Computed Tomography for Imaging the Breast

Despite the success of screening mammography contributing to the reduction of cancer mortality, a number of other imaging techniques are being studied for breast cancer screening. In our laboratory, a dedicated breast computed tomography (CT) system has been developed and is currently undergoing patient testing. The breast CT system is capable of scanning the breast with the woman lying prone on a tabletop, with the breast in the pendant position. A 360° scan currently requires 16.6 s, and a second scanner with a 9-second scan time is nearly operational. Extensive effort was placed on computing the radiation dose to the breast under CT geometry, and the scan parameters are selected to utilize the same radiation dose levels as two-view mammography. A total of 55 women have been scanned, ten healthy volunteers in a Phase I trial, and 45 women with a high likelihood of having breast cancer in a Phase II trial. The breast CT process leads to the production of approximately three hundred 512 × 512 images for each breast. Subjective evaluation of the breast CT images reveals excellent anatomical detail, good depiction of microcalcifications, and exquisite visualization of the soft tissue components of the tumor when contrasted against adipose tissues. The use of iodine contrast injection dramatically enhances the visualization of tumors. While a thorough scientific investigation based upon observer performance studies is in progress, initial breast CT images do appear promising and it is likely that breast CT will play some role in breast cancer imaging.     

Virtual Three-dimensional Computed Tomography Assessment of the Gastric Pouch Following Laparoscopic Roux-Y Gastric Bypass

Background The construction of the gastric pouch during surgery is largely based on the prevailing dogma of Roux-Y gastric bypass (RYGB) surgery. The scarce data that exist suggest that the smaller the gastric pouch, the greater the weight loss after surgery. Current estimations of pouch volume have inherent limitations. We describe the use of virtual three-dimensional computed tomography (3D CT) to assess pouch volume in the immediate postoperative period. Methods We performed 3D CT on three patients 1 day after laparoscopic RYGB using a 16-channel multidetector CT scan. Effervescent granules were administered, along with 1 oz of water, orally to achieve gastric pouch distension. Transaxial images were transferred to the 3D workstation (Vitrea, Vital Images, Inc.) and endoluminal views of the gastric pouch were generated with perspective volume rendering. Pouch area was also measured from the standard postoperative upper gastrointestinal (UGI) contrast study. Results All three patients were female, with a mean preoperative body mass index (BMI) of 43.7 kg/m² and a mean age of 44.3 years. Mean pouch height was 4.07 cm, mean pouch width was 3.79 cm, and mean pouch depth was 2.1 cm. The mean calculated pouch volume was 31.6 cm³. The calculated pouch area using 3D CT was statistically indistinct from the pouch area calculated using the UGI study (15.2 cm² vs 16.9 cm²; p = 0.549.) Conclusion For the first time, we describe the use of 3D CT to accurately measure postoperative pouch volume. In addition, we were able to confirm the utility of area (postoperative UGI) as an accurate surrogate for pouch volume.     

Weightbearing Computed Tomography as a Novel Imaging Modality: Assessment of Peritalar Instability

Peritalar instability is a complex pathological entity of the hindfoot. The main characteristics of peritalar instability include pathological alignment of the talus at the talocalcaneal joint level. Very often, peritalar instability is observed in patients with progressive collapsing foot deformity (PCFD). In the last decade, weightbearing computed tomography (WBCT) is increasingly accepted as an advanced imaging modality among foot and ankle surgeons. In patients with PCFD, WBCT can provide invaluable information for a better understanding of underlying deformity, including the presence of subfibular and/or sinus tarsi impingement, subluxation of the subtalar joint at the posterior and/or middle facet, and extent of degeneration of the subtalar and talonavicular joints.     

