Siemens Medical Solutions USA Research Articles

Transesophageal Echocardiography in Critically Ill Acute Postoperative Infants: Comparison of AcuNav Intracardiac Echocardiographic and microTEE Miniaturized Transducers

Multiple barriers to transthoracic echocardiography are present in critically ill infants immediately after surgery. Transesophageal echocardiography (TEE) is sometimes needed to obtain specific important information that transthoracic echocardiography fails to demonstrate. Formerly, the investigators used the AcuNav intracardiac echocardiographic (ICE) intravascular ultrasound transducer (8 Fr, 2.5 mm, 64-element crystal array, multifrequency [5.5-10 MHz], single longitudinal plane, linear phased array [Siemens Medical Solutions USA, Inc., Mountain View, CA]). Recently, the investigators have also used the microTEE transducer (8-mm transducer tip, 5.2-mm shaft, multifrequency [3-8 MHz], multiplane phased array, 32-element probe [Philips Medical Systems, Andover, MA]). Both transducers have two-dimensional, M-mode, color Doppler, and pulsed-wave and continuous-wave Doppler capabilities. The aim of this study was to compare the efficacy, safety, ease of insertion, capabilities, utilization, and cost of the AcuNav ICE transducer versus those of the microTEE transducer. A retrospective review of all 50 postoperative critically ill infants who underwent TEE using the AcuNav and microTEE in the past 5 years was conducted. TEE was performed as ordered by the attending physician to answer a specific question not answered by transthoracic echocardiography. In all cases, the clinical information sought was obtained. The AcuNav ICE transducer was safe, easy to insert through the transnasal route, and did not require paralysis; however, it had a limited number of echocardiographic views and had greater sterilization cost. The microTEE transducer had greater echocardiographic capabilities and lower sterilization cost; however, it was slightly more difficult to insert, had a few manageable complications, and required more sedation and paralysis. TEE in this setting has increased because of demonstrated efficacy and safety. Both the AcuNav ICE and microTEE transducers are useful and effective in this critical clinical scenario.

TU‐G‐BRA‐06: Motion Adaptive Rotational Intensity Modulated Radio Therapy (MA‐RIMRT) with Image Guidance

Purpose: Commercial intensity‐modulated‐arc‐therapy (IMAT) implementations rely on a 100% beam‐on duty‐cycle to achieve high efficiency. With moving targets, real‐time tracking or gating may be applied. Tracking is technically challenging and gating reduces efficiency by lowering the duty‐cycle. By combining burst‐mode rIMRT (in which all dose is administered while the gantry is within a few degrees of a beam optimization point [OP]), with a motion pre‐emption strategy and intrafractional imaging, we demonstrate an efficient implementation of motion‐adaptive rIMRT. Methods: 1. An rIMRT plan is created with 36–72 OPs. A gantry rotating at 6 degrees/s takes 3–6s to reach successive OPs. This co‐incides with the natural breathing period. 2. A Fourier‐descriptor‐based trajectory model is fitted to target features identified in pre‐treatment CBCT projections. The model predicts feature location at any combination of gantry angle and breathing phase. 3. The model sets the gantry speed to place the gantry at the next beam OP just in time as the target arrives at the planned position. In‐line projection images are acquired immediately before and during beam delivery. Treatment ensues only if the target position is correct (verification completes within 50ms, so maximum misdelivery possible at 2000MU/min is within 2MU). In cases of irregular breathing, the system gracefully defaults to gated‐IMRT. Results: For a MA‐rIMRT delivery of 750MU at 2000MU/min, treatment duration increases from 154s (regular rIMRT) to 199s (5s respiration cycle). Conclusions: With predictable patient breathing, MA‐rIMRT delivery times are competitive with conventional IMAT. High treatment accuracy is easily achieved, since there is no tracking lag and since the beam shape is static during delivery. Contemporary linacs rely on non‐realtime communication systems (typically Ethernet) to control time‐critical elements such as the MLC. Since such variable‐delay systems pose formidable problems in terms of predictive control, our approach offers a pragmatic alternative to tracking. Siemens Medical Solutions USA

