Digital coincidence counting with 4πβ(PPC)-γ for the standardization of 60Co

A 4πβ(PPC)-γ coincidence system has been made at KRISS based on a digital DAQ. 60Co sources were measured to verify the system. The maximum detection efficiency for beta particles was estimated to be 96.7 %. Massic activities for sample sources had 0.005 % of the sample variability error, which was well within the expanded standard uncertainty of 0.54 % (k = 2).

The primary system for measurement of beta emitting radioactive gases at KRISS

Korea Research Institute of Standards and Science (KRISS) is developing a length-compensated proportional counting (LCPC) system as a primary system for standardization of beta emitting radioactive gases. The pilot experiment was performed with ⁸⁵Kr and the optimized high voltage and pressure were found to be 1700 V and 0.203 MPa, respectively. The total activity of ⁸⁵Kr was deduced by the length compensation of each count. The expanded uncertainty was estimated to be around 0.8% (k = 2) for the ⁸⁵Kr measurement.

Design of optimal digital filter and digital signal processing for a CdZnTe high resolution gamma-ray system

We have developed an online digital signal processing system based on an FPGA. The system consists of pile-up rejection, baseline restorer, peak detection and pole-zero cancellation for evaluation of deposited energy in the detector. The shaping algorithm employed is a Moving Window Deconvolution (MWD) to shape digitized data into a trapezoidal form. For the purpose of verification, the developed digital system was tested for ¹³⁷Cs gamma rays. The entire system is programmed using the LabVIEW environment.

3D reconstructions of spinal segmental arteries using CT angiography: applications in minimally invasive spinal procedures

BACKGROUND AND PURPOSE

Injury to spinal segmental arteries may potentially occur during spinal surgery, particularly during anterior or minimally invasive approaches. Use of a noninvasive radiologic tool to evaluate these arteries before surgery may reduce this risk.

MATERIAL AND METHODS

We performed spinal CT angiography and reconstructed 3D images of segmental arteries in 41 patients. We classified the pathways and locations of the segmental arteries into 4 zones (A, B, C, and D) according to pedicle and vertebral endplates. We designated segmental arteries from T8 to L1 as "high-level segmental arteries" and those from L2 to L4, as "low-level segmental arteries." We compared the distribution of segmental arteries between these 2 groups. We also investigated anatomic variations of segmental arteries and the rate of occurrence of the artery of Adamkiewicz.

RESULTS

In all patients, 3D reconstruction images from spinal CT angiography clearly showed the pathways of segmental arteries on the vertebral bodies. Most of the segmental arteries passed the middle portion of the vertebral body (zones B and C). However, 51 of 738 segmental arteries (6.9%) had uncommon pathways (zones A and D), and segmental arteries from L2 to L4 had a higher incidence of uncommon pathways than higher level vertebrae (P < .05). We also observed 2 types of segmental artery anatomic variation, agenesis and dual supply.

CONCLUSIONS

We suggest that spinal CT angiography can help to precisely visualize the spinal segmental arteries and surrounding bony structures and can aid clinicians in deciding on optimal approaches for spinal surgery.

Morphological changes of injected calcium phosphate cement in osteoporotic compressed vertebral bodies

SUMMARY

This study was undertaken to investigate the radiologic and clinical outcomes of vertebroplasty with calcium phosphate (CaP) cement in patients with osteoporotic vertebral compression fractures. The morphological changes of injected CaP cement in osteoporotic compressed vertebral bodies were variable and unpredictable. We suggest that the practice of vertebroplasty using CaP should be reconsidered.

INTRODUCTION

Recently, CaP, an osteoconductive filler material, has been used in the treatment of osteoporotic compression fractures. However, the clinical results of CaP-cement-augmented vertebrae are still not well established. The purpose of this study is to assess the clinical results of vertebroplasty with CaP by evaluating the morphological changes of CaP cement in compressed vertebral bodies.

METHODS

Fourteen patients have been followed for more than 2 years after vertebroplasty. The following parameters were reviewed: age, sex, T score, compliance with osteoporosis medications, visual analog scale score, compression ratio, subsequent compression fractures, and any morphological changes in the filler material.

RESULTS

The morphological changes of injected CaP included reabsorption, condensation, bone formation (osteogenesis), fracture of the CaP solid hump, and heterotopic ossification. Out of 14 patients, 11 (78.6%) developed progression of the compression of the CaP-augmented vertebral bodies after vertebroplasty.

CONCLUSIONS

The morphological changes of the injected CaP cement in the vertebral bodies were variable and unpredictable. The compression of the CaP-augmented vertebrae progressed continuously for 2 years or more. The findings of this study suggest that vertebroplasty using CaP cement should be reconsidered.

Recollapse of previous vertebral compression fracture after percutaneous vertebroplasty

This study was undertaken to investigate the incidence rate, characteristics, and predisposing factors associated with recollapse of the same vertebrae after percutaneous vertebroplasty (PVP). Recollapse of the same vertebra after PVP is the one of the complications of the procedure, and the incidence rate in our study was 3.21%. The most important predisposing factor was pre-operative osteonecrosis. Recollapse was not related to trauma.

INTRODUCTION

PVP using polymethylmethacrylate has become a popular treatment for osteoporotic vertebral compression fracture. Recollapse of the same vertebrae after PVP has rarely been reported. This study was undertaken to investigate the incidence, characteristics, and predisposing factors associated with recollapse of the same vertebrae after PVP.

METHODS

Eleven patients (seven females and four males; mean age, 69.91 +/- 5.49 years), out of a total of 343 patients, developed recollapse of the same vertebra after PVP. The 11 patients who developed recollapse comprised the "recollapse group", while the remaining 332 patients comprised the "well-maintained group".

RESULTS

Pre-operative magnetic resonance imaging revealed that the incidence of osteonecrosis was significantly higher in the recollapse group than the well-maintained group (p < 0.05). The degree of re-expansion of the compressed vertebral body after PVP was significantly higher in the recollapse group than in the well-maintained group (p < 0.05).

CONCLUSIONS

The most important predisposing factor for recollapse was pre-operative osteonecrosis. Recollapse was not related to trauma. Osteoporotic vertebral compression fracture with osteonecrosis or pseudoarthrosis has been regarded as a relative indication for PVP; however, the findings of this study suggest that this disease category may be a relative contraindication for PVP.