High-resolution ultrasound perfusion imaging of therapeutic angiogenesis.
OBJECTIVE
The purpose of this study was to test the feasibility of contrast pulse sequence (CPS) ultrasound imaging for high-resolution perfusion imaging after gene transfer (GT) for therapeutic angiogenesis.


BACKGROUND
Imaging modalities capable of accurate and feasible perfusion measurement are essential for the preclinical and clinical development of therapeutic angiogenesis. However, current methods suffer from compromises between spatial and temporal resolution and sensitivity. Contrast pulse sequence ultrasound is a recently developed real-time perfusion imaging method that generates high-contrast agent-to-tissue specificity and spatial resolution.


METHODS
Contrast pulse sequence ultrasound was used to noninvasively assess parameters of blood flow 6 days after adenoviral vascular endothelial growth factor (AdVEGF) GT in rabbit and mouse hind limbs with bolus intravenous injection of a microbubble contrast medium. Blood volume, mean transit time, perfusion, and time to the arrival of the contrast bolus were calculated with the gamma variate function. Contrast-enhanced power Doppler ultrasound (CEU), dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI), and histological capillary measurements were used as reference methods.


RESULTS
Blood volume and perfusion increased over 40- and 20-fold, respectively, 6 days after AdVEGF GT in rabbit skeletal muscles. Perfusion values measured with CPS correlated well with those obtained with CEU (r = 0.975) and DCE-MRI (r = 0.854). However, CPS provided superior spatial and temporal resolution showing blood flow in vessels of only 10 to 20 mum in diameter. Contrast pulse sequence ultrasound was also feasible for imaging of therapeutic angiogenesis in mouse hind limbs both at the arterial and capillary levels. The CPS ultrasound revealed that AdVEGF mainly induces angiogenesis in adipose tissue rather than in the skeletal muscle of mouse hind limbs.


CONCLUSIONS
Contrast pulse sequence ultrasound is an efficient and accurate noninvasive real-time perfusion imaging modality in small laboratory animals and also offers a means for the assessment of muscle perfusion in future clinical trials of therapeutic angiogenesis.
Department of Biotechnology and Molecular Medicine, A I Virtanen Institute, Kuopio, Finland.
Tuomas T
TT
Rissanen
Petra
P
Korpisalo
Henna
H
Karvinen
Timo
T
Liimatainen
Svetlana
S
Laidinen
Olli H
OH
Gröhn
Seppo
S
Ylä-Herttuala
D000256:Adenoviridae / Q000235:genetics; D000273:Adipose Tissue / Q000098:blood supply*; D000818:Animals; D001810:Blood Volume; D003287:Contrast Media / Q000008:administration & dosage; D005240:Feasibility Studies; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors; D007275:Injections, Intravenous; D008279:Magnetic Resonance Imaging; D051379:Mice; D045423:Microbubbles; D023421:Models, Animal; D018482:Muscle, Skeletal / Q000098:blood supply*; D018919:Neovascularization, Physiologic / Q000235:genetics; D010743:Phospholipids / Q000008:administration & dosage; D011817:Rabbits; D012039:Regional Blood Flow; D013459:Sulfur Hexafluoride / Q000008:administration & dosage; D013997:Time Factors; D018617:Ultrasonography, Doppler, Pulsed; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics
D003287:Contrast Media; D010743:Phospholipids; D042461:Vascular Endothelial Growth Factor A; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride