SU-E-I-11: A Novel High Resolution CT Imager for a Breast SPECT-CT System

PURPOSE

To evaluate the intrinsic characteristics of a new high resolution, large area, small bezel, digital imager developed for a dedicated SPECT-CT system for fully-3D mammotomographic imaging applications.

METHODS

A new flat panel digital imager was developed having 127μm pixels (identical to those in the Paxscan 2520) with an active 40×30cm area and 3200×2304 total pixels, which is well suited for pendant breast imaging close to the chest wall. The readout and driver ASIC TAB bonding pads were arranged on only two sides of the imager plate, to eliminate dead edge spacing. A special housing was developed to accommodate this imaging plate providing very narrow 8mm edges (bezels) on two orthogonal sides The TFT array imager was coated with 600μm thick micro-columnar CsI, which provides >90% absorption in the breast CT (60-80kVp) x-ray energy range. It provides better than 70% absorption for RQA5 (70kVp 21mm Al filter) x- ray radiation. The readout ASICs are connected to 14 bit A/D converters, and special readout ASICs with gain switching feature, which provide an additional 4bit virtual (2-3 effective) dynamic range.

RESULTS

The MTF is ∼7.5% at the 3.9 lp/mm Nyquist frequency. The NPS curves continuously decrease with increasing spatial frequencies, characteristic of scintillator based imagers. The excellent DQE (0) measured at RQA5 is ∼75% in the 0.1-1mR dose range and ∼10% at the Nyquist frequency. The imager has excellent linearity over the full dynamic range, and high contrast images are readily acquired.

CONCLUSIONS

The new 4030 flat panel imager is a high resolution, state of the art detector, ideal for breast imaging and other applications. This detector is included in the SPECT-CT device in development.

SU-E-l-01: Investigating the Dependence of 2D and 3D Scatter-To-Primary Ratios on Breast Density in Clinical Breast CT

PURPOSE

To characterize 2D and 3D scatter-to-primary ratios (SPR) and investigate the dependence of SPR on breast density based on clinicalpatient imaging on our dedicated SPECT-CT mammotomography system.

METHODS

As a part of an on-going IRB approved protocol, 7 consented women underwent a breast imaging study with our SPECT-CT system. Using a quasi-monochromatic x-ray cone beam and flat panel detector, 240 projections were obtained. 6 beam stop array (BSA) projections were also obtained over 40 degree intervals. The CT data were scatter corrected using a phantom-validated algorithm based on the BSA technique. For each projection, 2D scatter fluence was determined behind each beam stop shadow through the patient's breast, and cubic spline interpolated throughout the thresholded breast region. 2D SPRs were calculated as the average of 6 measured ratios of scatter projections to scatter corrected (primary) projections. Angular cubic spline interpolation was performed to obtain the remaining 234 azimuthal BSA projections for reconstruction correction. Corrected and uncorrected projection images were individually reconstructed and 3D SPRs calculated as the ratio of difference between primary and un-corrected volumes to primary volumes. Histograms of the reconstructed patient data-sets yielded distinct peaks representing linear attenuation coefficients of glandular+skin and fatty tissue. Percentage glandular and fatty tissue was estimated by fitting a double Gaussian to the histogram and integrating area under the curve.

RESULTS

Only 4 CT data sets devoid of motion and truncation artifacts were suitable for scatter correction. Preliminary results show that 2D SPR values peak at the center of breast volumes and were greatest (∼50%) for the most glandular breast, whereas 3D SPR values remained fairly constant throughout the breast and did not obviously correlate with density, consistent with prior phantom results.

CONCLUSIONS

2D SPR values are greater in breasts with higher glandular tissue composition, whereas 3D SPR values appear independent of breast composition. This work is funded by the National Cancer Institute of the National Institutes of Health grant RO1-CA096821, with partial support (JHP) from NIH T32-EB001040. MPT is the inventor of this CT technology, and is named as an inventor on the patent for this technology awarded to Duke University. If this technology becomes commercially successful, MPT and Duke could benefit financially.

Standardization of fetal ultrasound biometry measurements: improving the quality and consistency of measurements

OBJECTIVE

To assess whether a standardization exercise prior to commencing a fetal growth study involving multiple sonographers can reduce interobserver variation.

METHODS

In preparation for an international study assessing fetal growth, nine experienced sonographers from eight countries participated in a standardization exercise consisting of theoretical and practical sessions. Each performed a set of seven standard fetal measurements on pregnant volunteers at 20-37 weeks' gestation, and these were repeated by the lead sonographer; all measurements were taken in a blinded fashion. After this the sonographers had hands-on practice and feedback sessions on other volunteers. This process was repeated three times. Measurement differences between sonographers and the lead sonographer, expressed as a gestational-age-specific Z-score, between the first and third scans were compared using the Wilcoxon signed ranks test, and variance was assessed using Pitman's test. Interobserver agreement was also assessed using the intraclass correlation coefficient (ICC), and all images were scored for quality in a blinded fashion.

