Amir Huda

Voxel-based diffusion tensor magnetic resonance imaging evaluation of low-grade hepatic encephalopathy

To quantify the changes in brain water diffusivity in hepatic encephalopathy (HE) associated with cirrhosis using diffusion tensor imaging (DTI) and to correlate with neuropsychological (NP) scores.

Clinical correlation of neuropsychological tests with 1H magnetic resonance spectroscopy in hepatic encephalopathy.

Objective The purpose of this project was to correlate neuropsychological test results with in vivo measures of regional cerebral biochemistry determined by (1) H MRS in patients with subclinical and mild hepatic encephalopathy. Methods Baseline1 H MRS scans and neuropsychological testing of patients occurred at entry into the study. The primary localized volume chosen for the1 H MRS study was the posteromedial parietal cortex, which consisted predominantly of white matter. Some of these patients were scanned again if they received a liver transplantation. In a subset of patients, the effect on cerebral biochemistry and neuropsychological test performance due to a dietary intervention of reduced protein intake was monitored. These patients underwent a baseline examination and a repeat examination after 2 weeks of dietary intervention. Measures were made of the correlation between the dietary intervention and1 H MRS determined biochemistry and the results of neuropsychological tests. Results in both patient groups (dietary intervention and no dietary intervention) were compared with healthy control subjects. Results Subclinical and low grade HE patients showed a significant reduction in mI/Cr and Cho/Cr ratio when compared with healthy control subjects. These patients also showed impairment in frontal lobe mediated cognitive tasks and in motor ability that were not appreciated in a bedside examination. The patients did not return to normal cerebral metabolic states within 30 to 60 days of liver transplantation. In fact, reductions remained in mI/Cr. Cho/Cr values increased after transplantation compared with healthy control subjects. Conclusions (1) H MRS studies showed changes in regional cerebral biochemistry associated with all grades of HE. There was a reduction in mI/Cr and a reduction in Cho/Cr in patients with low grade and subclinical forms of HE compared with normal subjects. The reduction in mI correlated well with abnormalities observed in neuropsychological tests. Liver transplantation was not associated with significant improvement in these variables.

Adding another spectral dimension to 1H magnetic resonance spectroscopy of hepatic encephalopathy

To evaluate a localized two‐dimensional correlated magnetic resonance spectroscopic (L‐COSY) technique in patients with hepatic encephalopathy (HE) and healthy subjects, and to correlate the cerebral metabolite changes with neuropsychological (NP) test scores.

Two-dimensional MR spectroscopy of minimal hepatic encephalopathy and neuropsychological correlates in vivo.

To evaluate regional cerebral metabolic and structural changes in patients with minimal hepatic encephalopathy (MHE) using two‐dimensional (2D) MR spectroscopy (MRS) and T   1 ‐weighted MRI, to correlate the observed MR changes with neuropsychological (NP) test scores, and to compare the diagnostic accuracy of MRI, 2D MRS, and NP tests in discriminating between patients and healthy subjects.

Multidimensional MR spectroscopic imaging of prostate cancer in vivo

Prostate cancer (PCa) is the second most common type of cancer among men in the United States. A major limitation in the management of PCa is an inability to distinguish, early on, cancers that will progress and become life threatening. One‐dimensional (1D) proton (1H) MRS of the prostate provides metabolic information such as levels of choline (Ch), creatine (Cr), citrate (Cit), and spermine (Spm) that can be used to detect and diagnose PCa. Ex vivo high‐resolution magic angle spinning (HR‐MAS) of PCa specimens has revealed detection of more metabolites such as myo‐inositol (mI), glutamate (Glu), and glutamine (Gln). Due to the J‐modulation and signal overlap, it is difficult to quantitate Spm and other resonances in the prostate clearly by single‐ and multivoxel‐based 1D MR spectroscopy. This limitation can be minimized by adding at least one more spectral dimension by which resonances can be spread apart, thereby increasing the spectral dispersion. However, recording of multivoxel‐based two‐dimensional (2D) MRS such as J‐resolved spectroscopy (JPRESS) and correlated spectroscopy (L‐COSY) combined with 2D or three‐dimensional (3D) magnetic resonance spectroscopic imaging (MRSI) using conventional phase‐encoding can be prohibitively long to be included in a clinical protocol. To reduce the long acquisition time required for spatial encoding, the echo‐planar spectroscopic imaging (EPSI) technique has been combined with correlated spectroscopy to give four‐dimensional (4D) echo‐planar correlated spectroscopic imaging (EP‐COSI) as well as J‐resolved spectroscopic imaging (EP‐JRESI) and the multi‐echo (ME) variants. Further acceleration can be achieved using non‐uniform undersampling (NUS) and reconstruction using compressed sensing (CS). Earlier versions of 2D MRS, theory of 2D MRS, spectral apodization filters, newer developments and the potential role of multidimensional MRS in PCa detection and management will be reviewed here. Copyright

Effects of ionizing radiation exposure on Arabidopsis thaliana.

