Phillip M. Young

Automatic Selection of Tube Potential for Radiation Dose Reduction in Vascular and Contrast-Enhanced Abdominopelvic CT

OBJECTIVE The purpose of this study is to assess the ability of a novel automatic tube potential selection tool to reduce radiation dose while maintaining diagnostic quality in CT angiography (CTA) and contrast-enhanced abdominopelvic CT. MATERIALS AND METHODS One hundred one CTA examinations and 90 contrastenhanced abdominopelvic examinations were performed using an automatic tube potential selection tool on a 128-MDCT scanner. Two vascular radiologists and two abdominal radiologists evaluated the image quality for sharpness, noise, artifact, and diagnostic confidence. In a subset of patients who had undergone prior studies (CTA, 28 patients; abdominopelvic CT, 25 patients), a side-by-side comparison was performed by a separate radiologist. Dose reduction and iodine contrast-to-noise ratio resulting from use of the tool were calculated. RESULTS For CTA, 80 or 100 kV was selected for 73% of the scans, with a mean dose reduction of 36% relative to the reference 120-kV protocol. For abdominopelvic CT examinations, 80 or 100 kV was used for 55% of the scans, with a mean dose reduction of 25%. Overall dose reduction relative to the reference 120-kV protocol was 25% and 13% for CTA and abdominopelvic CT scans, respectively. Over 98% of scans had acceptable sharpness, noise texture, artifact, and diagnostic confidence for both readers and diagnostic tasks; 94-100% of scans had acceptable noise. Iodine contrast-to-noise ratio was significantly higher than (p < 0.001) or similar to (p = 0.11) that of prior scans, and equivalent quality was achieved despite the dose reduction. CONCLUSION Automatic tube potential selection provides an efficient and quantitativeway to guide the selection of the optimal tube potential for CTA and abdominopelvic CT examinations.

Pilot prospective evaluation of 99mTc-MDP scintigraphy, 18F NaF PET/CT, 18F FDG PET/CT and whole-body MRI for detection of skeletal metastases.

Objective The aim of this study was to compare 99mTc-MDP bone scanning, 18F NaF PET/CT, 18F FDG PET/CT, and whole-body MRI (WBMRI) for detection of known osseous metastases. Patients and Methods This prospective pilot trial (September 2007-April 2009) enrolled 10 participants (5 men, 5 women, 47–81 years old) diagnosed with cancer and known osseous metastases. 18F NaF PET/CT, 18F FDG PET/CT, and WBMRI were performed within 1 month for each participant. Results The image quality and evaluation of extent of disease were superior by 18F NaF PET/CT compared to 99mTc-MDP scintigraphy in all patients with skeletal lesions and compared to 18F FDG PET/CT in 3 of the patients with skeletal metastases. 18F NaF PET/CT showed osseous metastases where 18F FDG PET/CT was negative in another 3 participants. Extraskeletal metastases were identified by 18F FDG PET/CT in 6 participants. WBMRI with the combination of iterative decomposition of water and fat with echo asymmetry and least-squares estimation, short tau inversion recovery, and diffusion-weighted imaging pulse sequences showed fewer lesions than 18F NaF PET/CT in 5 patients, same number of lesions in 2 patients, and more lesions in 1 patient. WBMRI showed fewer lesions than 18F FDG in 3 patients and same lesions in 6 patients. Conclusions Our pilot phase prospective trial demonstrated superior image quality and evaluation of skeletal disease extent with 18F NaF PET/CT compared to 99mTc-MDP scintigraphy and 18F FDG PET/CT, as well as the feasibility of multisequence WBMRI. In addition, 18F FDG PET/CT provided valuable soft-tissue information that can change disease management. Further evaluation of these findings using the recently introduced PET/MRI scanners is warranted.

CT and MR Imaging of the Mitral Valve: Radiologic-Pathologic Correlation

Computed tomography (CT) and magnetic resonance (MR) imaging are increasingly important adjuncts to echocardiography for the evaluation of mitral valve disease. The mitral valve may be involved in various acquired or congenital conditions with resultant regurgitation or stenosis, and many of these conditions can be identified with CT or MR imaging. In addition, CT is useful for detecting and monitoring postoperative complications after mitral valve repair or replacement. As the use of CT and MR imaging increases, awareness of the CT and MR imaging appearances of the normal mitral valve and the various disease processes that affect it may foster recognition of unsuspected mitral disease in patients undergoing imaging for other purposes. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.306105518/-/DC1.

