William J. Davros

Spine Fusion Using Cell Matrix Composites Enriched in Bone Marrow-Derived Cells

Bone marrow-derived cells including osteoblastic progenitors can be concentrated rapidly from bone marrow aspirates using the surface of selected implantable matrices for selective cell attachment. Concentration of cells in this way to produce an enriched cellular composite graft improves graft efficacy. The current study was designed to test the hypothesis that the biologic milieu of a bone marrow clot will significantly improve the efficacy of such a graft. An established posterior spinal fusion model and cancellous bone matrix was used to compare an enriched cellular composite bone graft alone, bone matrix plus bone marrow clot, and an enriched bone matrix composite graft plus bone marrow clot. Union score, quantitative computed tomography, and mechanical testing were used to define outcome. The union score for the enriched bone matrix plus bone marrow clot composite was superior to the enriched bone matrix alone and the bone matrix plus bone marrow clot. The enriched bone matrix plus bone marrow clot composite also was superior to the enriched bone matrix alone in fusion volume and in fusion area. These data confirm that the addition of a bone marrow clot to an enriched cell-matrix composite graft results in significant improvement in graft performance. Enriched composite grafts prepared using this strategy provide a rapid, simple, safe, and inexpensive method for intraoperative concentration and delivery of bone marrow-derived cells and connective tissue progenitors that may improve the outcome of bone grafting.

3-DIMENSIONAL VOLUME RENDERED COMPUTERIZED TOMOGRAPHY FOR PREOPERATIVE EVALUATION AND INTRAOPERATIVE TREATMENT OF PATIENTS UNDERGOING NEPHRON SPARING SURGERY

PURPOSE Computerized tomography (CT) is the diagnostic and staging modality of choice for renal neoplasms. Existing imaging modalities are limited by a 2-dimensional (D) format. Recent advances in computer technology now allow the production of high quality 3-D images from helical CT. Nephron sparing surgery requires a detailed understanding of renal anatomy. Preoperative evaluation must delineate the relationship of the tumor to adjacent normal structures and demonstrate the vascular supply to the tumor for the surgeon to conserve as much normal parenchyma as possible. We propose that helical CT combined with 3-D volume rendering provides all of the information required for preoperative evaluation and intraoperative management of nephron sparing surgery cases. We prospectively evaluated the role of 3-D volume rendering CT in 60 patients undergoing nephron sparing surgery for renal cell carcinoma at the Cleveland Clinic Foundation. MATERIALS AND METHODS Triphasic spiral CT was performed preoperatively in 60 consecutive patients undergoing nephron sparing surgery for renal neoplasms. A 3 to 5-minute videotape was prepared using volume rendering software which demonstrated the position of the kidney, location and depth of extension of the tumor(s), renal artery(ies) and vein(s), and relationship of the tumor to the collecting system. These videotapes were viewed by a radiologist and urologist in the operating room at surgery, and immediately correlated with surgical findings. Corresponding renal arteriograms of 19 patients were retrospectively compared to 3-D volume rendering CT and operative findings. RESULTS A total of 97 renal masses were identified in 60 cases evaluated with 3-D volume rendering CT before nephron sparing surgery. There were no complications related to the 3-D protocol and 3-D rendering was successful in all patients. The number and location of lesions identified by 3-D volume rendering CT were accurate in all cases, while enhancement and diagnostic characteristics were consistent with pathological findings in 95 of 97 tumors (98%). Of 77 renal arteries identified at surgery 74 were detected by 3-D volume rendering CT (96%). Helical CT missed 3 small accessory arteries, including 1 in a cross fused ectopic kidney. All major venous branches and anomalies were identified, including 3 circumaortic left renal veins. Of 69 renal veins identified at surgery 64 were detected by 3-D volume rendering CT (93%). All 5 renal veins missed by CT were small, short, duplicated right branches of the main renal vein. Renal fusion and malrotation anomalies were correctly identified in all 4 patients. CONCLUSIONS The 3-D volume rendering CT accurately depicts the renal parenchymal and vascular anatomy in a format familiar to most surgeons. The data integrate essential information from angiography, venography, excretory urography and conventional 2-D CT into a single imaging modality, and can obviate the need for more invasive imaging. Additionally, the use of videotape in an intraoperative setting provides concise, accurate and immediate 3-D information to the surgeon, and it has become the preferred means of data display for these procedures at our center.

