Quantifying differences in femoral head and neck asphericity in CAM type femoroacetabular impingement and hip dysplasia versus controls using radial 3DCT imaging and volumetric segmentation.

OBJECTIVE: Femoroacetabular impingement (FAI) and hip dysplasia are the most common causes of groin pain originating from the hip joint. To date, there is controversy over cut-off values for the evaluation of abnormal femoral head-neck anatomy with significant overlap between the normal and abnormal hips. Our aim was to perform three-dimensional CT analysis of femoral head and bump anatomy to quantify common hip pathologies (FAI and hip dysplasia) vs controls. METHODS: Consecutive patients who underwent three-dimensional CT imaging for hip dysplasia or CAM type FAI were compared to asymptomatic controls. α angles on radial CT and 3D volumetric femoral head and bump segmentations were performed by two readers. Inter- and intrapatient comparisons were performed including interreader and receiver operating characteristic analyses. RESULTS: 25 FAI patients, 16 hip dysplasia patients and 38 controls were included. FAI and dysplasia patients exhibited higher α angles and higher bump-head volume ratios than the controls (p < 0.05). Larger bump volumes were found among FAI than dysplasia patients and contralateral hips of FAI patients were also different than the controls. α angle at 2 o'clock and bump to head ratio showed the highest area under the curve for patients vs controls. The interreader reliability was better for volumetric segmentation (intraclass correlation coefficient = 0.35-0.84) as compared to the α angles (intraclass correlation coefficient = 0.11-0.44). CONCLUSION: Patients with FAI and dysplasia exhibit different femoral head anatomy than asymptomatic controls. Volumetric segmentation of femoral head and bump is more reliable and better demonstrates the bilateral femoral head anatomy differences in hip patients vs controls. ADVANCES IN KNOWLEDGE: Utilizing information from 3D volumetric bump assessment in patients with FAI and dysplasia, the physicians may be able to more objectively and reliably evaluate the altered anatomy for better pre-surgical evaluation.

Cam-type femoroacetabular impingement-correlations between alpha angle versus volumetric measurements and surgical findings.

AIM: Determine correlations of 3DCT cam-type femoroacetabular impingement (FAI) measurements with surgical findings of labral tear and cartilage loss. METHODS: Digital search of symptomatic cam-type FAI from July 2013 to August 2016 yielded 43 patients. Two readers calculated volumes of femoral head, bump, and alpha angles on 3DCT images. Correlations between CT and surgical findings, inter-, and intra-reader reliabilities were assessed using Spearman rank correlation and intraclass correlation coefficients (ICC). RESULTS: Thirteen men and 14 women aged 37 ± 10 (mean ± SD) years were included. Most common clinical finding was positive flexion-adduction-internal rotation (70.4%). Twenty-seven labral tears and 20 cartilage defects were surgically detected. Significant correlations existed between femoral bump, head volumes, and extent of the labral tear (p = 0.008 and 0.003). No significant correlations were found between the alpha angles at 12 to 3 o'clock and the extent of labral tear (p = 0.2, 0.8, 0.9, and 0.09) or any measurement with the cartilage loss (p values for alpha 12 to 3, bump, and head volumes = 0.7, 0.3, 0.9, 0.9, 0.07, and 0.2). Inter- and intra-reader reliabilities were excellent to moderate for femoral head and bump volumes (ICC = 0.85, 0.52, and 0.8, 0.5) and moderate to poor for alpha angles (ICC = 0.48, 0.40, 0.05, 0.25 and 0.3, 0.24, 0.29, 0.49). CONCLUSION: Three dimensional volumetric measurements of cam-type FAI significantly correlate with the extent of intraoperative labral tears. Superior inter- and intra-reader reliability to that of alpha angles renders it a more clinically relevant measurement for quantifying cam morphology. KEY POINTS: • The 3DCT bump volume and femoral head volume showed significant correlations with the extent of labral tear (p values = 0.008 and 0.003). • No significant correlations were seen between alpha angles and the extent of labral tear (p values > 0.05). • Inter- and intra-reader reliability was excellent to moderate (ICC = 0.85 and 0.52, 0.8, and 0.5) for femoral head and bump volumes while inter- and intra-reader reliability was fair to poor (ICC = 0.48, 0.40, 0.05, 0.25 and 0.3, 0.24, 0.29, 0.49) for alpha angles.

3D CT segmentation of CAM type femoroacetabular impingement-reliability and relationship of CAM lesion with anthropomorphic features.

OBJECTIVE:: Evaluate feasibility and reliability of 3DCT semi-automatic segmentation and volumetrics of CAM lesions in femoroacetabular impingement and determine correlations with anthropometrics. METHODS:: A consecutive series of 43 patients with CAM type FAI underwent 3DCT. 20 males and 23 females (30 unilateral and 13 bilateral symptomatic hips) were included. 56 CAM lesions and femoral heads were segmented by two readers. Radial images were obtained for alpha angles. Pearson and ICC correlations were used for analysis. RESULTS:: In 43 patients (male: female = 1 : 1.15), mean ± SD of age, height, BMI were 36.6 ± 11.47 years, 1.72 ± 0.10 meters and 26.25 ± 4.31 kg m-². Femoral head and bumps were segmented in 4 min. Inter reader reliability was good to excellent for volumetrics and poor for alpha angles. Mean ± SD of CAM lesion and femoral head volumes were significantly larger (6.7 ± 2.5 cc3 and 62.9 ± 10.8 cc3) for males than females (p < 0.001) and these increased with increasing patient height (Pearson correlation and p-values = 0.45, 0.0006; 0.82, < 0.0001 respectively). CONCLUSION:: Volumetric analysis of CAM lesion shows better inter reader reliability than alpha angle measurements. CAM and femoral head volumes exhibit significant positive correlations with patient heights and male gender that may aid in pre-operative planning for femoroplasty. ADVANCES IN KNOWLEDGE:: Femoral head & CAM volumes are segmented three times faster than alpha angles with superior inter reader reliability than alpha angles. Femoral head & CAM volumes are significantly larger in males and positively correlate with patients' heights.

Remote acoustic sensing as a safety mechanism during exposure of metal implants to alternating magnetic fields.

Treatment of prosthetic joint infections often involves multiple surgeries and prolonged antibiotic administration, resulting in a significant burden to patients and the healthcare system. We are exploring a non-invasive method to eradicate biofilm on metal implants utilizing high-frequency alternating magnetic fields (AMF) which can achieve surface induction heating. Although proof-of-concept studies demonstrate the ability of AMF to eradicate biofilm in vitro, there is a legitimate safety concern related to the potential for thermal damage to surrounding tissues when considering heating implanted metal objects. The goal of this study was to explore the feasibility of detecting acoustic emissions associated with boiling at the interface between a metal implant and surrounding soft tissue as a wireless safety sensing mechanism. Acoustic emissions generated during in vitro and in vivo AMF exposures were captured with a hydrophone, and the relationship with surface temperature analyzed. The effect of AMF exposure power, surrounding media composition, implant location within the AMF transmitter, and implant geometry on acoustic detection during AMF therapy was also evaluated. Acoustic emissions were reliably identified in both tissue-mimicking phantom and mouse studies, and their onset coincided with the implant temperature reaching the boiling threshold. The viscosity of the surrounding medium did not impact the production of acoustic emissions; however, emissions were not present when the medium was oil due to the higher boiling point. Results of simulations and in vivo studies suggest that short-duration, high-power AMF exposures combined with acoustic sensing can be used to minimize the amount of thermal damage in surrounding tissues. These studies support the hypothesis that detection of boiling associated acoustic emissions at a metal/tissue interface could serve as a real-time, wireless safety indicator during AMF treatment of biofilm on metallic implants.

Correcting B0 Field Distortions in MRI Caused by Stainless Steel Orthodontic Appliances at 1.5 T Using Permanent Magnets - A Head Phantom Study.