Magnetic Resonance Elastography. A Novel Technique for the Detection of Hepatic Fibrosis and Hepatocellular Carcinoma After the Fontan Operation

OBJECTIVE To evaluate the utility of magnetic resonance elastography (MRE) in screening patients for hepatic fibrosis, cirrhosis, and hepatocellular carcinoma after the Fontan operation. PATIENTS AND METHODS Hepatic MRE was performed in conjunction with cardiac magnetic resonance imaging in patients who had undergone a Fontan operation between 2010 and 2014. Liver stiffness was calculated using previously reported techniques. Comparisons to available clinical, laboratory, imaging, and histopathologic data were made. RESULTS Overall, 50 patients at a median age of 25 years (range, 21-33 years) who had undergone a Fontan operation were evaluated. The median interval between Fontan operation and MRE was 22 years (range, 16-26 years). The mean liver stiffness values were increased: 5.5 ± 1.4 kPa relative to normal participants. Liver stiffness directly correlated with liver biopsy-derived total fibrosis score, time since operation, mean Fontan pressure, γ-glutamyltransferase level, Model for End-Stage Liver Disease score, creatinine level, and pulmonary vascular resistance index. Liver stiffness was inversely correlated with cardiac index. All 3 participants with hepatic nodules exhibiting decreased contrast uptake on delayed postcontrast imaging and increased nodule stiffness had biopsy-proven hepatocellular carcinoma. CONCLUSION The association between hepatic stiffness and fibrosis scores, Model for End-Stage Liver Disease scores, and γ-glutamyltransferase level suggests that MRE may be useful in detecting (and possibly quantifying) hepatic cirrhosis in patients after the Fontan operation. The correlation between stiffness and post-Fontan time interval, mean Fontan pressure, pulmonary vascular resistance index, and reduced cardiac index suggests a role for long-term hepatic congestion in creating these hepatic abnormalities. Magnetic resonance elastography was useful in detecting abnormal nodules ultimately diagnosed as hepatocellular carcinoma. The relationship between stiffness with advanced fibrosis and hepatocellular carcinoma provides a strong argument for additional study and broader application of MRE in these patients.

Image-Guided Placement of Occipitocervical Instrumentation Using a Reference Arc Attached to the Headholder

OBJECTIVE To develop a safe and accurate method of image-guided placement of instrumentation in the upper cervical spine and occiput in which the reference arc is fixed to the headholder. METHODS The authors describe a technique for placing screws at the occipital, C1, and C2 levels using 3-dimensional image guidance in which the reference arc is fixed to the headholder. Technical details are discussed as well as modifications to the technique to maximize navigation accuracy and decrease the need for re-registration. One of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB Inc., Westchester, IL) used in conjunction with the Arcadis Orbic Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany) or the Stealth Treon system (Medtronic, Littleton, MA) paired with the O-arm (Medtronic), was used for image guidance in this study. A total of 18 patients had 82 screws placed at the occipital, C1, or C2 level using this technique. An independent radiologist interpreted postoperative computed tomographic scans of these patients and graded the screws for bony breach. RESULTS No complications resulted from the use of image guidance or from the placement of instrumentation. Postoperative computed tomography revealed 1 screw with a minimal breach of the outer lamina of C2. Another screw was replaced intraoperatively secondary to a minimal bony breach. No other bony breach occurred. CONCLUSIONS This technique allows safe and accurate placement of instrumentation in the posterior occipitocervical junction using 3-dimensional image guidance in which the reference arc is attached to the headholder.

CT and MRI assessment of the aortic root and ascending aorta.

OBJECTIVE We provide an outline of aortic anatomy and disease patterns, describe methods of aortic measurement, and highlight measurement thresholds for surgical intervention. We also discuss findings that can assist in preoperative planning and in detecting underlying connective tissue disorders. CONCLUSION A standardized approach to the measurement of the aorta is needed and features suggestive of an underlying connective tissue disorder should be recognized. Radiologists should be aware of the image limitations and clinical implications of reported measurements.

Hypermetabolic activity in patients with active retroperitoneal fibrosis on F-18 FDG PET: Report of three cases

Idiopathic retroperitoneal fibrosis is an uncommon disease characterized by periaortic inflammation with gradual fibrosis and distortion of retroperitoneal structures such as the ureter. Several earlier case reports have documented hypermetabolic retroperitoneal activity on fluorodeoxyglucose positron emission tomography (FDG PET) in patients with active disease, and a decrease in the activity following immunosuppressive therapy. We report FDG PET positive findings in three patients presenting with active retroperitoneal fibrosis. In two cases, enhancing periaortic soft tissue seen on computed tomography (CT) markedly diminished following immunosuppressive therapy. In one patient, repeat FDG PET was performed following immunosuppressive therapy, with complete resolution of the retroperitoneal FDG avidity. We suggest that FDG PET may play a useful adjunct to anatomic imaging and serum inflammatory markers in assessing the severity of inflammation in retroperitoneal fibrosis, and in assessing the likelihood of response to immunosuppressive therapy. FDG PET may also be used in follow-up to assess therapeutic response if CT findings are unclear.