Selective retention of bone marrow-derived cells to enhance spinal fusion.

Connective tissue progenitors can be concentrated rapidly from fresh bone marrow aspirates using some porous matrices as a surface for cell attachment and selective retention, and for creating a cellular graft that is enriched with respect to the number of progenitor cells. We evaluated the potential value of this method using demineralized cortical bone powder as the matrix. Matrix alone, matrix plus marrow, and matrix enriched with marrow cells were compared in an established canine spinal fusion model. Fusions were compared based on union score, fusion mass, fusion volume, and by mechanical testing. Enriched matrix grafts delivered a mean of 2.3 times more cells and approximately 5.6 times more progenitors than matrix mixed with bone marrow. The union score with enriched matrix was superior to matrix alone and matrix plus marrow. Fusion volume and fusion area also were greater with the enriched matrix. These data suggest that the strategy of selective retention provides a rapid, simple, and effective method for concentration and delivery of marrow-derived cells and connective tissue progenitors that may improve the outcome of bone grafting procedures in various clinical settings.

Effect of Altering Automatic Exposure Control Settings and Quality Reference mAs on Radiation Dose, Image Quality, and Diagnostic Efficacy in MDCT Enterography of Active Inflammatory Crohn's Disease

OBJECTIVE The purpose of our study was to determine whether the MDCT enterography dose can be reduced by changing automatic exposure control (AEC) setting and quality reference milliampere-seconds (mAs) without altering subjective image quality or efficacy in active inflammatory Crohns disease. SUBJECTS AND METHODS This is a prospective study of 2,310 MDCT enterography procedures performed using 16- and 64-MDCT in three cohorts (original, intermediate, and final dose levels). For 16-MDCT, the original and intermediate dose level quality reference mAs was 200, and weight-based (1 pound [0.45 kg] = 1 mAs) for the final dose level. For 64-MDCT, the original dose level quality reference mAs was 260; the mAs was 220 for intermediate and weight-based for the final dose level. For the intermediate and final dose levels, AEC was changed from strong to weak increase for obese and weak to strong decrease for slim patients. Demographic data and volume CT dose index (CTDI(vol)) were analyzed. Three readers evaluated the cases for image quality and efficacy differentiating normal from active inflammatory Crohns disease. RESULTS For 16-MDCT, CTDI(vol) decreased from 12.82 to 10.14 mGy and 10.14 to 8.7 mGy between original to intermediate and intermediate to final dose levels. For 64-MDCT, the CTDI(vol) decreased from 15.72 to 11.42 mGy and 11.42 to 9.25 mGy between original to intermediate and intermediate to final dose levels. Images were rated suboptimal or nondiagnostic more often in the intermediate dose level (p < 0.05) but not in the final. There was no reduction in diagnostic efficacy as measured by area under the ROC curve (p > 0.1443 except for one comparison with one reader). CONCLUSION Substantial dose reduction can be achieved using weight-based quality reference mAs and altering AEC settings without affecting diagnostic efficacy in active inflammatory Crohns disease of the terminal ileum. However, subjective image quality can be compromised at these dose settings, depending on radiologist preference.

Noninvasive imaging for the new century

Noninvasive imaging technologies are expected to play a significant role in the area of medical diagnosis and industrial imaging. The engineers of the 21st century will need the appropriate skill to master the power of new technologies. To face the challenges of the new century, a strong impulse toward a multidisciplinary and diversified engineering knowledge will be essential. Some examples of noninvasive imaging (spiral CT, microwave imaging, hybrid modalities) and image enhancement techniques are presented.

