Comparative studies of the sensitivities of sparse and full geometries of Total-Body PET scanners built from crystals and plastic scintillators

BACKGROUND

Alongside the benefits of Total-Body imaging modalities, such as higher sensitivity, single-bed position, low dose imaging, etc., their final construction cost prevents worldwide utilization. The main aim of this study is to present a simulation-based comparison of the sensitivities of existing and currently developed tomographs to introduce a cost-efficient solution for constructing a Total-Body PET scanner based on plastic scintillators.

METHODS

For the case of this study, eight tomographs based on the uEXPLORER configuration with different scintillator materials (BGO, LYSO), axial field-of-view (97.4 cm and 194.8 cm), and detector configurations (full and sparse) were simulated. In addition, 8 J-PET scanners with different configurations, such as various axial field-of-view (200 cm and 250 cm), different cross sections of plastic scintillator, and multiple numbers of plastic scintillator layers (2, 3, and 4), based on J-PET technology have been simulated by GATE software. Furthermore, Siemens' Biograph Vision has been simulated to compare the results with standard PET scans. Two types of simulations have been performed. The first one with a centrally located source with a diameter of 1 mm and a length of 250 cm, and the second one with the same source inside a water-filled cylindrical phantom with a diameter of 20 cm and a length of 183 cm.

RESULTS

With regards to sensitivity, among all the proposed scanners, the ones constructed with BGO crystals give the best performance ([Formula: see text] 350 cps/kBq at the center). The utilization of sparse geometry or LYSO crystals significantly lowers the achievable sensitivity of such systems. The J-PET design gives a similar sensitivity to the sparse LYSO crystal-based detectors while having full detector coverage over the body. Moreover, it provides uniform sensitivity over the body with additional gain on its sides and provides the possibility for high-quality brain imaging.

CONCLUSION

Taking into account not only the sensitivity but also the price of Total-Body PET tomographs, which till now was one of the main obstacles in their widespread clinical availability, the J-PET tomography system based on plastic scintillators could be a cost-efficient alternative for Total-Body PET scanners.

Efficiency determination of J-PET: first plastic scintillators-based PET scanner

BACKGROUND

The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in [Formula: see text] annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons.

RESULTS

By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70-270 keV, where it varies between 20 and 100[Formula: see text]. In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons.

CONCLUSION

A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion-beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine.

Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography

Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron–positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner to record ortho-positronium (o-Ps) annihilations with single-event estimation of o-Ps spin and determine the complete spectrum of an angular correlation operator sensitive to CPT-violating effects. We find no violation at the precision level of 10⁻⁴, with an over threefold improvement on the previous measurement.

CPT violation could manifest itself in annihilating positronium events, but searching for this effect would require to know the spin of the annihilating system. Here, the authors do this using a positron-emission tomography scanner, finding no violation with a statistical precision of 10⁻⁴.

Simulating NEMA characteristics of the modular total-body J-PET scanner-an economic total-body PET from plastic scintillators

The purpose of the presented research is estimation of the performance characteristics of the economic total-body Jagiellonian-PET system (TB-J-PET) constructed from plastic scintillators. The characteristics are estimated according to the NEMA NU-2-2018 standards utilizing the GATE package. The simulated detector consists of 24 modules, each built out of 32 plastic scintillator strips (each with cross section of 6 mm times 30 mm and length of 140 or 200 cm) arranged in two layers in regular 24-sided polygon circumscribing a circle with the diameter of 78.6 cm. For the TB-J-PET with an axial field-of-view (AFOV) of 200 cm, a spatial resolutions (SRs) of 3.7 mm (transversal) and 4.9 mm (axial) are achieved. The noise equivalent count rate (NECR) peak of 630 kcps is expected at 30 kBq cc^-1. Activity concentration and the sensitivity at the center amounts to 38 cps kBq^-1. The scatter fraction (SF) is estimated to 36.2 %. The values of SF and SR are comparable to those obtained for the state-of-the-art clinical PET scanners and the first total-body tomographs: uExplorer and PennPET. With respect to the standard PET systems with AFOV in the range from 16 to 26 cm, the TB-J-PET is characterized by an increase in NECR approximately by factor of 4 and by the increase of the whole-body sensitivity by factor of 12.6 to 38. The time-of-flight resolution for the TB-J-PET is expected to be at the level of CRT = 240 ps full width at half maximum. For the TB-J-PET with an AFOV of 140 cm, an image quality of the reconstructed images of a NEMA IEC phantom was presented with a contrast recovery coefficient and a background variability parameters. The increase of the whole-body sensitivity and NECR estimated for the TB-J-PET with respect to current commercial PET systems makes the TB-J-PET a promising cost-effective solution for the broad clinical applications of total-body PET scanners. TB-J-PET may constitute an economic alternative for the crystal TB-PET scanners, since plastic scintillators are much cheaper than BGO or LYSO crystals and axial arrangement of the strips significantly reduces the costs of readout electronics and SiPMs.