Quantitative assessment of right ventricular function in pectus excavatum

Pectus excavatum is a common congenital chest wall deformity. Underlying cardiac chambers, in particular the right atrium and right ventricle (RV), may be compressed between the vertebral column and the depressed sternum in patients with this thoracic deformity. Citing improvement in indices of cardiovascular function after corrective surgery, some investigators have suggested that the deformed chest may contribute to cardiopulmonary impairment. Although cardiopulmonary impairment certainly may contribute to symptoms in patients with pectus excavatum and guide the need for and timing of corrective surgery, guidelines for the assessment of resting cardiovascular function remain undefined. Furthermore, the qualitative echocardiographic assessment of RV function and volumes among patients with pectus excavatum may be technically difficult and limited by subjectivity. Quantitative echocardiographic parameters, such as tricuspid annular plane systolic excursion (TAPSE) and RV fractional area change, may offer a more accurate assessment of RV function in this anatomically distinct population. Cardiac magnetic resonance (CMR) imaging has emerged as the criterion standard in RV functional assessment and, more recently, has been validated in patients with pectus excavatum. We compared qualitative assessment of RV systolic impairment by visual echocardiographic inspection with quantitative assessment of RV function with CMR and echocardiographically derived TAPSE and RV fractional area change in a series of patients referred to our institution with mild to severe symptomatic pectus excavatum. Patients were being considered for corrective surgery. Our hypothesis was that the patients would be found to have normal RV function when assessed quantitatively, either through CMR or quantitative echocardiographic examination, despite impairment seen qualitatively.

Ultrasound Visualization of the Spinal Accessory Nerve In Vivo

Inadvertent injury of the spinal accessory nerve during surgical procedures is a cause of significant morbidity with medicolegal repercussions. Surface anatomy is an unreliable guide to the nerve's location. We suggest that ultrasound can be used to map the course of the nerve in the posterior triangle of the neck. Fifty healthy subjects (28 females, mean age 37 y) were scanned using a VF13-5 linear probe and a Siemens Sonoline Antares ultrasound machine (Siemens Medical Solutions USA Inc., Malvern, PA). The caliber, course, and distribution of the nerve in the posterior triangle of the neck were recorded. The nerve was visualized bilaterally in all subjects, running superficially across the posterior triangle with either a straight (56%) or tortuous (44%) course at a depth of about 3 mm beneath the skin surface. It had a mean caliber of 0.76 ± 0.12 mm. It exited the posterior border of sternocleidomastoid at a mean of 6.7 (4.0-9.4) cm below the mastoid process and 1.1 (0.1-2.1) cm above the great auricular point and penetrated the anterior border of trapezius 5.4 (2.1-9.2) cm above the clavicle. Importantly, 58% of nerves divided into 2-4 branches before penetrating trapezius; the nerve branched on at least one side in 49 of 50 individuals. The spinal accessory nerve and its anatomical variants can be consistently and reliably demonstrated by ultrasound in normal individuals. Surface anatomical landmarks are not a reliable guide to the position and course of the nerve in the posterior triangle. Preoperative mapping of the nerve with ultrasound may reduce the risk of iatrogenic injury.

Physical and clinical performance of the mCT time-of-flight PET/CT scanner

Time-of-flight (TOF) measurement capability promises to improve PET image quality. We characterized the physical and clinical PET performance of the first Biograph mCT TOF PET/CT scanner (Siemens Medical Solutions USA, Inc.) in comparison with its predecessor, the Biograph TruePoint TrueV. In particular, we defined the improvements with TOF. The physical performance was evaluated according to the National Electrical Manufacturers Association (NEMA) NU 2-2007 standard with additional measurements to specifically address the TOF capability. Patient data were analyzed to obtain the clinical performance of the scanner. As expected for the same size crystal detectors, a similar spatial resolution was measured on the mCT as on the TruePoint TrueV. The mCT demonstrated modestly higher sensitivity (increase by 19.7 ± 2.8%) and peak noise equivalent count rate (NECR) (increase by 15.5 ± 5.7%) with similar scatter fractions. The energy, time and spatial resolutions for a varying single count rate of up to 55 Mcps resulted in 11.5 ± 0.2% (FWHM), 527.5 ± 4.9 ps (FWHM) and 4.1 ± 0.0 mm (FWHM), respectively. With the addition of TOF, the mCT also produced substantially higher image contrast recovery and signal-to-noise ratios in a clinically-relevant phantom geometry. The benefits of TOF were clearly demonstrated in representative patient images.

