- Nuclear Medicine
Clinical Professor, Radiology - Rad/Nuclear Medicine
Board Certification: Nuclear Medicine, American Board of Nuclear Medicine (2005)
Residency: Stanford Hospital and Clinics (2005) CA
Medical Education: Universitat de Valencia (1992) Spain
Engaging Self-regulation Targets to Improve Mood and Weight and Understand Mechanism in Depressed and Obese Adults
Multimorbidity (i.e., the coexistence of 2 or more chronic conditions in an individual) is increasingly recognized as a pressing public health problem. Effective interventions targeting coexisting depression and obesity are critical given the high prevalence and worsened outcomes for patients with both conditions. ENGAGE-2 is a pilot randomized controlled trial (RCT). The objective is to investigate the outcomes and mechanisms of an integrated depression and obesity intervention that combines collaborative stepped depression treatment and evidence-based behavioral weight loss treatment. The Integrated Coaching for Better Mood and Weight-2 (I-CARE2) intervention synergistically integrates 2 proven national programs: the Program to Encourage Active and Rewarding Lives (PEARLS) for depression care and the Group Lifestyle Balance (GLB) program for weight loss and cardiometabolic risk reduction. In Phase 1 of the ENGAGE project, investigators developed a new protocol to quantify activation and connectivity of the Affective, Cognitive Control, and Default Mode brain circuits from functional magnetic resonance imaging (fMRI) among 108 depressed obese patients. Investigators implement the same fMRI protocol in this second phase of the project to examine the mechanistic role of these brain circuits as potential neural targets in treatment engagement and response in the I-CARE2 intervention. A new sample of 105 depressed obese patients are randomized in a 2:1 ratio to receive the I-CARE2 intervention (n=70) or usual care (n=35). Study assessments occur at 0 (baseline), 2 and 6 months. Investigators hypothesize that 1 or more of the neural targets under study will moderate (baseline state) and/or mediate (change at follow-up) the effect of the I-CARE2 intervention versus usual care on health behaviors (problem-solving ability, dietary intakes, physical activity) and clinical outcomes (weight loss, depression, anxiety).
Stanford is currently not accepting patients for this trial.
Correction: Shaped Magnetic Field Pulses by Multi-Coil Repetitive Transcranial Magnetic Stimulation (rTMS) Differentially Modulate Anterior Cingulate Cortex Responses and Pain in Volunteers and Fibromyalgia Patients.
; 10: 174480691016
View details for PubMedID 30110879
Evaluation of Toxicity in Peptide Receptor Radionuclide Therapy (PRRT) for Neuroendocrine Tumors (NET)
KARGER. 2020: 252
View details for Web of Science ID 000522166100252
Extrahepatic 68Ga-DOTATATE-Avid Tumor Volume and Serum Chromogranin A Predict Short-Term Outcome of 177Lu-DOTATATE in Late-Stage Metastatic Gastroenteropancreatic Neuroendocrine Tumors
KARGER. 2020: 274
View details for Web of Science ID 000522166100274
Fungal endocarditis resembling primary cardiac malignancy in a patient with B-cell ALL with culture confirmation.
Radiology case reports
2020; 15 (2): 117–19
Fungal endocarditis is a rare subtype of infective endocarditis that often presents with nonspecific symptoms in patients with complex medical histories, making diagnosis challenging. Patients with a history of ALL may present with congestive heart failure, chemo-induced cardiomyopathy, acute coronary syndrome, cardiac lymphomatous metastasis, or infections. We present the case of a patient with a history of ALL who presented with acute coronary syndrome and imaging concerning for primary cardiac lymphoma, when in fact the patient ended up suffering from culture proven fungal endocarditis.
View details for DOI 10.1016/j.radcr.2019.10.022
View details for PubMedID 31768196
Single institution experience with peptide receptor radionuclide therapy (PRRT) in neuroendocrine tumors (NET)
AMER SOC CLINICAL ONCOLOGY. 2020
View details for Web of Science ID 000530922700601
Prognostic value of volumetric PET parameters at early response evaluation in melanoma patients treated with immunotherapy.
European journal of nuclear medicine and molecular imaging
The purpose of this study was to investigate the prognostic value of whole-body metabolic tumor volume (MTV) and other metabolic tumor parameters, obtained from baseline and first restaging 18F-FDG PET/CT scans in melanoma patients treated with immune checkpoint inhibitors (ICIs).Eighty-five consecutive melanoma patients (M, 57; F, 28) treated with ICIs who underwent PET/CT scans before and approximately 3 months after the start of immunotherapy were retrospectively enrolled. Metabolic tumor parameters including MTV for all melanoma lesions were measured on each scan. A Cox proportional hazards model was used for univariate and multivariate analyses of metabolic parameters combined with known clinical prognostic factors associated with overall survival (OS). Kaplan-Meier curves for patients dichotomized based on median values of imaging parameters were generated.The median OS time in all patients was 45 months (95% CI 24-45 months). Univariate analysis demonstrated that MTV obtained from first restaging PET/CT scans (MTVpost) was the strongest prognostic factor for OS among PET/CT parameters (P < 0.0001). The median OS in patients with high MTVpost (≥ 23.44) was 16 months (95% CI 12-32 months) as compared with more than 60 months in patients with low MTVpost (< 23.44) (P = 0.0003). A multivariate model including PET/CT parameters and known clinical prognostic factors revealed that MTVpost and the presence of central nervous system lesions were independent prognostic factors for OS (P = 0.0004, 0.0167, respectively). One pseudoprogression case (1.2%) was seen in this population and classified into the high MTVpost group.Whole-body metabolic tumor volume from PET scan acquired approximately 3 months following initiation of immunotherapy (MTVpost) is a strong prognostic indicator of OS in melanoma patients. Although the possibility of pseudoprogression must be considered whenever evaluating first restaging PET imaging, it only occurred in 1 patient in our cohort.
