The Dartmouth Center for Cancer Nanotechnology Excellence - one of nine funded by the National Ca... more The Dartmouth Center for Cancer Nanotechnology Excellence - one of nine funded by the National Cancer Institute as part of the Alliance for Nanotechnology in Cancer - focuses on the use of magnetic nanoparticles for cancer diagnostics and hyperthermia therapy. It brings together a diverse team of engineers and biomedical researchers with expertise in nanomaterials, molecular targeting, advanced biomedical imaging and translational in vivo studies. The goal of successfully treating cancer is being approached by developing nanoparticles, conjugating them with Fabs, hyperthermia treatment, immunotherapy and sensing treatment response.
Proceedings IEEE International Symposium on Biomedical Imaging, 2002
Magnetic Resonance Elastography (MRE) is an exciting imaging technique with application to clinic... more Magnetic Resonance Elastography (MRE) is an exciting imaging technique with application to clinical settings where quantitative maps of tissue mechanical properties may be diagnostic. This certainly includes breast imaging where hardness has been associated with malignancy. We have been developing time-harmonic MRE methods for the breast in anticipation of evaluating the approach in a controlled series of clinical exams. In this paper, we present initial experience with a 3-parameter image reconstruction technique which is based on a damped Maxwellian model approximation to tissue viscoelasticity. The algorithm estimates shear modulus and Poisson ratio along with a damping coefficient. Preliminary results in phantoms and in vivo in the breast show that the damping coefficient images recovered are likely to augment the diagnostic power of the technique for discriminating breast tissue characteristics.
Medical Imaging 2006: Physiology, Function, and Structure from Medical Images, 2006
MR elastography (MRE) images the intrinsic mechanical properties of soft tissues; e.g., the shear... more MR elastography (MRE) images the intrinsic mechanical properties of soft tissues; e.g., the shear modulus, mu. The mu of the plantar soft tissues is important in understanding the mechanisms whereby the forces induced during normal motion produce ulcers that lead to amputation in diabetic feet. We compared the compliance of the heel fat pad to compressive forces and to shearing
A significant effort has been expended to measure the accuracy of the shear modulus estimates. Co... more A significant effort has been expended to measure the accuracy of the shear modulus estimates. Conversely, very little effort has been expended to establish the reproducibility of the method in a clinical context. Previously we established the reproducibility in phantoms to be 3% for repeated measurements without moving the phantom and 5% when the phantom was moved,however, the clinical reproducibility
Medical Imaging 2012: Biomedical Applications in Molecular, Structural, and Functional Imaging, 2012
Recent advances in nanotechnology have allowed for the effective use of iron oxide nanoparticles ... more Recent advances in nanotechnology have allowed for the effective use of iron oxide nanoparticles (IONPs) for cancer imaging and therapy. When activated by an alternating magnetic field (AMF), intra-tumoral IONPs have been effective at controlling tumor growth in rodent models. To accurately plan and assess IONP-based therapies in clinical patients, noninvasive and quantitative imaging technique for the assessment of IONP uptake and biodistribution will be necessary. Proven techniques such as confocal, light and electron microscopy, histochemical iron staining, ICP-MS, fluorescent labeled mNPs and magnetic spectroscopy of Brownian motion (MSB), are being used to assess and quantify IONPs in vitro and in ex vivo tissues. However, a proven noninvasive in vivo IONP imaging technique has not yet been developed. In this study we have demonstrated the shortcomings of computed tomography (CT) and magnetic resonance imaging (MRI) for effectively observing and quantifying iron/IONP concentrations in the clinical setting. Despite the poor outcomes of CT and standard MR sequences in the therapeutic concentration range, ultra-short T2 MRI methods such as, Sweep Imaging With Fourier Transformation (SWIFT), provide a positive iron contrast enhancement and a reduced signal to noise ratio. Ongoing software development and phantom and in vivo studies, will further optimize this technique, providing accurate, clinically-relevant IONP biodistribution information.