Changes in left ventricular twist after mitral valve repair

We performed echocardiographic tissue tracking to investigate whether mitral valve repair preserves left ventricular function. We studied 16 subjects without heart disease (11 male; mean age, 54.6 ± 15.1 years) and 18 patients in normal sinus rhythm undergoing solitary mitral valve repair (12 male; mean age, 53.6 ± 16.6 years). Transthoracic echocardiography was performed before and after surgery, and left ventricular apical and basal short-axis images were recorded. Left ventricular rotation angle was measured with off-line Vector Velocity Imaging (Siemens Medical Solutions USA Inc, Mountain View, Calif) at each slice level. Left ventricular ejection fraction was significantly higher in the control (68.4% ± 3.6%) and preoperative groups (70.9% ± 6.5%) than the postoperative group (59.4% ± 11.4%, P < .05). Left ventricular end-diastolic and end-systolic volumes were significantly greater in the preoperative group than the control group (130.0 ± 41.5 mL and 41.6 ± 16.6 mL vs 80.0 ± 16.7 mL and 26.6 ± 9.2 mL, respectively, P < .05). Left ventricular end-diastolic volume normalized postoperatively. Left ventricular twist was significantly greater in the preoperative group than the other groups (11.7° ± 4.1° versus 7.1° ± 3.8° and 8.2° ± 5.7°, P < .05). Left ventricular twist did not differ significantly between control and postoperative groups. New York Heart Association functional class improved from 1.6 ± 0.5 to 1.0 ± 0.0 after surgery (P < .05). Although preoperative left ventricular ejection fraction seemed normal, left ventricular twist was greater. Left ventricular twist normalized after surgery, suggesting that it preserves left ventricular function.

Acoustic Radiation Force Impulse Imaging of Human Prostates Ex Vivo

It has been challenging for clinicians using current imaging modalities to visualize internal structures and detect lesions inside human prostates. Lack of contrast among prostatic tissues and high false positive or negative detection rates of prostate lesions have limited the use of current imaging modalities in the diagnosis of prostate cancer. In this study, acoustic radiation force impulse (ARFI) imaging is introduced to visualize the anatomical and abnormal structures in freshly excised human prostates. A modified Siemens Antares ultrasound scanner (Siemens Medical Solutions USA Inc., Malvern, PA) and a Siemens VF10-5 linear array were used to acquire ARFI images. The transducer was attached to a three-dimensional (3-D) translation stage, which was programmed to automate volumetric data acquisition. A depth dependent gain (DDG) method was developed and applied to 3-D ARFI datasets to compensate for the displacement gradients associated with spatially varying radiation force magnitudes as a function of depth. Nine human prostate specimens were collected and imaged immediately after surgical excision. Prostate anatomical structures such as seminal vesicles, ejaculatory ducts, peripheral zone, central zone, transition zone and verumontanum were visualized with high spatial resolution and in good agreement with McNeal's zonal anatomy. The characteristic appearance of prostate pathologies, such as prostate cancerous lesions, benign prostatic hyperplasia, calcified tissues and atrophy were identified in ARFI images based upon correlation with the corresponding histologic slides. This study demonstrates that ARFI imaging can be used to visualize internal structures and detecting suspicious lesions in the prostate and appears promising for image guidance of prostate biopsy. (E-mail: liang.zhai@duke.edu)

Characterization of clutter in ultrasonic imaging using a nonlinear full-wave simulation method and in vivo human tissue.