View details for DOI 10.1007/s00259-020-04792-0
View details for PubMedID 32296882
Preclinical SPECT and SPECT-CT in Oncology.
Recent results in cancer research. Fortschritte der Krebsforschung. Progres dans les recherches sur le cancer
2020; 216: 359–404
Molecular imaging enables both spatial and temporal understanding of the complex biologic systems underlying carcinogenesis and malignant spread. Single-photon emission tomography (SPECT) is a versatile nuclear imaging-based technique with ideal properties to study these processes in vivo in small animal models, as well as to identify potential drug candidates and characterize their antitumor action and potential adverse effects. Small animal SPECT and SPECT-CT (single-photon emission tomography combined with computer tomography) systems continue to evolve, as do the numerous SPECT radiopharmaceutical agents, allowing unprecedented sensitivity and quantitative molecular imaging capabilities. Several of these advances, their specific applications in oncology as well as new areas of exploration are highlighted in this chapter.
View details for DOI 10.1007/978-3-030-42618-7_11
View details for PubMedID 32594393
Prospective Evaluation in an Academic Center of 18F-DCFPyL PET/CT in Biochemically Recurrent Prostate Cancer: A Focus on Localizing Disease and Changes in Management.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
18F-DCFPyL is a promising PET radiopharmaceutical targeting prostate specific membrane antigen (PSMA). We present our experience in this single academic center prospective study evaluating the positivity rate of 18F-DCFPyL PET/CT in patients with biochemical recurrence (BCR) of prostate cancer (PC). Methods: We prospectively enrolled 72 men (52-91 years old, mean±SD: 71.5±7.2) with BCR after primary definitive treatment with prostatectomy (n = 42) or radiotherapy (n = 30). The presence of lesions compatible with PC was evaluated by two independent readers. Fifty-nine patients had concurrent scans with at least one other conventional scan: bone scan (24), CT (21), MR (20), 18F-Fluciclovine PET/CT (18) and/or 18F-NaF PET (14). Findings from 18F-DCFPyL PET/CT were compared with those from other modalities. Impact on patient management based on 18F-DCFPyL PET/CT was recorded from clinical chart review. Results: 18F-DCFPyL PET/CT had an overall positivity rate of 85%, which increased with higher prostate specific antigen (PSA) levels (ng/mL): 50% (PSA<0.5), 69% (0.5≤PSA<1), 100% (1≤PSA<2), 91% (2≤PSA<5) and 96% (PSA≥5), respectively. 18F-DCFPyL PET detected more lesions than conventional imaging. For anatomic imaging, 20/41 (49%) CT/MRI had congruent findings with 18F-DCFPyL, while 18F-DCFPyL PET was positive in 17/41 (41%) cases with negative CT/MRI. For bone imaging, 26/38 (68%) bone scan/18F-NaF PET were congruent with 18F-DCFPyL PET, while 18F-DCFPyL PET localized bone lesions in 8/38 (21%) patients with negative bone scan/18F-NaF PET. In 8/18 (44%) patients, 18F-Fluciclovine PET had located the same lesions as the 18F-DCFPyL PET, while 5/18 (28%) patients with negative 18F-Fluciclovine had positive 18F-DCFPyL PET findings and 1/18 (6%) patient with negative 18F-DCFPyL had uptake in the prostate bed on 18F-Fluciclovine PET. In the remaining 4/18 (22%) patients, 18F-DCFPyL and 18F-Fluciclovine scans showed different lesions. Lastly, 43/72 (60%) patients had treatment changes after 18F-DCFPyL PET and, most noticeably, 17 of these patients (24% total) had lesion localization only on 18F-DCFPyL PET, despite negative conventional imaging. Conclusion: 18F-DCFPyL PET/CT is a promising diagnostic tool in the work-up of biochemically recurrent prostate cancer given the high positivity rate as compared to FDA-approved currently available imaging modalities and its impact on clinical management in 60% of patients.
