An improved optical flow tracking technique for real-time MR-guided beam therapies in moving organs

Magnetic resonance (MR) guided high intensity focused ultrasound and external beam radiotherapy interventions, which we shall refer to as beam therapies/interventions, are promising techniques for the non-invasive ablation of tumours in abdominal organs. However, therapeutic energy delivery in these areas becomes challenging due to the continuous displacement of the organs with respiration. Previous studies have addressed this problem by coupling high-framerate MR-imaging with a tracking technique based on the algorithm proposed by Horn and Schunck (H and S), which was chosen due to its fast convergence rate and highly parallelisable numerical scheme. Such characteristics were shown to be indispensable for the real-time guidance of beam therapies. In its original form, however, the algorithm is sensitive to local grey-level intensity variations not attributed to motion such as those that occur, for example, in the proximity of pulsating arteries.In this study, an improved motion estimation strategy which reduces the impact of such effects is proposed. Displacements are estimated through the minimisation of a variation of the H and S functional for which the quadratic data fidelity term was replaced with a term based on the linear L(1)norm, resulting in what we have called an L(2)-L(1) functional.The proposed method was tested in the livers and kidneys of two healthy volunteers under free-breathing conditions, on a data set comprising 3000 images equally divided between the volunteers. The results show that, compared to the existing approaches, our method demonstrates a greater robustness to local grey-level intensity variations introduced by arterial pulsations. Additionally, the computational time required by our implementation make it compatible with the work-flow of real-time MR-guided beam interventions.To the best of our knowledge this study was the first to analyse the behaviour of an L(1)-based optical flow functional in an applicative context: real-time MR-guidance of beam therapies in moving organs.

Clinical and audiological findings in children with acute otitis media

CONCLUSION

It is recommended to perform follow-up tympanometry and if necessary tonal audiometry in children who have normal plain otoscopy findings after recovering from acute otitis media (AOM). Children with Type B tympanogram, 3 months following the onset of AOM, are very likely to have a conductive hearing loss. Type B tympanogram is a much better indicator of effusion in the middle ear compared to plain otoscopy.

OBJECTIVE

This study was undertaken to investigate the frequency and duration of middle ear effusion in children following an episode of acute otitis media, to track changes in tonal audiometry and tympanometry findings in the post-AOM period, and recognize the optimal timing for performing both tests.

METHODS

In this study, 125 children aged 5-7 years with bilateral AOM were randomly selected and separately followed up for 3 months. The children underwent six ear, nose, and throat (ENT 1-6) examinations, six tympanometries (TM 1-6), and three tonal audiometries (TA 1-3). Evaluation of nasopharynx was done at the ENT 1 examination. Children who received ventilation tubes were followed for 21 month altogether.

RESULTS

At the first otoscopy, pathological findings were recorded in 250 ears/125 children (100.0%). The number of pathological otoscopy findings decreased at each subsequent examination. At ENT 6 all children had normal otoscopy findings. Type B tympanogram was detected in 49/250 (19.6%) ears at TM 6, performed 3 months following the onset of the disease. At the TA 1 conductive hearing impairment was recorded in 158/250 (63.2%) ears, at TA 2 in 66/250 (26.4%), and at TA 3 in 39/250 (15.6%). Most of them were associated with Type B tympanogram.

[Nora's Lesion: A Rare Differential Diagnosis for Benign Peripheral Bone Tumours]

We report on a bizarre parosteal osteochondromatous proliferation (BPOP), also known as Nora's lesion, in a 43-year-old female patient.

Nasopharyngeal bacterial flora in healthy preschool children during winter-spring months

The paper aimed to determine the incidence of colonization of Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae type b and Neisseria meningitidis in the nasopharynges of healthy children in two preschool institutions during winter and spring months, without using antimicrobial treatment or serotyping of these bacteria. In addition to colonization of the above bacteria, the research that continued for 3 months monitored the length of their persistence in and disappearance from children's nasopharynges, children's health statuses, and provision of adequate medical interventions in children demonstrating clinical signs of disease. The ultimate aim of the paper was based on contributing to clearer and more accurate determination of a medical procedure in case of a positive result for bacteria intended to be found in the nasopharynx of a healthy child who spends time in a preschool institution.