Susceptibility artifacts caused by stainless steel orthodontic appliances (braces) pose significant challenges in clinical brain MRI examinations. We introduced field correction device (FCD) utilizing permanent magnets to cancel the induced B0 inhomogeneity and mitigate geometric distortions in MRI. We evaluated a prototype FCD using a 3D-printed head phantom in this proof of concept study. The phantom was compartmented into anterior frontal lobe, temporal lobe, fronto-parieto-occipital lobe, basal ganglia and thalami, brain stem, and cerebellum and had built-in orthogonal gridlines to facilitate the quantification of geometric distortions and volume obliterations. Stainless steel braces were mounted on dental models of three different sizes with total induced magnetic moment 0.15 to 0.17 A·m2. With braces B0 standard deviation (SD) ranged from 2.8 to 3.7 ppm in the temporal and anterior frontal lobes vs. 0.2 to 0.3 ppm without braces. The volume of brain regions in diffusion weighted imaging was obliterated by 32-38% with braces vs. 0% without braces in the cerebellum. With the FCD the SD of B0 ranged from 0.3 to 1.2 ppm, and obliterated volume ranged from 0 to 6% in the corresponding brain areas. These results showed that FCD can effectively decrease susceptibility artifacts from orthodontic appliances.

Development of a Patient-specific Tumor Mold Using Magnetic Resonance Imaging and 3-Dimensional Printing Technology for Targeted Tissue Procurement and Radiomics Analysis of Renal Masses.

OBJECTIVE: To implement a platform for colocalization of in vivo quantitative multiparametric magnetic resonance imaging features with ex vivo surgical specimens of patients with renal masses using patient-specific 3-dimensional (3D)-printed tumor molds, which may aid in targeted tissue procurement and radiomics and radiogenomic analyses. MATERIALS AND METHODS: Volumetric segmentation of 6 renal masses was performed with 3D Slicer (http://www.slicer.org) to create a 3D tumor model. A slicing guide template was created with specialized software, which included notches corresponding to the anatomic locations of the magnetic resonance images. The tumor model was subtracted from the slicing guide to create a depression in the slicing guide corresponding to the exact size and shape of the tumor. A customized, tumor-specific, slicing guide was then printed using a 3D printer. After partial nephrectomy, the surgical specimen was bivalved through the preselected magnetic resonance imaging (MRI) plane. A thick slab of the tumor was obtained, fixed, and processed as a whole-mount slide and was correlated to multiparametric MRI findings. RESULTS: All patients successfully underwent partial nephrectomy and adequate fitting of the tumor specimens within the 3D mold was achieved in all tumors. Distinct in vivo MRI features corresponded to unique pathologic characteristics in the same tumor. The average cost of printing each mold was US$160.7 ± 111.1 (range: US$20.9-$350.7). CONCLUSION: MRI-based preoperative 3D printing of tumor-specific molds allow for accurate sectioning of the tumor after surgical resection and colocalization of in vivo imaging features with tissue-based analysis in radiomics and radiogenomic studies.

Employing high-frequency alternating magnetic fields for the non-invasive treatment of prosthetic joint infections.

Treatment of prosthetic joint infection (PJI) usually requires surgical replacement of the infected joint and weeks of antibiotic therapy, due to the formation of biofilm. We introduce a non-invasive method for thermal destruction of biofilm on metallic implants using high-frequency (>100 kHz) alternating magnetic fields (AMF). In vitro investigations demonstrate a >5-log reduction in bacterial counts after 5 minutes of AMF exposure. Confocal and scanning electron microscopy confirm removal of biofilm matrix components within 1 minute of AMF exposure, and combination studies of antibiotics and AMF demonstrate a 5-log increase in the sensitivity of Pseudomonas aeruginosa to ciprofloxacin. Finite element analysis (FEA) simulations demonstrate that intermittent AMF exposures can achieve uniform surface heating of a prosthetic knee joint. In vivo studies confirm thermal damage is confined to a localized region (<2 mm) around the implant, and safety can be achieved using acoustic monitoring for the presence of surface boiling. These initial studies support the hypothesis that AMF exposures can eradicate biofilm on metal implants, and may enhance the effectiveness of conventional antibiotics.

Improved Magnetic Resonance Imaging-Pathology Correlation With Imaging-Derived, 3D-Printed, Patient-Specific Whole-Mount Molds of the Prostate.