To test the feasibility of applying the magnetic resonance elastography (MRE) technique to map th... more To test the feasibility of applying the magnetic resonance elastography (MRE) technique to map the elastic modulus of the plantar fat pads in diabetic and nondiabetic subjects. A prototype MRE imaging apparatus was used to produce quantitative maps of the heel fat pad in a pilot study of 12 volunteers and 4 patients with diabetes with neuropathy. Anatomic images corresponding to MRE maps allowed precise selection of regions of interest in the fat. Magnetic resonance elastograms of the heel fat pads were successfully created; mean measurements in the volunteers and the diabetic patients were 4.85 and 5.26 kPa, respectively. It is feasible to perform MRE on the plantar fat pads and to produce elasticity maps. The trend toward stiffer fat pads, as demonstrated in patients with diabetes, suggests that the fat pads were qualitatively different. Magnetic resonance elastography offers great potential to investigate the mechanical properties of soft tissues in vivo noninvasively.
An imaging system that simultaneously performs near infrared (NIR) tomography and magnetic resona... more An imaging system that simultaneously performs near infrared (NIR) tomography and magnetic resonance imaging (MRI) is used to study breast tissue phantoms and a healthy woman in vivo. An NIR image reconstruction that exploits the combined data set is presented that implements the MR structure as a soft-constraint in the NIR property estimation. The algorithm incorporates the MR spatially segmented regions into a regularization matrix that links locations with similar MR properties, and applies a Laplacian-type filter to minimize variation within each region. When prior knowledge of the structure of phantoms is used to guide NIR property estimation, root mean square (rms) image error decreases from 26 to 58%. For a representative in vivo case, images of hemoglobin concentration, oxygen saturation, water fraction, scattering power, and scattering amplitude are derived and the properties of adipose and fibroglandular breast tissue types, identified from MRI, are quantified. Fibroglandular tissue is observed to have more than four times as much water content as adipose tissue, almost twice as much blood volume, and slightly reduced oxygen saturation. This approach is expected to improve recovery of abnormalities within the breast, as the inclusion of structural information increases the accuracy of recovery of embedded heterogeneities, at least in phantom studies.
The Dartmouth Center for Cancer Nanotechnology Excellence - one of nine funded by the National Ca... more The Dartmouth Center for Cancer Nanotechnology Excellence - one of nine funded by the National Cancer Institute as part of the Alliance for Nanotechnology in Cancer - focuses on the use of magnetic nanoparticles for cancer diagnostics and hyperthermia therapy. It brings together a diverse team of engineers and biomedical researchers with expertise in nanomaterials, molecular targeting, advanced biomedical imaging and translational in vivo studies. The goal of successfully treating cancer is being approached by developing nanoparticles, conjugating them with Fabs, hyperthermia treatment, immunotherapy and sensing treatment response.
Proceedings IEEE International Symposium on Biomedical Imaging, 2002
Magnetic Resonance Elastography (MRE) is an exciting imaging technique with application to clinic... more Magnetic Resonance Elastography (MRE) is an exciting imaging technique with application to clinical settings where quantitative maps of tissue mechanical properties may be diagnostic. This certainly includes breast imaging where hardness has been associated with malignancy. We have been developing time-harmonic MRE methods for the breast in anticipation of evaluating the approach in a controlled series of clinical exams. In this paper, we present initial experience with a 3-parameter image reconstruction technique which is based on a damped Maxwellian model approximation to tissue viscoelasticity. The algorithm estimates shear modulus and Poisson ratio along with a damping coefficient. Preliminary results in phantoms and in vivo in the breast show that the damping coefficient images recovered are likely to augment the diagnostic power of the technique for discriminating breast tissue characteristics.