Optimisation of the event-based TOF filtered back-projection for online imaging in total-body J-PET

We perform a parametric study of the newly developed time-of-flight (TOF) image reconstruction algorithm, proposed for the real-time imaging in total-body Jagiellonian PET (J-PET) scanners. The asymmetric 3D filtering kernel is applied at each most likely position of electron-positron annihilation, estimated from the emissions of back-to-back γ-photons. The optimisation of its parameters is studied using Monte Carlo simulations of a 1-mm spherical source, NEMA IEC and XCAT phantoms inside the ideal J-PET scanner. The combination of high-pass filters which included the TOF filtered back-projection (FBP), resulted in spatial resolution, 1.5 times higher in the axial direction than for the conventional 3D FBP. For realistic 10-minute scans of NEMA IEC and XCAT, which require a trade-off between the noise and spatial resolution, the need for Gaussian TOF kernel components, coupled with median post-filtering, is demonstrated. The best sets of 3D filter parameters were obtained by the Nelder-Mead minimisation of the mean squared error between the resulting and reference images. The approach allows training the reconstruction algorithm for custom scans, using the IEC phantom, when the temporal resolution is below 50 ps. The image quality parameters, estimated for the best outcomes, were systematically better than for the non-TOF FBP.

Performance assessment of the 2 γpositronium imaging with the total-body PET scanners

Purpose

In living organisms, the positron-electron annihilation (occurring during the PET imaging) proceeds in about 30% via creation of a metastable ortho-positronium atom. In the tissue, due to the pick-off and conversion processes, over 98% of ortho-positronia annihilate into two 511 keV photons. In this article, we assess the feasibility for reconstruction of the mean ortho-positronium lifetime image based on annihilations into two photons. The main objectives of this work include the (i) estimation of the sensitivity of the total-body PET scanners for the ortho-positronium mean lifetime imaging using 2γ annihilations and (ii) estimation of the spatial and time resolution of the ortho-positronium image as a function of the coincidence resolving time (CRT) of the scanner.

Methods

Simulations are conducted assuming that radiopharmaceutical is labeled with ⁴⁴Sc isotope emitting one positron and one prompt gamma. The image is reconstructed on the basis of triple coincidence events. The ortho-positronium lifetime spectrum is determined for each voxel of the image. Calculations were performed for cases of total-body detectors build of (i) LYSO scintillators as used in the EXPLORER PET and (ii) plastic scintillators as anticipated for the cost-effective total-body J-PET scanner. To assess the spatial and time resolution, the four cases were considered assuming that CRT is equal to 500 ps, 140 ps, 50 ps, and 10 ps.

Results

The estimated total-body PET sensitivity for the registration and selection of image forming triple coincidences (2γ+γ_prompt) is larger by a factor of 13.5 (for LYSO PET) and by factor of 5.2 (for plastic PET) with respect to the sensitivity for the standard 2γ imaging by LYSO PET scanners with AFOV = 20 cm. The spatial resolution of the ortho-positronium image is comparable with the resolution achievable when using TOF-FBP algorithms already for CRT = 50 ps. For the 20-min scan, the resolution better than 20 ps is expected for the mean ortho-positronium lifetime image determination.

Conclusions

Ortho-positronium mean lifetime imaging based on the annihilations into two photons and prompt gamma is shown to be feasible with the advent of the high sensitivity total-body PET systems and time resolution of the order of tens of picoseconds.

Efficacy and safety of denosumab vs. bisphosphonates in postmenopausal women previously treated with oral bisphosphonates

Transitioning postmenopausal women with osteoporosis from a bisphosphonate to denosumab appears to be safe and more effective at improving BMD than continuing treatment with a bisphosphonate.

