Houbei Dai

Diagnosis of neuroblastoma and ganglioneuroma using Raman spectroscopy.

BACKGROUND Raman spectroscopy has proven to be useful in studying premalignant and malignant lesions in adults. This is the first report to evaluate Raman spectroscopy in the diagnosis and classification of neuroblastoma in children. METHODS A biopsy or resection of fresh tissue samples from normal adrenal glands, neuroblastomas, ganglioneuromas, nerve sheath tumors, and pheochromocytoma at our hospital were equally divided between routine histology and spectroscopic studies. At least 12 spectra were collected from different regions of each sample using a Renishaw Raman microscope. Raw spectra were processed to remove noise, fluorescence, and shot noise, and then analyzed using principle component analysis and discriminant function analysis. RESULTS We collected 698 spectra from 16 neuroblastomas, 5 ganglioneuromas, 3 normal adrenal glands, 6 nerve sheath tumors, and 1 pheochromocytoma. Raman spectroscopy differentiated between normal adrenal gland, and neuroblastoma and ganglioneuroma with 100% sensitivity and 100% specificity. It correlated well with the Shimada histologic classification system with 100% sensitivity and 100% specificity. It was also able to differentiate neuroblastoma from nerve sheath tumors and pheochromocytoma with high sensitivity and specificity. CONCLUSION This technique can differentiate neuroblastoma from ganglioneuroma and other tumors. It has a potential as a noninvasive real-time diagnostic tool in classifying pediatric tumors.

Evaluation of pancreatic cancer with Raman spectroscopy in a mouse model.

Objectives: Detection of neoplastic changes using optical spectroscopy has been an active area of research in recent times. Raman spectroscopy is a vibrational spectroscopic technique that can be used to diagnose various tumors with high sensitivity and specificity. We evaluated the ability of Raman spectroscopy to differentiate normal pancreatic tissue from malignant tumors in a mouse model. Methods: We collected 920 spectra, 475 from 31 normal pancreatic tissue and 445 from 29 tumor nodules using a 785-nm near-infrared laser excitation. Discriminant function analysis was used for classification of normal and tumor samples. Results: Using principal component analysis, we were able to highlight subtle chemical differences in normal and malignant tissue. Using histopathology as the gold standard, Raman analysis gave sensitivities between 91% and 96% and specificities between 88% and 96%. Conclusions: Raman spectroscopy along with discriminant function analysis is a useful method to detect cancerous changes in the pancreas. Pancreatic tumors were characterized by increased collagen content and decreased DNA, RNA, and lipids components compared with normal pancreatic tissue.

Optical and Electrical Properties of Low to Highly-Degenerate InN Films

The optical and electrical properties of InN films with different levels of carrier concentrations have been investigated. Hall effect measurements at room temperature show that the InN films are n-type with carrier concentration, n e , ranging from ∼ 7 ×10 17 cm -3 to ∼ 3 × 10 20 cm -3 and corresponding mobility, //, of ∼ 1300 to 50 cm 2 V -1 S -1 . Optical absorption spectra of these films show a bandgap absorption edge ∼ 0.6 eV for the InN sample with the lowest n e , and 1.5 eV for the InN sample with the highest n e . However, after corrections for the degeneracy effects, all samples show an intrinsic E g ∼ (0.60 ± 0.05) eV. Temperature dependent (5 – 600 K) electrical measurements show that n e is nearly independent of temperature below 300 K, perhaps due to the presence of donor energy levels resonating with the InN conduction band. However, all the samples show an exponential increase in n e above 300 K due to excitation of other shallow donor like sources. Mobility versus temperature graph shows a maximum ∼ 200 K for InN film with n e = 7 × 10 17 cm -3 and moves towards lower temperature with increasing n e .