Tuberculosis of the chest wall: CT findings

To assess the CT features of tuberculosis of the chest wall, the CT findings in four patients with documented tuberculous chest wall infection were reviewed. Two patients were Caucasian and two were of Chinese origin. All had normal immune status. In two cases tuberculosis involved the ribs, in one the costal cartilage, and in one the sternoclavicular joint. Computed tomography demonstrated osseous and cartilaginous destruction (in four), soft tissue masses with calcification (in two), and rim enhancement following intravenous contrast medium administration (in two). Underlying pleuroparenchymal tuberculosis was present in two cases. Tuberculosis of the chest wall is characterized by bone or costal cartilage destruction and soft tissue masses that may demonstrate calcification or rim enhancement with or without evidence of underlying lung or pleural disease.     

Mouse placental cells secrete soluble leptin receptor (sOB-R): cAMP inhibits sOB-R production

PURPOSE: To identify imaging features at unenhanced helical computed tomography (CT) that help differentiate distal ureteral calculi from pelvic phleboliths. MATERIALS AND METHODS: Retrospective analysis was performed of 184 pelvic calcifications identified at unenhanced helical CT in 113 patients. The size, shape, and attenuation of each calcification were recorded in addition to the presence of a central lucency and the appearance of the adjacent soft tissues. With profile analysis, a graphic representation was generated of attenuation in each pixel along a line drawn through each calcification. RESULTS: Geometric configuration was seen in eight (21%) calculi but not in any phleboliths. Differences were significant (P < .0001) between the mean attenuation of calculi and that of phleboliths. Among phleboliths, none had a mean attenuation greater than 278 HU, 13 (9%) had a visible central lucency, 31 (21%) had a bifid peak at profile analysis, 30 (21%) had the "comet sign" (adjacent eccentric, tapering soft-tissue mass corresponding to the noncalcified portion of a pelvic vein), and three (2%) had the soft-tissue rim sign (edema of the ureteral wall). Among calculi, none had a central lucency, bifid peak, or comet sign, but 29 (76%) had the soft-tissue rim sign. CONCLUSION: Analysis of pelvic calcifications at unenhanced helical CT can help differentiate calculi from phleboliths.     

Elastofibroma dorsi: prevalence in an elderly patient population as revealed by CT

OBJECTIVE: We wanted to determine the prevalence and appearance of elastofibroma dorsi in an elderly patient population (n = 258) who underwent CT of the chest for reasons other than to evaluate posterolateral chest wall pain, stiffness, or a mass. CONCLUSION: Five elastofibromas were detected in four patients; none of these elastofibromas were noted at initial examination. Our study suggests that the prevalence of elastofibroma dorsi revealed by CT is 2%, which is lower than the 11-24% found in autopsy series but higher than expected for such a rare tumor. Elastofibroma dorsi typically has a layered appearance on CT; however, in our study, homogeneous soft-tissue attenuation was noted. The diagnosis is often missed prospectively. Familiarity with the location and imaging appearance of elastofibroma dorsi may enhance detection and characterization of posterolateral chest wall masses in elderly patients.     

Immunocytochemical analysis of tissue kallikrein and the kinin moiety in rheumatoid synovial fluid neutrophils

A 73-year-old women was admitted to our hospital because of dyspnea, bloody sputum, and an apparent intratracheal tumor. A chest X-ray film from August 1991 showed a sharply circumscribed soft-tissue density in the trachea at the level of the aortic arch. By March 1993 the tumor had grown from 15 mm to 20 mm in diameter. A chest CT scan and fiberoptic bronchoscopy showed an intratracheal tumor that occupied 80% to 90% of the tracheal lumen. The tumor was resected on March 26, 1993. Histopathological study revealed a suspected leiomyosarcoma of the trachea. Only 18 cases of leiomyosarcoma of the trachea have previously been reported worldwide. We know of only 3 previous reports of the case of suspected leiomyosarcoma of the trachea in Japan.     