Bone and cartilage demonstrate changes localized to bone marrow edema-like lesions within osteoarthritic knees

OBJECTIVE

Our objective is to understand the biological and mechanical pathways linking cartilage, bone, and marrow changes in the progression of osteoarthritis (OA). The aim of the present study was to evaluate bone structure and composition within bone marrow edema-like lesion (BMEL) regions associated with knee OA.

METHODS

Tibial plateau specimens (n = 18) were collected from 10 subjects with knee OA during total knee arthroplasty (TKA). Magnetic resonance (MR) imaging was used to identify BMEL and quantify metrics of cartilage composition. Micro-computed tomography (μCT) and high-resolution peripheral quantitative computed tomography (HR-pQCT) were used to quantify density and microstructure of the subchondral trabecular bone. Fourier transform infrared (FTIR) spectroscopy was used to quantify tissue composition.

RESULTS

Trabecular bone within BMEL was higher in volume fraction, with more and thicker trabeculae that were more plate-like in structure compared to unaffected regions. BMEL trabecular tissue composition had decreased phosphate and carbonate content. Marrow infiltration by a fibrous collagen network and evidence of increased bone remodeling were present. Structural and compositional changes were specifically localized to regions underlying cartilage degradation.

CONCLUSION

These results support the paradigm of focal interactions among bone, marrow, and cartilage in the progression of knee OA. Quantitative evaluation of tissue changes and interactions may aid in the understanding of disease pathophysiology and provide imaging markers for disease progression.

Hidradenoma of the external auditory canal: clinical presentation and surgical treatment

The aim of this article is to present clinical features, diagnostic procedures and surgical treatment of a rare ear tumor. We report a case of 78 year old female with hidradenoma of the external auditory canal. Patient had a sensation of pain and fullness with permanent ottorhea from the right ear for one year Temporal bone computed tomography showed a tumor of the external ear, 6 centimeters in diameter, without bone, temporomandibular joint or intracranial invasion; the tumor was limited medially by the tympanic membrane. Biopsy was performed and pathohistology finding was: hydradenoma nodulare atypicum. Surgical intervention and wide tumor removal in general endotracheal anesthesia was performed. One year after the surgery there was no sign of tumor recurrence. Hidradenoma is rare ear tumor arising from the epithelial cells of sweat glands of the external auditory canal. Radiological evaluation and pathohistology confirmation of hidradenoma is necessary and wide excision of the tumor is the treatment of choice.

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation of liver tumours

Recent decades have seen a paradigm shift in the treatment of liver tumours from invasive surgical procedures to minimally invasive image-guided ablation techniques. Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a novel, completely non-invasive ablation technique that has the potential to change the field of liver tumour ablation. The image guidance, using MR imaging and MR temperature mapping, provides excellent planning images and real-time temperature information during the ablation procedure. However, before clinical implementation of MR-HIFU for liver tumour ablation is feasible, several organ-specific challenges have to be addressed. In this review we discuss the MR-HIFU ablation technique, the liver-specific challenges for MR-HIFU tumour ablation, and the proposed solutions for clinical translation.

Long-term functional outcomes after 10 years of bilateral cochlear implantat use

The aims were to determine the benefit of bilateral cochlear implantation in a 20 years old patient implanted in Croatia on hearing and speech development. The male patient, after 10 years of deafness, got cochlear implants Med-EL Combi 40+ on both sides in one-stage surgery. The etiology of his deafness was posttraumatic meningitis. Auditory capacity and speech recognition tests were performed for both ears separately and together Average hearing level on the right ear with right cochlear implant switched on started at 62 dB 1 month after the cochlear implantation and was on 55 dB after 10 years. Average hearing level on the left ear with left cochlear implant switched on started at 55 dB 1 month after the cochlear implantation and was on 32 dB after 10 years. Average hearing level on the both ears with 2 cochlear implants switched on started at 35 dB 1 month after the cochlear implantation and was on 27 dB after 10 years. Long-term functional outcomes with bilateral cochlear implantation provides advantages over unilateral implantation including improved hearing level, speech perception in noise and improved sound localization.