The effect of a silane coupling agent on the bond strength of bone cement and cobalt–chrome alloy

Debonding of the cement-implant interface has been hypothesized to be the leading initial indicator of failed total hip prostheses. Many attempts have been made to increase the bond strength of this interface by precoating the implant, increasing the implants surface roughness, and creating macro-grooves or channels on the implant. However, each of these approaches introduces new complications. This study introduces a unique silane coupling agent used to chemically bond the bone cement to the implant. Cylindrical cobalt-chrome samples were treated with the silane coupling agent, bonded to polymethylmethacrylate, and pushed out to failure. The mean shear strengths were compared to the failure strengths of untreated samples. Half of the specimens were tested immediately following cement curing, and the other half were tested after immersion in saline solution for 60 days. The mean shear strength of the silane-coated samples ranged from 18.2 to 24.1 MPa, and the mean shear strength of the uncoated samples ranged from 7.6 to 15.0 MPa. The increase in strength following silane coating noted in this study may increase the longevity of the implant by decreasing debonding at the interface and, therefore, subsequent failure due to loosening.

Nutritional status, CT body composition measures and survival in ovarian cancer

OBJECTIVE Body composition measures (BCMs) are an important predictor of nutritional status in patients with cancer. Poor nutritional status is common in ovarian cancer (OC) and is a well-known variable that influences cancer treatment and outcome. We aim to establish the role of BCMs measured by computed tomography (CT) in predicting outcomes in patients with OC. METHODS We retrospectively searched our institutional database for patients with stage IIIC/IV OC who underwent surgery as primary treatment at Mayo Clinic between 1996 and 2005 and had adequate presurgical CT images available. For each patient, 1 axial CT image at the level of the 3rd lumbar vertebra was evaluated. Adipose and lean tissues were discriminated using commercially available software. Cox models were fit to evaluate the relationship between patient factors and overall survival (OS). Associations were summarized using hazard ratios (HRs) and corresponding 95% CIs. RESULTS A total of 82 patients were identified, with a median age of 68.4 years. OS at 1 and 5 years was 84.1% and 24.1%, respectively. Older age (P=.01), stage IV disease (P<.001), and subcutaneous and muscular fat<77.21cm(2) (P<.001) were independently associated with poor OS. Longer hospital stay was independently predicted by albumin≤3g/dL (P=.03), suboptimal surgery (P=.02), and subcutaneous and muscular fat<77.21cm(2) (P<.001). Surgical complications were independently predicted only by albumin≤3g/dL (P<.01). CONCLUSIONS CT BCMs, as indicators of nutritional status, are independent predictors of longer hospital stay and poor OS in patients with OC.

Muscle composition measured by CT scan is a measurable predictor of overall survival in advanced ovarian cancer

OBJECTIVES To assess the impact of muscle composition and sarcopenia on overall survival in advanced epithelial ovarian cancer (EOC) after primary debulking surgery (PDS). METHODS Women with stage IIIC/IV EOC who underwent PDS with curative intent between 1/1/2006 and 12/31/2012 were included. Patient variables and vital status were abstracted. Body composition was evaluated in a semi-automated process using Slice-O-Matic software v4.3 (TomoVision). Skeletal muscle area and mean skeletal muscle attenuation were recorded. Associations with overall survival were evaluated using Cox proportional hazards models and recursive partitioning. RESULTS We identified 296 patients and 132 (44.6%) were classified as sarcopenic. The average mean skeletal muscle attenuation of the entire cohort was 33.4 Hounsfield units (HU). A multivariate model of overall risk of death included histology, residual disease, and mean skeletal attenuation. Among patients without residual disease, overall survival, but not progression free survival was significantly different between patients with low versus high mean skeletal attenuation (median survival, 2.8 vs. 3.3years). Among patients with residual disease, overall survival was significantly different between patients with low versus high mean skeletal attenuation ≥36.40 vs. <36.40 HU (median survival, 2.0 vs. 3.3years). CONCLUSIONS Sarcopenia and low mean skeletal muscle attenuation are common in women undergoing PDS for advanced EOC. These factors are associated with poorer outcomes, and can be used in preoperative risk stratification and patient counseling. Further research into body composition and whether this risk factor can be altered via nutrition or fitness in this population is warranted.