Faculty Bibliography

PURPOSE: To evaluate if differences exist in the interpretation of thin- and thick-section reconstructions at computed tomographic (CT) colonography. MATERIALS AND METHODS: Twenty-five patients underwent multi-detector row CT colonography prior to colonoscopy. CT images were reconstructed with two methods: 1.25-mm sections reconstructed every 1 mm (thin) and 5-mm sections reconstructed every 2 mm (thick). Two independent readers interpreted thin sections, then waited a minimum of 15 days before interpreting thick sections. With colonoscopy as the reference standard, comparisons were made between interpretation of thin and thick sections, including sensitivity, specificity, and number of false-positive observations. Interpretation times were recorded, and comparisons were made by using repeated measures analysis of variance. For all tests, P <.05 indicated a statistically significant difference. RESULTS: At colonoscopy, 10 patients had 12 polyps (</=5 mm, n = 7; 6-9 mm, n = 2; >/=10 mm, n = 3). Sensitivity for polyp detection was statistically indistinguishable for thin and thick sections. Reader 1 had three false-positive findings with thin sections and six with thick sections. Reader 2 had six false-positive findings with thin sections and 11 with thick sections. For both readers, the number of false-positive findings was significantly lower for thin sections than for thick sections (P =.035). Specificity was 93.3% with thin sections and 80.0% with thick sections for reader 1 and 80.0% with thin sections and 73.3% with thick sections for reader 2. Mean interpretation time for reader 1 was significantly longer with thin sections (P <.001). Mean interpretation time for reader 2 was 13.0 minutes for both thin and thick sections. CONCLUSION: Specificity improved for both readers with thin sections, with no difference in sensitivity.

The aim of this study was to develop an MRI protocol to evaluate the growth and vascularity of implanted GL261 mouse gliomas on a 7T microimaging system. Both conventional T(1)- and T(2)-weighted imaging and dynamic, contrast-enhanced T(2)*-weighted imaging were performed on 34 mice at different stages of tumor development. MRI measurements of relative cerebral blood volume (rCBV) were compared to histological assessments of microvascular density (MVD). Enhancement on postcontrast T(1)-weighted images was compared to histological assessments of Evan's blue extravasation. Conventional T(2)-weighted and postcontrast T(1)-weighted images demonstrated tumor growth characteristics consistent with previous descriptions of GL261 glioma. Furthermore, measurements of rCBV from MRI data were in good agreement with histological measurements of MVD from the same tumors. Postcontrast enhancement on T(1)-weighted images was observed at all stages of GL261 glioma progression, even before evidence of angiogenesis, indicating that the mechanism of conventional contrast enhancement in MRI does not require neovascularization. These results provide quantitative support for MRI approaches currently used to assess human brain tumors, and form the basis for future studies of angiogenesis in genetically engineered mouse brain tumor models. Magn Reson Med 49:848-855, 2003

It is well known that multiple sclerosis (MS) pathogenesis continues even during periods of clinical silence. To quantify the metabolic characteristics of this activity we compared the absolute levels of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) in the normal-appearing white matter (NAWM) between relapsing-remitting (RR) MS patients and controls. Metabolite concentrations were obtained with 3D proton MR spectroscopy at 1.5 T in a 480 cm(3) volume-of-interest (VOI), centered on the corpus callosum of 11 MS patients and 9 matched controls. Gray/white-matter/cerebral-spinal-fluid (CSF) volumes were obtained from MRI segmentation. Patients' average VOI tissue volume (V(T)), 410.8 +/- 24.0 cm(3), and metabolite levels, NAA = 6.33 +/- 0.70, Cr = 4.67 +/- 0.52, Cho = 1.40 +/- 0.17 mM, were different from the controls by -8%, -9%, +22% and +32%. The Cho level was the only single metric differentiating patients from controls at 100% specificity and >90% sensitivity. Diffusely elevated Cho and Cr probably reflect widespread microscopic inflammation, gliosis, or de- and remyelination in the NAWM. Both metabolites are potential prognostic indicators of current disease activity, preceding NAA decline and atrophy

BACKGROUND AND PURPOSE: Magnetization transfer ratio (MTR) histogram analysis and volumetric MR imaging are sensitive tools with which to quantify the tissue destructive effects in patients with white matter or neurodegenerative disease. Our purpose was to determine whether whole brain MTR and fractional brain parenchyma volume measurements are altered in HIV-1-infected patients who are neurologically symptomatic and in those who are asymptomatic. METHODS: We performed MR imaging and MTR studies of 15 neurologically symptomatic (seven patients) and asymptomatic (eight patients) HIV-1-seropositive patients and compared their findings with those of 10 seronegative normal control participants. MTR was computed on the basis of whole brain parenchyma segmented by using thin section dual echo MR images. RESULTS: The loss of brain tissue, indicated by fractional brain parenchyma volume, was more pronounced in neurologically symptomatic patients (P =.003) but not in asymptomatic patients (P =.23) when compared with control participants. As for whole brain MTR histogram analysis, both patient groups showed significant decrease in mean (P =.02) and median (P < or =.009) values, compared with normal control participants. There was a trend toward positive correlation (r > or = 0.56) between MTR histogram statistics and fractional brain parenchyma volume. CONCLUSION: Our results suggest that MTR histogram analysis is sensitive in detecting early involvement in neurologically asymptomatic patients with HIV and may, therefore, be used as a combined tool with volumetric measurement, which showed significant tissue loss only in symptomatic patients, to assess various stages of brain damage induced by HIV