Quantitative Assessment of Experimental Fracture Repair by Peripheral Computed Tomography

An experimental fracture model was used to assess bone mineral density at the fracture site by peripheral computed tomography and to compare the model with biomechanical, histological, and radiographic methods for the quantification of the fracture repair process. Transverse osteotomies in the mid-diaphysis of 28 tibia of sheep were externally fixed and mineral densities, cross-sectional areas, flexural rigidities, tissue composition, and projected callus area were calculated after 9 weeks of healing time. BMD measured by pQCT was strongly correlated with histologically determined percentages of mineralized tissue in the osteotomy gap (R ²= 0.71) and in the periosteal callus (R ²= 0.62). The percentage of mineralized tissue in the osteotomy gap was the best predictor of the flexural rigidity of the tibiae (R ²= 0.74). Because of high correlations with the histological findings, the volumetric BMD at the level of the osteotomy gap was also strongly correlated with the biomechanical findings (R ²= 0.70). Neither the cross-sectional area in pQCT nor the projected callus area in plane film radiography were positively correlated to the flexural rigidity of the tibiae. Quantitative computed tomography proved to be a successful estimator for the prediction of the mechanical stability of healing bones. The noninvasive procedure is a reliable tool for the quantification of the fracture repair process in experimental studies and may be useful for treatment decisions in particular clinical situations. Received: 2 May 1996 / Accepted: 24 June 1996     

Off-Pump Coronary Artery Bypass Grafts Assessment by Multislice Computed Tomography

Abstract Background: Selective coronary angiography is the standard but invasive procedure for postoperative assessment of coronary artery bypass graft patency. The aim of this prospective study is to evaluate the multislice computed tomography (CT) as a means of postoperative patency assessment and anastomotic site control of arterial and venous coronary bypass grafts performed with off-pump coronary artery bypass techniques. Methods: Over a 6-month period, 20 patients underwent isolated coronary artery bypass (beating heart technique) and benefited, 7 days later, from a patency and anastomotic site control by multidetector angio multislice CT with cardiac gating. Results: Whole internal thoracic artery bypasses and venous grafts were visualized perfectly on their entire length, including the anastomotic site, and 3-dimensional reconstruction was possible. The relationship between cardiac cavities and the bypasses were well visualized, allowing quantification of bypass stenosis ensured by software analysis. Conclusions: Postoperative control of coronary bypasses is possible by multislice CT with a very satisfactory resolution, thus making it possible to check the patency of coronary bypasses and the quality of anastomosis with a noninvasive method. Three-dimensional reconstructions are very useful in the event of redo surgery.     

High-resolution Computed Tomography for Clinical Imaging of Bone Microarchitecture

Background  

The role of bone structure, one component of bone quality, has emerged as a contributor to bone strength. The application of high-resolution imaging in evaluating bone structure has evolved from an in vitro technology for small specimens to an emerging clinical research tool for in vivo studies in humans. However, many technical and practical challenges remain to translate these techniques into established clinical outcomes.     

A Simple Approach to Assessment of a Total Knee Replacement's Rotationary Profile Using Computed Tomography

Malrotation is a cause of persistent pain and poor functioning postoperatively in those who undergo a total knee replacement (TKR). The accurate measurement of malrotation is not routinely available in most hospital settings due to an absence of three‐dimensional computed tomography (CT) software. An accessible, uncomplicated technique to demonstrate TKR prosthesis malrotation would be of benefit to orthopaedic surgeons worldwide. A patient was reviewed with persistent postoperative pain, having undergone a right TKR 3 years previously for progressive osteoarthritis. Postoperative prosthetic infection, instability, loosening, and fracture were ruled out as causes for the persistent pain. A two‐dimensional CT scan was obtained of the patient's affected right knee. Adhesive pieces of paper (Post‐it notes) were used to highlight the posterior tibial prosthesis axis, the tibial tuberosity axis, the posterior condylar axis of the femoral prosthesis and the femoral surgical transepicondylar axis, as per the technique described by Berger et al. A protractor was used to assess the degree of malrotation of the tibial and femoral prostheses. Allowing for human error and that of parallax, an immediate assessment was made of the patient's prosthesis using a readily available imaging modality, and malrotation was quickly identified using accessible, affordable everyday stationary equipment.