Clutter is a well known image degradation mechanism in ultrasonic imaging that is patient dependent. Despite widespread agreement on clutter sources, there are few studies on sources and their contribution to overall image clutter. We have performed simulations of clutter using a nonlinear, full-wave method to demonstrate the characteristics and sources of ultrasonic clutter. Representations of human abdominal layers, created from histological stains of human abdominal layers, were placed at the surface of the transducer. Point targets and anechoic cysts were simulated to demonstrate the characteristics of clutter resulting from these near-field layers. We have also performed matching in vivo experimental studies in human bladders and livers. The simulations and experiments show consistent results. Clutter resulting from near-field tissue layers is spatially coherent with respect to axial motion and incoherent in the sampled pressure field. The contribution of off-axis clutter resulting from the tails of the point-spread-function is shown to be relatively small (&amp;lt;5%) compared to the contribution of clutter associated with near-field layers (approximately 68%). Thus, the dominating source of clutter is associated with multiple reflections in near-field tissue layers. Clutter due to off-axis scattering dominates only when an interfering target is close to the imaging target. [This work is supported by the NIH Grant R21-EB008481 from the NIBIB. Technical support was provided by the Ultrasound Division at Siemens Medical Solutions USA, Inc.]

In vivo Quantification of Liver Stiffness in a Rat Model of Hepatic Fibrosis with Acoustic Radiation Force

Liver fibrosis is currently staged using needle biopsy, a highly invasive procedure with a number of disadvantages. Measurement of liver stiffness changes that accompany progression of the disease may provide a quantitative and noninvasive method to assess the health of the liver. The purpose of this study is to investigate the correlation between liver stiffness measured by radiation force induced shear waves and disease related changes in the liver. An additional aim is to present initial findings on the effects of liver viscosity on radiation force induced shear wave morphology. Liver fibrosis was induced in 10 rats using carbon tetrachloride (CCl 4), while five rats acted as controls. Liver stiffness was measured in vivo in all rats after a treatment period of 8 weeks using a modified Siemens SONOLINE Antares scanner (Siemens Medical Solutions USA, Ultrasound Division, Issaquah, WA, USA). The spatial coherence of radiation force induced shear waves propagating in the viscoelastic rat liver decreased significantly with propagation distance, compared with shear waves in an elastic phantom and a finite element model of a purely elastic medium. Animals were sacrificed after imaging and liver samples were taken for histopathologic analysis and collagen quantification using picrosirius red staining and hydroxyproline assay. At the end of the treatment period, five rats had healthy livers (stage F0), while six had severe fibrosis (F3) and the rest had light to moderate fibrosis (F1 and F2). The measured liver stiffness for the F0 group was 1.5 ± 0.1 kPa (mean ± 95% confidence interval) and for F3 livers was 1.8 ± 0.2kPa. In this study, liver stiffness was found to be linearly correlated with the amount of collagen in the liver measured by picrosirius red staining (r 2 = 0.43, p = 0.008). In addition, stiffness spatial heterogeneity was also linearly correlated with liver collagen content (r 2 = 0.58, p = 0.001) by picrosirius red staining. These results are consistent with those obtained by Salameh et al. (2007) and Yin et al. (2007b) using animal models of liver fibrosis and MR elastography. This suggests that stiffness measurement using acoustic radiation force can provide a quantitative assessment of the extent of fibrosis in the liver and can be potentially used for the diagnosis, management and study of liver fibrosis. (E-mail: michael.h.wang@duke.edu)

Three-Dimensional Electrode Displacement Elastography Using the Siemens C7F2 fourSight Four-Dimensional Ultrasound Transducer

Because ablation therapy alters the elastic modulus of tissues, emerging strain imaging methods may enable clinicians for the first time to have readily available, cost-effective, real-time guidance to identify the location and boundaries of thermal lesions. Electrode displacement elastography is a method of strain imaging tailored specifically to ultrasound-guided electrode-based ablative therapies ( e.g., radio-frequency ablation). Here tissue deformation is achieved by applying minute perturbations to the unconstrained end of the treatment electrode, resulting in localized motion around the end of the electrode embedded in tissue. In this article, we present a method for three-dimensional (3D) elastographic reconstruction from volumetric data acquired using the C7F2 fourSight four-dimensional ultrasound transducer, provided by Siemens Medical Solutions USA, Inc. (Issaquah, WA, USA). Lesion reconstruction is demonstrated for a spherical inclusion centered in a tissue-mimicking phantom, which simulates a thermal lesion embedded in a normal tissue background. Elastographic reconstruction is also performed for a thermal lesion created in vitro in canine liver using radio-frequency ablation. Postprocessing is done on the acquired raw radio-frequency data to form surface-rendered 3D elastograms of the inclusion. Elastographic volume estimates of the inclusion compare reasonably well with the actual known inclusion volume, with 3D electrode displacement elastography slightly underestimating the true inclusion volume. (E-mail: tvarghese@wisc.edu)

