Development of a focal lesion phantom with clinically relevant lesion characteristics for image quality evaluation of breast ultrasound scanners.

PURPOSE: Contrast-detail (C-D) and anechoic-target (A-T) detectability are measures of an ultrasound scanner's ability to image lesions of varying contrast and size from background tissue and, as such, they are important tools for grading the imaging capabilities of ultrasound scanners. The objective of this study was to develop a range of contrast- and anechoic-detail phantoms with clinically relevant lesions, of various contrast and sizes, for performance testing of breast ultrasound equipment. METHODS: Tissue mimicking materials that represent the acoustic properties of breast fibroglandular tissue were produced and moulded to construct a range of C-D and A-T phantoms. Two phantom designs were produced, containing cylindrical and spherical targets. Both phantom types were constructed with contrast targets covering the range anechoic, -1, -2, -3 and -4 dB, with lesion diameters of 1-4 mm, positioned at four clinically relevant depths (10, 25, 40 and 55 mm). An image analysis program was developed to objectively analyse the lesion images and to determine the lesion-signal-noise-ratio (LSNR). RESULTS: Both phantoms were used to evaluate the performance of a breast ultrasound scanner. The use of cylindrical phantoms led to an artificially higher image quality performance compared with the more clinically relevant spherical lesion phantom, thus indicating the importance of using the appropriate targets in ultrasound phantoms. CONCLUSION: The spherical lesion phantoms, coupled with the quantitative metric of LSNR, provides a comprehensive approach for performance and quality control testing, as well as the evaluation of advanced ultrasound imaging modes and technologies.

Rotational laxity greater in patients with contralateral anterior cruciate ligament injury than healthy volunteers.

Rotational stability of the knee has been traditionally difficult to quantify, limiting the ability of the orthopedic community to determine the potential role of rotational laxity in the etiology of anterior cruciate ligament (ACL) injuries. The purposes of this multicenter cohort study were to evaluate the reliability of a robotic axial rotation measurement system, determine whether the uninjured knees of patients that had previous contralateral ACL reconstruction demonstrated different rotational biomechanical characteristics than a group of healthy volunteers, and determine whether knee rotational biomechanical characteristics differ between male and female non-injured limbs in groups of both healthy volunteers and patients with a previous contralateral ACL injury. Fourteen healthy volunteers and 79 patients with previous unilateral ACL injury participated in this study. Patients were tested using a computerized tibial axial rotation system. Only the normal (non-operated) knee data were used for analysis. In order to assess the reliability of the robotic measurement system, 10 healthy volunteers were tested daily over four consecutive days by four different examiners. Rotational laxity and compliance measures demonstrated excellent reliability (ICC = 0.97). Patients with a contralateral ACL injury demonstrated significantly increased tibial internal rotation (20.6° vs. 11.4°, P < 0.001) and reduced external rotation (16.7° vs. 26.6°, P < 0.001) compared to healthy volunteers. Females demonstrated significantly increased internal and external rotation, as well as significantly increased rotational compliance compared with males (P < 0.05). Computer-assisted measurement techniques may offer clinicians an accurate, reliable, non-invasive method to select the most appropriate preventative or surgical interventions for patients with increased knee rotational laxity.

Practical implementation of robust MR-thermometry during clinical MR-guided microwave ablations in the liver at 1.5 T.

Practical non-invasive equipment modifications and effective acquisition methods to achieve robust and reliable real-time MR thermometry for monitoring of clinical hepatic microwave ablations were implemented. These included selection of the microwave generator location (inside versus outside the MR scan room), the number of radiofrequency chokes added to the microwave generator's coaxial lines, and the use of copper wool to maximize their electrical grounding. Signal-to-noise ratio (SNR) of MR thermometry images of a small fluid-filled phantom acquired during activation of microwave antenna were used to evaluate image quality as a function of each modification. SNR measurements corresponding to both locations of the microwave generator were comparable and so it was located outside the MR scan room. For this location, addition of one RF choke on the power and four chokes on the sensor coaxial lines was found to be optimal, corresponding to a 68% increase in SNR. Furthermore, image quality strongly depended on the proper electrical grounding of the power and sensor lines. SNR ratio (relative to SNR of baseline images) during activation of microwave generator was found to be 0.49 ±â€¯0.28 without adequate grounding, and 0.88 ±â€¯0.08 with adequate grounding (p = 0.002, Student's t-test). These SNR measurements were sufficiently sensitive to detect issues related to equipment performance and hence formed part of the quality assurance testing performed prior to each clinical treatment. Incorporating these non-invasive approaches resulted in significant improvements to image quality and, importantly while maintaining the clinical integrity of the microwave system which is of paramount importance in a highly regulated healthcare environment.