INTRODUCTION

We conducted a patient-level pooled analysis of four studies to estimate the efficacy and safety of transitioning to denosumab vs. continuing bisphosphonate treatment in postmenopausal women who previously received oral bisphosphonates.

METHODS

Patients received 60 mg denosumab once every 6 months or a bisphosphonate (oral alendronate, risedronate, ibandronate, or intravenous zoledronic acid). Endpoints were change from baseline in lumbar spine, total hip, femoral neck, and 1/3 radius BMD at month 12, change from baseline in serum CTX-1 and P1NP, and incidence of adverse events.

RESULTS

A total of 2850 randomized patients (1424 bisphosphonate:1426 denosumab) were included in the analysis. Percentage change in BMD was significantly greater (p < 0.001) for denosumab vs. bisphosphonate at each skeletal site; differences in BMD changes ranged from 0.6 to 2.0%. Percentage decrease in serum CTX-1 and P1NP was significantly greater (p < 0.0001) for denosumab vs. bisphosphonate at months 1, 6, and 12; in the denosumab group only, percentage change in serum CTX-1 at month 1 was significantly correlated with percentage change in lumbar spine and total hip BMD at month 12. The incidences of adverse events were similar between treatment groups. Three patients (one bisphosphonate and two denosumab) had atypical femoral fractures, all from the denosumab vs. zoledronic acid study.

CONCLUSION

Postmenopausal women can safely transition from a bisphosphonate to denosumab, which is more effective at improving BMD than continuing with a bisphosphonate.

CLINICAL TRIALS REGISTRATION

NCT00377819, NCT00919711, NCT00936897, NCT01732770.

Relationship Between Bone Mineral Density T-Score and Nonvertebral Fracture Risk Over 10 Years of Denosumab Treatment

Although treat-to-target strategies are being discussed in osteoporosis, there is little evidence of what the target should be to reduce fracture risk maximally. We investigated the relationship between total hip BMD T-score and the incidence of nonvertebral fracture in women who received up to 10 years of continued denosumab therapy in the FREEDOM (3 years) study and its long-term Extension (up to 7 years) study. We report the percentages of women who achieved a range of T-scores at the total hip or femoral neck over 10 years of denosumab treatment (1343 women completed 10 years of treatment). The incidence of nonvertebral fractures was lower with higher total hip T-score. This relationship plateaued at a T-score between -2.0 and -1.5 and was independent of age and prevalent vertebral fractures, similar to observations in treatment-naïve subjects. Reaching a specific T-score during denosumab treatment was dependent on the baseline T-score, with higher T-scores at baseline more likely to result in higher T-scores at each time point during the study. Our findings highlight the importance of follow-up BMD measurements in patients receiving denosumab therapy because BMD remains a robust indicator of fracture risk. These data support the notion of a specific T-score threshold as a practical target for therapy in osteoporosis. © 2019 The Authors Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research (ASBMR).

Feasibility study of the positronium imaging with the J-PET tomograph

A detection system of the conventional PET tomograph is set-up to record data from [Formula: see text] annihilation into two photons with energy of 511 keV, and it gives information on the density distribution of a radiopharmaceutical in the body of the object. In this paper we explore the possibility of performing the three gamma photons imaging based on ortho-positronium annihilation, as well as the possibility of positronium mean lifetime imaging with the J-PET tomograph constructed from plastic scintillators. For this purposes simulations of the ortho-positronium formation and its annihilation into three photons were performed taking into account distributions of photons' momenta as predicted by the theory of quantum electrodynamics and the response of the J-PET tomograph. In order to test the proposed ortho-positronium lifetime image reconstruction method, we concentrate on the decay of the ortho-positronium into three photons and applications of radiopharmaceuticals labeled with isotopes emitting a prompt gamma. The proposed method of imaging is based on the determination of hit-times and hit-positions of registered photons which enables the reconstruction of the time and position of the annihilation point as well as the lifetime of the ortho-positronium on an event-by-event basis. We have simulated the production of the positronium in point-like sources and in a cylindrical phantom composed of a set of different materials in which the ortho-positronium lifetime varied from 2.0 ns to 3.0 ns, as expected for ortho-positronium created in the human body. The presented reconstruction method for total-body J-PET like detector allows to achieve a mean lifetime resolution of  ∼40 ps. Recent positron annihilation lifetime spectroscopy measurements of cancerous and healthy uterine tissues show that this sensitivity may allow to study the morphological changes in cell structures.