Glycogen Synthase Kinase-3α Reduces Cardiac Growth and Pressure Overload-induced Cardiac Hypertrophy by Inhibition of Extracellular Signal-regulated Kinases

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase having multiple functions and consisting of two isoforms, GSK-3alpha and GSK-3beta. Pressure overload increases expression of GSK-3alpha but not GSK-3beta. Despite our wealth of knowledge about GSK-3beta, the function of GSK-3alpha in the heart is not well understood. To address this issue, we made cardiac-specific GSK-3alpha transgenic mice (Tg). Left ventricular weight and cardiac myocyte size were significantly smaller in Tg than in non-Tg (NTg) mice, indicating that GSK-3alpha inhibits cardiac growth. After 4 weeks of aortic banding (transverse aortic constriction (TAC)), increases in left ventricular weight and myocyte size were significantly smaller in Tg than in NTg, indicating that GSK-3alpha inhibits cardiac hypertrophy. More severe cardiac dysfunction developed in Tg after TAC. Increases in fibrosis and apoptosis were greater in Tg than in NTg after TAC. Among signaling molecules screened, ERK phosphorylation was decreased in Tg. Adenovirus-mediated overexpression of GSK-3alpha, but not GSK-3beta, inhibited ERK in cultured cardiac myocytes. Knockdown of GSK-3alpha increased ERK phosphorylation, an effect that was inhibited by PD98059, rottlerin, and protein kinase Cepsilon (PKCepsilon) inhibitor peptide, suggesting that GSK-3alpha inhibits ERK through PKC-MEK-dependent mechanisms. Knockdown of GSK-3alpha increased protein content and reduced apoptosis, effects that were abolished by PD98059, indicating that inhibition of ERK plays a major role in the modulation of cardiac growth and apoptosis by GSK-3alpha. In conclusion, up-regulation of GSK-3alpha inhibits cardiac growth and pressure overload-induced cardiac hypertrophy but increases fibrosis and apoptosis in the heart. The anti-hypertrophic and pro-apoptotic effect of GSK-3alpha is mediated through inhibition of ERK.

SU‐FF‐I‐105: Dosimetric Comparison of Planar and 3‐Dimensional Methods of Anatomic Localization for Breast Lymphoscintigraphy

Purpose: To estimate the absorbed dose for a range of settings of CT topograms and scans to determine the best technique for node localization in breast lymphoscintigraphy while minimizing the dose to the patient. Method and Materials: This study was performed with an anthropomorphic thorax phantom on a Symbia‐T6® SPECT/CT to produce mechanically registered datasets [Siemens Medical Solutions USA, Hoffman Estates IL]. The data included a SPECT, anterior and lateral topograms, a CT, and static anterior and lateral emission scintigrams. CT topograms and scans were acquired at 80, 110, and 130 kVp with varied mAs settings to compare the quality of the images and dose estimates for lower dose settings. Scintigram and SPECT scans were fused to each topogram and CT, respectively, to allow for qualitative comparison of localization. Exposure measurements for topograms were acquired using an ion chamber at isocenter, and entrance skin doses were estimated for the CT topograms. A CTDI body phantom was used to acquire data for estimation of effective dose for the CT scans. Results: The skin dose for a CT topogram ranges from 0.089 mGy to 0.235 mGy, and the effective dose for the CT scan ranges from 0.308 mSv (lowest dose settings) to 5.265 mSv (clinical scan setting). Qualitative comparison showed the 80 kVp, 20 mA topogram and 110 kVp, 10 mAs CT to be sufficient for localization. The skin dose is 0.089 uSv and the effective dose is 0.392 uSv for these techniques, respectively. Conclusion: The absorbed dose to the patient can be substantially reduced for CT topograms and CTs that are to be used for localization. These do not have to be of diagnostic quality in order to provide enough anatomical information to localize the sentinel nodes in breast lymphoscintigraphy. Conflict of Interest: Research sponsored by Siemens Medical Solutions USA.