RESULTS

At baseline the level of agreement and image scoring were high. A significant reduction in the differences between sonographers and the lead sonographer were seen for fetal biometry overall (head circumference, abdominal circumference and femur length) between the first and third scans (median Z-scores, 0.46 and 0.24; P = 0.005), and a reduction in the variance was also observed (P < 0.001). The ICCs for measurement pairs for every fetal measurement showed a clear trend of increasing ICC (better agreement) with consecutive training scan sessions, although no improvement in image scores was seen.

CONCLUSION

Even for experienced sonographers, a standardization exercise before starting a study of fetal biometry can improve consistency of measurements. This could be of relevance for studies assessing fetal growth in multicenter sites.

A randomized trial of a single-dose rasburicase versus five-daily doses in patients at risk for tumor lysis syndrome

BACKGROUND

Tumor lysis syndrome (TLS) is a life-threatening disorder characterized by hyperuricemia and metabolic derangements. The efficacy of rasburicase, administered daily for 5 days, has been well established. However, the optimal duration of therapy is unknown in adults.

PATIENTS AND METHODS

We evaluated the efficacy of rasburicase (0.15 mg/kg) administered as single dose followed by as needed dosing (maximum five doses) versus daily dosing for 5 days in adult patients at risk for TLS.

RESULTS

Eighty of the 82 patients enrolled received rasburicase; 40 high risk [median uric acid (UA) 8.5 mg/dl; range, 1.5-19.7] and 40 potential risk (UA = 5.6 mg/dl; range, 2.4-7.4). Seventy-nine patients (99%) experienced normalization in their UA within 4 h after the first dose; 84% to an undetectable level (<0.7 mg/dl). Thirty-nine of 40 (98%) patients in the daily-dose arm and 34 of 40 (85%) patients in single-dose arm showed sustained UA response. Six high-risk patients within the single-dose arm required second dose for UA >7.5 mg/dl. Rasburicase was well tolerated; one patient with glucose-6-phosphate dehydrogenase deficiency developed methemoglobinemia and hemolysis.

CONCLUSIONS

Rasburicase is highly effective for prevention and management of hyperuricemia in adults at risk for TLS. Single-dose rasburicase was effective in most patients; only a subset of high-risk patients required a second dose.

A novel lumen-apposing stent for transluminal drainage of nonadherent extraintestinal fluid collections

BACKGROUND AND STUDY AIMS

Tubular stents have been used to accomplish endoscopic transluminal drainage, but do not impart lumen-to-lumen anchorage. We evaluated a novel lumen-apposing stent designed for enteric drainage of nonadherent lumens.

MATERIAL AND METHODS

Ex vivo benchtop testing was performed to quantify various physical and performance metrics of the stent (Axios). A simulator was developed to test the stent deployment through an echoendoscope. Survival experiments were performed on four pigs. Under endosonographic guidance, a cholecystogastrostomy tract was created and the stent was deployed across the lumens. Direct cholecystoscopy was performed. Surveillance gastroscopy was performed at weekly intervals for up to 8 weeks. Measured outcomes were procedural success, safety, and device durability and patency.

RESULTS

In benchtop testing, the Axios stent withstood various vector forces of movement, yet allowed easy removability from the simulated tissue. The stent was successfully deployed across the stomach and gallbladder lumens in all four animals without complication. Direct cholecystoscopy and contrast injection documented the absence of tissue trauma and leakage. Gastroscopy at weekly intervals showed the stent in stable position without dislodgment. The stent remained patent in all animals. The covering remained intact and there was no hyperplastic tissue ingrowth or overgrowth, or tissue injury. One stent was removed at 4 weeks. On necropsy, the gallbladders showed focal adherence to the stomach at the site of cystogastrostomy with a negative leak test.

CONCLUSIONS

The Axios stent enables the creation of a robust and reliable conduit between nonadherent lumens around the gastrointestinal tract.

A novel lumen-apposing stent for transluminal drainage of nonadherent extraintestinal fluid collections

BACKGROUND AND STUDY AIMS

Tubular stents have been used to accomplish endoscopic transluminal drainage, but do not impart lumen-to-lumen anchorage. We evaluated a novel lumen-apposing stent designed for enteric drainage of nonadherent lumens.