Towards optimized MR thermometry of the human heart at 3T

Catheter ablation using radio frequency (RF) has been used increasingly for the treatment of cardiac arrhythmias and may be combined with proton resonance frequency shift (PRFS) -based MR thermometry to determine the therapy endpoint. We evaluated the suitability of two different MR thermometry sequences (TFE and TFE-EPI) and three blood suppression techniques. Experiments were performed without heating, using an optimized imaging protocol including navigator respiratory compensation, cardiac triggering, and image processing for the compensation of motion and susceptibility artefacts. Blood suppression performance and its effect on temperature stability were evaluated in the ventricular septum of eight healthy volunteers using multislice double inversion recovery (MDIR), motion sensitized driven equilibrium (MSDE), and inflow saturation by saturation slabs (IS). It was shown that blood suppression during MR thermometry improves the contrast-to-noise ratio (CNR), the robustness of the applied motion correction algorithm as well as the temperature stability. A gradient echo sequence accelerated by an EPI readout and parallel imaging (SENSE) and using inflow saturation blood suppression was shown to achieve the best results. Temperature stabilities of 2 °C or better in the ventricular septum with a spatial resolution of 3.5 × 3.5 × 8mm(3) and a temporal resolution corresponding to the heart rate of the volunteer, were observed. Our results indicate that blood suppression improves the temperature stability when performing cardiac MR thermometry. The proposed MR thermometry protocol, which optimizes temperature stability in the ventricular septum, represents a step towards PRFS-based MR thermometry of the heart at 3 T.

Local tissue properties of human osteoarthritic cartilage correlate with magnetic resonance T(1) rho relaxation times

The objective of this study is to examine the local relationship between T(1ρ) relaxation times and the mechanical behavior of human osteoarthritic articular cartilage using high-resolution magnetic resonance imaging (MRI) and local in situ microindentation. Seven human tibial plateaus were obtained from patients who underwent total knee arthroplasty due to severe osteoarthritis (OA). Three to six sites were selected from each sample for visual classification using the ICRS Outerbridge scale (a total of 36 sites). Samples were imaged by MR, and the local distribution of T(1ρ) relaxation times were obtained at these selected sites. The elastic and viscoelastic characteristics of the tissue were quantified nondestructively using dynamic microindentation to measure peak dynamic modulus, energy dissipation, and phase angle. Measured Outerbridge scores, MR T(1ρ) relaxation times, and mechanical properties were highly heterogeneous across each cartilage surface. Site-specific measures of T(1ρ) relaxation times correlated significantly with the phase angle (p < 0.001; R = 0.908), a viscoelastic mechanical behavior of the cartilage. The novel combination of high-resolution MR imaging and microindentation allows the investigation of the local relationship between quantitative MRI and biomechanical properties in highly heterogeneous OA cartilage. These findings suggest that MRI T(1ρ) can provide a functional assessment of articular cartilage.

Enzyme replacement therapy with agalsidase alfa in patients with Fabry's disease: an analysis of registry data

BACKGROUND

We analysed 5-year treatment with agalsidase alfa enzyme replacement therapy in patients with Fabry's disease who were enrolled in the Fabry Outcome Survey observational database (FOS).

METHODS

Baseline and 5-year data were available for up to 181 adults (126 men) in FOS. Serial data for cardiac mass and function, renal function, pain, and quality of life were assessed. Safety and sensitivity analyses were done in patients with baseline and at least one relevant follow-up measurement during the 5 years (n=555 and n=475, respectively).

FINDINGS

In patients with baseline cardiac hypertrophy, treatment resulted in a sustained reduction in left ventricular mass (LVM) index after 5 years (from 71.4 [SD 22.5] g/m(2.7) to 64.1 [18.7] g/m(2.7), p=0.0111) and a significant increase in midwall fractional shortening (MFS) from 14.3% (2.3) to 16.0% (3.8) after 3 years (p=0.02). In patients without baseline hypertrophy, LVM index and MFS remained stable. Mean yearly fall in estimated glomerular filtration rate versus baseline after 5 years of enzyme replacement therapy was -3.17 mL/min per 1.73 m(2) for men and -0.89 mL/min per 1.73 m(2) for women. Average pain, measured by Brief Pain Inventory score, improved significantly, from 3.7 (2.3) at baseline to 2.5 (2.4) after 5 years (p=0.0023). Quality of life, measured by deviation scores from normal EuroQol values, improved significantly, from -0.24 (0.3) at baseline to -0.17 (0.3) after 5 years (p=0.0483). Findings were confirmed by sensitivity analysis. No unexpected safety concerns were identified.

