Cadaveric Phantom Research Articles

Impact of computed tomography metal artifact reduction protocol on periprosthetic tissue characterization after total hip arthroplasty:A cadaveric study.

Metal artifact reduction (MAR) has improved computed tomography (CT) imaging of total hip arthroplasty (THA) but the assessment of osteolysis and implant to bone contact relies on the accurate depiction of bone defects, cancellous bone, and cement. This study evaluates the impact of available single and dual-energy protocols on periprosthetic tissue characterization in a cadaveric phantom. Bilateral THA was performed on a fresh frozen cadaveric pelvis with simulated osteolytic cavities. CT acquisitions with projection-basedMAR and noise equivalence were performed using single energy 140 kVp, single energy 150 kVp with 0.6 mm tin filtration, and dual-energy at 100/150 kVp with 0.6 mm tin filtration, from which simulated energies were extracted. Image subtraction, segmentation, region of interest histograms, and line profiles were used to characterize tissue density and separation. Tissue densities were heavily dependent on the energy profile of the protocol. Cancellous bone ranged from 182to 45 HU and cement from 1012to 131 HU using 140 kVp compared to dual-energy with weighted high energy tube, respectively. Spectral separation between cancellous bone, osteolytic defect, and cement was reduced for all protocols compared with 140 kVp. Spectral overlap was most severe using dual-energy with heavily weighted high-energy tubes. Dual-energy algorithms reduced trabecular contrast within the cancellous bone and cortical edge response. Althoughthe dual-energy acquisition has been proposed as an additive to projection-based MAR techniques in THA, reduced density and contrast in clinically relevant periprosthetic tissue compared to 140 kVp single energy may limit its use in characterizing periprosthetic tissues.

Abstract No. : ABS0260: Comparison of phantom cadaver based simulations with blue phantom model for teaching ultrasound guided regional anaesthesia: a randomised controlled trial

Background and Aims:Various methods of simulation have different advantages and disadvantages.This study was aimed to compare the block performance of novice post-graduate students of anaesthesiology after teaching them ultrasound guided regional anaesthesia on blue phantom model or cadaver-based phantom model.Methods:This study was conducted in the Department of Anaesthesiology and Critical Care and Department of Anatomy at a tertiary medical college hospital.Video lecture on ultrasound knobology and transducer movement was given to all study participants. In group BP, participants trained on blue phantom model. In group CP, participants trained on fresh human cadaver model. After training, participants were shown video of supraclavicular brachial plexus block,and finally performance was assessed on patients.Results:The median block performance time was 525.0 seconds in group BP with an interquartile(IQR) of (494-552.5) and 440.0 seconds in group CP with an IQR of (419.5-487.5)(table 1).Table 1Block performance time between the groupsGroup BP (n=25) Median (interquartile range)Group CP (n=25) Median (interquartile range) P Block performance time (in sec)525.0 (494-552.5)440.0 (419.5-487.5)<0.001This difference was statistically significant (p<0.001). The median image quality score was 3.0 in group BP with an IQR of 2-3, and it was also 3.0 in group CP with an IQR of 3-4, and it was statistically significant (p = 0.00398) (table 2).Table 2Ultrasonographic image quality in the two groupsImage quality scoreGroup BP (n=25) n (%)Group CP (n=25) n (%)Unsatisfactory00Poor7 (28)0Satisfactory15 (60)14 (56)Outstanding3 (12)11 (44)Conclusion:Time taken to perform brachial plexus block was less in the cadaver phantom group compared to the blue phantom group. The image quality scores and number of attempts required to perform brachial plexus block were statistically significant between groups. Novices trained on cadavers had better transducer target orientation and were able to identify ultrasonographic artifacts better than those trained on the blue phantom.

A 5 nW Quasi-Linear CMOS Hot-Electron Injector for Self-Powered Monitoring of Biomechanical Strain Variations

Piezoelectricity-driven hot-electron injectors (p-HEI) are used for self-powered monitoring of mechanical activity in biomechanical implants and structures. Previously reported p-HEI devices operate by harvesting energy from a piezoelectric transducer to generate current and voltage references which are then used for initiating and controlling the process of hot-electron injection. As a result, the minimum energy required to activate the device is limited by the power requirements of the reference circuits. In this paper we present a p-HEI device that operates by directly exploiting the self-limiting capability of an energy transducer when driving the process of hot-electron injection in a pMOS floating-gate transistor. As a result, the p-HEI device can activate itself at input power levels less than 5 nW. Using a prototype fabricated in a 0.5-μm bulk CMOS process we validate the functionality of the proposed injector and show that for a fixed input power, its dynamics is quasi-linear with respect to time. The paper also presents measurement results using a cadaver phantom where the fabricated p-HEI device has been integrated with a piezoelectric transducer and is used for self-powered monitoring of mechanical activity.

