Ultrasound-assisted convection-enhanced delivery to the brain in vivo with a novel transducer cannula assembly

Laboratory investigation

Restricted access


In convection-enhanced delivery (CED), drugs are infused locally into tissue through a cannula inserted into the brain parenchyma to enhance drug penetration over diffusion strategies. The purpose of this study was to demonstrate the feasibility of ultrasound-assisted CED (UCED) in the rodent brain in vivo using a novel, low-profile transducer cannula assembly (TCA) and portable, pocket-sized ultrasound system.


Forty Sprague-Dawley rats (350–450 g) were divided into 2 equal groups (Groups 1 and 2). Each group was divided again into 4 subgroups (n = 5 in each). The caudate of each rodent brain was infused with 0.25 wt% Evans blue dye (EBD) in phosphate-buffered saline at 2 different infusion rates of 0.25 μl/minute (Group 1), and 0.5 μl/minute (Group 2). The infusion rates were increased slowly over 10 minutes from 0.05 to 0.25 μl/minute (Group 1) and from 0.1 to 0.5 μl/minute (Group 2). The final flow rate was maintained for 20 minutes. Rodents in the 4 control subgroups were infused using the TCA without ultrasound and without and with microbubbles added to the infusate (CED and CED + MB, respectively). Rodents in the 4 UCED subgroups were infused without and with microbubbles added to the infusate (UCED and UCED + MB) using the TCA with continuous-wave 1.34-MHz low-intensity ultrasound at a total acoustic power of 0.11 ± 0.005 W and peak spatial intensity at the cannula tip of 49.7 mW/cm2. An additional 4 Sprague-Dawley rats (350–450 g) received UCED at 4 different and higher ultrasound intensities at the cannula tip ranging from 62.0 to 155.0 mW/cm2 for 30 minutes. The 3D infusion distribution was reconstructed using MATLAB analysis. Tissue damage and morphological changes to the brain were assessed using H & E.


The application of ultrasound during infusion (UCED and UCED + MB) improved the volumetric distribution of EBD in the brain by a factor of 2.24 to 3.25 when there were no microbubbles in the infusate and by a factor of 1.16 to 1.70 when microbubbles were added to the infusate (p < 0.001). On gross and histological examination, no damage to the brain tissue was found for any acoustic exposure applied to the brain.


The TCA and ultrasound device show promise to improve the distribution of infused compounds during CED. The results suggest further studies are required to optimize infusion and acoustic parameters for small compounds and for larger molecular weight compounds that are representative of promising antitumor agents. In addition, safe levels of ultrasound exposure in chronic experiments must be determined for practical clinical evaluation of UCED. Extension of these experiments to larger animal models is warranted to demonstrate efficacy of this technique.

Abbreviations used in this paper:AP = anteroposterior; CED = convection-enhanced delivery; CNC = computer numeric controlled; EBD = Evans blue dye; MB = microbubbles; MI = mechanical index; MOSFET = metal oxide semiconductor field-effect transistor; OCT = optimal cutting temperature; TCA = transducer cannula assembly; UCED = ultrasound-assisted CED.

Article Information

Address correspondence to: George K. Lewis Jr., Ph.D., ZetrOZ LLC, 421 Aurora Street, Ithaca, New York 14850. email: george@cornellbme.com.

Please include this information when citing this paper: published online September 21, 2012; DOI: 10.3171/2012.7.JNS11144.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Construction of the transducer cannula assembly. I: Machine the PZT-4 into a disk with center hole. II and III: Connect a brass tube to front face of ceramic using solder. IV: Place the ceramic in a watertight PVC/aluminum housing with sterotactic guide arm and connect ground and hot leads to the transducer through the guide arm. V and VI: Attach the guide cannula and infusion cannula to the transducer and secure to the proper height with epoxy. VII: Actual finished device. coax = coaxial.

  • View in gallery

    Animal experimental setup for using the TCA in rodent brain. The rodent is secured with ear bars in a stereotactic frame, and a small craniotomy is performed over the left hemisphere. The TCA is guided 5.5 mm deep into the caudate of the rodent brain.

  • View in gallery

    Electrical impedance of TCA. Resonance occurs at 1.18 MHz with 380-Ω impedance. The phase angle (not shown) is approximately 0× at resonance. Parallel resonance occurs at 3.1 MHz.

