Double Push Acoustic Radiation Force (DP ARF) Ultrasound for Monitoring Degeneration in Duchenne Muscular Dystrophy

Double Push Acoustic Radiation Force (DP ARF) imaging will be performed in 3 cohorts of up to
10 boys with DMD and in age-matched boys with no known neuromuscular disorders.

The first DMD cohort will enroll at age 5-6, the second at age 7-8, and the third at age
9-10. The rectus femoris (RF), cranial sartorius (CS), gastrocnemius (GAST), and lateral
deltoid (DT) muscles will be targeted for their known phenotypic variation in response to
dystrophin deficiency. The RF undergoes early necrosis and fatty deposition, the CS is
thought to be relatively spared, and the GAST seems to undergo true hypertrophy. The DT,
which undergoes hypertrophy like the GAST, will also be examined to determine if the impact
of dystrophin deficiency varies between upper and lower limbs. All boys will be imaged 3
times annually for 4 years. In addition to DP ARF imaging every 4 mos, the boys will undergo
standard quantitative muscle testing (QMT) and timed function tests (TFT) of time to
standing, 6-minute walk, and 30-feet walk. Age at loss of ambulation will also be recorded
for each boy. Boys with DMD generally loose ambulation by age 10, so we expect that the 20
boys in the 7-11 and 9-13 aged cohorts will lose ambulation over the course of this study.
The 10 boys in the 5-9 aged cohort will likely not lose ambulation during the study. Because
the primary objective of this clinical investigation is to evaluate the potential of DP ARF
imaging as a relevant surrogate for monitoring disease progression and response to therapies,
the focus of the study will be on correlating DP ARF results to change in functional
degeneration and time to loss of ambulation.

There are two experimental components to this study beyond what is standard practice for DMD
patients: 1) DP ARF ultrasound imaging of the rectus femoris (RF), cranial sartorius (CS),
gastrocnemius (GAST), and lateral deltoid (DT) muscles and 2) standard quantitative muscle
testing (QMT) and timed function tests (TFTs) of time to standing, 6-minute walk, and 30-feet
walk repeated every four months (three times annually) throughout the four-year duration of
the study.

This study will commence with DP ARF ultrasound imaging in the Clinical Neurophysiology
Laboratory during the patient volunteer's first regularly scheduled research visit. Patient
volunteers are expected to be outpatients. However, if a patient volunteer is an inpatient,
DP ARF ultrasound imaging may be performed at the patient volunteer's hospital bedside.
Immediately following DP ARF examination, the patient volunteer will undergo QMT and TFTs in
the Physical Therapy Department. QMT and TFT will be conducted by trained physical
therapists. DP ARF ultrasound imaging, QMT and TFT will be repeated as described above at
each of the patient volunteers' twelve regularly scheduled research visits over the four-year
study duration. Whenever possible, we will schedule research visits to coincide with other
clinical visits to UNC. The patients' parents or caregivers will be compensated $50 per visit
to defray the costs of travel to UNC, parking and lunch.

DP ARF will also be performed in 30 boys ages 5-14 with no known neuromuscular disorders.
Imaging will be performed as described for the boys with DMD. The DP ARF results obtained in
boys with no known neuromuscular disorders will be compared to those obtained in boys with
neuromuscular disorders to serve as a control for changes in muscle mechanical property to
occur with normal muscle growth and development.

DP ARF ultrasound is a noninvasive diagnostic imaging technology performed using commercially
available clinical ultrasound imaging equipment - the Siemens Acuson Antares imaging system
equipped for research purposes and VF10-5 or VF7-3 linear array transducers (Siemens Medical
Solutions, USA Inc. Ultrasound Division). DP ARF imaging will be carried out by a
professional sonographer, faculty and/or graduate student research assistants in the UNC-CH
Joint Department of Biomedical Engineering. The sonographer will acquire DP ARF ultrasound
data with matched B-Mode (for anatomical reference) in the right RF, CS, GAST, and DT muscles
of patient volunteers. Patient volunteers will be asked to lie on an examination table in the
Clinical Neurophysiology Clinic (outpatients) or to remain in their hospital beds
(inpatients). The head of the exam table/bed may be raised to an approximate 45 degree angle
to best visualize the muscles of interest with ultrasound imaging.

Once the patient volunteer is positioned, ultrasound gel will be applied to the patient
volunteer's skin surface above the muscles of interest. The ultrasound imaging transducer
will then be placed on top of the gel. Once the first muscle of interest is located, DP ARF
ultrasound imaging will begin. We will orient the transducer to acquire ultrasound data
transverse to the muscle fibers in the middle of the muscle length-wise, with three repeated
acquisitions. We will then rotate our transducer 90 degrees to orient the imaging plane
parallel to the muscle fibers. The previously imaged cross-section will be positioned in the
approximate middle of the imaging field of view, with three repeated acquisitions. Muscle
fiber orientation will be approximate, as surmised from anatomy. The DP ARF axial focal depth
will be directed to the center of the muscle, approximately 20 - 30 mm.

The length of time for DP ARF data collection in each muscle is estimated to be less than 10
minutes. Once DP ARF imaging is completed on one muscle, DP ARF imaging will be performed on
the other muscles of interest. Once all 4 muscles (RF, CS, GAST and DT) are imaged, the study
procedure will be completed for the DP ARF imaging portion of the study.

For the second part of the study, beginning shortly (less than 4 hours) after DP ARF imaging
is completed, the patient volunteer will undergo clinically standard quantitative muscle
testing (QMT) of maximum voluntary isometric contraction (MVIC) in the right RF, CS, GAST and
DT. The patient volunteer will also undergo clinically standard timed function tests (TFTs)
of (1) time to rise from supine to standing, (2) distance walked in six minutes and (3) time
to walk 30 feet.

Patient volunteers' participation will end once both study parts one (DP ARF ultrasound
imaging) and two (QMT and TFT) are completed twelve times over 4 years. Therefore, there will
be regularly scheduled follow-up visits required of the patient volunteers every four months.
The patient volunteer is asked to assent and his parents are asked to permit their son to
undergo (1) DP ARF ultrasound imaging of his right RF, CS, GAST and DT muscles, and (2) QMT
and TFTs of time to standing, 6-minute walk, and 30-feet walk. No additional procedures or
requirements are proposed. Every other aspect of the patient volunteers' care for DMD will be
carried out in the normal standard of care as clinically indicated.

Inclusion Criteria:

- Clinical diagnosis of Duchenne muscular dystrophy with clinical onset by age 5

- Ability to stand, alone or with assistance, at time of enrollment

- Ability to communicate with pertinent staff

- Ability to understand and comply with study requirements

- Ability to give informed consent.

Exclusion Criteria:

- Confirmed diagnosis of other muscle disease

- Previous compartment syndrome

- Previous injury to selected limbs

- Previous vascular surgery to selected limbs

- History of a compressive neuropathy (e.g., sciatic, femoral or tibial palsy in leg)

- History of rhabdomyolysis