is turned off. More complex patterning can be achieved by use of more than one ultrasound transducer.


Figure 1. Acoustic-patterning of microparticles (dark bands) using an ultrasound standing wave field. Distance between planar bands is 750 µm. Scale bar = 100 μm

An exciting application of this technology involves the fabrication of microvascular networks within artificial tissue constructs. Specifically, acoustic-patterning of endothelial cells into planar bands within collagen hydrogels leads to the rapid development of microvessel networks throughout the entire volume of the hydrogel. Interestingly, the structure of the resultant microvessel network can be controlled by choice of the ultrasound exposure parameters. As shown in Figure 2, ultrasound standing wave fields can be employed to fabricate microvessel networks with different physiologically relevant morphologies, including capillary-like networks (left panel), aligned non-branching vessels (center panel) or aligned vessels with hierarchically branching microvessels. Ultrasound fields provide an ideal technology for microvascular engineering; the technology is rapid, noninvasive, can be broadly applied to many types of cells and hydrogels, and can be adapted to commercial fabrication processes.

To learn more about this research, please view this informative video (https://www.youtube.com/watch?v=ZL-cx21SGn4).

Figure 2. Ultrasound-fabricated microvessel networks within collagen hydrogels. The ultrasound pressure amplitude used for initial patterning determines the final microvessel morphology, which can resemble torturous capillary-like networks (left panel), aligned non-branching vessels (center panel) or aligned vessels with hierarchically branching microvessels. Scale bars = 100 μm.


[1] Dalecki D, Hocking DC. Ultrasound technologies for biomaterials fabrication and imaging. Annals of Biomedical Engineering 43:747-761; 2015.

[2] Garvin KA, Hocking DC, Dalecki D. Controlling the spatial organization of cells and extracellular matrix proteins in engineered tissues using ultrasound standing wave fields. Ultrasound Med. Biol. 36:1919-1932; 2010.

[3] Garvin KA, Dalecki D, Hocking DC. Vascularization of three-dimensional collagen hydrogels using ultrasound standing wave fields. Ultrasound Med. Biol. 37:1853-1864; 2011.

[4] Garvin KA, Dalecki D, Youssefhussien M, Helguera M, Hocking DC. Spatial patterning of endothelial cells and vascular network formation using ultrasound standing wave fields. J. Acoust. Soc. Am. 134:1483-1490; 2013.

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



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

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