  • View in gallery

    Brain sections from the 4 subgroups of Group 2 after 30 minutes of Evans blue infusions at 0.5 μl/minute with a 30-gauge cannula. A and B: Convection-enhanced delivery (A) and CED with microbubbles (CED + MB) provide similar infusion profiles for the rodents in each group. C: Ultrasound-assisted CED delivers EBD further into the brain and more diffusely spread across the caudate. D: Ultrasound-assisted CED with microbubbles (UCED + MB) shows further EBD penetration than CED and CED + MB, but is more localized in the rodent caudate than UCED, which spreads EBD out of the caudate region. Backflow of EBD along the needle track into the white matter tract of the corpus callosum is reduced with UCED and UCED + MB as compared with controls.

  • View in gallery

    Three-dimensional infusion reconstructions of brain sections from the 4 subgroups of Group 2 shown in Fig. 4. The cannula is in the plane of the figure; the TCA is positioned at the top of each figure. A: Convection-enhanced delivery. B: Convection-enhanced delivery with microbubbles. C: Ultrasound-assisted CED. D: Ultrasoundassisted CED with microbubbles.

  • View in gallery

    Analysis of total EBD volume distribution in the rodent brain with subgroup standard error bars. Ultrasound-assisted CED and UCED + MB increased EBD volume distribution by factors of 2.24 and 1.37 in the left hemisphere and 2.44 and 1.70 in the left caudate, respectively, as compared with CED and CED + MB in Group 1 animals receiving 0.25 μl/minute infusions. In the animals receiving 0.5 μl/minute infusions (Group 2), UCED and UCED + MB increased EBD volume distribution by factors of 2.96 and 1.16 in the left hemisphere and 3.25 and 1.54 in the left caudate, respectively. *The differences in volume distributions in the left hemisphere and left caudate subgroups of Group 1 and Group 2 are statistically significant with independent means p < 0.05 and p < 0.001.

  • View in gallery

    Group 1 (0.25 μl/minute infusion) analysis of EBD distribution profile in the rodent caudate as a function of the AP distance in the region ± 4 mm from the infusion site. The black line represents the average area of EBD at the given position. The shaded region represents the standard deviation of EBD area (n = 5).

  • View in gallery

    Group 2 (0.5 μl/minute infusion) analysis of EBD distribution profile in the rodent caudate as a function of the AP distance in the region ± 4 mm from the infusion site. The black line represents the average area of EBD at the given position. The shaded region represents the standard deviation of EBD area (n = 5).

  • View in gallery

    The area of EBD in rodent caudate for each slice plotted as a function of the square of the AP distance from the infusion site for Group 1 and Group 2. Each solid colored line represents the mean area for each treatment at the given position. A dotted line segment with a slope magnitude of π is drawn for reference. Data that fall on a line with slope of π or −π indicate regions where the infusion of EBD is locally isotropic. Deviations from the slope indicate an anisotropic volume distribution.

  • View in gallery

    An H & E stain of rodent brains (10-μm coronal slices) in the cannula insertion path for the 40 rodents that received CED, CED + MB, UCED, and UCED + MB. Arrows point from the ×2.5 to ×20 magnification of histological results found in the cortex and caudate of the rodent brains. Mild parenchymal disruption, edema, and hemorrhage around the needle track and injection site are equivalent for all specimens.

  • View in gallery

    An H & E stain of rodent brains (10-μm coronal slices) in the cannula insertion path for the four rodents that received UCED of increased ultrasonic intensity. Arrows point from the ×2.5 to ×20 magnification of histological results found in the cortex and caudate of the rodent brains. Mild parenchymal disruption, edema, and hemorrhage around the needle track and injection site are equivalent for all specimens.



Abbott JGCarson PLHarris GR: Acoustic Output Labeling Standard for Diagnostic Ultrasound Equipment Laurel, MDAmerican Institute of Ultrasound in Medicine Publications1998


American Institute of Ultrasound in Medicine: Bioeffects and Safety of Diagnostic Ultrasound Laurel, MDAmerican Institute of Ultrasound in Medicine Publications1993


American Institute of Ultrasound in Medicine: Bioeffects considerations for the safety of diagnostic ultrasound. J Ultrasound Med 7:9 SupplS1S381988


American Institute of Ultrasound in Medicine: Mechanical Bioeffects from Diagnostic Ultrasound: AIUM Consensus Statements Laurel, MDAmerican Institute of Ultrasound in Medicine Publications2000. 67170


Bobo RHLaske DWAkbasak AMorrison PFDedrick RLOldfield EH: Convection-enhanced delivery of macromolecules in the brain. Proc Natl Acad Sci U S A 91:207620801994


Boucaud AGarrigue MAMachet LVaillant LPatat F: Effect of sonication parameters on transdermal delivery of insulin to hairless rats. J Control Release 81:1131192002


Brightman MW: The brain's interstitial clefts and their glial walls. J Neurocytol 31:5956032002