Police and mental health professionals. Collaborative responses to the impact of violence on children and families

Most pediatric patients with hydrocephalus are treated with ventriculoperitoneal (VP) shunt placement. However, shunt malfunction is common and is usually caused by mechanical failure. Shunt obstructions may be confirmed with radioisotope examination or with fluoroscopically guided injection of iodinated contrast material into the shunt reservoir. Disconnections or breaks are more readily detected at radiography in cases in which barium-impregnated shunt tubing was used. Migration and leakage may also occur. Cerebrospinal pseudocysts may be demonstrated with plain radiography and further evaluated with computed tomography (CT) and sonography. In increasing hydrocephalus, plain radiography may reveal sutural diastasis and increased cranial cavity size, and CT can be used to evaluate ventricle size. In cases of enlarging intracranial cysts, injection of iodinated contrast material followed by CT can help document a connection between the cyst and the ventricles. Ventriculitis and meningitis can be visualized at CT and magnetic resonance imaging as enhancement of the ventricular ependymal lining or cerebral cortical sulci. Other complications associated with VP shunts include surgery-related complications, shunt overdrainage and slit-ventricle syndrome, neoplastic metastasis, pleural effusion, and complications related to shunt variants. Imaging analysis is an essential adjunct to the clinical evaluation of patients with suspected VP shunt malfunctions or complications. Radiologists should be familiar with these potential problems and the diagnostic utility of various imaging modalities.     

Mediastinal abscess diagnosed after its rupture into the trachea in a patient after esophagectomy

A 52-yr-old man with esophageal cancer underwent esophagectomy and retrosternal reconstruction using stomach under general anesthesia. In the postoperative period, the patient developed mediastinal abscess which failed to be diagnosed by daily routine chest X-rays, because of surgical alterations of mediastinal anatomy. On the 11th postoperative day, the abscess ruptured into the trachea and severe hypoxemia (PaO2 73 mmHg, FIO2 1.0) developed while the patient was still on mechanical ventilation. A chest X-ray on that day showed a radiolucent cavity with defined margins in the right superior mediastinum. Thoracic CT scanning on the 15th postoperative day disclosed a capsulated cavity which indicated abscess formation in the posterior mediastinum. Although surgical drainage was not undertaken, the patient's severe hypoxemia was resolved within 4 days by the supportive therapies including chest physiotherapy, postural drainage and administration of antibiotics and corticosteroids. Although mediastinal abscess after esophagectomy is a rare complication, it may rupture into the trachea and lead to severe hypoxemia. In this case thoracic CT scanning was useful to detect the mediastinal abscess which had not been diagnosed by routine chest X-rays.     

Atherosclerotic plaque components in human aortas contrasted by ex vivo imaging using fast spin-echo magnetic resonance imaging and spiral computed tomography

RATIONALE AND OBJECTIVES: Imaging techniques that distinguish atherosclerotic plaque components may be useful in identifying the nature of the atherosclerotic lesion and determining the best method of treatment for obstructive vascular mining the best method of treatment for obstructive vascular disease. This study compares fast spin-echo (FSE) magnetic resonance (MR) and spiral computed tomography (CT) images of excised human atherosclerotic aortas to determine which imaging technique provides the best contrast between plaque components ex vivo. METHODS: Aortas were imaged using four FSE sequences in MR with and without frequency-selective fat saturation, and using spiral CT without contrast. The average signal intensity of a region of calcification, thrombosis, fatty plaque, and normal vessel wall was measured on all images and compared. RESULTS: The use of fat saturation pulses in MR did not significantly alter the signal from atherosclerotic plaque for the sequences used. Proton density-weighted FSE sequences that collected early echoes were better than other FSE sequences and CT at differentiating calcification from all soft tissues. T2-weighted FSE sequences that collected later echoes were best at soft-tissue discrimination. CONCLUSIONS: The FSE techniques used were superior to nonenhanced spiral CT in discriminating plaque components ex vivo, including calcification.     