Radiation Exposure to the Surgeon and the Patient During Kyphoplasty

Study Design Prospective study of patients who underwent single or multilevel kyphoplasty for vertebral fractures. Objective To quantify the radiation exposure to the surgeon and to the patient during kyphoplasty, and also to provide a procedural algorithm that effectively minimizes the radiation exposure to the surgeon during any fluoroscopic-guided procedure. Summary of Background Data Spine surgeons who perform minimally invasive procedures often employ fluoroscopy for intraoperative navigation. Methods Twenty-seven patients were enrolled. Two fluoroscopes (1 anterior/posterior and 1 lateral) were used for localization, navigation, and monitoring cement flow. All surgeons wore thyroid shields and lead aprons. The dose of radiation exposure was measured by dosimeter badges. One badge was attached to each patient. The surgeons wore 3 badges: under the thyroid shield (protected), under the lead apron over the left chest (protected), and outside the lead apron over the left chest (unprotected). A thermoluminescent ring dosimeter was worn on the right hand for 18 cases, and on the left hand for 9 cases. Results The exposure time was 5.7±2.0 minutes/vertebra for a single level (n=10), 3.9±0.8 minutes/vertebra for a 2 level (n=9), 2.9±1.2 minutes/vertebra for a 3 level kypholasty (n=8). The exposure time of single level kyphoplasy was significantly different from that of multilevel kyphoplasy (2 level, P=0.040; 3 level, P=0.002). Surgeon exposure as measured by the protected dosimeter was less than the minimum reportable dose (<0.010 mSv). Exposure as measured by the unprotected dosimeter, which is equivalent to deep whole body exposure was 0.248±0.170 mSv/vertebra. The eye exposure was 0.271±0.200 mSv/vertebra, and the shallow exposure (hand/skin) was 0.273±0.200 mSv/vertebra. The hand exposure was 1.744±1.173 mSv/vertebra. Conclusions Without eye or hand protection, the total radiation exposure dose to these areas would exceed the occupational exposure limit after 300 cases per year. Surgeons should wear lead lined glasses and keep their hands out of the radiation beam.

Comparison of indirect radiation dose estimates with directly measured radiation dose for patients and operators during complex endovascular procedures

BACKGROUND A great deal of attention has been directed at the necessity and potential for deleterious outcomes as a result of radiation exposure during diagnostic evaluations and interventional procedures. We embarked on this study in an attempt to accurately determine the amount of radiation exposure given to patients undergoing complex endovascular aortic repair. These measured doses were then correlated with radiation dose estimates provided by the imaging equipment manufacturers that are typically used for documentation and analysis of radiation-induced risk. METHODS Consecutive patients undergoing endovascular thoracoabdominal aneurysm (eTAAA) repair were prospectively studied with respect to radiation dose. Indirect parameters as cumulative air kerma (CAK), kerma area product (KAP), and fluoroscopy time (FT) were recorded concurrently with direct measurements of dose (peak skin dose [PSD]) and radiation exposure patterns using radiochromatic film placed in the back of the patient during the procedure. Simultaneously, operator exposure was determined using high-sensitivity electronic dosimeters. Correlation between the indirect and direct parameters was calculated. The observed radiation exposure pattern was reproduced in phantoms with over 200 dosimeters located in mock organs, and effective dose has been calculated in an in vitro study. Scatter plots were used to evaluate the relationship between continuous variables and Pearson coefficients. RESULTS eTAAA repair was performed in 54 patients over 5 months, of which 47 had the repair limited to the thoracoabdominal segment. Clinical follow-up was complete in 98% of the patients. No patients had evidence of radiation-induced skin injury. CAK exceeded 15 Gy in 3 patients (the Joint Commission on Accreditation of Healthcare Organizations [JCAHO] threshold for sentinel events); however, the direct measurements were well below 15 Gy in all patients. PSD was measured by quantifying the exposure of the radiochromatic film. PSD correlated weakly with FT but better with CAK and KAP (r = 0.55, 0.80, and 0.76, respectively). The following formula provides the best estimate of actual PSD = 0.677 + 0.257 CAK. The average effective dose was 119.68 mSv (for type II or III eTAAA) and 76.46 mSv (type IV eTAAA). The operator effective dose averaged 0.17 mSv/case and correlated best with the KAP (r = 0.82, P < .0001). CONCLUSION FT cannot be used to estimate PSD, and CAK and KAP represent poor surrogate markers for JCAHO-defined sentinel events. Even when directly measured PSDs were used, there was a poor correlation with clinical event (no skin injuries with an average PSD >2 Gy). The effective radiation dose of an eTAAA is equivalent to two preoperative computed tomography scans. The maximal operator exposure is 50 mSv/year, thus, a single operator could perform up to 294 eTAAA procedures annually before reaching the recommended maximum operator dose.