Broaddus WCPrabhu SSGillies GTNeal JConrad WSChen ZJ: Distribution and stability of antisense phosphorothioate oligonucleotides in rodent brain following direct intraparenchymal controlled-rate infusion. J Neurosurg 88:7347421998


Chen MYLonser RRMorrison PFGovernale LSOldfield EH: Variables affecting convection-enhanced delivery to the striatum: a systematic examination of rate of infusion, cannula size, infusate concentration, and tissue-cannula sealing time. J Neurosurg 90:3153201999


Collis JManasseh RLiovic PTho POoi APetkovic-Duran K: Cavitation microstreaming and stress fields created by microbubbles. Ultrasonics 50:2732792010


Drappatz JNorden AWen P: Treatment of high-grade gliomas in adults. Therapeutic Ribonucleic Acids in Brain Tumors BerlinSpringer2009. 355382


Ferrara KPollard RBorden M: Ultrasound microbubble contrast agents: fundamentals and application to gene and drug delivery. Annu Rev Biomed Eng 9:4154472007


Frenkel VKimmel EIger Y: Ultrasound-facilitated transport of silver chloride (AgCl) particles in fish skin. J Control Release 68:2512612000


Frenkel VOberoi JPark MDeng CStone MJNeeman Z: Pulsed-high intensity ultrasound (HIFU) enhances thrombolysis in an in vitro model. Radiology 239:86932006


Groothuis DRWard SItskovich ACDobrescu CAllen CVDills C: Comparison of 14C-sucrose delivery to the brain by intravenous, intraventricular, and convection-enhanced intracerebral infusion. J Neurosurg 90:3213311999


Guzmán HRNguyen DXMcNamara AJPrausnitz MR: Equilibrium loading of cells with macromolecules by ultrasound: effects of molecular size and acoustic energy. J Pharm Sci 91:169317012002


Hamilton JFMorrison PFChen MYHarvey-White JPernaute RSPhillips H: Heparin coinfusion during convection-enhanced delivery (CED) increases the distribution of the glial-derived neurotrophic factor (GDNF) ligand family in rat striatum and enhances the pharmacological activity of neurturin. Exp Neurol 168:1551612001


Henderson PWLewis GKShaikh NSohn AWeinstein ALOlbricht WL: A portable high intensity focused ultrasound device for the noninvasive treatment of varicose veins. J Vasc Surg 51:7077112010


Hochberg FHPruitt A: Assumptions in the radiotherapy of glioblastoma. Neurology 30:9079111980


Huynh GHDeen DFSzoka FCJ Jr: Barriers to carrier mediated drug and gene delivery to brain tumors. J Control Release 110:2362592006


Hynynen KClement G: Clinical applications of focused ultrasound-the brain. Int J Hyperthermia 23:1932022007


Institute of Electrical and Electronics Engineers Standards: IEEE Guide for Medical Ultrasound Field Parameter Measurements New YorkInstitute of Electrical and Electronics Engineers1990


Keyhani KGuzmán HRParsons ALewis TNPrausnitz MR: Intracellular drug delivery using low-frequency ultrasound: quantification of molecular uptake and cell viability. Pharm Res 18:151415202001


Kunwar SPrados MDChang SMBerger MSLang FFPiepmeier JM: Direct intracerebral delivery of cintredekin besudotox (IL13-PE38QQR) in recurrent malignant glioma: a report by the Cintredekin Besudotox Intraparenchymal Study Group. J Clin Oncol 25:8378442007


Lewis GK JrFilinger LLewis GK SrOlbricht WLSarvazyan A: Time-reversal techniques in ultrasound-assisted convectionenhanced drug delivery to the brain: technology development and in vivo evaluation. J Acoust Soc Am 128:23352010. (Abstract)


Lewis GK JrLewis GK SrOlbricht WL: Cost-effective broad-band electrical impedance spectroscopy measurement circuit and signal analysis for piezo-materials and ultrasound transducers. Meas Sci Technol 19:1051022008


Lewis GK JrOlbricht WL: Design and characterization of a high-power ultrasound driver with ultralow-output impedance. Rev Sci Instrum 80:1147042009


Lewis GK JrOlbricht WL: Development of a portable therapeutic and high intensity ultrasound system for military, medical, and research use. Rev Sci Instrum 79:1143022008


Lewis GK JrOlbricht WL: Development of a portable therapeutic ultrasound system for military, medical and research use. J Acoust Soc Am POMA 5:25512008


Lewis GK JrOlbricht WL: A phantom feasibility study of acoustic enhanced drug perfusion in neurological tissue. IEEE Life Science Systems and Applications Workshop Washington, DCIEEE2007. 6770


Lewis GK JrOlbricht WL: Cornell University assignee: Wave generating apparatus. US Patent 2011/0285244A1.Nov.242011


