Michael M. Maher

Crohn's disease: factors associated with exposure to high levels of diagnostic radiation

Aims: Exposure to diagnostic radiation may be associated with increased risk of malignancy. The aims of this study were: (a) to examine patterns of use of imaging in Crohn9s disease; (b) to quantify the cumulative effective dose (CED) of diagnostic radiation received by patients; and (c) to identify patients at greatest risk of exposure to high levels of diagnostic radiation. Methods: 409 patients with Crohn9s disease were identified at a tertiary centre. CED was calculated retrospectively from imaging performed between July 1992 and June 2007. High exposure was defined as CED>75 milli-Sieverts (mSv), an exposure level which has been reported to increase cancer mortality by 7.3%. Complete data were available for 399 patients. 45 were excluded (20 attended outside study period, 25 primarily managed at other centres). Results: Use of computed tomography increased significantly and accounted for 77.2% of diagnostic radiation. Mean CED was 36.1mSv and exceeded 75mSv in 15.5% of patients. Factors associated with high cumulative exposure were: age 1) surgeries (OR 2.7, CI 1.4-5.4). Conclusions: Identifiable subsets of patients with Crohn9s disease are at risk of exposure to significant amounts of diagnostic radiation. Given the background risk of neoplasia and exposure to potentially synergistic agents such as purine analogues and other immune-modulators, specialist centres should develop low-radiation imaging protocols.

Significance of incidental thyroid lesions detected on CT: correlation among CT, sonography, and pathology.

OBJECTIVE The purpose of our study was to determine the prevalence of malignancy in incidental abnormalities of the thyroid gland detected on CT and to determine the relative accuracy of characterizing these abnormalities on CT as compared with sonography and pathology. MATERIALS AND METHODS We searched our departments computerized clinical database for all thoracic and cervical CT scans in which a new abnormality was incidentally identified in the thyroid gland from 1998-2001. Two hundred thirty patients with abnormal findings in the gland on CT subsequently underwent thyroid sonography, and 118 of the 230 patients underwent a diagnostic biopsy or resection. CT and sonographic images were directly reviewed to identify imaging features of each thyroid abnormality, including the location, size, appearance, and presence or absence of calcifications. Associations were evaluated using Fishers exact test of significance and the Students t test. The overall rate of malignant and potentially malignant lesions among these incidental abnormalities of the thyroid gland was calculated. RESULTS CT findings matched the sonographic characterization in 122 patients (53.0%), correctly identified the dominant nodule but missed multinodularity in 69 (30.0%) patients, and underestimated the number of nodules in 24 (10.4%) patients. CT overestimated the number of nodules in 5 (2.2%) patients and was false-positive for lesions in 10 patients (4.3%). Ninety-one patients with a single or dominant nodule on CT had pathologic correlation: 7 nodules were malignant, 17 showed malignant potential, and 67 were benign. Of 27 patients with multinodular or enlarged thyroid glands on CT and histopathologic correlation, 2 lesions were malignant and 25 benign. The presence of punctate calcifications on CT significantly correlated to the presence of microcalcifications on sonography (p < 0.02). Benign nodules were significantly smaller (mean, 2.16 +/- 1.01 cm; range, 0.6-4.5 cm) than malignant and potentially malignant nodules (mean, 2.79 +/- 0.99 cm; range, 0.7-4.6 cm) (p = 0.01). Patients 35 years or younger who had a thyroid lesion on CT were more likely to have malignancy (p < 0.01). Overall, among incidentally detected lesions of the thyroid gland, there was at least a 3.9% rate of malignancy (95% CI: 1.8-7.3%) and 7.4% rate of malignant potential (95% CI: 4.4-11.6%). CONCLUSION There is at least an 11.3% prevalence of malignant or potentially malignant lesions among incidental thyroid abnormalities detected on CT. Patients 35 years or younger who have incidental abnormalities have a significantly greater rate of malignancy. No CT feature reliably distinguishes benign from malignant lesions in the thyroid gland. CT underestimates the number of nodules relative to sonography, which suggests that sonography is a useful adjunctive test after the incidental detection of a thyroid abnormality on CT.