Medical Imaging 2006: Physiology, Function, and Structure from Medical Images, 2006
MR elastography (MRE) images the intrinsic mechanical properties of soft tissues; e.g., the shear... more MR elastography (MRE) images the intrinsic mechanical properties of soft tissues; e.g., the shear modulus, mu. The mu of the plantar soft tissues is important in understanding the mechanisms whereby the forces induced during normal motion produce ulcers that lead to amputation in diabetic feet. We compared the compliance of the heel fat pad to compressive forces and to shearing
A significant effort has been expended to measure the accuracy of the shear modulus estimates. Co... more A significant effort has been expended to measure the accuracy of the shear modulus estimates. Conversely, very little effort has been expended to establish the reproducibility of the method in a clinical context. Previously we established the reproducibility in phantoms to be 3% for repeated measurements without moving the phantom and 5% when the phantom was moved,however, the clinical reproducibility
Medical Imaging 2012: Biomedical Applications in Molecular, Structural, and Functional Imaging, 2012
Recent advances in nanotechnology have allowed for the effective use of iron oxide nanoparticles ... more Recent advances in nanotechnology have allowed for the effective use of iron oxide nanoparticles (IONPs) for cancer imaging and therapy. When activated by an alternating magnetic field (AMF), intra-tumoral IONPs have been effective at controlling tumor growth in rodent models. To accurately plan and assess IONP-based therapies in clinical patients, noninvasive and quantitative imaging technique for the assessment of IONP uptake and biodistribution will be necessary. Proven techniques such as confocal, light and electron microscopy, histochemical iron staining, ICP-MS, fluorescent labeled mNPs and magnetic spectroscopy of Brownian motion (MSB), are being used to assess and quantify IONPs in vitro and in ex vivo tissues. However, a proven noninvasive in vivo IONP imaging technique has not yet been developed. In this study we have demonstrated the shortcomings of computed tomography (CT) and magnetic resonance imaging (MRI) for effectively observing and quantifying iron/IONP concentrations in the clinical setting. Despite the poor outcomes of CT and standard MR sequences in the therapeutic concentration range, ultra-short T2 MRI methods such as, Sweep Imaging With Fourier Transformation (SWIFT), provide a positive iron contrast enhancement and a reduced signal to noise ratio. Ongoing software development and phantom and in vivo studies, will further optimize this technique, providing accurate, clinically-relevant IONP biodistribution information.
To test the feasibility of applying the magnetic resonance elastography (MRE) technique to map th... more To test the feasibility of applying the magnetic resonance elastography (MRE) technique to map the elastic modulus of the plantar fat pads in diabetic and nondiabetic subjects. A prototype MRE imaging apparatus was used to produce quantitative maps of the heel fat pad in a pilot study of 12 volunteers and 4 patients with diabetes with neuropathy. Anatomic images corresponding to MRE maps allowed precise selection of regions of interest in the fat. Magnetic resonance elastograms of the heel fat pads were successfully created; mean measurements in the volunteers and the diabetic patients were 4.85 and 5.26 kPa, respectively. It is feasible to perform MRE on the plantar fat pads and to produce elasticity maps. The trend toward stiffer fat pads, as demonstrated in patients with diabetes, suggests that the fat pads were qualitatively different. Magnetic resonance elastography offers great potential to investigate the mechanical properties of soft tissues in vivo noninvasively.
An imaging system that simultaneously performs near infrared (NIR) tomography and magnetic resona... more An imaging system that simultaneously performs near infrared (NIR) tomography and magnetic resonance imaging (MRI) is used to study breast tissue phantoms and a healthy woman in vivo. An NIR image reconstruction that exploits the combined data set is presented that implements the MR structure as a soft-constraint in the NIR property estimation. The algorithm incorporates the MR spatially segmented regions into a regularization matrix that links locations with similar MR properties, and applies a Laplacian-type filter to minimize variation within each region. When prior knowledge of the structure of phantoms is used to guide NIR property estimation, root mean square (rms) image error decreases from 26 to 58%. For a representative in vivo case, images of hemoglobin concentration, oxygen saturation, water fraction, scattering power, and scattering amplitude are derived and the properties of adipose and fibroglandular breast tissue types, identified from MRI, are quantified. Fibroglandular tissue is observed to have more than four times as much water content as adipose tissue, almost twice as much blood volume, and slightly reduced oxygen saturation. This approach is expected to improve recovery of abnormalities within the breast, as the inclusion of structural information increases the accuracy of recovery of embedded heterogeneities, at least in phantom studies.
Uploads
Papers by John Weaver