View details for DOI 10.2967/jnumed.119.231654
View details for PubMedID 31628216
- Evaluating the Role of Theranostics in Grade 3 Neuroendocrine Neoplasms JOURNAL OF NUCLEAR MEDICINE 2019; 60 (7): 882–91
Preliminary Results of a Prospective Study of Ga-68-RM2 PET/MRI for Detection of Recurrent Prostate Cancer in Patients with Negative Conventional Imaging
SOC NUCLEAR MEDICINE INC. 2019
View details for Web of Science ID 000473116801014
Prospective evaluation of F-18- DCFPyL in Patients with Biochemically Recurrent Prostate Cancer: Positivity Rate and Correlation with PSA levels
SOC NUCLEAR MEDICINE INC. 2019
View details for Web of Science ID 000473116801610
Prospective Comparison of F-18-DCFPyL PET/CT with F-18-NaF PET/CT for Detection of Skeletal Metastases in Biochemically Recurrent Prostate Cancer
SOC NUCLEAR MEDICINE INC. 2019
View details for Web of Science ID 000473116801621
Comparison of three interpretation criteria of Ga-68-PS A PET based on in er and intra-reader agreement
SOC NUCLEAR MEDICINE INC. 2019
View details for Web of Science ID 000473116801600
Quantification of uptake in Ga-68-DOTATATE PET: Correlation between standardized uptake values and patient factors
SOC NUCLEAR MEDICINE INC. 2019
View details for Web of Science ID 000473116800434
Prospective Evaluation of F-18-DCFPyL PET/CT and Conventional Imaging in Patients with Biochemically Recurrent Prostate Cancer
SOC NUCLEAR MEDICINE INC. 2019
View details for Web of Science ID 000473116801016
State of the Art: Evaluating the Role of Theranostics in G3 Neuroendocrine Neoplasms.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
The diagnosis and subsequent therapy of neuroendocrine neoplasms (NENs) have long-relied on somatostatin receptor (SSTR) expression. The field of theranostics now uses newer SSTR based Positron Emission Tomography (SSTR-PET) imaging with 68Ga-DOTA0-Tyr3-Octreotate (68Ga-DOTATATE) or 68Ga-DOTA0-Tyr3-Octreotide (68Ga-DOTATOC), as a prerequisite for the administration of peptide receptor radionuclide therapy (PRRT). In the US, 177Lu-Dotatate, a form of PRRT, gained FDA approval in 2018 for use in gastroenteropancreatic NENs and was based on prolonged progression-free survival (PFS) vs. high dose Octreotide LAR in a phase III clinical trial of well-differentiated midgut NENs. Well-differentiated, grade 1 and grade 2 NENs have a low proliferation index (Ki-67 < 20%) and longer overall survival > 10 years while higher grade (grade 3) NENs have a high Ki-67 > 20% and shorter overall survival < 1 year. Here, we present a review on the newest histologic classification of NENs and the role of both SSTR-based imaging and PRRT in grade 3 (G3) NENs. Some studies suggest that G3 disease is less likely to be positive on SSTR-based imaging (but more likely in FDG PET) as compared to low grade disease, but these data are limited. Additionally, we found only eleven studies mentioning the use of PRRT in G3 NENs and a total of only forty-nine patients across these studies in which radiologic response was measured. Out of these forty-nine patients, twenty-seven (55%) demonstrated at least stable disease or a partial response, indicating that some G3 NENs can be responsive to PRRT. We suggest that patients with G3 NENs should receive both 18F-FDG PET and SSTR-based imaging to aide in both diagnosis and treatment selection. However, prospective studies are needed to understand the role of PRRT in G3 NENs, especially in well- versus poorly-differentiated G3 disease.
View details for PubMedID 30850504
Comparison of three interpretation criteria of 68Ga-PSMA11 PET based on inter- and intra-reader agreement.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Positron emission tomography (PET) using radiolabeled prostate specific membrane antigen (PSMA) is now more and more widely adopted as a valuable tool to evaluate patients with prostate cancer (PC). Recently, three different criteria for interpretation of PSMA PET were published: European Association of Nuclear Medicine (EANM) criteria, prostate cancer molecular imaging standardized evaluation (PROMISE) criteria, and PSMA-reporting and data system (PSMA-RADS). We compared these three criteria in terms of inter-reader, intra-reader, and inter-criteria agreement. Methods: Data from 104 patients prospectively enrolled in research protocols at our institution were retrospectively reviewed. The cohort consisted of two groups: 47 patients (mean age: 64.2 years old) who underwent Glu-NH-CO-NH-Lys-(Ahx)-[68Ga(HBED-CC)] (68Ga-PSMA11) PET/magnetic resonance imaging (MRI) for initial staging of biopsy-proven intermediate- or high-risk PC, and 57 patients (mean age: 70.5 years old) who underwent 68Ga-PSMA11 PET/computed tomography (CT) due to biochemically recurrent (BCR) PC. Three nuclear medicine physicians independently evaluated all 68Ga-PSMA11 PET/MRI and PET/CT studies according to the three interpretation criteria. Two of them reevaluated all studies 6 months later in the same manner and blinded to the initial reading. Gwet's AC was calculated to evaluate inter- and intra-reader, and inter-criteria agreement based on the following sites: local lesion (primary tumor or prostate bed after radical prostatectomy), lymph node metastases, and other metastases. Results: In the PET/MRI group, inter-reader, intra-reader, and inter-criteria agreements were substantial to almost perfect in any sites according to all of the three criteria. In the PET/CT group, inter-reader agreement was substantial to almost perfect except judgement of distant metastases based on PSMA-RADS (Gwet's AC = 0.57, moderate agreement), in which the most frequent cause of disagreement was lung nodules. Intra-reader agreements were substantial to almost perfect in any sites according to all of the three criteria. Inter-criteria agreements of each site were also substantial to almost perfect. Conclusion: Although the three published criteria have good inter-reader and intra-reader reproducibility in evaluating 68Ga-PSMA11 PET, there are factors bringing inter-reader disagreement. This indicates that further work is needed to address the issue.
