T2* mapping for articular cartilage assessment: principles,current applications,and future prospects

With advances in joint preservation surgery that are intended to alter the course of osteoarthritis by early intervention, accurate and reliable assessment of the cartilage status is critical. Biochemically sensitive MRI techniques can add robust biomarkers for disease onset and progression, and therefore, could be meaningful assessment tools for the diagnosis and follow-up of cartilage abnormalities. T2* mapping could be a good alternative because it would combine the benefits of biochemical cartilage evaluation with remarkable features including short imaging time and the ability of high-resolution three-dimensional cartilage evaluation—without the need for contrast media administration or special hardware. Several in vitro and in vivo studies, which have elaborated on the potential of cartilage T2* assessment in various cartilage disease patterns and grades of degeneration, have been reported. However, much remains to be understood and certain unresolved questions have become apparent with these studies that are crucial to the further application of this technique. This review summarizes the principles of the technique and current applications of T2* mapping for articular cartilage assessment. Limitations of recent studies are discussed and the potential implications for patient care are presented.     

In situ radiotherapy with 111In-pentetreotide. State of the art and perspectives.

111In-pentetreotide (Octreoscan) and other radiolabeled somatostatin analogs are useful in the management of well differentiated neuroendocrine malignancies such as carcinoid or islet cell neoplasms. These radiopeptides bind to membrane bound somatostatin receptors (sst 1-5) which are over-expressed in a wide variety of neoplasms, especially those arising from the neuroectoderm. Imaging advances allow for the noninvasive determination of the presence of sst receptors by combining radioactivity [111Indium with a somatostatin analog, DTPA-D-phe1-octreotide (pentetreotide)]. Radiolabeled somatostatin analogs bind to membrane receptors and internalization of the complex occurs. Auger emitting somatostatin analogs offer a novel and significantly less toxic approach to controlling neoplastic diseases by delivering targeted radiation specifically to receptor bearing cells while sparing receptor negative cells. Responses of 62-69% in 85 patients with metastatic neuroendocrine tumors treated with high dose (6-19.6 GBq) 111In-pentetreotide, specifically targeting tumor somatostatin receptors, have been reported. Objective responses observed included biochemical and radiographic responses with prolonged survival. This article will discuss and review the multi-center data available to date, the mechanisms of action of radiolabeled somatostatin analogs, dosimetry, clinical response parameters, and toxicity.     

Sex estimation of the Cretan humerus: a digital radiometric study

Sex estimation based on measurements of unidentified skeletal remains recovered in crime and death scenes can be accomplished with accuracy. In mass disasters, however, the remains are often fleshed, burned, and/or commingled. As a result, osteometric methods are difficult to apply. In such cases, radiography can be of great use during the examination process. A total of 101 (53 males and 48 females) adult humeri were radiographed using digital equipment (Technix TCA 4R PLUS). Specific measurements were taken on the radiographs and then analyzed. Multivariate discriminant function analysis was applied, and the results showed up to 89.1% classification accuracy. Single variables performed equally well for both epiphyses reaching 86.1% correct group membership. The method proposed here is successful, offering an alternative sex estimation technique applicable to the identification of deceased individuals whose remains are semi-fleshed, burned, mutilated, or otherwise unrecognizable. Specifically, this method is extremely useful when maceration of the remains is not an option.     

Development of a low cost, GPS-based upgrade to a standard handheld gamma detector for mapping environmental radioactive contamination.

A low cost extension to a standard handheld radiation monitor was developed, allowing one to perform outdoor georeferenced gamma measurements. It consists of a commercial wireless Bluetooth GPS receiver, a commercial RS-232 to Bluetooth converter combined with a standard Bluetooth enabled pocket personal computer (PPC). The system is intended for use in difficult to access areas, typically for foot campaigns. As the operator walks, a straightforward homemade visual basic program alternately reads GPS position and gamma dose rate into the PPC, creating a data log. This allows a single operator on foot to map between 50 and 200 ha of environmental radiation per day in very rugged areas, depending on the accessibility of the terrain and the detail required. On a test field with known contamination, a spatial precision of about 5-10 m was obtainable. The device was also used to reveal complex contamination patterns in the flooding zones of a radioactively contaminated small river.     

In vivo mapping of the fast and slow diffusion tensors in human brain.

Recent studies have shown that the diffusional signal decay in human brain is non-monoexponential and may be described in terms of compartmentalized water fractions. Diffusion tensor imaging (DTI), which provides information about tissue structure and orientation, typically uses b values up to 1000 s x mm(-2) so that the signal is dominated by the fast diffusing fraction. In this study b factors up to 3500 s x mm(-2) are utilized, allowing the diffusion tensor properties of the more slowly diffusing fraction to be mapped for the first time. The mean diffusivity (MD) of the slow diffusion tensor was found to exhibit strong white/gray matter (WM/GM) contrast. Maps depicting the principal direction of the slow tensor indicated alignment with the fast tensor and the known orientation of the WM pathways.     

In vivo assessment of liver size in the rat.