OBJECTIVES: The aim of this study was to compare the anatomical registration of preoperative magnetic resonance imaging (MRI) and prostate whole-mount obtained with 3D-printed, patient-specific, MRI-derived molds (PSM) versus conventional whole-mount sectioning (WMS). MATERIALS AND METHODS: Based on an a priori power analysis, this institutional review board-approved study prospectively included 50 consecutive men who underwent 3 T multiparametric prostate MRI followed by radical prostatectomy. Two blinded and independent readers (R1 and R2) outlined the contours of the prostate, tumor, peripheral, and transition zones in the MRI scans using regions of interest. These were compared with the corresponding regions of interest from the whole-mounted histopathology, the reference standard, using PSM whole-mount results obtained in the study group (n = 25) or conventional WMS in the control group (n = 25). The spatial overlap across the MRI and histology data sets was calculated using the Dice similarity coefficient (DSC) for the prostate overall (DSCprostate), tumor (DSCtumor), peripheral (DSCPZ), and transition (DSCTZ) zone. Results in the study and control groups were compared using Wilcoxon rank sum test. RESULTS: The MRI histopathology anatomical registration for the prostate gland overall, tumor, peripheral, and transition zones were significantly superior with the use of PSMs (DSCs for R1: 0.95, 0.86, 0.84, and 0.89; for R2: 0.93, 0.75, 0.78, and 0.85, respectively) than with the use of standard WMS (R1: 0.85, 0.46, 0.66, and 0.69; R2: 0.85, 0.46, 0.66, and 0.69) (P < 0.0001). CONCLUSIONS: The use of PSMs for prostate specimen whole-mount sectioning provides significantly superior anatomical registration of in vivo multiparametric MRI and ex vivo prostate whole-mounts than conventional WMS.

Three-dimensional printing for preoperative planning of total hip arthroplasty revision: case report.

Three dimensional (3D) printing can be used to create material models to aid preoperative planning of complex orthopedic procedures as exemplified by this case of total hip arthroplasty failure due to infection with resulting severe acetabular bone stock deficiency. The 3D model allowed for trialing of the acetabular component to determine cup size, position, and screw placement. Most importantly, the model confirmed that there was not a pelvic discontinuity and the revision shell would be sufficient for the reconstruction. Previously, the cost and complexity of utilization of 3D printers were prohibitive. Recent improvements in commercially available 3D printers have made rapid prototype model creation a realistic option, which can facilitate difficult surgery.

Localised hyperthermia in rodent models using an MRI-compatible high-intensity focused ultrasound system.

PURPOSE: Localised hyperthermia in rodent studies is challenging due to the small target size. This study describes the development and characterisation of an MRI-compatible high-intensity focused ultrasound (HIFU) system to perform localised mild hyperthermia treatments in rodent models. MATERIAL AND METHODS: The hyperthermia platform consisted of an MRI-compatible small animal HIFU system, focused transducers with sector-vortex lenses, a custom-made receive coil, and means to maintain systemic temperatures of rodents. The system was integrated into a 3T MR imager. Control software was developed to acquire images, process temperature maps, and adjust output power using a proportional-integral-derivative feedback control algorithm. Hyperthermia exposures were performed in tissue-mimicking phantoms and in a rodent model (n = 9). During heating, an ROI was assigned in the heated region for temperature control and the target temperature was 42 °C; 30 min mild hyperthermia treatment followed by a 10-min cooling procedure was performed on each animal. RESULTS: 3D-printed sector-vortex lenses were successful at creating annular focal regions which enables customisation of the heating volume. Localised mild hyperthermia performed in rats produced a mean ROI temperature of 42.1 ± 0.3 °C. The T10 and T90 percentiles were 43.2 ± 0.4 °C and 41.0 ± 0.3 °C, respectively. For a 30-min treatment, the mean time duration between 41-45 °C was 31.1 min within the ROI. CONCLUSIONS: The MRI-compatible HIFU system was successfully adapted to perform localised mild hyperthermia treatment in rodent models. A target temperature of 42 °C was well-maintained in a rat thigh model for 30 min.