Potential of organic cation-saturated montmorillonite as treatment for poisoning by weak bases.

The preferential adsorption of the protonated form of weak bases by montmorillonite causes an increase in the pKeff of atrazine. The effect on the acid-base equilibrium of atrazine is related to the exchangeable cation on the surface of montmorillonite. The greatest effect was produced by the presence of 3-hydroxypropylammonium-saturated montmorillonite, which caused the pKeff of atrazine to increase 5.3 units to 6.9. This shift in pKeff causes the protonated form of atrazine to be the predominate species in the pH range encountered in the GI tract and should result in a high degree of adsorption of atrazine. Fraction-bound studies confirmed this hypothesis by demonstrating virtually complete absorption of atrazine by 3-hydroxypropylammonium-saturated montmorillonite up to pH 6. The fraction-bound studies also verified that protonated atrazine is adsorbed more completely by 3-hydroxypropylammonium-saturated montmorillonite than by bentonite USP or sodium-saturated montmorillonite. It is believed that saturation of the clay surface by an organic cation alters the surface environment of the clay, which results in enhanced adsorption of the protonated form of atrazine. The potential utility of montmorillonite saturated with an organic cation as an adsorbent for the emergency treatment of poisoning by weak bases is suggested.

Acid-base equilibria of tetracycline in sodium montmorillonite suspensions.

Changes in the partial molar free energy of the ionic species of tetracycline as a result of interaction with sodium-saturated montmorillonite were monitored by UV spectroscopic titrations. The stronger interaction between the clay and the protonated (H3T+) species relative to the zwitterionic (H2T0) species is responsible for the apparent displacement of pK1 in clay suspensions. The displacement of the first equilibrium favors in H3T+ species due to its stabilization by the negative clay surface. Little effect of the clay was observed on pK2 and pK3, because the ionic species of tetracycline associated with these equilibria (H2T0, HT-, and T2-) did not interact strongly with the negative clay surface. Therefore, the ionic species distribution of tetracycline in a sodium montmorillonite suspension is significantly different than that expected based on solution equilibria. The degree of equilibrium displacement depended on the accessibility of the negative charge at the clay surface. Fraction bound curves support the hypothesis that the clay surface causes a change in tetracycline equilibria. The H3T+ form of tetracycline was highly bound to the sodium montmorillonite, but little adsorption was observed for the H2T0 species.

Characterization and adsorptive properties of pharmaceutical grade clays.

The adsorption of tetracycline by clays commonly used in pharmacy can be predicted if the identity and character of the commerical clay sample are established. X-ray diffraction. IR spectroscopy, and chemical analysis were used to identify the clay component and any nonclay diluents present in a series of commerical pharmaceutical grade clays. The major clay components were montmorillonite, hectorite, attapulgite, saponite, and kaolinite. The clay structure, the nature of the exchangeable cation, and the presence of nonclay components are important factors affecting the tetracycline-clay interaction. In general, clay structures with a high surface charge lead to a greater interaction with the protonated form of tetracycline, while interaction with the zwitterionic form of tetracycline occurs in clay structures with minimal surface charge. The presence of multivalent, exchangeable cations on the clay surface diminishes interaction with the protonated form of tetracycline. Nonclay components such as calcite and dolomite increase the interactions of the zwitterionic and anionic forms of tetracycline with the clay.

Assessment of the acoustic properties of common tissue-mimicking test phantoms.

