Tzu-Chen Yen

Magnetic resonance monitoring of focused ultrasound/magnetic nanoparticle targeting delivery of therapeutic agents to the brain

The superparamagnetic properties of magnetic nanoparticles (MNPs) allow them to be guided by an externally positioned magnet and also provide contrast for MRI. However, their therapeutic use in treating CNS pathologies in vivo is limited by insufficient local accumulation and retention resulting from their inability to traverse biological barriers. The combined use of focused ultrasound and magnetic targeting synergistically delivers therapeutic MNPs across the blood–brain barrier to enter the brain both passively and actively. Therapeutic MNPs were characterized and evaluated both in vitro and in vivo, and MRI was used to monitor and quantify their distribution in vivo. The technique could be used in normal brains or in those with tumors, and significantly increased the deposition of therapeutic MNPs in brains with intact or compromised blood–brain barriers. Synergistic targeting and image monitoring are powerful techniques for the delivery of macromolecular chemotherapeutic agents into the CNS under the guidance of MRI.

Blood-Brain Barrier Disruption with Focused Ultrasound Enhances Delivery of Chemotherapeutic Drugs for Glioblastoma Treatment

PURPOSE To demonstrate the feasibility of using focused ultrasound to enhance delivery of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) to glioblastomas in rats with induced tumors and determine if such an approach increases treatment efficacy. MATERIALS AND METHODS All animal experiments were approved by the animal committee and adhered to the experimental animal care guidelines. A 400-kHz focused ultrasound generator was used to transcranially disrupt the blood-brain barrier (BBB) in rat brains by delivering burst-tone ultrasound energy in the presence of microbubbles. The process was monitored in vivo by using magnetic resonance (MR) imaging. Cultured C6 glioma cells implanted in Sprague-Dawley rats were used as the tumor model. BCNU (13.5 mg/kg) was administered intravenously and its concentration in brains was quantified by using high-performance liquid chromatography. MR imaging was used to evaluate the effect of treatments longitudinally, including analysis of tumor progression and animal survival, and brain tissues were histologically examined. Methods including the two-tailed unpaired t test and the Mantel-Cox test were used for statistical analyses, with a significance level of .05. RESULTS Focused ultrasound significantly enhanced the penetration of BCNU through the BBB in normal (by 340%) and tumor-implanted (by 202%) brains without causing hemorrhaging. Treatment of tumor-implanted rats with focused ultrasound alone had no beneficial effect on tumor progression or on animal survival up to 60 days. Administration of BCNU only transiently controlled tumor progression; nevertheless, relative to untreated controls, animal survival was improved by treatment with BCNU alone (increase in median survival time [IST(median)], 15.7%, P = .023). Treatment with focused ultrasound before BCNU administration controlled tumor progression (day 31: 0.05 cm(3) + or - 0.1 [standard deviation] vs 0.28 cm(3) + or - 0.1) and improved animal survival relative to untreated controls (IST(median), 85.9%, P = .0015). CONCLUSION This study demonstrates a means of increasing localized chemotherapeutic drug delivery for brain tumor treatment and strongly supports the feasibility of this treatment in a clinical setting.

Prospective Study of [18F]Fluorodeoxyglucose Positron Emission Tomography and Computed Tomography and Magnetic Resonance Imaging in Oral Cavity Squamous Cell Carcinoma With Palpably Negative Neck