Feasibility studies of the polarization of photons beyond the optical wavelength regime with the J-PET detector

J-PET is a detector optimized for registration of photons from the electron-positron annihilation via plastic scintillators where photons interact predominantly via Compton scattering. Registration of both primary and scattered photons enables to determinate the linear polarization of the primary photon on the event by event basis with a certain probability. Here we present quantitative results on the feasibility of such polarization measurements of photons from the decay of positronium with the J-PET and explore the physical limitations for the resolution of the polarization determination of 511 keV photons via Compton scattering. For scattering angles of about 82∘ (where the best contrast for polarization measurement is theoretically predicted) we find that the single event resolution for the determination of the polarization is about 40∘ (predominantly due to properties of the Compton effect). However, for samples larger than ten thousand events the J-PET is capable of determining relative average polarization of these photons with the precision of about few degrees. The obtained results open new perspectives for studies of various physics phenomena such as quantum entanglement and tests of discrete symmetries in decays of positronium and extend the energy range of polarization measurements by five orders of magnitude beyond the optical wavelength regime.

Isotensor Dibaryon in the pp→ppπ^{+}π^{-} Reaction?

Exclusive measurements of the quasifree pp→ppπ^{+}π^{-} reaction have been carried out at WASA@COSY by means of pd collisions at T_{p}=1.2  GeV. Total and differential cross sections have been extracted covering the energy region T_{p}=1.08-1.36  GeV, which is the region of N^{*}(1440) and Δ(1232)Δ(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor ΔN dibaryon resonance with I(J^{P})=2(1^{+}) produced associatedly with a pion is able to overcome these deficiencies.

Spin Dependence of η Meson Production in Proton-Proton Collisions Close to Threshold

Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high polarization degree of the proton beam of COSY, the reaction p[over →]p→ppη has been measured close to threshold to explore the analyzing power A_{y}. The angular distribution of A_{y} is determined with the precision improved by more than 1 order of magnitude with respect to previous results, allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q=15  MeV, signaling s-wave production with no evidence for higher partial waves. At Q=72  MeV the data reveal strong interference of Ps and Pp partial waves and cancellation of (Pp)^{2} and Ss^{*}Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the η meson.

Time resolution of the plastic scintillator strips with matrix photomultiplier readout for J-PET tomograph

Recent tests of a single module of the Jagiellonian Positron Emission Tomography system (J-PET) consisting of 30 cm long plastic scintillator strips have proven its applicability for the detection of annihilation quanta (0.511 MeV) with a coincidence resolving time (CRT) of 0.266 ns. The achieved resolution is almost by a factor of two better with respect to the current TOF-PET detectors and it can still be improved since, as it is shown in this article, the intrinsic limit of time resolution for the determination of time of the interaction of 0.511 MeV gamma quanta in plastic scintillators is much lower. As the major point of the article, a method allowing to record timestamps of several photons, at two ends of the scintillator strip, by means of matrix of silicon photomultipliers (SiPM) is introduced. As a result of simulations, conducted with the number of SiPM varying from 4 to 42, it is shown that the improvement of timing resolution saturates with the growing number of photomultipliers, and that the [Formula: see text] configuration at two ends allowing to read twenty timestamps, constitutes an optimal solution. The conducted simulations accounted for the emission time distribution, photon transport and absorption inside the scintillator, as well as quantum efficiency and transit time spread of photosensors, and were checked based on the experimental results. Application of the [Formula: see text] matrix of SiPM allows for achieving the coincidence resolving time in positron emission tomography of [Formula: see text]0.170 ns for 15 cm axial field-of-view (AFOV) and [Formula: see text]0.365 ns for 100 cm AFOV. The results open perspectives for construction of a cost-effective TOF-PET scanner with significantly better TOF resolution and larger AFOV with respect to the current TOF-PET modalities.