Efficient implementation of the rank correlation merit function for 2D/3D registration

A growing number of clinical applications using 2D/3D registration have been presented recently. Usually, a digitally reconstructed radiograph is compared iteratively to an x-ray image of the known projection geometry until a match is achieved, thus providing six degrees of freedom of rigid motion which can be used for patient setup in image-guided radiation therapy or computer-assisted interventions. Recently, stochastic rank correlation, a merit function based on Spearman's rank correlation coefficient, was presented as a merit function especially suitable for 2D/3D registration. The advantage of this measure is its robustness against variations in image histogram content and its wide convergence range. The considerable computational expense of computing an ordered rank list is avoided here by comparing randomly chosen subsets of the DRR and reference x-ray. In this work, we show that it is possible to omit the sorting step and to compute the rank correlation coefficient of the full image content as fast as conventional merit functions. Our evaluation of a well-calibrated cadaver phantom also confirms that rank correlation-type merit functions give the most accurate results if large differences in the histogram content for the DRR and the x-ray image are present.

Impact of image noise levels, scout scan dose and lens shield on image quality and radiation exposure in z-axis dose-modulated neck MSCT on 16- and 64-slice Toshiba Aquilion scanners

Objective Assessing the impact of image noise (IN) levels, scout scan dose and lens shield use on image quality and radiation exposure in neck multislice CT (MSCT) when using z-axis dose modulation (DM). Methods Neck MSCT phantom studies with/without z-axis DM were performed by using different IN levels (S.D. 7.5–30 HU) and scout scan tube currents (7.5–50 mA) on Toshiba Aquilion scanners (16-/64-slice). Image quality indices were evaluated by two radiologists and radiation exposure parameters calculated. Cadaveric phantom measurements elucidated lens shield interactions with DM efficacy. The lowest dose scan protocol with diagnostic image quality was introduced into the clinical imaging routine and retrospectively evaluated in 20 age-matched patients undergoing neck MSCT with/without DM. Results The highest image noise level in DM neck studies with comparable image quality to standard neck CT amounted to 20 HU, resulting in a mean tube current of 50 mAs (CTDI w 6.3 mGy). DM reduced effective dose by 35% and organ dose figures (lens, thyroid) by 33%. Scout scan dose lowering to 20 mA resulted in an effective dose (ED) decrease of 0.06 mSv (5%). Avoiding lens shield placement during scout scan effected an organ dose decrease of 20%. Overall contour sharpness and image contrast did not differ significantly (DM/without DM) whereas image noise was rated higher in DM neck CT studies ( p < 0.05). Conclusions z-Axis dose modulation, as assessed on 16- and 64-slice Toshiba Aquilion scanners, is effective and mandatory in neck MSCT. DM efficacy can be enhanced by optimising scout scan doses and lens shield use.

Dose related, comparative evaluation of a novel bone-subtraction algorithm in 64-row cervico-cranial CT angiography

Purpose Comparative evaluation of a low-dose scan protocol for a novel bone-subtraction (BS) algorithm, applicable to 64-row cervico-cranial (cc) CT angiography (MSCTA). Methods and patients BS algorithm assessment was performed in cadaveric phantom studies by stepwise variation of tube current and head malrotation using a 64-row CT scanner. In order to define minimum dose requirements and the rotation correction capacity, a low dose BS MSCTA protocol was defined and evaluated in 12 patients in comparison to a common manual bone removal algorithm. Standard MIPs of both modalities were evaluated in a blinded manner by two neuroradiologists for image quality composed, of vessel contour sharpness and bony vessel superposition, by using a five-point score each. Effective Dose (E) and data post-processing times were defined. Results In experimental studies prescan tube current could be cut down to one-sixth of post-contrast scan doses without compromise of bone-subtraction whereas incomplete subtraction appeared from four degrees head malrotation on. Prescan E amounted to additional 1.1 mSv (+25%) in clinical studies. BS MSCTA performed significantly superior in terms of bony superposition for vascular segments C3–C7 ( p < 0.001), V1–V2, V3–V4 ( p < 0.05, p < 0.001 respectively) and the ophthalmic artery ( p < 0.05), whereas vessel contour sharpness in BS MSCTA only proved superior for arterial segments V3–V4 ( p < 0.001) and C3–C7 ( p < 0.001). MBR MSCTA received higher ratings in vessel contour sharpness for C1–C2 ( p < 0.001), callosomarginal artery ( p < 0.001), M1, M2, M3 ( p < 0.001 each) and the basilar artery ( p < 0.001). Reconstruction times amounted to an average of 1.5 (BS MSCTA) and 3 min (MBR MSCTA) respectively. Conclusion The novel BS algorithm provides superior skull base artery visualisation as compared to common manual bone removal algorithms, increasing the Effective Dose by one-fourth. Yet, inferior vessel contour sharpness was noted intracranially, thus limiting the BS algorithm use to patients with suspected vessel pathology at the skull base level.