PURPOSE To assess the clinical usefulness of [(18)F]fluorodeoxyglucose positron emission tomography ([18F]FDG PET) as well as computed tomography (CT) or magnetic resonance imaging (MRI) in oral squamous cell carcinoma (SCC) patients with palpably negative neck. PATIENTS AND METHODS In total, 134 oral SCC patients with palpably negative neck were prospectively evaluated with [18F]FDG PET, CT/MRI, and their visual correlation. Histopathologic analysis was used as the gold standard for assessment of these imaging techniques. RESULTS Thirty-five (26.1%) of our 134 patients were found to have neck metastases. On a level-by-level basis, the sensitivity of [18F]FDG PET for nodal metastases was two-fold higher than that of CT/MRI (41.2% v 21.6%, respectively; P = .021). Visual correlation of [(18)F]FDG PET and CT/MRI yielded slightly higher sensitivity and specificity than [18F]FDG PET alone (47.1% v 41.2%, P = .25; 98.0% v 96.8%, P = .125, respectively). On a patient-by-patient basis, the sensitivity of [18F]FDG PET for neck metastases was 51.4% and increased to 57.1% after visual correlation with CT/MRI. The probabilities of occult neck metastasis after using [(18)F]FDG PET were 6.7% in T1 tumors, 10.8% in T2 tumors, 13.3% in T3 tumors, and 25% in T4 tumors and decreased to 3.3% in T1 tumors and to 9.2% in T2 tumors after visual correlation with CT/MRI. CONCLUSION [(18)F]FDG PET was superior to CT/MRI for detecting palpably occult neck metastasis of oral SCC. Because [(18)F]FDG PET could reduce the probability of occult neck metastasis to less than 15% in T1 to T3 tumors, it should be indicated for evaluation of these subpopulations.

Detection of lymph node metastasis in cervical and uterine cancers by diffusion‐weighted magnetic resonance imaging at 3T

To evaluate diffusion‐weighted imaging (DWI) for detection of pelvic lymph node metastasis in patients with cervical and uterine cancers.

Myometrial Invasion in Endometrial Cancer: Diagnostic Accuracy of Diffusion-weighted 3.0-T MR Imaging—Initial Experience

PURPOSE To assess the diagnostic accuracy of fused T2-weighted and high-b-value diffusion-weighted (DW) magnetic resonance (MR) images at 3 T for evaluation of myometrial invasion in patients with endometrial cancer. MATERIALS AND METHODS Institutional review board approval and informed consent were obtained. From May 2006 to October 2007, 48 consecutive patients aged 25-80 years (mean age, 57 years) who had endometrial cancer were prospectively enrolled for preoperative evaluation by using a 3-T MR unit. Two radiologists interpreted the depth of myometrial invasion on T2-weighted images, dynamic contrast material-enhanced MR images, and fused T2-weighted and DW MR images (b = 1000 sec/mm(2)). Statistical methods included kappa statistics for reader agreement, Pearson analysis for pathologic correlation, accuracy assessment, and receiver operating characteristic analysis for diagnostic performance comparison. Surgical pathologic findings were the reference standard. RESULTS Reader agreement was excellent for fused T2-weighted and DW images (weighted kappa, 0.79), with a significant pathologic correlation regarding the depth of myometrial invasion (r = 0.94, P < .0001). For assessing any myometrial involvement, addition of fused T2-weighted and DW imaging to dynamic contrast-enhanced or dynamic contrast-enhanced and T2-weighted imaging was significantly better compared with dynamic contrast-enhanced imaging alone (P < .001) or dynamic contrast-enhanced and T2-weighted (P = .001) imaging; T2-weighted imaging combined with fused T2-weighted and DW imaging also was better than dynamic contrast-enhanced and T2-weighted imaging (P = .001). Tumor apparent diffusion coefficients were 0.60-1.32 x 10(-3) mm(2)/sec (median, 0.75 x 10(-3) mm(2)/sec), with no significant correlation with the depth of myometrial invasion (P = .31, r = -0.15). CONCLUSION Fused T2-weighted and high-b-value DW images at 3 T can provide accurate information for preoperative evaluation of myometrial invasion.

Value of Dual-Phase 2-Fluoro-2-Deoxy-d-Glucose Positron Emission Tomography in Cervical Cancer