View details for DOI 10.2967/jnumed.119.232504
View details for PubMedID 31562226
- Correction: shaped magnetic field pulses by multi-coil repetitive transcranial magnetic stimulation (rTMS) differentially modulate anterior cingulate cortex responses and pain in volunteers and fibromyalgia patients. Molecular pain 2014; 10: 16-?
Shaped magnetic field pulses by multi-coil repetitive transcranial magnetic stimulation (rTMS) differentially modulate anterior cingulate cortex responses and pain in volunteers and fibromyalgia patients
Repetitive transcranial magnetic stimulation (rTMS) has shown promise in the alleviation of acute and chronic pain by altering the activity of cortical areas involved in pain sensation. However, current single-coil rTMS technology only allows for effects in surface cortical structures. The ability to affect activity in certain deep brain structures may however, allow for a better efficacy, safety, and tolerability. This study used PET imaging to determine whether a novel multi-coil rTMS would allow for preferential targeting of the dorsal anterior cingulate cortex (dACC), an area always activated with pain, and to provide preliminary evidence as to whether this targeted approach would allow for efficacious, safe, and tolerable analgesia both in a volunteer/acute pain model as well as in fibromyalgia chronic pain patients.Part 1: Different coil configurations were tested in a placebo-controlled crossover design in volunteers (N = 16). Tonic pain was induced using a capsaicin/thermal pain model and functional brain imaging was performed by means of H215O positron emission tomography -- computed tomography (PET/CT) scans. Differences in NRS pain ratings between TMS and sham treatment (NRSTMS-NRSplacebo) which were recorded each minute during the 10 minute PET scans. Part 2: 16 fibromyalgia patients were subjected to 20 multi-coil rTMS treatments over 4 weeks and effects on standard pain scales (Brief Pain Inventory, item 5, i.e. average pain NRS over the last 24 hours) were recorded.A single 30 minute session using one of 3 tested rTMS coil configurations operated at 1 Hz consistently produced robust reduction (mean 70% on NRS scale) in evoked pain in volunteers. In fibromyalgia patients, the 20 rTMS sessions also produced a significant pain inhibition (43% reduction in NRS pain over last 24 hours), but only when operated at 10 Hz. This degree of pain control was maintained for at least 4 weeks after the final session.Multi-coil rTMS may be a safe and effective treatment option for acute as well as for chronic pain, such as that accompanying fibromyalgia. Further studies are necessary to optimize configurations and settings as well as to elucidate the mechanisms that lead to the long-lasting pain control produced by these treatments.
View details for DOI 10.1186/1744-8069-9-33
View details for Web of Science ID 000323054600001
Steerable Electrical Currents using Multi-coil rTMS: Clinical Effects of Modifying Current Direction
ELSEVIER SCIENCE INC. 2012: 282S
View details for Web of Science ID 000302466001205
Pattern of 18F-FDG Uptake in the Spinal Cord in Patients With Non-Central Nervous System Malignancy
2011; 36 (21): E1395-E1401
Retrospective review.To (1) propose a standard method to quantitate 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) uptake in the spinal cord and (2) use this methodology to retrospectively characterize the pattern of uptake within the entire spinal cord using whole-body positron emission tomography/computed tomography (PET/CT) imaging.A physiologic understanding of glucose metabolism within the spinal cord may provide insight regarding infectious, inflammatory, vascular, and neoplastic spinal cord diseases.Institutional review board approval was obtained. A total of 131 consecutive whole-body PET/CT studies from July to August 2004 were reviewed, and using exclusionary criteria of: (1) severe spinal arthropathy or curvature, (2) motion artifact, (3) canal hardware, (4) spinal tumor, and (5) marrow hyperplasia, 92 studies of neurologically intact patients (49 men and 43 women) were selected for a retrospective review of spinal cord 18F-FDG activity. The transaxial CT was used to define the canal and circular regions of interests were placed within the canal at the level of the vertebral body midpoint from C1 to L3. Region of interest total count, area, and maximum standardized uptake value (SUVmax) were recorded. Measurements at L5 served as an internal control. For comparative analysis, the cord-to-background (CTB) ratio was defined as spinal cord SUVmax to L5 SUVmax.Mean CTB decreased along each spinal level from cranial to caudal (P < 0.001). Significant relative increases were observed at the T11-T12 vertebral body levels (P < 0.001). Although insignificant, a relative increase was observed at C4. No significant interactions of age or sex on CTB were observed.The pattern of 18F-FDG uptake within the spinal cord, observed in patients with non-central nervous system malignancy, may be helpful in understanding glucose physiology of spinal cord diseases and warrants further research.
View details for DOI 10.1097/BRS.0b013e31820a7df8
View details for Web of Science ID 000295318000005
View details for PubMedID 21311407
F-18-FDG-PET/CT evaluation of response to treatment in lymphoma: when is the optimal time for the first re-evaluation scan?
