[Changes in shape and signal intensity of high intensity zone in lumbar intervertebral discs on magnetic resonance images: a longitudinal study].

OBJECTIVE: To investigate changes over time in the shape and signal intensity of high intensity zone (HIZ) in the lumbar intervertebral discs on magnetic resonance images in patients with low back pain. METHODS: The imaging data were collected from 27 patients with low back pain, who underwent lumbar magnetic resonance (MR) imaging examinations that identified HIZ lesions and received follow-up MR examinations at least 1.5 years later over the period from January 2009 to January 2017. The initial and follow-up MR T2WI images of the patients were read by two experienced radiologists to categorize the changes in the shape of the HIZ lesions into enlarged, unchanged, shrunk, and disappeared. The volume and signal/cerebrospinal fluid signal intensity (T2/CSF) ratio of the HIZ were measured on sagittal MR images using ImageJ software. RESULTS: Of the 43 HIZ lesions found in the initial examinations, 22 (51.2%) remained unchanged in the follow-up examinations, 10 (21.3%) were enlarged, 9 (20.9%) shrank, and 2 (23.3%) disappeared. The follow-up examinations revealed 4 new HIZ lesions in the intervertebral discs. The volumes of these lesions did not vary significantly in the follow-up examinations (P=0.653), but the T2/CSF ratio was significantly higher in the follow-up than in the initial examinations (P=0.043). CONCLUSIONS: After observation for an average of 3 years and 3 months, most of the HIZ lesions in the lumbar intervertebral discs of the patients with low back pain remained stable in shape, but their signal intensity on MR images increased.

Design and integration of a high accuracy multichannel analog CMOS peak detect and hold circuit for APD-based PET imaging.

This paper presents the design of a high accuracy multichannel peak detect and hold (PDH) circuit. This PDH measures the energy of an event and is one part of a readout chain for avalanche photo diodes (APD)-based positron emission tomography (PET) imaging. The circuit is designed in a 0.35µm CMOS process. The proposed PDH is dedicated to ultra low amplitude, large amplitude range from several tens millivolts to 1.1 V, and fast peaking time (190 ns) semi-Gaussian pulses. The two-phase technique has been used to cancel the major error source of the classical CMOS PDH: offset. A two-gain OTA is applied to minimize the DC error. A peak error less 1% for a small input signal (amplitude is between 40 mV and 300 mV) and a peak error less than 0.2% for a large input signal (amplitude is between 300 mV and 1.1 V) have been obtained from test. The area of a PDH is equal to about 200 µm × 40 µm. In our PDH system, the drop rate is negligible.