SU‐FF‐I‐107: Improving the Accuracy of CT Topograms for Node Localization in Breast Lymphoscintigraphy

Purpose: To characterize and compensate for fan‐beam distortion of a CT topogram, thereby improving a technique for localization using planar lymphoscintigram/topogram fusion by minimizing misregistration between modalities. Method and Materials: We are currently investigating the feasibility of fusing planar scintigrams and CT topograms as a means of localization for breast lymphoscintigraphy and determined a maximum expected lateral offset between modalities of ±2.8 cm for an average size patient. The spatial distortion due to the fan‐beam of the topogram is linearly related to offset from isocenter, suggesting the possibility of rescaling the topograms used for localization. In this work, we have adjusted the anterior topogram by determining the location of the node in the lateral scintigram and using the distance above or below isocenter to apply the appropriate magnification to the topogram so that it is correctly scaled for the plane of the node (vice versa for the lateral topogram). An IDL program [ITT Visual Information Solutions, Boulder CO] was written to facilitate the modification of the topograms; the program was tested with a data set of an anthropomorphic thorax phantom acquired using a hybrid SPECT/CT camera [Symbia®, Siemens Medical Solutions USA, Hoffman Estates IL]. Registration was visually assessed by fusing the scintigram with the original topogram, with the modified topogram, and with the fullthickness coronal‐projection CT to verify the localization. Results: The IDL program has been executed and is successfully modifying topograms to minimize distortion. The visual comparison of the scintigram/modified topogram and scintigram/full‐thickness coronal‐projection CT demonstrates less than ±0.34 cm offset. Conclusion: Appropriately magnified CT topograms have been generated and fused with planar scintigrams that have potential for producing images with improved anatomic localization for breast lymphoscintigraphy compared to the standard‐of‐care Co‐57 sheet source backlighting method. Conflict of Interest: Research sponsored by Siemens Medical Solutions USA.

Serial Multimodality Assessment of Myocardial Infarction in Mice Using Magnetic Resonance Imaging and Micro–Positron Emission Tomography Provides Complementary Information on the Progression of Scar Formation

Recent technological advances have made imaging the mouse heart possible using both 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI),1–4 thus facilitating the investigation of mechanisms underlying the progression toward heart failure after myocardial infarction (MI). These imaging modalities provide complementary information regarding cellular metabolism and infarct location, respectively. To demonstrate this, we used FDG PET and MRI in a serial study of male C57Bl/6 mice that were subjected to a 1-hour coronary occlusion and then 30 days of reperfusion. Imaging was performed 1, 7, and 28 days after coronary occlusion. Gd-enhanced ECG-gated cardiac MRI was performed using a 4.7-T MRI scanner (Varian, Inc, …

INTRAOPERATIVE ULTRASOUND USING PHASE INVERSION HARMONIC IMAGING

To study the feasibility of intraoperative ultrasound using the phase inversion harmonic imaging (PIHI) technique. Eight patients with intracranial middle cerebral artery aneurysms and five patients with arteriovenous malformations were studied after written informed consent. A first ultrasound study was performed through the intact dura mater after cranial trepanation to assess the pathology, its feeding artery, and downstream segments. A second ultrasound study was performed immediately after intervention to monitor the success of the procedure. All patients were studied using a Siemens Sonoline Antares ultrasound machine (Siemens Medical Solutions USA, Inc., Malvern, PA) before and after intravenous administration of an ultrasound contrast agent (Optison; GE Healthcare, Milwaukee, WI). Other than conventional brightness mode, PIHI is sensitive to the nonlinear acoustic response of tissue, and especially to ultrasound contrast agent microbubbles. The latter enables contrast-specific vascular imaging. PIHI provided anatomically detailed information. In combination with an ultrasound contrast agent, angiography-like views of the vascular pathologies, including their surrounding vessels, could be obtained. Flow velocities in afferent and downstream vascular segments, as well as inside the pathology, could be assessed. Flow dynamics inside the aneurysm sac or the arteriovenous malformation could be studied in real-time. Postintervention, contrast-enhanced PIHI could be used to immediately monitor the success of the surgical procedure. PIHI enables intraoperative visualization and morphological assessment of neurovascular pathologies, such as middle cerebral artery aneurysms or arteriovenous malformations. In combination with an ultrasound contrast agent, the flow dynamics of these lesions can be displayed in real-time.