HELLENIC JOURNAL OF NUCLEAR MEDICINE
2008; 11 (3): 153-156
Assessing the response to treatment as soon after treatment initiation is one of the key reasons for imaging lymphoma patients. The optimal time after initiating treatment for assessing response to treatment has yet to be determined. Therefore, we were prompted to review our experience with serial (18)F-FDG PET/CT in patients undergoing treatment for Hodgkin's disease (HD) and non Hodgkin's lymphoma (NHL). This is a retrospective study (Feb 2003 - Oct 2004) of 20 patients, 11 men and 9 women, with age range of 7-75 years with diagnosis of HD (10) and NHL (10), who had PET/CT at our institution prior, during and at the completion of therapy. Restaging PET/CT was done after 2 cycles of chemotherapy in 10 patients (group A) and after 4 cycles of chemotherapy in 10 pts (group B). A total of 60 scans were reviewed. The DeltaSUV from baseline to first PET/CT was on average 67.6% in group A and 75.1% in group B. This had no statistical significance (P value: 0.31). The DeltaSUV from baseline to post-therapy PET/CT was on average 72.9% in group A and 79.8% in group B. This difference also had no statistical significance (P value: 0.24). The correlation coefficient was 0.98 in group A and 0.80 in group B. Results of PET/CT after 2 cycles of chemotherapy did not statistically differ from the results of PET/CT after 4 cycles of chemotherapy. These results need to be confirmed in larger, prospective, randomized trials.
View details for Web of Science ID 000262093600003
View details for PubMedID 19081857
[Introduction to the molecular imaging].
Revista espanola de medicina nuclear
2006; 25 (6): 394-409
View details for PubMedID 17173791
F-18FDG PET evaluation of bronchial plasmacytoma with CT and MRI correlation
CLINICAL NUCLEAR MEDICINE
2006; 31 (5): 279-280
View details for PubMedID 16622337
The role of a positron- and high-energy gamma photon probe in intraoperative localization of recurrent melanoma
CLINICAL NUCLEAR MEDICINE
2005; 30 (12): 787-791
This preliminary study retrospectively evaluated the ability of intraoperative localization of recurrent melanoma using F-18 fluorodeoxyglucose (FDG) and a probe sensitive to both high-energy gamma rays and positrons to enable complete tumor resection and improved patient outcome.Three hours before surgery for resection of recurrent melanoma, 5 patients (mean age, 52 +/- 22 years) with a history of local surgery, radiation therapy, and/or large habitus received 14.6 +/- 3.2 mCi of F-18 FDG. Intraoperative tumor localization was performed with a radiation probe (PET-Probe; IntraMedical Imaging LLC, Los Angeles, CA). Intraoperative tumor tissue activities, background tissue activities, pathology results, and patient follow up (clinical/imaging) were recorded.Eight of the 19 surgical specimens were identified by the probe as having increased FDG uptake when compared with the surrounding tissues before resection. All 8 specimens contained melanoma. Of the 11 specimens that were not identified using the probe, one contained melanoma, yielding a sensitivity of 89% (8 of 9) and a specificity of 100% (10 of 10). In 3 of the 5 cases, the probe allowed the identification of nonvisualized and nonpalpable tumor foci that were later confirmed pathologic. At an average follow up of 210 days (range, 30-515 days), 2 of 5 patients had no evidence of recurrent melanoma by clinical or radiographic evaluations.In the setting of recurrent melanoma, there appear to be potential benefits to intraoperative detection with FDG and a positron-detecting probe, particularly in cases with challenging or altered anatomy.
View details for Web of Science ID 000233455500003
View details for PubMedID 16319633
Bone morphogenetic protein 2 and retinoic acid accelerate in vivo bone formation, osteoclast recruitment, and bone turnover
2005; 11 (3-4): 645-658
Reconstruction of craniofacial defects presents a substantial biomedical burden, and requires complex surgery. Interestingly, children after age 2 years and adults are unable to heal large skull defects. This nonhealing paradigm provides an excellent model system for craniofacial skeletal tissueengineering strategies. Previous studies have documented the in vivo osteogenic potential of adipose-derived stromal (ADS) cells and bone marrow-derived stromal (BMS) cells. This study investigates the ability to accelerate in vivo osteogenesis on ex vivo recombinant human bone morphogenetic protein 2 (BMP-2) and retinoic acid stimulation. Mouse osteoblasts, ADS cells, and BMS cells were seeded onto apatite-coated PLGA scaffolds, stimulated with rhBMP-2 and retinoic acid ex vivo for 4 weeks, and subsequently implanted into critically sized (4 mm) calvarial defects. Samples were harvested after 2, 4, 8, and 12 weeks. Areas of complete bony bridging were noted as early as 2 weeks in vivo; however, osteoclasts were attracted to the scaffold as identified by calcitonin receptor staining and tartrate-resistant acid phosphatase activity staining. Although the optimal method of in vitro osteogenic priming for mesenchymal cells remains unknown, these results provide evidence that BMP-2 and retinoic acid stimulation of multipotent cells ex vivo can subsequently induce significant quantities of bone formation within a short time period in vivo.