BACKGROUND AND PURPOSE: In contrast to 'normal-appearing' white matter (NAWM) in patients with multiple sclerosis (MS), there are subtle, abnormal and diffuse signal intensity changes often seen on T2-weighted MR images, which we have referred to as 'dirty-appearing' white matter (DAWM). These areas of DAWM have slightly higher signal intensity than that of NAWM, but lower than that of lesion plaques. Our study was designed to determine the volumetric and magnetization transfer ratio (MTR) features of DAWM in patients with MS. METHODS: Dual-echo fast spin-echo MR imaging and magnetization transfer imaging were performed in 22 patients with relapsing-remitting MS. Slightly hyperintense DAWM areas were manually outlined on the basis of T2-weighted imaging findings. The volume and MTR of DAWM were calculated and compared with the volume and MTR of NAWM and T2 lesion plaques. RESULTS: The average volume of DAWM (18.3 mL) was greater than the average volume of T2 lesion plaques (11.0 mL, P =.04), and the mean MTR in DAWM (38.7%) differed significantly (P <.0001) from that in NAWM (40.7%) and plaques (33.3%). There was a modest negative correlation between either mean MTR (r = -0.60; P =.003) of DAWM or peak height (r = -0.50; P =.02) of DAWM with T2 lesion load. Neither DAWM volume nor total T2 abnormality (DAWM + plaques) volume correlates with the Expanded Disability Status Scale. CONCLUSION: The results of this study indicate that MTR is able to differentiate DAWM from lesion plaques and NAWM and that DAWM might be a different pathologic process of the disease. The notion and quantification of these subtle imaging findings of DAWM areas may improve our understanding of certain stages of disease progression and disease burden in patients with relapsing-remitting MS

Three-dimensional methods for quantifying pulmonary nodule volume at computed tomography (CT) and the effect of imaging variables were studied by using a realistic phantom. Two fixed-threshold methods, a partial-volume method (PVM) and a variable method, were used to calculate volumes of 40 plastic nodules (largest dimension, <5 mm: 20 nodules with solid attenuation and 20 with ground-glass attenuation) of known volume. Tube current times (20 and 120 mAs), reconstruction algorithms (high and low frequency), and nodule characteristics were studied. Higher precision was associated with use of a PVM with predetermined pure nodule attenuation, high-frequency algorithm, and diagnostic CT technique (120 mAs). A PVM is promising for volume quantification and follow-up of nodules

BACKGROUND: There is a need for research to identify factors influencing intentions to undergo colorectal cancer (CRC) screening among family members at risk for CRC. This study tested a mediational model primarily guided by Ronis' elaboration of the Health Belief Model in predicting intention to have colorectal cancer screening among siblings of individuals diagnosed with colorectal cancer prior to age 56 years. METHODS: Data were collected from 534 siblings of individuals diagnosed with CRC. A baseline survey was administered by telephone. Measures included perceived susceptibility, CRC severity, physician and family support for CRC screening, cancer-specific distress, the closeness of the relationship with the affected sibling, and future intention to have a colonoscopy. Participant age, gender, and number of prior colonoscopies, as well as the stage of the affected patient's cancer and time from the patient's diagnosis to the interview, were controlled for in the analyses. RESULTS: The proposed model was not a good fit to the data. A respecified model was fit to the data. In this model, physician support, family support, and sibling closeness were significantly associated with both perceived benefits and barriers. Perceived severity was associated with barriers. Benefits and barriers, as well as cancer-specific distress, were directly associated with colonoscopy intentions. Results were consistent with a mediational role for benefits and barriers in the associations of sibling closeness and with a mediational role for barriers in the association between perceived severity and colonoscopy intentions. Family and physician support impacted intentions both directly and indirectly through effects on benefits and barriers. Perceived risk was not associated with benefits, barriers, or colonoscopy intentions. CONCLUSION: Intervention efforts to increase colonoscopy intentions may benefit from targeting family influences, particularly the affected proband in the family, as well as physician influence, cancer-related distress, perceived CRC severity, and perceived benefits and barriers to colonoscopy