INTERPRETATION

By comparison with historical natural history data for patients with Fabry's disease who were not treated with enzyme replacement therapy, long-term treatment with agalsidase alfa leads to substantial and sustained clinical benefits.

FUNDING

Shire Human Genetic Therapies AB.

Etiology of deafness in children cochlear implant candidates in Croatia

The aim of this study was to provide more information on the causes of sensorineural hearing loss (SNHL) in children cochlear implant candidates in Croatia. The retrospective study included 270 children candidates for cochlear implantation between January 1997 and January 2005 at our institution. The medical assessment of the candidates included the history, physical examination, radiologic evaluation of the temporal bone and audiologic assessment. A family history of SNHL had 82 (30.4%) candidates. The prematurity and/or complicated perinatal course was found in 35 (12.9%) of candidates. Computerized tomography (CT) scan analysis identified 44 (16.3%) candidates presenting with an inner ear malformation. Overall, a definite or probable cause of SNHL was identified in 58.9% of candidates and 41.1% had no obvious cause. The results of the study might give us better insight into the potential causes of SNHL and allow more timely intervention, allowing children with SNHL to reach their potential.

High-flexion, motion-guided total knee arthroplasty: who benefits the most?

A multicenter study was performed to determine which patients have the most potential to benefit from total knee arthroplasty (TKA) with a high-flexion, guided-motion design. In 201 consecutive TKAs, the mean gain in range of motion (ROM) was 14 degrees at 3 months and 24 degrees at 6 months. The gain in flexion was significant at 3 and 6 months postoperatively. No differences were found based on preoperative diagnosis, age, or sex. There was a poor correlation between body mass index and ROM. Pre- and postoperative flexion also displayed a weak correlation. Patients with the least preoperative flexion (<90 degrees) gained the most degrees of flexion (26 degrees). We conclude that the use of a high-flexion, guided-motion TKA allows a significant functional improvement in patients with preoperative stiffness and the preservation of good flexion in patients with normal preoperative flexion.

In vivo T(1rho) and T(2) mapping of articular cartilage in osteoarthritis of the knee using 3 T MRI

OBJECTIVE

Evaluation and treatment of patients with early stages of osteoarthritis (OA) is dependent upon an accurate assessment of the cartilage lesions. However, standard cartilage dedicated magnetic resonance (MR) techniques are inconclusive in quantifying early degenerative changes. The objective of this study was to determine the ability of MR T1rho (T(1rho)) and T(2) mapping to detect cartilage matrix degeneration between normal and early OA patients.

METHOD

Sixteen healthy volunteers (mean age 41.3) without clinical or radiological evidence of OA and 10 patients (mean age 55.9) with OA were scanned using a 3Tesla (3T) MR scanner. Cartilage volume and thickness, and T(1rho) and T(2) values were compared between normal and OA patients. The relationship between T(1rho) and T(2) values, and Kellgren-Lawrence scores based on plain radiographs and the cartilage lesion grading based on MR images were studied.

RESULTS

The average T(1rho) and T(2) values were significantly increased in OA patients compared with controls (52.04+/-2.97ms vs 45.53+/-3.28ms with P=0.0002 for T(1rho), and 39.63+/-2.69ms vs 34.74+/-2.48ms with P=0.001 for T(2)). Increased T(1rho) and T(2) values were correlated with increased severity in radiographic and MR grading of OA. T(1rho) has a larger range and higher effect size than T(2), 3.7 vs 3.0.

CONCLUSION

Our results suggest that both in vivo T(1rho) and T(2) relaxation times increase with the degree of cartilage degeneration. T(1rho) relaxation time may be a more sensitive indicator for early cartilage degeneration than T(2). The ability to detect early cartilage degeneration prior to morphologic changes may allow us to critically monitor the course of OA and injury progression, and to evaluate the success of treatment to patients with early stages of OA.

Myeloperoxidase predicts risk of vasculopathic events in hemizgygous males with Fabry disease

Fabry disease results in a global vasculopathy leading to early-onset stroke and renal and cardiac failure. We found that random myeloperoxidase in serum and plasma was significantly elevated in 73 consecutive male patients with Fabry disease. Random serum myeloperoxidase level in men predicted the risk of a Fabry vasculopathy-related event in subsequent years. Long-term enzyme replacement therapy did not reduce myeloperoxidase level or eliminate the risk of vasculopathic events.