View details for PubMedID 15869441
Tumor imaging using a standardized radiolabeled adapter protein docked to vascular endothelial growth factor
JOURNAL OF NUCLEAR MEDICINE
2004; 45 (8): 1373-1380
Direct radiolabeling of proteins can result in the loss of targeting activity, requires highly customized procedures, and yields heterogeneous products. Here we describe a novel imaging complex comprised of a standardized (99m)Tc-radiolabeled adapter protein noncovalently bound to a "Docking tag" fused to a "Targeting protein". The assembly of this complex is based on interactions between human 109-amino acid (HuS) and 15-amino acid (Hu-tag) fragments of ribonuclease I, which serve as an "Adapter protein" and a Docking tag, respectively.HuS modified with hydrazinonicotinamide (HYNIC) was radiolabeled using (99m)Tc-tricine to a specific activity of 3.4-7.4 MBq/microg. Protein complexes were then formed by mixing (99m)Tc-HuS with equimolar amounts of either Hu-tagged VEGF(121) (Hu-VEGF [vascular endothelial growth factor]) or Hu-tagged anti-VEGFR-2 single-chain antibody (Hu-P4G7) and incubating on ice for 15 min. 4T1 luc/gfp luciferase-expressing murine mammary adenocarcinoma cells (1 x 10(4)) were implanted subcutaneously or injected intravenously into BALB/c mice. Bioluminescent imaging (BLI) was performed 10 d later. Immediately after BLI visualization of tumor, 18.5-37 MBq of tracer (5-10 microg of protein) were injected via tail vein. One hour later planar or SPECT images were obtained, followed by killing the mice.There was significantly (P = 0.0128) increased uptake of (99m)Tc-HuS/Hu-VEGF (n = 10) within subcutaneous tumor as compared with (99m)Tc-HuS/Hu-P4G7 (n = 5) at biodistribution assay (2.68 +/- 0.75 vs. 1.8 +/- 0.21; tumor-to-subcutaneous tissue [ratio of specific activities], respectively), despite similar molecular weights. The focal (99m)Tc-HuS/Hu-VEGF uptake seen on planar images (3.44 +/- 1.16 [tumor to soft-tissue background]) corresponded directly to the locations of tumor observed by BLI. Region of interest analyses of SPECT images revealed a significant increase of (99m)Tc-HuS/Hu-VEGF (n = 5) within the lungs with BLI-detectable pulmonary tumor nodules as compared with controls (n = 4) (right: 4.47 +/- 2.07 vs. 1.79 +/- 0.56; left: 3.66 +/- 1.65 vs. 1.62 +/- 0.45, tumor lung [counts/pixel]/normal lung [counts/pixel], respectively).(99m)Tc-HuS/Hu-VEGF complex is stable for at least 1 h in vivo and can be effectively used to image mouse tumor neovasculature in lesions as small as several millimeters in soft tissue. We expect that a similar approach can be adapted for in vivo delivery of other targeting proteins of interest without affecting their bioactivity.
View details for PubMedID 15299064
Apoptosis in a rodent model of cranial suture fusion: In situ imaging and gene expression analysis
PLASTIC AND RECONSTRUCTIVE SURGERY
2004; 113 (7): 2037-2047
Craniosynostosis, the premature fusion of cranial sutures, is one of the most common craniofacial anomalies, with a reported incidence of up to one in 2500 live births. Despite its prevalence, the cause of craniosynostosis remains unknown. Previously, apoptosis has been postulated to be a contributing factor in the pathogenesis of craniosynostosis, although the role of programmed cell death in cranial sutures is poorly understood. To address this problem, the authors used an established rodent model of posterior-frontal suture fusion and sagittal suture patency to globally examine apoptosis in cranial sutures. Apoptosis was evaluated by systemically coinjecting Sprague-Dawley rats with both fluorescent and technetium-99m-labeled annexin V at time points before, during, and after the period of predicted posterior-frontal suture fusion to determine the magnitude and time course of overall apoptotic activity in both fusing and patent sutures. Using these novel in situ imaging techniques, the authors observed a significant increase in the overall levels of apoptosis in both the posterior-frontal and sagittal suture complexes during the period of predicted posterior-frontal suture fusion. To further explore this increase in apoptotic activity, they used microarray technology to study apoptosis-related genes within the suture complex. Interestingly, there was activation of distinct apoptotic pathways in the posterior-frontal and sagittal sutures during the period of predicted posterior-frontal suture fusion. Whereas increased transcription of genes associated with the mitochondria-mediated apoptotic pathway occurred in the posterior-frontal suture during fusion, activation of genes associated with the death receptor-mediated apoptotic pathway predominated in the patent sagittal suture during the same time period. These data suggest that although overall apoptotic activity in rat patent and fusing sutures is similar, the pathways mediating apoptosis within each suture are distinct.
View details for DOI 10.1097/01.prs.000012118201199.c1
View details for PubMedID 15253194
Detection of focal hypoxic-ischemic injury and neuronal stress in a rodent model of unilateral MCA occlusion/reperfusion using radiolabeled annexin V
EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
2004; 31 (5): 733-739
In this study we wished to determine whether technetium-99m annexin V, an in vivo marker of cellular injury and death, could be used to noninvasively monitor neuronal injury following focal middle cerebral artery (MCA) occlusion/reperfusion injury. Sixteen adult male Sprague-Dawley rats (along with four controls) underwent left (unilateral) MCA intraluminal beaded thread occlusion for 2 h followed by reperfusion. One hour following tail vein injection of 5-10 mCi of (99m)Tc-annexin V, animals underwent either single-photon emission computerized tomography (SPECT) or autoradiography followed by immunohistochemical analyses. There was abnormal, bilateral, multifocal uptake of (99m)Tc-annexin V in each cerebral hemisphere as seen by both SPECT and autoradiography at 4 h and 1, 3, and 7 days after initiation of occlusion. The average maximal annexin V uptake at 4 h was 310%+/-85% and 365%+/-151% above control values (P<0.006) within the right and left hemispheres, respectively, peaking on day 3 with values of 925%+/-734% and 1,194%+/-643% (P<0.03) that decreased by day 7 to 489%+/-233% and 785%+/-225% (P<0.01). Total lesional volume of the left hemisphere was 226%, 261%, and 451% ( P<0.03) larger than the right at 4, 24, and 72 h after injury, respectively. Annexin V localized to the cytoplasm of injured neurons ipsilateral to the site of injury as well as to otherwise normal-appearing neurons of the contralateral hemisphere as confirmed by dual fluorescent microscopy. It is concluded that there is abnormal bilateral, multifocal annexin V uptake, greater on the left than on the right side, within 4 h of unilateral left MCA ischemic injury and that the uptake peaks at 3 days and decreases by 7 days after injury. This pattern suggests that neuronal stress may play a role in the response of the brain to focal injury and be responsible for annexin V uptake outside the region of ischemic insult.