MATERIAL AND METHODS

Ex vivo benchtop testing was performed to quantify various physical and performance metrics of the stent (Axios). A simulator was developed to test the stent deployment through an echoendoscope. Survival experiments were performed on four pigs. Under endosonographic guidance, a cholecystogastrostomy tract was created and the stent was deployed across the lumens. Direct cholecystoscopy was performed. Surveillance gastroscopy was performed at weekly intervals for up to 8 weeks. Measured outcomes were procedural success, safety, and device durability and patency.

RESULTS

In benchtop testing, the Axios stent withstood various vector forces of movement, yet allowed easy removability from the simulated tissue. The stent was successfully deployed across the stomach and gallbladder lumens in all four animals without complication. Direct cholecystoscopy and contrast injection documented the absence of tissue trauma and leakage. Gastroscopy at weekly intervals showed the stent in stable position without dislodgment. The stent remained patent in all animals. The covering remained intact and there was no hyperplastic tissue ingrowth or overgrowth, or tissue injury. One stent was removed at 4 weeks. On necropsy, the gallbladders showed focal adherence to the stomach at the site of cystogastrostomy with a negative leak test.

CONCLUSIONS

The Axios stent enables the creation of a robust and reliable conduit between nonadherent lumens around the gastrointestinal tract.

Parathyroid hormone stimulates circulating osteogenic cells in hypoparathyroidism

CONTEXT

The osteoanabolic properties of PTH may be due to increases in the number and maturity of circulating osteogenic cells. Hypoparathyroidism is a useful clinical model because this hypothesis can be tested by administering PTH.

OBJECTIVE

The objective of the study was to characterize circulating osteogenic cells in hypoparathyroid subjects during 12 months of PTH (1-84) administration.

DESIGN

Osteogenic cells were characterized using flow cytometry and antibodies against osteocalcin, an osteoblast-specific protein product, and stem cell markers CD34 and CD146. Changes in bone formation from biochemical markers and quadruple-labeled transiliac crest bone biopsies (0 and 3 month time points) were correlated with measurements of circulating osteogenic cells.

SETTING

The study was conducted at a clinical research center.

PATIENTS

Nineteen control and 19 hypoparathyroid patients were included in the study.

INTERVENTION

Intervention included the administration of PTH (1-84).

RESULTS

Osteocalcin-positive cells were lower in hypoparathyroid subjects than controls (0.7 ± 0.1 vs. 2.0 ± 0.1%; P < 0.0001), with greater coexpression of the early cell markers CD34 and CD146 among the osteocalcin-positive cells in the hypoparathyroid subjects (11.0 ± 1.0 vs. 5.6 ± 0.7%; P < 0.001). With PTH (1-84) administration, the number of osteogenic cells increased 3-fold (P < 0.0001), whereas the coexpression of the early cell markers CD34 and CD146 decreased. Increases in osteogenic cells correlated with circulating and histomorphometric indices of osteoblast function: N-terminal propeptide of type I procollagen (R(2) = 0.4, P ≤ 0.001), bone-specific alkaline phosphatase (R(2) = 0.3, P < 0.001), osteocalcin (R(2) = 0.4, P < 0.001), mineralized perimeter (R(2) = 0.5, P < 0.001), mineral apposition rate (R(2) = 0.4, P = 0.003), and bone formation rate (R(2) = 0.5, P < 0.001).

CONCLUSIONS

It is likely that PTH stimulates bone formation by stimulating osteoblast development and maturation. Correlations between circulating osteogenic cells and histomorphometric indices of bone formation establish that osteoblast activity is being identified by this methodology.

Controlled and extended drug release behavior of chitosan-based nanoparticle carrier

Controlled drug release is presently gaining significant attention. In this regard, we describe here the synthesis (based on the understanding of chemical structure), structural morphology, swelling behavior and drug release response of chitosan intercalated in an expandable layered aluminosilicate. In contrast to pure chitosan, for which there is a continuous increase in drug release with time, the chitosan-aluminosilicate nanocomposite carrier was characterized by controlled and extended release. Drug release from the nanocomposite particle carrier occurred by degradation of the carrier to its individual components or nanostructures with a different composition. In both the layered aluminosilicate-based mineral and chitosan-aluminosilicate nanocomposite carriers the positively charged chemotherapeutic drug strongly bound to the negatively charged aluminosilicate and release of the drug was slow. Furthermore, the pattern of drug release from the chitosan-aluminosilicate nanocomposite carrier was affected by pH and the chitosan/aluminosilicate ratio. The study points to the potential application of this hybrid nanocomposite carrier in biomedical applications, including tissue engineering and controlled drug delivery.