Ultrasound (US) test phantoms incorporating tissue-mimicking materials (TMMs) play an important role in the quality control (QC) and performance testing of US equipment. Three commercially available TMMs (Zerdine from CIRS Inc.; condensed-milk-based gel from Gammex RMI; urethane-rubber-based from ATS Labs) and a noncommercial agar-based TMM, were investigated. Acoustic properties were measured over the frequency range 2.25 to 15 MHz at a range of ambient temperatures (10 to 35 degrees C). The acoustic velocity of the TMMs remained relatively constant with increasing frequency. Only the agar-based TMM had a linear increase of attenuation with frequency, with the other materials exhibiting nonlinear responses to varying degrees (f(1.08) to f(1.83)). The acoustic velocity and attenuation coefficient of all the TMMs varied with temperature, with the urethane-rubber TMM showing the greatest variation of +/- 1.2% for acoustic velocity and +/- 12% for attenuation coefficient. The data obtained in this study highlight the importance of greater knowledge of the acoustic behavior of TMMs to variations in both frequency and temperature, to ensure that accurate and precise measurements are obtained during QC and performance testing.

Surgical alternatives for treatment of articular cartilage lesions.

Articular cartilage injuries in the knee are common; fortunately, full-thickness articular cartilage defects constitute only a small portion of this group. These lesions may be incidentally encountered during ligament or meniscal surgery, having been silent or asymptomatic for an unknown period of time. However, when they are large and symptomatic, the surgeon may choose from a wide array of techniques available for treatment. The relatively small number of natural history studies regarding full-thickness articular surface lesions complicates the decision-making process. Accurate evaluation and classification of the anatomic defect aids in the development of a clinical algorithm for treatment. Surgical techniques are either reparative or restorative in nature. Reparative techniques fall short of complete reestablishment of the articular cartilage; however, the resultant repairs may remain quite functional for varying periods of time. Restorative techniques attempt to reestablish the native articular surface. To date, no peer-reviewed, prospective, randomized, controlled studies of operative versus nonoperative treatment for full-thickness articular cartilage lesions have been published. Even though the long-term results of surgical treatment for full-thickness articular surface lesions remain unknown, the early results are encouraging.

An audit of a hospital-based Doppler ultrasound quality control protocol using a commercial string Doppler phantom.

Results from a four-year audit of a Doppler quality assurance (QA) program using a commercially available Doppler string phantom are presented. The suitability of the phantom was firstly determined and modifications were made to improve the reliability and quality of the measurements. QA of Doppler ultrasound equipment is very important as data obtained from these systems is used in patient management. It was found that if the braided-silk filament of the Doppler phantom was exchanged with an O-ring rubber filament and the velocity range below 50 cm/s was avoided for Doppler quality control (QC) measurements, then the maximum velocity accuracy (MVA) error and intrinsic spectral broadening (ISB) results obtained using this device had a repeatability of 18 ± 3.3% and 19 ± 3.5%, respectively. A consistent overestimation of the MVA of between 12% and 56% was found for each of the tested ultrasound systems. Of more concern was the variation of the overestimation within each respective transducer category: MVA errors of the linear, curvilinear and phased array probes were in the range 12.3-20.8%, 32.3-53.8% and 27-40.7%, respectively. There is a dearth of QA data for Doppler ultrasound; it would be beneficial if a multicentre longitudinal study was carried out using the same Doppler ultrasound test object to evaluate sensitivity to deterioration in performance measurements.

The effects of fatty deposits on the accuracy of the Fibroscan® liver transient elastography ultrasound system.