Lewis GK JrOlbricht WLLewis GK Sr: Acoustic targeted chemotherapy in neurological tissue. J Acoust Soc Am 122:30072007. (Abstract)


Lewis GK JrWang PLewis GK SrOlbricht WL: Therapeutic ultrasound enhancement of drug delivery to soft tissues. AIP Conf Proc 1113:4034072009


Lieberman DMLaske DWMorrison PFBankiewicz KSOldfield EH: Convection-enhanced distribution of large molecules in gray matter during interstitial drug infusion. J Neurosurg 82:102110291995


Liu YPaliwal SBankiewicz KSBringas JRHeart GMitragotri S: Ultrasound-enhanced drug transport and distribution in the brain. AAPS PharmSciTech 11:100510172010


Lonser RRCorthésy MEMorrison PFGogate NOldfield EH: Convection-enhanced selective excitotoxic ablation of the neurons of the globus pallidus internus for treatment of parkinsonism in nonhuman primates. J Neurosurg 91:2943021999


Lopez KAWaziri AECanoll PDBruce JN: Convection-enhanced delivery in the treatment of malignant glioma. Neurol Res 28:5425482006


Lowe JTechniques in neuropathology. Bancroft JDGamble M: Theory and Practice of Histological Techniques ed 6PhiladelphiaElsevier2008. 371414


Machet LBoucaud A: Phonophoresis: efficiency, mechanisms and skin tolerance. Int J Pharm 243:1152002


Mardor YRoth YLidar ZJonas TPfeffer RMaier SE: Monitoring response to convection-enhanced taxol delivery in brain tumor patients using diffusion-weighted magnetic resonance imaging. Cancer Res 61:497149732001


Mitragotri SBlankschtein DLanger R: Ultrasound-mediated transdermal protein delivery. Science 269:8508531995


Morrison PFChen MYChadwick RSLonser RROldfield EH: Focal delivery during direct infusion to brain: role of flow rate, catheter diameter, and tissue mechanics. Am J Physiol Regul Integr Comp Physiol 277:4 Pt 2R1218R12291999


Neeves KBSawyer AJFoley CPSaltzman WMOlbricht WL: Dilation and degradation of the brain extracellular matrix enhances penetration of infused polymer nanoparticles. Brain Res 1180:1211322007


Ohl CDArora MIkink Rde Jong NVersluis MDelius M: Sonoporation from jetting cavitation bubbles. Biophys J 91:428542952006


Patrick JTNolting MNGoss SADines KAClendenon JLRea MA: Ultrasound and the blood-brain barrier. Adv Exp Med Biol 267:3693811990


Rainov NGSöling AHeidecke V: Novel therapies for malignant gliomas: a local affair?. Neurosurg Focus 20:4E92006


Ren HBoulikas TLundstrom KSöling AWarnke PCRainov NG: Immunogene therapy of recurrent glioblastoma multiforme with a liposomally encapsulated replication-incompetent Semliki forest virus vector carrying the human interleukin-12 gene—a phase I/II clinical protocol. J Neurooncol 64:1471542003


Sakamoto SWatanabe Y: Effects of existence of microbubbles for increase of acoustic streaming. Jpn J Appl Phys 38:305030521999


Sampson JHAkabani GArcher GEBigner DDBerger MSFriedman AH: Progress report of a Phase I study of the intracerebral microinfusion of a recombinant chimeric protein composed of transforming growth factor (TGF)-α and a mutated form of the Pseudomonas exotoxin termed PE-38 (TP-38) for the treatment of malignant brain tumors. J Neurooncol 65:27352003


Smith NBLee SShung KK: Ultrasound-mediated transdermal in vivo transport of insulin with low-profile cymbal arrays. Ultrasound Med Biol 29:120512102003


Vogelbaum MA: Convection enhanced delivery for treating brain tumors and selected neurological disorders: symposium review. J Neurooncol 83:971092007


Weber FAsher ABucholz RBerger MPrados MChang S: Safety, tolerability, and tumor response of IL4-Pseudomonas exotoxin (NBI-3001) in patients with recurrent malignant glioma. J Neurooncol 64:1251372003


Yamashita YKrauze MTKawaguchi TNoble CODrummond DCPark JW: Convection-enhanced delivery of a topoisomerase I inhibitor (nanoliposomal topotecan) and a topoisomerase II inhibitor (pegylated liposomal doxorubicin) in intracranial brain tumor xenografts. Neuro Oncol 9:20282007




All Time Past Year Past 30 Days
Abstract Views 22 22 19
Full Text Views 97 97 38
PDF Downloads 86 86 34
EPUB Downloads 0 0 0


Google Scholar