Screening for Early Pancreatic Neoplasia in High-Risk Individuals: A Prospective Controlled Study

Individuals with a strong family history of pancreatic cancer and persons with Peutz-Jeghers syndrome (PJS) have an increased risk for pancreatic cancer. This study screened for early pancreatic neoplasia and compared the pancreatic abnormalities in high-risk individuals and control subjects. High-risk individuals with PJS or a strong family history of pancreatic cancer were prospectively evaluated with baseline and 12-month computed tomography (CT) scan and endoscopic ultrasonography (EUS). If EUS was abnormal, EUS-fine-needle aspiration and endoscopic retrograde cholangiopancreatography (ERCP) were performed. Surgery was offered to patients with potentially neoplastic lesions. Radiologic findings and pathologic diagnoses were compared. Patients undergoing EUS and/or ERCP for benign non-pancreatic indications were concurrently enrolled as control subjects. Seventy-eight high-risk patients (72 from familial pancreatic cancer kindreds, 6 PJS) and 149 control patients were studied. To date, 8 patients with pancreatic neoplasia have been confirmed by surgery or fine-needle aspiration (10% yield of screening); 6 patients had 8 benign intraductal papillary mucinous neoplasms (IPMNs), 1 had an IPMN that progressed to invasive ductal adenocarcinoma, and 1 had pancreatic intraepithelial neoplasia. EUS and CT also diagnosed 3 patients with 5 extrapancreatic neoplasms. At EUS and ERCP abnormalities suggestive of chronic pancreatitis were more common in high-risk patients than in control subjects. Screening EUS and CT diagnosed significant asymptomatic pancreatic and extrapancreatic neoplasms in high-risk individuals. IPMN should be considered a part of the phenotype of familial pancreatic cancer. Abnormalities suggestive of chronic pancreatitis are identified more commonly at EUS and ERCP in high-risk individuals.

Transesophageal Echocardiography Using Cypress‐Miniaturized Echocardiogram Unit: Initial Clinical Experience

Transesophageal echocardiography (TEE) was introduced clinically in the United States in 1987. Recent technologic advances have resulted in the creation of a small portable hand-carried ultrasound (HCU) device that can be easily carried throughout the hospital with greater flexibility for cardiac imaging. These HCU devices have harmonic, color, and spectral Doppler (continuous/pulsed wave). Siemens Medical Solutions USA, Inc. has incorporated a TEE connector, which connects to its Cypress (highly miniaturized echocardiogram unit) and allows the performance of a TEE with this unit, which is mildly heavier than a typical HCU. We describe our initial clinical experience with this unit. The image quality is comparable to routine TEEs, with the advantages of shorter duration, portability, affordable cost, avoiding the use of high-end machine from the echo lab, availability of non-HCU units for other studies, and preventing the need for an echo technician to be involved in the procedure.

The Essential Light Chain N-terminal Extension Alters Force and Fiber Kinetics in Mouse Cardiac Muscle