A new generation of ultrasound transient elastography (TE) systems have emerged which exploit the well-known correlation between the liver's pathological and mechanical properties through measurements of the Young's elastic modulus; however, little work has been carried out to examine the effect that fatty deposits may have on the TE measurement accuracy. An investigation was carried out on the effects on the measurement accuracy of a TE ultrasound system, the Fibroscan®, caused by overlaying fat layers of varying thickness on healthy liver-mimicking phantoms, simulating in vivo conditions for obese patients. Furthermore, a steatosis effect similar to that in non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) was simulated to investigate its effect on the TE system. A range of novel elastography fat-mimicking materials were developed using 6-10 wt% poly(vinyl alcohol) cryogel capable of achieving a range of acoustic velocities (1482-1530 m s(-1)) and attenuation coefficients (0.4-1 dB MHz(-1) cm(-1)) for simulating different liver states. Laboratory-based acoustic velocities and attenuation coefficients were measured while the Young's modulus was established through a gold standard compression testing method. A significant variation of the Young's elastic modulus was measured in healthy phantoms with overlaying fat layers of thicknesses exceeding 45 mm, impinging on the scanners region of interest, overestimating the compression tested values by up to 11 kPa in some cases. Furthermore, Fibroscan® measurements of the steatosis phantoms showed a consistent overestimation (∼54%), which strongly suggests that the speed of sound mismatch between that of liver tissue and that assumed by the scanner is responsible for the high clinical cut-offs established in the case of ALD and NAFLD.

Assessment of the accuracy of an ultrasound elastography liver scanning system using a PVA-cryogel phantom with optimal acoustic and mechanical properties.

The accuracy of a transient elastography liver-scanning ultrasound system was assessed using a novel application of PVA-cryogel as a tissue-mimicking material with acoustic and shear elasticity properties optimized to best represent those of liver tissue. Although the liver-scanning system has been shown to offer a safer alternative for diagnosing liver cirrhosis through stiffness measurement, as compared to the liver needle biopsy exam, the scanner's accuracy has not been fully established. Young's elastic modulus values of 5-6 wt% PVA-cryogel phantoms, also containing glycerol and 0.3 µm Al(2)O(3) and 3 µm Al(2)O(3), were measured using a 'gold standard' mechanical testing technique and transient elastography. The mechanically measured values and acoustic velocities of the phantoms ranged between 1.6 and 16.1 kPa and 1540 and 1570 m s(-1), respectively, mimicking those observed in liver tissue. The values reported by the transient elastography system overestimated Young's elastic modulus values representative of the progressive stages of liver fibrosis by up to 32%. These results were attributed to the relative rather than absolute nature of the measurement arising from the single-point acoustic velocity calibration of the system, rendering the measurements critically dependent on the speed of sound of the sample under investigation. Given the wide range of acoustic velocities which exist in the liver, spanning healthy tissue to cirrhotic pathology, coupled with the system's assumption that the liver is approximately elastic when it is rather highly viscoelastic, care should be exercised when interpreting the results from this system in patient groups.

Complete rupture of the distal semimembranosus complex in a professional athlete.

Complete ruptures of the distal hamstring tendons rarely cause functional disability significant enough to warrant surgical intervention. Isolated ruptures of the distal semimembranosus tendon complex have not been reported previously in the literature. A case of a complete rupture of the distal semimembranosus tendon complex occurring in a professional football player with resultant functional disability is reported here. The magnetic resonance imaging scan was essential for an accurate diagnosis. Subsequent surgical repair and postoperative rehabilitation is described. Strict attention to recreating the multiple attachments of the semimembranosus tendon complex is recommended.

The influence of MRI on treatment decisions regarding knee injuries.

This study evaluated whether the information gained from magnetic resonance imaging (MRI) of the knee would provide information that was useful in the treatment algorithm. Three orthopedic surgeons completed a questionnaire immediately after the initial evaluation of a patient with a knee injury and for whom an MRI also was ordered by that surgeon. The questionnaire asked the surgeons' what their proposed clinical diagnoses and treatment plans would be if MRI was not available. Eighty-five patients were included in the study. Initial treatment recommendation was altered for 18 patients (21%) solely because of the MRI results. The physicians and MRI were most accurate for anterior cruciate ligament (ACL) tears followed by medial meniscus tears, and lateral meniscus tears, and significantly behind in accuracy for patellofemoral chondral pathology. These diagnoses were more frequently missed in the face of acute ACL pathology for the clinician and MRI. In 19 cases in which the surgeon was confident of ACL insufficiency, in only 1 (5%) case did the MRI scan provide useful information. In 19 cases in which an ACL reconstruction was performed, the decision to proceed with the reconstruction was hastened in 3 patients because of the MRI results. These results indicate that the use of MRI for decision making in acute ACL tears is not of much benefit unless the diagnosis of ACL insufficiency is in question. Magnetic resonance imaging is more useful for the decision-making process when the pathology involves the menisci or chondral surfaces. In this study, MRI of the knee beneficially altered the treatment plan of the orthopedist in 18% of the patients and resulted in the prolongation of symptoms in 4% of patients.