A feasibility study of ortho-positronium decays measurement with the J-PET scanner based on plastic scintillators

We present a study of the application of the Jagiellonian positron emission tomograph (J-PET) for the registration of gamma quanta from decays of ortho-positronium (o-Ps). The J-PET is the first positron emission tomography scanner based on organic scintillators in contrast to all current PET scanners based on inorganic crystals. Monte Carlo simulations show that the J-PET as an axially symmetric and high acceptance scanner can be used as a multi-purpose detector well suited to pursue research including e.g. tests of discrete symmetries in decays of ortho-positronium in addition to the medical imaging. The gamma quanta originating from o-Ps decay interact in the plastic scintillators predominantly via the Compton effect, making the direct measurement of their energy impossible. Nevertheless, it is shown in this paper that the J-PET scanner will enable studies of the [Formula: see text] decays with angular and energy resolution equal to [Formula: see text] and [Formula: see text], respectively. An order of magnitude shorter decay time of signals from plastic scintillators with respect to the inorganic crystals results not only in better timing properties crucial for the reduction of physical and instrumental background, but also suppresses significantly the pile-ups, thus enabling compensation of the lower efficiency of the plastic scintillators by performing measurements with higher positron source activities.

The effect of 8 or 5 years of denosumab treatment in postmenopausal women with osteoporosis: results from the FREEDOM Extension study

The FREEDOM study and its Extension provide long-term information about the effects of denosumab for the treatment of postmenopausal osteoporosis. Treatment for up to 8 years was associated with persistent reduction of bone turnover, continued increases in bone mineral density, low fracture incidence, and a favorable benefit/risk profile.

INTRODUCTION

This study aims to report the results through year 5 of the FREEDOM Extension study, representing up to 8 years of continued denosumab treatment in postmenopausal women with osteoporosis.

METHODS

Women who completed the 3-year FREEDOM study were eligible to enter the 7-year open-label FREEDOM Extension in which all participants are scheduled to receive denosumab, since placebo assignment was discontinued for ethical reasons. A total of 4550 women enrolled in the Extension (2343 long-term; 2207 cross-over). In this analysis, women in the long-term and cross-over groups received denosumab for up to 8 and 5 years, respectively.

RESULTS

Throughout the Extension, sustained reduction of bone turnover markers (BTMs) was observed in both groups. In the long-term group, mean bone mineral density (BMD) continued to increase significantly at each time point measured, for cumulative 8-year gains of 18.4 and 8.3 % at the lumbar spine and total hip, respectively. In the cross-over group, mean BMD increased significantly from the Extension baseline for 5-year cumulative gains of 13.1 and 6.2 % at the lumbar spine and total hip, respectively. The yearly incidence of new vertebral and nonvertebral fractures remained low in both groups. The incidence of adverse and serious adverse events did not increase over time. Through Extension year 5, eight events of osteonecrosis of the jaw and two events of atypical femoral fracture were confirmed.

CONCLUSIONS

Denosumab treatment for up to 8 years was associated with persistent reductions of BTMs, continued BMD gains, low fracture incidence, and a consistent safety profile.

Determination of the η(')-proton scattering length in free space

Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation function for the pp→ppη(') reaction close to threshold. Combining these data with previous results, we extract the scattering length for the η(')-proton potential in free space to be Re(a(pη(')))=0±0.43  fm and Im(a(pη(')))=0.37(-0.16)(+0.40)  fm.

Abashian-Booth-Crowe effect in basic double-pionic fusion: a new resonance?

We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn→dπ(0)π(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the ππ-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ΔΔ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m=2.37  GeV, Γ≈70  MeV and I(J(P))=0(3(+)) in both pn and ΔΔ systems. Necessary further tests of the resonance interpretation are discussed.

Determination of the total width of the η' meson

Taking advantage of both the low-emittance proton beam of the cooler synchrotron COSY and the high momentum precision of the COSY-11 detector system, the mass distribution of the η' meson was measured with a resolution of 0.33  MeV/c2 (FWHM), improving the experimental mass resolution by almost an order of magnitude with respect to previous results. Based on the sample of more than 2300 reconstructed pp → ppη' events, the total width of the η' meson was determined to be Γ(η') = 0.226 ± 0.017(stat) ± 0.014(syst)  MeV/c2.

Mechanism of near-threshold production of the eta meson

Measurements of the analyzing power for the pp-->pp eta reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with zero, implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S11(1535) resonance is predominantly due to the exchange of the pi meson between the colliding nucleons.