PURPOSE The role of positron emission tomography (PET) with fluorine-18-labeled fluoro-2-deoxy-d-glucose (FDG) in cervical cancer has not yet been well defined. We conducted a prospective study to investigate its efficacy in comparison with magnetic resonance imaging and/or computed tomography (MRI-CT). MATERIALS AND METHODS Patients with untreated locally advanced (35%) or recurrent (65%) cervical cancer were enrolled onto this study. In the first part of this study, 41 patients had a conventional FDG-PET (40 minutes after injection), and in the second part, 94 patients received dual-phase PET (at both 40 minutes and 3 hours after injection). The overall results of PET scans were compared with MRI-CT, and the two protocols of PET were also compared with each other. Lesion status was determined by pathology results or clinical follow-up. The receiver operating characteristic curve method with area under the curve (AUC) calculation was used to evaluate the discriminative power. RESULTS Overall (N = 135), FDG-PET was significantly superior to MRI-CT in identifying metastatic lesions (AUC, 0.971 v 0.879; P =.039), although the diagnostic accuracy was similar for local tumors. Dual-phase PET was also significantly better than the 40-minute PET (n = 94). The latter accurately recognized 70% of metastatic lesions and the former detected 90% (AUC, 0.943 v 0.951; P =.007). Dual-phase FDG-PET changed treatment of 29 patients (31%; upstaging 27% and downstaging 4%). CONCLUSION This study shows that dual-phase FDG-PET is superior to conventional FDG-PET or MRI-CT in the evaluation of metastatic lesions in locally advanced or recurrent cervical cancer.

Biodistribution, pharmacodynamics and pharmacokinetics of insulin analogues in a rat model: Oral delivery using pH-Responsive nanoparticles vs. subcutaneous injection

In this study, we report the biodistribution of aspart-insulin, a rapid-acting insulin analogue, following oral or subcutaneous (SC) administration to rats using the single-photon emission computed tomography (SPECT)/computed tomography (CT). Oral delivery of aspart-insulin was achieved using a pH-responsive nanoparticle (NP) system composed of chitosan (CS) and poly(gamma-glutamic acid). The results obtained in the SPECT/CT study indicate that the orally administered aspart-insulin was absorbed into the systemic circulation, while the drug carrier (CS) was mainly retained in the gastrointestinal tract.Via the SC route, the peak aspart-insulin concentration in the peripheral tissue/plasma was observed at 20 min after injection. Within 3 h, half of the initial dose (ID) of aspart-insulin was degraded and excreted into the urinary bladder. In contrast, via oral delivery, there was constantly circulating aspart-insulin in the peripheral tissue/plasma during the course of the study, while 20% of the ID of aspart-insulin was metabolized and excreted into the urinary bladder. In the pharmacodynamic (PD) and pharmacokinetic (PK) evaluation in a diabetic rat model, the orally administered aspart-insulin loaded NPs produced a slower hypoglycemic response for a prolonged period of time, whereas the SC injection of aspart-insulin produced a more pronounced hypoglycemic effect for a relatively shorter duration. Finally, comparison of the PD/PK profiles of the orally administered aspart-insulin with those of the SC injection of NPH-insulin, an intermediate-acting insulin preparation, suggests the suitability of our NP system to be used as a non-invasive alternative for the basal insulin therapy.

Concurrent blood-brain barrier opening and local drug delivery using drug-carrying microbubbles and focused ultrasound for brain glioma treatment.

Glioblastoma multiforme (GBM) is a highly malignant brain tumor. The blood-brain barrier (BBB) provides a major obstacle to chemotherapy since therapeutic doses cannot be achieved by traditional drug delivery without severe systemic cytotoxic effects. Recently, microbubble (MB)-enhanced focused ultrasound (FUS) was shown to temporally and locally disrupt the BBB thereby enhancing drug delivery into brain tumors. Here we propose the concept of smart, multifunctional MBs capable of facilitating FUS-induced BBB disruption while serving as drug-carrying vehicles and protecting drugs from rapid degradation. The designed MBs had a high loading capacity (efficiency of 68.01 ± 4.35%) for 1,3-bis(2-chloroethyl)-1- nitrosourea (BCNU). When combined with FUS (1-MHz), these BCNU-MBs facilitated local BBB disruption and simultaneously released BCNU at the target site, thus increasing local BCNU deposition. Encapsulation of BCNU in MBs prolonged its circulatory half-life by 5-fold, and accumulation of BCNU in the liver was reduced 5-fold due to the slow reticuloendothelial system uptake of BCNU-MBs. In tumor-bearing animals, BCNU-MBs with FUS controlled tumor progression (915.3%-39.6%) and improved median survival (29 days-32.5 days). This study provides a new approach for designing multifunctional MBs to facilitate FUS-mediated chemotherapy for brain tumor treatment.