The effects of ionizing radiation on Arabidopsis thaliana were investigated using 6 MV x-rays produced by a linear accelerator. Photosynthesis and respiration rates, chlorophyll fluorescence (fv/fm ratio and yield), plant height, total leaf area, stem mass, leaf mass, and above-ground biomass were measured to evaluate both physiological and physical impacts of ionizing radiation. The statistical analysis examined the radiation effects with respect to four different total doses (0.5 Gy, 5 Gy, 50 Gy, and 150 Gy), two different treatment types (single and fractionated), and irradiation at one of three different life stages (15 days, 20 days, and 25 days old). Results indicate that the age at the time of radiation exposure plays an important role in integrating radiation effects, and the irradiated A. thaliana indicated greater divergences in terms of physical growth compared to the internal physiological reactions. The results suggest that flowering plants like A. thaliana are capable of being utilized as a biodosimeter and further studies can be performed on specific areas, such as microscopic analysis of a plants internal structure in order to assess the effects of ionizing radiation for a practical application.

Magnetic resonance T2‐relaxometry and 2D L‐correlated spectroscopy in patients with minimal hepatic encephalopathy

To evaluate T2‐relaxation changes in patients with minimal hepatic encephalopathy (MHE) using T2 relaxometry and to correlate T2 values with brain metabolites evaluated using 2D magnetic resonance spectroscopy (MRS).

Adding a New Spectral Dimension to Localized 1H MR Spectroscopy of Human Prostates using an Endorectal Coil

Localized 2D shift-correlated MR spectra (L-COSY) of human prostates were recorded using an endorectal “receive” coil. Typically, 4 ml voxels were placed in the peripheral zones of the prostate. Seven healthy volunteers and one BPH patient have participated in this study so far. The total acquisition time for a 2D L-COSY was approximately 20 minutes. A 1.5 Tesla GE scanner with a body coil for RF transmission and a pelvic phased-array coil combined with a disposable rectal coil for reception was used. The 2D L-COSY spectra showed cross peaks due to citrate, spermine and occasionally choline, creatine and lipids. The 2D cross peaks due to both the multiplets of spermine were clearly resolved from choline and creatine which has been a major problem with the conventional MR spectroscopic techniques. In contrast to 2D JPRESS, improved spectral dispersion, less crowded 2D cross peaks and unequivocal detection of both multiplets of spermine were monitored in 2D L-COSY. Pilot results suggest that localized 2D L-COSY can be successfully implemented in human prostates on a clinical scanner.

Radiation exposure to patients and medical staff in hepatic chemoembolisation interventional procedures in Recife, Brazil

The purpose of this study was to evaluate patient and medical staff absorbed doses received from transarterial chemoembolisation of hepatocellular carcinoma, which is the most common primary liver tumour worldwide. The study was performed in three hospitals in Recife, capital of the state of Pernambuco, located in the Brazilian Northeastern region. Two are public hospitals (A and B), and one is private (C). For each procedure, the number of images, irradiation parameters (kV, mA and fluoroscopy time), the air kerma-area product (PKA) and the cumulative air kerma (Ka,r) at the reference point were registered. The maximum skin dose (MSD) of the patient was estimated using radiochromic film. For the medical staff dosimetry, thermoluminescence dosemeters (TLD-100) were attached next to the eyes, close to the thyroid (above the shielding), on the thorax under the apron, on the wrist and on the feet. The effective dose to the staff was estimated using the algorithm of von Boetticher. The results showed that the mean value of the total PKA was 267.49, 403.83 and 479.74 Gy cm(2) for Hospitals A, B and C, respectively. With regard to the physicians, the average effective dose per procedure was 17 µSv, and the minimum and maximum values recorded were 1 and 41 µSy, respectively. The results showed that the feet received the highest doses followed by the hands and lens of the eye, since the physicians did not use leaded glasses and the equipment had no lead curtain.

Dosimetric study of mandible examinations performed with three cone-beam computed tomography scanners

The objective of this work was to evaluate the air kerma-area product (PKA) and the skin absorbed dose in the region of the eyes, salivary glands and thyroid of the patient from mandible examinations performed with three cone-beam computed tomography (CBCT) scanners, i.e. i-CAT classic, Gendex CB-500 and PreXion 3D. For the dosimetric evaluation, an anthropomorphic head phantom (model RS-250) was used to simulate an adult patient. The CBCT examinations were performed using standard and high-resolution protocols for mandible acquisitions for adult patients. During the phantoms exposure, the PKA was measured using an ionising chamber and the absorbed doses to the skin in the region of the eyes, thyroid and salivary glands were estimated using thermoluminescence dosemeters (TLDs) positioned on the phantoms surface. The PKA values estimated with the CBCT scanners varied from 26 to 138 µGy m(2). Skin absorbed doses in the region of the eyes varied from 0.07 to 0.34 mGy; at the parotid glands, from 1.31 to 5.93 mGy; at the submandibular glands, from 1.41 to 6.86 mGy; and at the thyroid, from 0.18 to 2.45 mGy. PKA and absorbed doses showed the highest values for the PreXion 3D scanner due to the use of the continuous exposure mode and a high current-time product.