Preoperative assessment of abdominal aortic aneurysm: The value of helical and three-dimensional computed tomography

PURPOSE The purpose of this study was to evaluate the utility of helical computed tomography (CT) in the preoperative assessment of abdominal aortic aneurysms (AAA) and to compare its accuracy with aortography and operative findings. METHODS Thirty-two patients with suspected AAA were evaluated by helical CT with either 5 mm collimation (slice thickness) or a combination of 3 mm collimation through the renal and mesenteric arteries and 7 mm collimation through the remainder of the AAA. Three-dimensional reconstructions were performed with use of three different techniques, and results were compared with aortography and surgery. RESULTS Twenty-five patients were found to have an aneurysm, and 19 subsequently underwent surgery. Standard angiography was also performed in 13. The location, size, and extent of the aneurysm, as well as the wall calcification and intraaneurysmal thrombus, were well depicted with helical CT. The visceral aortic branches, including the detection of renal artery stenosis and accessory renal arteries, were consistently seen with the 3 mm/7 mm collimation protocol and three-dimensional reconstruction. CONCLUSION Helical CT with three-dimensional display of the aorta and its branches combines the advantages of conventional CT imaging and aortography. This technique appears to provide comprehensive preoperative evaluation of AAA.

Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies

Abstract.Background:. Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB. Objective: To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique. Materials and methods: Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system. Results: The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity < 35 %). The optimal technique for visualizing the LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans. Conclusion: Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized.

Optimization of kVp and mAs for pediatric low-dose simulated abdominal CT: is it best to base parameter selection on object circumference?

OBJECTIVE The objective of our study was to determine the effect of mAs and kVp reduction on pediatric phantoms based on patient circumference to optimize dose reduction and maintain image quality for abdominal CT. SUBJECTS AND METHODS Three polymethylmethacrylate right cylindric CT dose index (CTDI) phantoms with diameters of 10, 16, and 32 cm simulated the abdomen of an infant, child, and adolescent, respectively. Using a National Institute of Standards & Technology ion chamber and Victoreen 660 electrometer, doses at centerline were recorded on a 16-MDCT scanner. Measurements were obtained in incremental steps from 50 to 400 mAs and from 80 to 140 kVp. Noise was calibrated to clinical images through a calibration factor. RESULTS For phantoms of all circumferences, doses increased linearly with an increase in mAs and by the power function of kVp(n) for increases in kVp. There was an associated decrease in noise for all circumferences and a sharp decrease at lower doses with a plateau at higher doses. Using a noise threshold of 20 HU and a dose threshold of 2.5 cGy, a range of imaging parameters was established for each circumference from which technique optimization curves were created to determine optimal mAs and kVp pairs. The mean measured dose was 2.435 ± 0.019 cGy. The mean measured noise was 29.35 ± 1.45 HU. CONCLUSION For pediatric CT, the most accurate way to strike the balance between image quality and radiation dose is to adjust dose to abdominal circumference, not body weight or age. Our data support the use of technique optimization curves to optimize kVp and mAs.