Oral weekly ibandronate prevents bone loss in postmenopausal women

OBJECTIVES

To investigate the efficacy, safety, and dose-response of once-weekly oral ibandronate in the prevention of postmenopausal bone loss.

DESIGN

This was a multi-centre, placebo-controlled, double-blind, randomized, 24-month phase II/III dose-finding study.

SETTING

Primary care units in 14 osteoporosis centres.

SUBJECTS

A total of 630 women were stratified into four strata according to time since menopause (TSM, 1-3 vs. >3 years) and baseline bone mineral density (BMD; normal: T-score > or =1 vs. osteopenic: -2.5 < or = T-score < or = 1) of the lumbar spine.

INTERVENTIONS

Within each stratum women were further randomized to receive once-weekly ibandronate (5, 10, or 20 mg week-1) or placebo for 24 months.

MAIN OUTCOME MEASURES

Efficacy parameters were the relative changes from baseline in spine (L1-4) and hip BMD, and biochemical markers of bone turnover (serum and urinary C-telopeptide of collagen type I (CTx), osteocalcin, and alkaline phosphatase) measured by dual energy X-ray absorptiometry and enzyme immunoassays, respectively.

RESULTS

Once-weekly therapy with ibandronate induced dose-dependent increases in spine and hip BMD. At month 24, differences between the relative changes in spine and hip BMD induced by 20 mg ibandronate and placebo was 4.0 and 2.7%, respectively. Similar or more pronounced differences were seen in osteopenic women of TSM 1-3 years (5.3 and 3.5%) and of TSM >3 years (3.5 and 2.9%), respectively. A dose-dependent suppression of all biochemical markers of bone turnover was observed with significant decreases in the 20 mg dose groups of all strata at month 24. The overall safety results indicated that once-weekly oral ibandronate was well-tolerated at all three doses.

CONCLUSION

Once-weekly oral therapy with 20 mg ibandronate provides an effective and safe therapy for the prevention of postmenopausal bone loss.

[Causes and clinical picture of osteopenia and osteoporosis in children]

The causes and clinical picture of osteopenia and osteoporosis were analyzed in 13 children (7 girls and 6 boys aged 6-15 years of life, mean age 10.2 years). The diagnosis was based on X-ray and densitometric studies. Upper gastrointestinal tract diseases were noted in 7 patients (one child received additional anti-epileptic drugs) and 5 had juvenile osteoporosis. Children with Gl tract diseases and these on anti-epileptic management may develop osteoporosis and osteopenia as a consequence of vitamin D3 deficit and calcium malabsorption leading to hypocalcemia and secondary hyperparathyroidism.

Thromboembolic complications after total hip arthroplasty and prevention of thrombosis: own experience

Background. Total hip arthroplasty (THA) is today one of the most frequently performed major surgical operations in orthopedics. Although it is the standard method of treatment for advanced degenerative changes in the joint, the operation is accompanied by a high risk of thromboembolic complications. Material and methods. The present study is a retrospective analysis of two groups of THA patients. Group I consisted of 80 patients (average age 62) operated 1980-1983, for whom no prophylaxis was applied. In Group II, low molecular weight heparin (LMWH) was applied pre- and postoperatively. This group consisted of 94 patients (average age 63.5) operated in the year 1998. Thromboembolic complications were diagnosed on the basis of reported symptoms, physical examinations and additional tests (chest x-ray, EKG, gasometry). Results. In Group I there were 11 complications (13.75%), including 10 cases (91%) of deep venous thromboembolic disease of the lower extremities (DVT) and 1 case (9%) of pulmonary embolism (PE), while in Group II there were only 2 complications (2.1%), 1 DVT and 1 PE. The difference between groups was statistically significant. The risk factors for venous thromboembolic disease were analyzed. In both study groups, the predominant risk factors were prolonged duration of surgery and diabetes accompanied by venous insufficiency. Conclusions. The results of our analysis showed that the use of DVT prophylaxis with low-molecular heparin in the preoperative and postoperative period reduced the occurrence of thromboembolic complications.