View details for DOI 10.1007/s00259-004-1473-5
View details for PubMedID 14985868
Adipose-derived adult stromal cells heal critical-size mouse calvarial defects
2004; 22 (5): 560-567
In adults and children over two years of age, large cranial defects do not reossify successfully, posing a substantial biomedical burden. The osteogenic potential of bone marrow stromal (BMS) cells has been documented. This study investigates the in vivo osteogenic capability of adipose-derived adult stromal (ADAS) cells, BMS cells, calvarial-derived osteoblasts and dura mater cells to heal critical-size mouse calvarial defects. Implanted, apatite-coated, PLGA scaffolds seeded with ADAS or BMS cells produced significant intramembranous bone formation by 2 weeks and areas of complete bony bridging by 12 weeks as shown by X-ray analysis, histology and live micromolecular imaging. The contribution of implanted cells to new bone formation was 84-99% by chromosomal detection. These data show that ADAS cells heal critical-size skeletal defects without genetic manipulation or the addition of exogenous growth factors.
View details for DOI 10.1038/nbt958
View details for PubMedID 15077117
Multi-modality imaging identifies key times for annexin V imaging as an early predictor of therapeutic outcome.
2004; 3 (1): 1-8
Radiolabeled annexin V may provide an early indication of the success or failure of anticancer therapy on a patient-by-patient basis as an in vivo marker of tumor cell killing. An important question that remains is when, after initiation of treatment, should annexin V imaging be performed. To address this issue, we obtained simultaneous in vivo measurements of tumor burden and uptake of radiolabeled annexin V in the syngeneic orthotopic murine BCL1 lymphoma model using in vivo bioluminescence imaging (BLI) and small animal single-photon emission computed tomography (SPECT). BCL1 cells labeled for fluorescence and bioluminescence assays (BCL1-gfp/luc) were injected into mice at a dose that leads to progressive disease within two to three weeks. Tumor response was followed by BLI and SPECT before and after treatment with a single dose of 10 mg/kg doxorubicin. Biodistribution analyses revealed a biphasic increase of annexin V uptake within the tumor-bearing tissues of mice. An early peak occurring before actual tumor cells loss was observed between 1 and 5 hr after treatment, and a second longer sustained rise from 9 to 24 hr after therapy, which heralds the onset of tumor cell loss as confirmed by BLI. Multimodality imaging revealed the temporal patterns of tumor cell loss and annexin V uptake revealing a better understanding of the timing of radiolabeled annexin V uptake for its development as a marker of therapeutic efficacy.
View details for PubMedID 15142407
The use of (99m)Technetium-labeled MCP-1 to assess, graft coronary artery disease in rat cardiac allografts
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2002; 21 (9): 1009-1015
Monocyte chemoattractant protein-1 (MCP-1) is associated with the development of graft coronary artery disease (GCAD) following cardiac transplantation. This study assessed whether technetium 99m ((99m)Tc)-labeled MCP-1 binds its receptors in chronic cardiac transplants and thereby provides a potential modality to assess GCAD.Allogeneic (PVG-->ACI, n = 9) and syngeneic (ACI-->ACI, n = 9) rat heterotopic heart transplants were performed. Allograft recipients were treated with 7.5 mg/kg per day of Cyclosporin A for 10 days until tolerance was achieved. After 90 days, animals were injected intravenously with (99m)Tc-MCP-1 and killed after 1 hour. Radioactivity of heart tissues was measured and standardized to uptake in the overall blood pool. Two-dimensional (99m)Tc-MCP-1 uptake (autoradiographs) was imaged by exposing 50-microm sections on a phosphoimager overnight. ED-1 staining of monocyte/macrophages was performed on serial sections. Additional sections were stained with elastin von Gieson and hematoxylin. Hearts were scored for luminal narrowing and intima/media ratio (I/M) with computerized image analysis.Allografts exhibited significantly more luminal narrowing (22.5 +/- 10.7% vs 2.6 +/- 4.6, p = 0.0005) and higher I/M (0.173 +/- 0.151 vs 0.015 +/- 0.029, p = 0.0088) than isografts. The ratio of (99m)Tc-MCP-1 uptake in allografts (1.04 +/- 0.4) was greater than that of isograft controls (0.72 +/- 0.11, p = 0.03). Pixel counts of autoradiographs and ED-1-stained sections demonstrated a modest correlation between the two (R(2) = 0.50). No significant differences were seen in acute rejection scores.(99m)Tc-MCP-1 uptake was higher in allografts vs isografts and was consistent with a greater degree of GCAD. These data demonstrating increased radiopharmaceutical uptake in hearts with GCAD provide a foundation for the development of a potentially non-invasive imaging assay of this disease process in heart transplantation.