In vivo assessment of liver mass in the rat was achieved using several parameters obtained by scintigraphy, including one computed using a Nuclear Data 50:50 analysis system. All correlated well with the directly measured liver weight. The simplest parameter, the area of the anterior view measured from the Polaroid scintigraph, was therefore the one preferred. The results so obtained were compared with those derived from the relationship between liver and body weights. It is suggested that this accurate in vivo measurement of liver mass is of value in the study of the pathophysiology of this organ.     

Incipient Alzheimer's disease as the underlying cause of a motor vehicle crash

A 75-year-old female driver died in a single vehicle crash. A forensic autopsy diagnosed the cause of death as blood loss due to laceration of the liver caused by the crash. Although she had neither clinical history of dementia nor gross abnormalities of the brain, neuropathological examinations showed a substantial number of senile plaques indicative of Alzheimer's disease (AD). An interview with a family member revealed that she had symptoms of dementia. Cognitive dysfunction due to AD was proposed as the underlying cause of the crash. It is recommended that forensic autopsy of older drivers should include neuropathological examinations to identify incipient AD. Recognition of AD as an underlying cause of crashes is also important to promote the health care of older people.     

In vivo comparison of two through-plane MR velocity mapping methods: Fast fourier encoding and phase mapping

Magnetic resonance imaging maps of velocity were acquired with a 1.5-T system in 10 subjects in a plane perpendicular to the main pulmonary artery. Velocity images were successively acquired with a method developed from Fourier-encoding velocity imaging (FEVI) principles with eight gradient steps and one excitation, and with two-point phase-subtraction mapping. Reconstruction in FEVI was implemented by zero-filling interpolation around the eight gradient steps and then around the four central steps. The methods were compared by using estimates of noise in velocity measurements based on the difference between the experimental map and a smooth fitted map. For the same acquisition time, FEVI with four encoding steps was more precise in velocity measurements than phase mapping. Precision was further increased by the use of eight encoding steps, but acquisition time was doubled.     

Measurement of folates in human plasma and erythrocytes by a radiometric microbiologic method.

A radiometric microbiologic assay for the determination of folic acid in human plasma and red blood cells is described. The assay is based upon the measurement of 14CO2 produced from the metabolism of [1-14C] gluconate by Lactobacillus casei. The 14CO2 evolved was shown to be proportional to the amount of added DL-N-5-methyltetrahydrofolage (DL-N-5-methyl FH4). A total of 26 normal plasma and 57 blood hemolysates were assayed in parallel by this radiometric and the standard (turbidimetric) microbiologic assay. The correlation coefficients for the two assays were r = 0.96 for plasma and r = 0.98 for red-cell folate. Lyophilization of L. casei was found to simplify this radiometric assay by eliminating routine maintenance and culture of this microorganism.     

In vivo assessment of neurodegeneration in Niemann-Pick type C mice by quantitative T2 mapping and diffusion tensor imaging

Purpose:

To quantitatively and noninvasively assess neurological disease progression in a mouse model of Niemann‐Pick type C (NPC) disease by measuring white matter status with magnetic resonance imaging (MRI) techniques of T2 mapping and diffusion tensor imaging (DTI).

Materials and Methods:

Quantitative T2 and DTI experiments were performed in vivo in NPC disease model and control mice at three timepoints to quantify differences and changes in white matter with measurements of T2 relaxation and DTI parameters. Histological staining for myelin content was also performed at two timepoints to compare with the MRI findings.

Results:

The results of the T2 and DTI measurements show significant differences in white matter areas of the brain in the NPC disease model compared to control mice at several timepoints, and were seen to change over time in both groups.

Conclusion:

The findings of this study suggest that quantitative MRI measurements may be suitable in vivo biomarkers of disease status for future studies of NPC disease models. The changes in white matter measurements between timepoints in both control and NPC disease groups suggest that white matter structures continue to change and develop over time in the NPC model and can be tracked with MRI techniques. J. Magn. Reson. Imaging 2012;35:528‐536. © 2011 Wiley Periodicals, Inc.     

Mechanical or thermal damage: differentiating between underlying mechanisms as a cause of bone fractures

International Journal of Legal Medicine - To investigate the differences between pre- and post-fire fractures, 30 human forearm bones were subjected to either blunt-force impact, burning, or both....     

In vivo BOLD contrast MRI mapping of subcutaneous vascular function and maturation: validation by intravital microscopy.

Bold contrast MRI was applied for mapping vascular maturation in tumor- and wound-induced skin angiogenesis using the response of mature vessels to hypercapnia (inhalation of air vs. air 5% CO(2)) and the response of all vessels to hyperoxia (air 5% CO(2) vs. oxygen 5% CO(2) (carbogen)). MRI signal enhancement with hypercapnia was reduced in centered vs. linear phase encoding, suggesting increased blood flow. However, intravital microscopy demonstrated constriction of arterioles and reduced flux and density of red blood cells in mature capillaries with hypercapnia, with no change in the diameter of wound-induced neovasculature. The discrepancy in flow between MRI and intravital microscopy is consistent with increased plasma flow and reduced hematocrit. Hyperoxia resulted in increased blood oxygenation and constriction of all vessels. These results provide a hemodynamic explanation for the selective registration of MRI response to hypercapnia with mature vessels and the response to hyperoxia with total vascular function.