Noninvasive Optical Tracking of Red Fluorescent Protein-Expressing Cancer Cells in a Model of Metastatic Breast Cancer

We have evaluated the use of the Xenogen IVIS 200 imaging system for real-time fluorescence protein- based optical imaging of metastatic progression in live animals. We found that green fluorescent protein- expressing cells (100 × 106) were not detectable in a mouse cadaver phantom experiment. However, a 10-fold lower number of tdTomato-expressing cells were easily detected. Mammary fat pad xenografts of stable MDA-MB-231-tdTomato cells were generated for the imaging of metastatic progression. At 2 weeks postinjection, barely palpable tumor burdens were easily detected at the sites of injection. At 8 weeks, a small contralateral mammary fat pad metastasis was imaged and, by 13 weeks, metastases to lymph nodes were detectable. Metastases with nodular composition were detectable within the rib cage region at 15 weeks. 3-D image reconstructions indicated that the detection of fluorescence extended to approximately 1 cm below the surface. A combination of intense tdTomato fluorescence, imaging at ≥ 620 nm (where autofluorescence is minimized), the sensitivity of the Xenogen imager made this possible. This study demonstrates the utility of the noninvasive optical tracking of cancer cells during metastatic progression with endogenously expressed fluorescence protein reporters using detection wavelengths of ≥ 620 nm.

Invited Commentary to: 'Virtual Dissection and Automated Polyp Detection of the Colon Based on Spiral CT - Techniques and Prelim inary Experience on a Cadaveric Phantom' (Eur. Surg. 2002;34:143 - 149)

Invited Commentary to: 'Virtual Dissection and Automated Polyp Detection of the Colon Based on Spiral CT - Techniques and Prelim inary Experience on a Cadaveric Phantom' (Eur. Surg. 2002;34:143 - 149)

Invited Commentary to: 'Virtual Dissection and Automated Polyp Detection of the Colon Based on Spiral CT - Techniques and Preliminary Experience on a Cadaveric Phantom' (Eur. Surg. 2002;34:143 - 149)

Invited Commentary to: 'Virtual Dissection and Automated Polyp Detection of the Colon Based on Spiral CT - Techniques and Preliminary Experience on a Cadaveric Phantom' (Eur. Surg. 2002;34:143 - 149)

Virtual Dissection and Automated Polyp Detection of the Colon Based on Spiral CT - Techniques and Preliminary Experience on a Cadaveric Phantom

Background: CT colonography was found to be sensitive and specific for detection of colonic polyps and colorectal cancer (CRC). Depending on the software used, CT colonography requires a certain amount of operator interaction, which limits it’s widespread usage. The goal of this papers is to present two novel automated techniques for displaying CT colonography: virtual dissection and automated colonic polyp detection.

Virtual endoscopy of the tympanic cavity based on high-resolution multislice computed tomographic data.

This study was designed to assess the value of high-resolution multislice computed tomography (MSCT) data of the petrous bone for the virtual endoscopic visualization of the tympanic cavity. The recently introduced MSCT technology has improved spatial resolution in the z axis as well as scan speed in computed tomography. Three-dimensional rendering of high-resolution MSCT data of the petrous bone may be expected to provide endoluminal views of superior image quality, thus competing with transtympanic endoscopy (otoendoscopy). This study was conducted at a university teaching hospital. Cadaveric phantom studies in a MSCT scanner were performed to define a data acquisition protocol, combining adequate detail resolution with low tube current. Subsequently, the cadaveric phantom underwent otoendoscopy. The postprocessing parameters of the three-dimensional rendering protocol were chosen to produce views closely resembling the corresponding otoendoscopic images. High-resolution data from 18 patients with pathologic conditions of the middle ear, as suggested by clinical findings and assessment of cross-sectional data, were postprocessed using the volume rendering technique to generate standardized virtual endoscopic views. A total of 36 virtual endoscopic scans of the tympanic cavity were generated. With regard to intermediate and high-density structures, virtual endoscopic images, based on MSCT data, yielded endoluminal views closely resembling corresponding otoendoscopic views. Virtual endoscopy seems useful for imaging ossicular pathologic conditions such as dysplasia and chain disruption as well as for assessing patient status before and after otosurgery. MSCT data sets allow for generating virtual endoscopic views closely resembling otoendoscopic images. The technique is especially useful when ossicular pathologic changes are present as well as for preoperative and postoperative imaging of otologic procedures.

High-resolution petrous bone imaging using multi-slice computerized tomography.