BACKGROUND AND PURPOSE: Sensitivity, positive predictive value (PPV), and negative predictive value (NPV) of conventional MR imaging in predicting glioma grade are not high. Relative cerebral blood volume (rCBV) measurements derived from perfusion MR imaging and metabolite ratios from proton MR spectroscopy are useful in predicting glioma grade. We evaluated the sensitivity, specificity, PPV, and NPV of perfusion MR imaging and MR spectroscopy compared with conventional MR imaging in grading primary gliomas. METHODS: One hundred sixty patients with a primary cerebral glioma underwent conventional MR imaging, dynamic contrast-enhanced T2*-weighted perfusion MR imaging, and proton MR spectroscopy. Gliomas were graded as low or high based on conventional MR imaging findings. The rCBV measurements were obtained from regions of maximum perfusion. Metabolite ratios (choline [Cho]/creatine [Cr], Cho/N-acetylaspartate [NAA], and NAA/Cr) were measured at a TE of 144 ms. Tumor grade determined with the three methods was then compared with that from histopathologic grading. Logistic regression and receiver operating characteristic analyses were performed to determine optimum thresholds for tumor grading. Sensitivity, specificity, PPV, and NPV for identifying high-grade gliomas were also calculated. RESULTS: Sensitivity, specificity, PPV, and NPV for determining a high-grade glioma with conventional MR imaging were 72.5%, 65.0%, 86.1%, and 44.1%, respectively. Statistical analysis demonstrated a threshold value of 1.75 for rCBV to provide sensitivity, specificity, PPV, and NPV of 95.0%, 57.5%, 87.0%, and 79.3%, respectively. Threshold values of 1.08 and 1.56 for Cho/Cr and 0.75 and 1.60 for Cho/NAA provided the minimum C2 and C1 errors, respectively, for determining a high-grade glioma. The combination of rCBV, Cho/Cr, and Cho/NAA resulted in sensitivity, specificity, PPV, and NPV of 93.3%, 60.0%, 87.5%, and 75.0%, respectively. Significant differences were noted in the rCBV and Cho/Cr, Cho/NAA, and NAA/Cr ratios between low- and high-grade gliomas (P <.0001,.0121,.001, and.0038, respectively). CONCLUSION: The rCBV measurements and metabolite ratios both individually and in combination can increase the sensitivity and PPV when compared with conventional MR imaging alone in determining glioma grade. The rCBV measurements had the most superior diagnostic performance (either with or without metabolite ratios) in predicting glioma grade. Threshold values can be used in a clinical setting to evaluate tumors preoperatively for histologic grade and provide a means for guiding treatment and predicting postoperative patient outcome

Even though continued smoking by cancer patients adversely affects survival and quality of life, about one third of patients who smoked prior to their diagnosis continue to smoke after their diagnosis. The implementation of smoking cessation treatments for cancer patients has been slowed by the lack of data on correlates of tobacco use in this population. Thus, this longitudinal study assessed demographic, medical, addiction, and psychological predictors of tobacco use among 74 head, neck, and lung cancer patients. Multivariable binary logistic regression analyses, with outcome categorized as smoker or nonsmoker, indicated that the likelihood that patients would be a smoker was associated with lower levels of perceived risk and a higher level of quitting cons. Multivariable nominal logistic regression, with outcome classified as continuous smoker, continuous quitter, relapser, or follow-up quitter, indicated that: (a). patients categorized as continuous smokers reported significantly lower quitting self-efficacy than follow-up quitters and continuous quitters, (b). relapsers reported a significantly lower level of quitting self-efficacy than either follow-up quitters or continuous quitters, and (c). continuous smokers exhibited a significantly lower level of risk perceptions than continuous abstainers. These findings can be useful for the development and evaluation of treatments to promote smoking cessation among cancer patients

Although the NCI is presently investigating whether enhanced detection of lung tumors via spiral CT reduces lung cancer mortality, use of this technology for lung cancer screening is already widespread in the US. Few data are available concerning level of interest in, or awareness of, spiral CT for lung cancer screening, correlates of participation in screening, or potential reactions to screening results (i.e. smoking cessation) among high-risk individuals. One-hundred-and-seventy-two current or former smokers with no personal cancer history were queried about their awareness of spiral CT for lung cancer screening, received information about the procedure, and completed a survey that assessed interest in screening, correlates of screening interest (i.e. demographic, health, psychological), and expected effects of screening results on smoking. Seventy-seven percent of respondents were unaware of spiral CT for lung cancer screening and 62% expressed high interest in screening. Screening interest was positively related to screening self-efficacy, knowledge of asymptomatic illness, and perceived lung cancer risk. In the face of a positive scan, 52% of smokers said that they would quit, 43% said they would consider quitting, and 3% would continue smoking. If the scan was negative, 19% of smokers said that they would quit, 61% said they would consider quitting, and 20% would continue smoking. Finally, 59% of smokers were interested in smoking cessation counseling, with screening. These findings can help guide the design of psychological interventions to promote the utilization of spiral CT for early lung cancer detection as well as the development of protocols to promote behavior change within lung cancer screening programs, should future studies indicate that spiral CT screening can effectively reduce the overall lung cancer mortality rate