Coordination and management of a large multicenter screening trial: the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial.

The Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial is a large and complex multi-institutional, multifaceted organization with a 20-year horizon. The implementation of the trial began with the creation of an organizational structure that supports strong leadership, cooperation, and effective communication among the trial collaborators including an operational framework for the development, review, and pretest of instruments, data collection, and management procedures; the setting of high-quality standards for training of trial staff; and the development of a comprehensive assessment plan for evaluation of all trial activities. This paper describes the process and methods used in the coordination and management of the PLCO trial. These include the role of the steering committee and its subcommittees and working groups, the establishment of regular and ad hoc communications among collaborators, the training of screening center coordinators and examiners, the PLCO manual of operations and procedures, and the development and implementation of a comprehensive quality assurance plan.

[Autologous chondrocyte transplantation for treatment of cartilage defects of the knee joint. Clinical results]. / Die autologe Chondrozyten-Transplantation zur Behandlung von Knorpeldefekten des Kniegelenkes. Klinische Ergebnisse.

Cartilage defects in the knee joint are common and have a bad tendency for healing due to the limited regeneration of hyaline cartilage. Surgeons have an ample choice of various operative treatment measures. Especially for the treatment of larger lesions first results of autologous chondrocyte transplantation (ACT) were published in 1994 [3]. Autologous chondrocytes are isolated from an arthoscopically harvested cartilage biopsy, cultured in vitro and implanted in the defect under a periostal flap in a second procedure. In an international multicenter study 1,051 patients treated with ACT between 6/95 and 12/98 were documented with follow-up examinations after 12 months (588 patients), 24 months (220 patients) and 36 months (40 patients). The majority of the defects (61.2%) were localized on the medial femoral condyle, measuring 4.6 cm2 and mostly described as grade III/IV lesions. The clinical evaluation was performed using a modified Cincinnati knee rating system independently for clinician and patient. Evaluations showed an increase from 3.35 to 6.25 after 24 months and from 3.10 to 6.77 in a scale from 1 (bad) to 10 (excellent). ACT favours defects of the femur with an improvement rate of 85%. Adverse events possibly related to ACT were described in 4.8% of the patients. Diagnostic second-look arthroscopies are included in the reoperation rate of 5.1%. The presented data indicate autologous chondrocyte transplantation as an effective and safe option for the treatment of large full thickness cartilage defects in the knee joint.

Autologous chondrocyte implantation of the knee: multicenter experience and minimum 3-year follow-up.

OBJECTIVE: To determine clinical outcome and graft survivorship in patients undergoing autologous chondrocyte implantation (ACI) for the repair of chondral defects of the knee. DESIGN: Prospective cohort study. SETTING: 19 centers in the United States. PATIENTS: 50 patients (37 males, 13 females). Mean age was 36 years (range: 19-53). Defects were grade III or IV with a mean size of 4.2 cm 2. All patients had a minimum of 36 months postoperative follow-up. MAIN OUTCOME MEASUREMENTS: Clinician and patient evaluation based on the modified Cincinnati Knee Rating System. Graft failure was defined as replacement or removal of the graft due to mechanical symptoms or pain. RESULTS: Clinician and patient evaluation indicated median improvements of 4 and 5 points, respectively, at 36 months following ACI (p < 0.001). Previous treatment with marrow stimulation techniques and size of defect did not impact the results with ACI. The most common adverse events reported were adhesions and arthrofibrosis and hypertrophic changes. Three patients had graft failure and required reimplantation or treatment with alternative cartilage repair techniques. Kaplan-Meier estimated freedom from graft failure was 94% at 36 months postoperatively (95% CI = 88-100%). CONCLUSIONS: These results of this study indicate excellent graft survivorship using ACI as well as substantial improvement in functional outcome.