Complications of CT-guided percutaneous needle biopsy of the chest: Prevention and management

OBJECTIVE The objective of this article is to describe potential complications of percutaneous needle biopsy of the chest, discuss the risk factors associated with the development of complications, and explain how to prevent complications and manage complications when they occur. CONCLUSION Pneumothorax and pulmonary hemorrhage are the most common complications of percutaneous needle biopsy of the chest, whereas air embolism and tumor seeding are extremely rare. Attention to biopsy planning and technique and postprocedural care help to prevent or minimize most potential complications.

Multidetector computed tomography technology: current status and emerging developments.

By virtue of its speed and isotropic resolution of thin slices, multidetector-row computed tomography (MDCT) offers unique advantages over previous single-detector-row CT, with improved temporal and spatial resolution. This review describes the historical perspective and growth trends of MDCT scanners and highlights the current status and emerging developments in multidetector technology based on presentations at the symposium “Advances in Multidetector CT,” under the auspices of the Institute for Advanced Medical Education in Washington, DC.

Development of Low-Dose Protocols for Thin-Section CT Assessment of Cystic Fibrosis in Pediatric Patients

PURPOSE To develop low-dose thin-section computed tomographic (CT) protocols for assessment of cystic fibrosis (CF) in pediatric patients and determine the clinical usefulness thereof compared with chest radiography. MATERIALS AND METHODS After institutional review board approval and informed consent from patients or guardians were obtained, 14 patients with CF and 11 patients without CF (16 male, nine female; mean age, 12.6 years ± 5.4 [standard deviation]; range, 3.5-25 years) who underwent imaging for clinical reasons underwent low-dose thin-section CT. Sections 1 mm thick (protocol A) were used in 10 patients, and sections 0.5 mm thick (protocol B) were used in 15 patients at six levels at 120 kVp and 30-50 mA. Image quality and diagnostic acceptability were scored qualitatively and quantitatively by two radiologists who also quantified disease severity at thin-section CT and chest radiography. Effective doses were calculated by using a CT dosimetry calculator. RESULTS Low-dose thin-section CT was performed with mean effective doses of 0.19 mSv ± 0.03 for protocol A and 0.14 mSv ± 0.04 for protocol B (P < .005). Diagnostic acceptability and depiction of bronchovascular structures at lung window settings were graded as almost excellent for both protocols, but protocol B was inferior to protocol A for mediastinal assessment (P < .02). Patients with CF had moderate lung disease with a mean Bhalla score of 9.2 ± 5.3 (range, 0-19), compared with that of patients without CF (1.1 ± 1.4; P < .001). There was excellent correlation between thin-section CT and chest radiography (r = 0.88-0.92; P < .001). CONCLUSION Low-dose thin-section CT can be performed at lower effective doses than can standard CT, approaching those of chest radiography. Low-dose thin-section CT could be appropriate for evaluating bronchiectasis in pediatric patients, yielding appropriate information about lung parenchyma and bronchovascular structures.

Does multidetector-row CT eliminate the role of diagnostic laparoscopy in assessing the resectability of pancreatic head adenocarcinoma?

BackgroundWe hypothesized that the high-quality images from multidetector-row computed tomography (MDCT) would lead to improved sensitivity and specificity for predicting resectable pancreatic head adenocarcinoma, thus diminishing the value of staging laparoscopy.MethodsForty four consecutive patients underwent thin-section dual-phase MDCT to stage their tumor, followed by an attempted pancreaticoduodenectomy. Four radiologists who were blinded to the operative outcome reviewed the scans and graded the presence of distant and nodal metastases, as well as the degree of arterial and portal involvement. The radiologic criteria for resectability were no distant metastasis, a patent portal vein, and <50% arterial involvement.ResultsThe overall resectability for this cohort was 52% (23/44). The 21 unresectable cases, included five liver metastases, three peritoneal metastases, and 13 locally invasive tumors. The negative margin resection rate was 34% (15/44). There were no portal vein resections. The sensitivity and specificity of MDCT for predicting resectability were 96% (22/23) and 33% (7/21), respectively. In this cohort, the positive and negative predictive values were 61% (22/36) and 87.5% (7/8), respectively. As determined by univariate logistic regression, only the degree of arterial involvement was a significant predictor of resectability (p = 0.02). As determined by multivariate logistic regression using both arterial and portal involvement, arterial involvement was predictive (p = 0.03) but portal vein involvement was not (p = 0.45).ConclusionsDespite the improvements in image quality obtained with multidetector-row technology, CT imaging remains a relatively nonspecific test for predicting resectability in patients with adenocarcinoma of the head of the pancreas. Minimally invasive modalities with higher specificity, particularly laparoscopy, continue to have an important role in staging pancreatic head adenocarcinoma.