Nodal metastases of nasopharyngeal carcinoma: patterns of disease on MRI and FDG PET

The patterns of nodal spread of nasopharyngeal carcinoma (NPC) have an important influence on treatment planning, but have not yet been fully addressed. We prospectively used MRI and FDG PET to document the patterns of nodal spread in NPC. One hundred and one patients with newly diagnosed NPC were studied with MRI and FDG PET. On MRI, nodes were considered as metastatic according to criteria regarding size, the presence of nodal necrosis, and extracapsular spread. FDG PET images were interpreted visually, and nodes were considered metastatic if they showed prominent FDG uptake against the background. Nodal metastases were found in 89 of our 101 patients. Analysis of the distributions of nodal metastases in these 89 patients showed that retropharyngeal nodes were less frequently involved than cervical nodes (82.0% vs 95.5%). The vast majority of cervical nodal metastases were to the internal jugular chain, including nodes at levels II, III, and IV, with decreasing incidences of 95.5%, 60.7%, and 34.8%, respectively. Level V nodal involvement was found in 27% of patients. Supraclavicular fossa nodal metastases were not uncommon and occurred in 22.5% of patients. Skip metastases in the lower-level nodes or supraclavicular fossa nodes occurred in 7.9% of patients. Mediastinal and abdominal metastatic adenopathy was present in 4.5% and 3.4% of patients, respectively, and was associated with advanced nodal metastasis in the supraclavicular fossa. Level VI (2.2%), level VII (1.1%), submandibular (2.2%), and parotid (3.4%) nodal metastases were uncommon and were always associated with advanced ipsilateral nodal metastases of the neck. We conclude that the combined use of FDG PET and MRI can comprehensively depict the pattern of nodal metastasis in NPC patients. Nodal metastases principally affected level II nodes, from which lymphatic spread extended down in an orderly manner to involve level III, level IV, and the supraclavicular fossa nodes, or extended posteriorly to involve level V nodes. The frequency of skip metastases was 7.9%. Distant spread to mediastinal or abdominal nodes was found in 3–5% of patients, usually in association with supraclavicular nodal metastases.

SPIO-conjugated, doxorubicin-loaded microbubbles for concurrent MRI and focused-ultrasound enhanced brain-tumor drug delivery

The blood-brain barrier (BBB) can be temporarily and locally opened by focused ultrasound (FUS) in the presence of circulating microbubbles (MBs). Currently, contrast-enhanced magnetic resonance imaging (CE-MRI) is used to monitor contrast agent leakage to verify BBB-opening and infer drug deposition. However, despite being administered concurrently, MBs, therapeutic agent, and contrast agent have distinct pharmacodynamic behaviors, thus complicating the quantification and optimization of BBB-opening and drug delivery. Here we propose multifunctional MBs loaded with therapeutic agent (doxorubicin; DOX) and conjugated with superparamagnetic iron oxide (SPIO) nanoparticles. These DOX-SPIO-MBs were designed to concurrently open the BBB and perform drug delivery upon FUS exposure, act as dual MRI and ultrasound contrast agent, and allow magnetic targeting (MT) to achieve enhanced drug delivery. We performed burst-tone FUS after injection of DOX-SPIO-MBs, followed by MT with an external magnet attached to the scalp in a rat glioma model. Animals were monitored by T2-weighted MRI and susceptibility weighted imaging and the concentration of SPIO particles was determined by spin-spin relaxivity. We found that DOX-SPIO-MBs were stable and provided significant superparamagnetic/acoustic properties for imaging. BBB-opening and drug delivery were achieved concurrently during the FUS exposure. In addition, MT increased local SPIO deposition in tumor regions by 22.4%. Our findings suggest that DOX-SPIO-MBs with FUS could be an excellent theranostic tool for future image-guided drug delivery to brain tumors.