Problems of revision hip arthroplasty in Poland and around the world

Background. Total hip arthroplasty (THA) is the most common surgical procedure in orthopedic surgery. The number of hip replacements per year is estimated at 150,000 in the US, 80,000 in Germany, and 40,000 in Great Britain. Given the population of Poland one would expect 30,000 per year.<br /> Material and methods. In order to find the actual number of hip prosthesis operations we sent a targeted questionnaire to every orthopedic center in Poland 9a total of 220), to every manufacturer supplying implants to the Polish market, and to the national Consultant for Orthopedics and Traumatology. Completed questionnaires were returned by 67 centers, i.e. 30,5%.<br /> Results. The data we obtained included 29,380 THA and 2,102 revision THA operations. Thus the number of revisions represents 10,0% (7,2% revision THA and 2,8% implant removal). Based on data from the questionnaires, information from the National Consultant, and numerous conversations with representatives of companies that manufacture prostheses, the number of operations can be estimated, with a fairly high margin of error, at ca. 12,000 annually.<br /> The number of revisions performed is described by the widely-used "rate of survival" of the implant. In highly specialized centers, such as the Centre for Hip Surgery in Wrightington, the rate of survival at 10 years is estimated at 100%; at 15 years, 98%; at 20 years, 93%. Optimistic data can also be found in the Swedish National Hip Arthroplasty Registry (138 centers, 138,830 implants). The 9-year survival rate is 94%, while after 16 years the rate is 84,1%. The survival rate for the Weller prosthesis has been calculated at 75% after 10 years. This poor outcome is the result of the size of the head (32 mm), which causes excessive wear on the polyethylene.<br /> Conclusions. The problems of revision hip arthroplasty are essentially the some around the world. Intensive research is still in progress on the pathogenesis of loosening, material (polyethylene) wear, the quality of cement, and new types of uncemented and cemented prostheses. More and more work is being done one surgical techniques, bone defect filling, and the application of various additional implants (rings, meshes). Revision hip arthroplasty with septic loosening continues to be a difficult problem.

Measurement of radial bone mineral density in patients after heart transplantation

Limited physical activity, steroidotherapy and immunosuppression are known risk factors for the development of osteoporosis. The purpose of our current work was to investigate whether patients after heart transplantation (Htx) have an increased incidence of osteoporosis. We compared bone mineral density (BMD) in 32 post-transplant patients with a reference group of 1548 healthy age-matched males. Measurement of BMD was carried out with a Dtx 100 Osteometer on the distal and ultradistal segment of the non-dominant radius. Our results revealed a decreased BMD in HTx patients ranging from 6.9 to 10% in the ultradistal (p = 0.0446) and from 0.4 to 3.5% in the distal segment (p = 0.0593).

[Radiologic diagnosis and densitometry of osteoporosis]

The principles of densitometric and radiological examination in diagnosing of osteoporosis are presented. Peripheral and whole body densitometers are described and their quality is assessed on basis of precision and accuracy of bone mineral density measurements (BMD). WHO criteria of diagnosis, which introduce clinical category of the basis of BMD (expressed in T-scores) are described as follows: normal-(T-score up to -1.0); osteopenia-(T-score below -1.0 but more than -2.5); osteoporosis-(T-score -2.5 or below); severe osteoporosis-(T-score below -2.5 and one or more fractures). Evaluation of osteoporotic changes on the spine, pelvis and hand radiographs are discussed. Quantitative and possible quantitative analysis of radiographs are described.

[Evaluation of mineral density in the distal radius during the course of rheumatoid arthritis]

Rheumatoid arthritis (RA) of progressive systemic disease predisposing for osteoporosis. Inflammatory process, applied treatment as well as considerably impared efficiency of motor organ create conditions for osteoporosis. The changes of bone mineral density in RA were assessed in 50 patients treated for various form of RA, at the Rheumatological and Rehabilitation Hospital in Cracow. The age of patients ranged from 21-79 yrs: the mean age was 50 years. The group consisted of 46 (92%) females and 4 (8%) males. Apart from standard clinical examinations there was assessed in all cases mineral density in distal radius using Osteometer DTX 100. Mineral density BMD was estimated in distal and ultradistal region of radius. All patients were qualified into 4 groups depending on the stage of radiological changes according to Steinbrocker. Group I included 16%, group II-30%, group III-30%, and IV-24% of patients. Steroid therapy was applied in 20 (40%) cases. The results showed progressive decrease of mineral density BMD in distal radius in patients with advanced RA. It was also observed that in RA patients mineral density defect occurs earlier in trabecular than in cortical bone.