Multi-slice computerized tomography (MSCT) is considered to provide superior image quality. We defined a data acquisition protocol for high-resolution (HR) temporal bone imaging using MSCT and assessed its impact on data acquisition and post-processing (PP). The data acquisition protocol was defined in cadaveric phantom studies performed by MSCT and subsequently applied to 38 patients referred for temporal bone assessment. The parameters image quality and diagnostic value of MSCT data were assessed for the cross-sectional source images as well as for 2-dimensional (2D) reformations and 3-dimensional (3D) reconstructions by 3 radiologists by comparison with incremental HR scans of 17 patients with suspected middle ear disorders. The data acquisition protocol yielded HR images with an excellent detail resolution and a comparable image quality of cross-sectional scans and related orthogonal reformations. MSCT achieved higher scores for image quality and diagnostic value (p < 0.001, t-test) than incremental HR CT with regard to both 2D and 3D reconstructions. MSCT improves the image quality of HR cross-sectional scans as well as that of 2D and 3D PP techniques in petrous bone imaging. The radiation exposure of the eye lenses is increased by MSCT as gantry angulation is not yet possible in the helical scan mode.

High-resolution Petrous Bone Imaging Using Multi-slice Computerized Tomography

Multi-slice computerized tomography (MSCT) is considered to provide superior image quality. We defined a data acquisition protocol for high-resolution (HR) temporal bone imaging using MSCT and assessed its impact on data acquisition and post-processing (PP). The data acquisition protocol was defined in cadaveric phantom studies performed by MSCT and subsequently applied to 38 patients referred for temporal bone assessment. The parameters image quality and diagnostic value of MSCT data were assessed for the cross-sectional source images as well as for 2-dimensional (2D) reformations and 3-dimensional (3D) reconstructions by 3 radiologists by comparison with incremental HR scans of 17 patients with suspected middle ear disorders. The data acquisition protocol yielded HR images with an excellent detail resolution and a comparable image quality of cross-sectional scans and related orthogonal reformations. MSCT achieved higher scores for image quality and diagnostic value (p < 0.001, t-test) than incremental HR CT with regard to both 2D and 3D reconstructions. MSCT improves the image quality of HR cross-sectional scans as well as that of 2D and 3D PP techniques in petrous bone imaging. The radiation exposure of the eye lenses is increased by MSCT as gantry angulation is not yet possible in the helical scan mode.

3D virtual endoscopy of the upper airway: optimization of the scan parameters in a cadaver phantom and clinical assessment.

Our goal was to evaluate the influence of the scan parameters on the 3D virtual endoscopy of the larynx and trachea and the clinical assessment. Helical CT (HiSpeed Advantage; GE, Milwaukee, WI, U.S.A.) of a cadaver phantom was performed with increased collimation (1-10 mm) and pitch (0.5-3). Seventy-two patients with complaints of the upper airways were investigated by virtual endoscopy and their results were compared with the findings of regular endoscopy. Best correlation between virtual endoscopy and anatomical findings, diagnostic quality of the axial slices, and useful longitudinal coverage of the examination were obtained with a collimation of 3 mm and a pitch of 1.5. Space-occupying tumors and stenosis were detected correctly, but the mucous membrane could not be visualized. 3D virtual endoscopy proved to be a valuable method for displaying anatomical structures. For an optimal protocol, a collimation of 3 mm with a pitch of 1.5 is recommended.

Reproducibility of lateral spine scans using dual energy X-ray absorptiometry.

Reproducibility of lateral spine dual energy X-ray absorptiometry (LAT DEXA) scans using a Lunar DPX-L scanner was assessed in a cadaveric phantom and in patients. One hundred phantom measurements over 7 months demonstrated a longitudinal stability of 1.7% (coefficient of variation, CV). Additional scans were performed with the phantom rotated by up to 20 degrees in each of the three orthogonal planes to assess the effects of variable patient positioning. Horizontal and vertical rotation of the spine had little effect on the estimated bone mineral density (BMD), however, axial rotation of greater than 8 degrees led to errors in the BMD measurement. One hundred consecutive patients had two lateral scans performed within 1 month. BMD (range 0.10-1.6 g/cm2) was determined for each scan by one operator. Significant overlap from ribs and pelvis was often seen with L2 and L4 vertebrae but one vertebra (L3) could be measured in every case. Intraoperator and interoperator variability was assessed by three experienced operators, each analyzing 10 patients' scans on five separate occasions, and was found to be less than 1.1% for a single vertebra. BMD estimation of vertebral bodies and midslices by lateral DEXA scans (CV% of 3.8% and 4.6%) have a 95% confidence interval of 0.074 g/cm2 and 0.096 g/cm2, respectively for two vertebrae. This variability is due mainly to axial rotation, with operator variability, horizontal rotation, and vertical rotation having little effect on BMD estimation.