Acute and Chronic Pulmonary Emboli: Angiography–CT Correlation

OBJECTIVE The objective of our study was to review the classic direct and indirect angiographic signs of acute and chronic pulmonary embolism (PE) and correlate these findings with MDCT. CONCLUSION CT and angiography have complementary roles in the accurate diagnosis of acute and chronic thromboembolic disease. Conventional angiography should be used as a problem-solving technique after CT angiography has been performed because CT angiography is less invasive.

Emergency CT brain: preliminary interpretation with a tablet device: image quality and diagnostic performance of the Apple iPad

Tablet devices have recently been used in radiological image interpretation because they have a display resolution comparable to desktop LCD monitors. We identified a need to examine tablet display performance prior to their use in preliminary interpretation of radiological images. We compared the spatial and contrast resolution of a commercially available tablet display with a diagnostic grade 2 megapixel monochrome LCD using a contrast detail phantom. We also recorded reporting discrepancies, using the ACR RADPEER system, between preliminary interpretation of 100 emergency CT brain examinations on the tablet display and formal review on a diagnostic LCD. The iPad display performed inferiorly to the diagnostic monochrome display without the ability to zoom. When the software zoom function was enabled on the tablet device, comparable contrast detail phantom scores of 163 vs 165 points were achieved. No reporting discrepancies were encountered during the interpretation of 43 normal examinations and five cases of acute intracranial hemorrhage. There were seven RADPEER2 (understandable) misses when using the iPad display and 12 with the diagnostic LCD. Use of software zoom in the tablet device improved its contrast detail phantom score. The tablet allowed satisfactory identification of acute CT brain findings, but additional research will be required to examine the cause of “understandable” reporting discrepancies that occur when using tablet devices.

Imaging of Hematuria

Hematuria may have a number of causes, of which the more common are urinary tract calculi, urinary tract infection, urinary tract neoplasms (including renal cell carcinoma and urothelial tumors), trauma to the urinary tract, and renal parenchymal disease. This article discusses the current status of imaging of patients suspected of having urologic causes of hematuria. The role of all modalities, including plain radiography, intravenous urography or excretory urography, retrograde pyelography, ultrasonography, and multidetector computed tomography (MDCT) in evaluation of these patients is discussed. The article highlights the current status of MDCT urography in imaging of patients with hematuria, and discusses various-often controversial-issues, such as optimal protocol design, accuracy of the technique in imaging of the urothelium, and the significant issue of radiation dose associated with MDCT urography.

Application of Rational Practice and Technical Advances for Optimizing Radiation Dose for Chest Ct

Though clinical benefits of CT exceed the adverse effects of radiation, the increasing use of CT has raised a compelling case for reducing radiation exposure. This controversy has been compounded by the sheer magnitude of CT examinations being performed annually, alleged overuse, and inappropriate selection of optimum scanning parameters, all of which expose the patient population to increased radiation exposure. Recommended clinical strategies for radiation dose optimization include optimization of scanning parameters and creating awareness and adopting guidelines for legitimate indications for CT scanning to avoid overuse and hence, the associated over-exposure. Whereas technological advances have increased the applications of the modality, it is also assisting in development of promising techniques to reduce associated radiation exposure, while maintaining “optimum image quality” needed to make a confident diagnosis. The present pictorial essay describes the fundamentals of CT radiation exposure and need for CT radiation dose reduction on the basis of documented scanning practices and technological advances.