[Densitometric evaluation of the distal radial epiphysis in patients after Colles fracture]

The results of bone mineral density measurements in both forearms of 50 patients aged from 51 to 83 yrs (av. 62.4) who sustained unilateral Colles fracture, were analysed. Time elapsed from fracture was from 0.5 to 6 yrs. The aim of this study was to assess the effect of previous Colles fracture on bone mineral density. It was found that after the preliminary increase of bone mineral density, there was a gradual decrease towards normal values as compared with the unbroken arm. The bone mineral density in the evaluated group with fracture was significantly lower than the control groups without fracture.

[Computer analysis of the radiographic image of bones and joints]

Various possibility of computerized analysis of radiographic image of bone and joint are presented. The principle of digital image recording and processing are described. Practical application of computer programs of bone structure analysis and measurement of joint width using image analysis procedure are presented.

[Evaluation of the prevalence of osteoporosis in a population of women living in Krakow based on densitometric measurements of the forearm]

Osteoporosis is considered a civilization disease, affecting populations living in big cities. It is detected in 10 percent of population and in 30 percent women over fifty. We tried to estimate prevalence of osteoporosis in people living in Kraków. For estimation purposes, 1000 people living in Kraków more than 40 years were chosen. 325 persons came to our Department for examination, 232 of which were women. All patient filled a special questionnaire on pathological changes in skeletal system and risk factor of osteoporosis. Densitometric measurements of nondominant forearm using Osteometer DTX 100 were performed in all patients. For osteoporosis criteria level of T-score less than -2.5 was taken. Because of lack of Polish reference data for densitometric measurements our data were compared to WHO data, concerning prevalence of osteoporosis in white women. Compared to WHO data, a higher frequency of osteoporosis was found in women living in Kraków more than 40 years.

[Evaluation of bone mineral density in the distal radius of former workers employed at the Aluminum Works]

Fluoride causes an increase in bone mass by stimulation of osteogenetic process. This effect is used in treatment of osteoporosis. Chronic exposure to fluoride in aluminium works can cause an industrial fluorosis, which is characterised by increased mineral content in bone tissue. It is well known that after cessation of fluoride is gradually eliminated from the bone. Probably this same process can exist in patients with osteoporosis after stopping of osteoporosis treatment, so we decided to estimate bone mineral density in former workers of aluminium works. For investigation a group of 169 of men in mean age of 50.0 years, all of whom had worked for at least five years (average 12.9 yrs) in Skawina aluminium works before their closure in 1981, was selected. The control group was 29 men in the same age not exposed for fluoride. In all patient bone densitometry in distal and ultradistal region were evaluated. Decreased bone mineral density was found in workers of aluminium workers, compared to the control group, particularly in age groups of 40-44 and 50-54 years. Differences were bigger in measurements of trabecular bone.

[Measurement of bone structure on the radiograph. Utopia or reality?]

A method of computerised analysis of bone structure assessment using a professional image analyser is described. Analyses of experimental radiographs of human radius taken over a period of time in a standard laboratory were performed. The radiographic technique was ascertained as the main source of a precision error. The reproducibility of the analysis using the method described was found to hold a limited range of error. The program Quantitrab makes possible a quantitative description of the bone structure parameters on the radiograph.

Malignant fibrous histiocytoma in the course of chronic osteomyelitis

Malignant fibrous histiocytoma (MFH) was found in the femur of a 28-year-old man who had suffered from chronic osteomyelitis. The patient had undergone surgery for a valgus knee deformity and the procedure was complicated by chronic osteomyelitis which lasted for 12 years. Four months after the onset of painful symptoms related to the occurrence of MFH, gross bone destruction with pathologic fracture and pulmonary metastases were present. The patient died 4 months later. Histopathological and immunohistochemical examinations indicated the diagnosis of MFH.

[Value of clinical examination and arthrography in diagnosis of meniscal lesions in light of arthroscopic results]

The results of clinical, arthrographic and arthroscopic examination in the group of 120 patients with suspected meniscal lesion have been compared. In the clinical examination the McMurray and the Apley tests revealed a good correlation with meniscal tears. Arthrography was found to be in accordance with arthroscopy in 62%. The results were falsely negative in 15% and falsely positive in 25% of patients respectively.