The functional significance of the actin-binding region at the N terminus of the cardiac myosin essential light chain (ELC) remains elusive. In a previous experiment, the endogenous ventricular ELC was replaced with a protein containing a 10-amino acid deletion at positions 5-14 (ELC1vDelta5-14, referred to as 1vDelta5-14), a region that interacts with actin. 1vDelta5-14 mice showed no discernable mutant phenotype in skinned ventricular strips. However, because the myofilament lattice swells upon skinning, the mutant phenotype may have been concealed by the inability of the ELC to reach the actin-binding site. Using the same mouse model, we repeated earlier measurements and performed additional experiments on skinned strips osmotically compressed to the intact lattice spacing as determined by x-ray diffraction. 1vDelta5-14 mice exhibited decreased maximum isometric tension without a change in calcium sensitivity. The decreased force was most evident in 5-6-month-old mice compared with 13-15-month-old mice and may account for the greater ventricular wall thickness in young 1vDelta5-14 mice compared with age-matched controls. No differences were observed in unloaded shortening velocity at maximum calcium activation. However, 1vDelta5-14 mice exhibited a significant difference in the frequency at which minimum complex modulus amplitude occurred, indicating a change in cross-bridge kinetics. We hypothesize that the ELC N-terminal extension interaction with actin inhibits the reversal of the power stroke, thereby increasing isometric force. Our results strongly suggest that an interaction between residues 5-14 of the ELC N terminus and the C-terminal residues of actin enhances cardiac performance.

TU‐D‐I‐611‐08: Cone Beam X‐Ray Scatter Removal Via Image Frequency Modulation and Filtering

Purpose: To develop a rapid method of patient scatter removal from cone beam (CB) projection images that requires no scatter measurement, physical modeling or strong assumptions regarding the spatial smoothness of the scatter distribution. Method and Materials: A modulator grid is placed between the imaged distribution and the detector that differentially frequency modulates primary and scattered photons. When photons travel through the grid, photons that originate directly from the CB source are modulated by a higher frequency than scattered photons that have more proximal, diffusely distributed sources. We employ non‐linear Fourier domain filtering to attenuate the contribution of scatter to the image spectrum. The theoretical validity of the method is verified using linear analysis of planar sources and its performance is evaluated using a simulator based on this analytical model. Results: Simulation experiments with an ideal modulator indicate that even unrealistically large amounts of scatter are almost entirely removed by this method. The recovered images are devoid of major artifacts and exhibit an RMS error of 10%. Conclusion: A disadvantage of the technique is that it will always produce a filtered image having at best 0.41 of the maximum detector resolution when maximum scatter rejection is desired. This is not a major issue in most medical X‐ray CB imaging applications using contemporary detector technology, especially since scatter often significantly reduces useful resolution. Conflict of Interest: Supported by Siemens Medical Solutions USA, Inc.

TU‐D‐I‐611‐02: Volumetric Cone Beam Reconstruction Engines for 4D Image Guidance

Purpose: Limited angle tomography (LAT) may be used to rapidly reconstruct longitudinal slice images from cone beam datasets. These images are useful for image guidance in radiotherapy applications. By sampling a limited angular range (AR) imaging time is reduced, particularly in prospectively gated studies. We compare the LAT performance, as a function of AR, of the standard FDK algorithm and the simultaneous algebraic reconstruction technique (SART). We propose an imaging protocol to minimize dose and imaging time, while providing image guidance. Method and Materials: We employ LAT reconstruction (LATview) to produce high contrast images of a target tumor in the presence of large amounts of overlying and underlying anatomy. The performance of the SART and FDK s compared for ARs of 15–60 degrees. Results: We demonstrate using a 4D clinical thorax dataset that a lung tumor may be well delineated from within the ribcage along longitudinal planes utilizing as few as 8 projections over 15 degrees of arc using FDK. Assuming an average patient respiration rate of 0.3Hz, gated imaging is completed within 24 seconds. This constitutes an 8‐fold reduction in imaging time when compared to a full AR tomographic acquisition involving 60 projections over 200 degrees. Conclusion: LATview offers significant speed advantages over full angular sampling for 4D studies. It is also more versatile than techniques of digital tomosynthesis as it is able to simultaneously generate multiple image planes of the target volume. Both FDK and SART appear useful for image guidance. Although the SART images subjectively provide more detail, this detail may reduce the tumor‐background contrast (TBC). As a result, TBC is higher for FDK for the lowest AR (15 degree) acquisitions, while SART performs better in terms of TBC for ranges of more than 30 degrees. Conflict of Interest: Supported by Siemens Medical Solutions USA, Inc.