PCA-based magnetic field modeling: application for on-line MR temperature monitoring

Magnetic Resonance (MR) temperature mapping can be used to monitor temperature changes during minimally invasive thermal therapies. However, MR-thermometry contains artefacts caused by phase errors induced by organ motion in inhomogeneous magnetic fields. This paper proposes a novel correction strategy based on a Principal Component Analysis (PCA) to estimate magnetic field perturbation assuming a linear magnetic field variation with organ displacement. The correction method described in this paper consists of two steps: a magnetic field perturbation model is computed in a learning step; subsequently, during the intervention, this model is used to reconstruct the magnetic field perturbation corresponding to the actual organ position which in turns allow computation of motion corrected thermal maps.

A review of ceramic bearing materials in total joint arthroplasty

Bearings made of ceramics have ultra-low wear properties that make them suitable for total hip arthroplasty (THA) and total knee arthroplasty (TKA). When compared to cobalt chrome (CoCr)-on-polyethylene (PE) articulations, ceramics offer drastic reductions in bearing wear rates. Lower wear rates result in fewer wear particles produced by the articulating surfaces. In theory, this should reduce the risk of periprosthetic osteolysis and premature implant loosening, thereby contributing to the longevity of total joints. In addition to ceramics, other alternative bearing couples, such as highly cross-linked PE (XLPE) and metal-on-metal also offer less wear than CoCr-on-PE articulations in total joint arthroplasty. Alumina and zirconia ceramics are familiar to orthopaedic surgeons since both materials have been used in total joints for several decades. While not new in Europe, alumina-on-alumina ceramic total hips have only recently become available for widespread use in the United States from various orthopaedic implant manufacturers. As the search for the ideal total joint bearing material continues, composite materials of existing ceramics, metal-on-ceramic articulations, and new ceramic technologies will offer more choices to the arthroplasty surgeon. The objective of this paper is to present an overview of material properties, clinical applications, evolution, and limitations of ceramic materials that are of interest to the arthroplasty surgeon.

Neuropathic and cerebrovascular correlates of hearing loss in Fabry disease

Fabry disease, OMIM 301500, is a progressive multisystem storage disorder due to the deficiency of alpha-galactosidase A (GALA). Neurological and vascular manifestations of this disorder with regard to hearing loss have not been analysed quantitatively in large cohorts. We conducted a retrospective cross sectional analysis of hearing loss in 109 male and female patients with Fabry disease who were referred to and seen at the Clinical Center of the National Institutes of Health, Bethesda, MD, USA on natural history and enzyme replacement study protocols. There were 85 males aged 6-58 years (mean 31 years, SD 13) and 24 females aged 22-72 years (mean 42 years, SD 12). All patients underwent a comprehensive audiological evaluation. In addition, cerebral white matter lesions, peripheral neuropathy, and kidney function were quantitatively assessed. HL(95), defined as a hearing threshold above the 95th percentile for age and gender matched normal controls, was present in 56% [95% CI (42.2-67.2)] of the males. Prevalence of HL(95) was lower in the group of patients with residual GALA enzyme activity compared with those without detectable activity (33% versus 63%) HL(95) was present in the low-, mid- and high-frequency ranges for all ages. Male patients with HL(95) had a higher microvascular cerebral white matter lesion load [1.4, interquartile range (IQR) 0-30.1 +/- versus 0, IQR 0-0], more pronounced cold perception deficit [19.4 +/- 5.5 versus 13.5 +/- 5.5 of just noticeable difference (JND) units] and lower kidney function [creatinine: 1.6 +/- 1.2 versus 0.77 +/- 0.2 mg/dl; blood urea nitrogen (BUN): 20.1 +/- 14.1 versus 10.3 +/- 3.28 mg/dl] than those without HL(95) (P < 0.001). Of the females, 38% had HL(95). There was no significant association with cold perception deficit, creatinine or BUN in the females. Word recognition and acoustic reflexes analyses suggested a predominant cochlear involvement. We conclude that hearing loss involving all frequency regions significantly contributes to morbidity in patients with Fabry disease. Our quantitative analysis suggests a correlation of neuropathic and vascular damage with hearing loss in the males. Residual GALA activity appears to have a protective effect against hearing loss.