View details for PubMedID 12231372
- Radiotracer characterization of coronary artery lesions NUCLEAR MEDICINE COMMUNICATIONS 2002; 23 (8): 703–6
Zinc chloride-mediated reduction of apoptosis as an adjunct immunosuppressive modality in cardiac transplantation
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2002; 21 (3): 360-365
Zinc (Zn) blocks caspase-3 activation in cardiac allografts and therefore may synergistically decrease apoptosis along with cyclosporine (CsA), which inhibits mitochondrial release of cytochrome c. Simultaneous treatment of rat recipients of heterotopic heart transplants with zinc chloride (ZnCl(2)) thus may allow lower doses of CsA for immunosuppression.PVG (RT1(c)) rat hearts were transplanted heterotopically into the abdomen of ACI (RT1(a)) rats. Group 1 (n = 15) rats received no treatment. Group 2 rats (n = 8) received 2 mg/kg/day CsA (sub-therapeutic dose) by oral gavage. Group 3 rats (n = 9) received 2 mg/kg/day oral CsA in addition to 1 mg/kg/day sub-cutaneous ZnCl(2) delivered by osmotic pump. All rats were imaged using Annexin V-bound (99m)Technetium ((99m)Tc-Annexin V) on post-operative Day 4 and subsequently killed. Annexin V avidly binds apoptotic cells in vivo. Region of interest per whole body (WB) data were calculated using the images. The allograft survival study was conducted with n = 11, 6, and 5 in control, CsA, and CsA+Zn groups, respectively. Finally, percentages of allografts that reached tolerance were measured in both CsA-only and CsA+Zn groups (n = 8 each).Zinc chloride had an additive effect with CsA on apoptotic blockade and graft survival. The regions of interest per WB uptake of (99m)Tc-Annexin V were 2.43% +/- 0.37%, 2.08% +/- 0.52%, and 1.49% +/- 0.29%*, and acute survivals were 6.4 +/- 1.7, 7.2 +/- 2.1, and 11.2 +/- 2.5* days for control, CsA, and CsA+Zn groups, respectively (*p < 0.001 vs controls). In addition, 87.5% of allografts became tolerant and survived for 90 days in the CsA+Zn group compared with only 37.5% in the CsA-only group (p = 0.049).Zinc-mediated reduction of apoptosis served as an effective adjunct immunosuppressive therapy to CsA in a rat model of cardiac transplantation.
View details for PubMedID 11897525
Development of radiocontrast agents for vascular imaging: progress to date.
American journal of cardiovascular drugs
2002; 2 (6): 357-365
The revolution in molecular imaging techniques is profoundly changing the understanding of the pathophysiology and treatment of atherosclerosis. With these rapid changes there is an increasing demand for development of sensitive and well tolerated novel imaging agents that can be rapidly translated from small animal models into patients with atherosclerosis. Nuclear medicine and positron emission tomography techniques have the ability to detect and serially monitor a variety of biologic and pathophysiologic processes usually with tracer quantities of radiolabeled peptides, drugs, and other molecules at dosages free of pharmacologic adverse effects unlike the current generation of intravenous agents required for magnetic resonance imaging (MRI) and computed axial tomography (CT) scanning. A representative sampling of the wide array of radiopharmaceuticals developed specifically for radionuclide imaging of atherosclerosis, that have been approved for clinical use and those in pre-clinical trials, have been reviewed in this article. The presence of an inflammatory stimulus increases expression of CC (cysteine-cysteine motif) chemokine receptor (CCR)-2 on monocytes and macrophages, and somatostatin receptors on T lymphocytes. Radiolabeled monocyte chemoattractant protein (MCP)-1 binds with high affinity to CCR-2 and can be used to detect subacute and chronic inflammatory lesions. Similarly, radiolabeled octreotide or depreotide can be used to detect activated T lymphocytes which may identify the vulnerable plaque. Animal models indicate that (99m)Tc-annexin V, (125)I-MCP-1 and [(18)F]-fluoro-2-deoxyglucose are effective in identifying apoptotic cell death, macrophage infiltration and metabolic activity in atheromatous lesions, respectively. Expression of alpha(v)beta(3) integrin is increased in activated endothelial cells and vascular smooth muscle cells after vascular injury, and alpha(v)beta(3) integrin is minimally expressed on smooth muscle cells and is not expressed on quiescent epithelial cells. Radiolabeled high-affinity peptides can be used to target the alpha(v)beta(3) integrin and visualize areas of vascular damage. Advances in technology such as the micro-single photon emission computed tomography (microSPECT) have the potential to overcome the drawbacks of older CT and MRI methodologies, such as lack of biologically relevant ligands and compatible blood pool contrast agents for imaging. Despite these advances in imaging technology, the small size of atheromatous lesions makes it difficult to detect using external imaging techniques. Therefore, recently there has been renewed interest in the use of intravascular catheter-based radiation detectors.
View details for PubMedID 14727951