Extraskeletal chondroma of the foot

Extraskeletal chondroma is a rare, benign cartilaginous tumor seen most frequently in the soft tissues of the hands and feet. The authors present a case of extraskeletal chondroma in a 52-year-old male patient who had a small mass on the left foot involving the flexor surface of the second toe. Radiographs showed the presence of a soft-tissue mass with scattered calcified foci. Surgical excision revealed a benign, lobulated cartilaginous tumor with prominent areas of calcification. Histologically; the lesion consisted of cartilage cells with centralized zones of cellular pleomorphism and giant-cell proliferation at the tumor margin consistent with extraskeletal chondroma.     

Enchondroma versus chondrosarcoma in the appendicular skeleton: differentiating features

Distinction of enchondroma versus intramedullary chondrosarcoma affecting the appendicular skeleton (proximal to the metacarpals and metatarsals) is a frequent diagnostic dilemma. The authors studied a large series of patients with these lesions (92 with enchondromas, 95 with chondrosarcomas) using statistical assessment of both clinical parameters and numerous radiologic manifestations on images from multiple modalities to identify differentiating features. Multiple clinical and imaging parameters demonstrated statistically significant differences between enchondroma and chondrosarcoma, particularly pain related to the lesion, deep endosteal scalloping (greater than two-thirds of cortical thickness), cortical destruction and soft-tissue mass (at computed tomography or magnetic resonance imaging), periosteal reaction (at radiography), and marked uptake of radionuclide (greater than the anterior iliac crest) at bone scintigraphy. All of these features strongly suggested the diagnosis of chondrosarcoma. These criteria allow distinction of appendicular enchondroma and chondrosarcoma in at least 90% of cases.     

Dieting behavior of Asian college women attending a US university

PURPOSE: Estimation of chest tube placement in patients with thoracic trauma with regard to chest tube malposition in chest radiography in the supine position compared to additional computed tomography of the thorax. MATERIAL AND METHODS: Apart from compulsory chest radiography after one or multiple chest tube insertions, 31 severely injured patients with thoracic trauma underwent a CT scan of the thorax. These 31 patients with 40 chest tubes constituted the basis for the present analysis. RESULTS: In chest radiography in the supine position there were no chest tube malpositions (n = 40); In the CT scans 25 correct positions, 7 pseudo-malpositions, 6 intrafissural and 2 intrapulmonary malpositions were identified. Moreover 16 sufficient, 18 insufficient and 6 indifferent functions of the chest tubes were seen. CONCLUSION: In case of lasting clinical problems and questionable function of the chest tube, chest radiography should be supplemented by a CT scan of the thorax in order to estimate the position of the chest tube.     

Chondroblastoma: classic and confusing appearance at MR imaging

PURPOSE: To define the characteristics of chondroblastoma at magnetic resonance (MR) imaging and the combination of findings that are diagnostic for chondroblastoma. MATERIALS AND METHODS: From January 1987 through December 1992, 22 patients with histologically confirmed chondroblastoma and prior MR imaging examinations were seen. Patients included 16 men and six women, aged 10-58 years (median, 17 years). Retrospective analysis of findings at MR imaging, plain radiography, computed tomography, and bone scanning was performed. RESULTS: Low to intermediate heterogeneous signal intensity, lobular internal architecture, and fine lobular margins were well defined with high-resolution T2-weighted (repetition time > or = 1,500 msec, echo time > or = 70 msec) MR imaging. Adjacent bone-marrow and soft-tissue edema and periosteal reactions were more dramatically demonstrated on MR images than on radiographs. Bone marrow edema was prominent in all but five cases. Obvious periosteal reaction and adjacent soft-tissue edema were visible in 17 cases. CONCLUSION: Knowledge of the MR imaging findings of chondroblastoma will allow accurate diagnosis and help avoid confusion with infection and aggressive neoplasms.     

Computed tomography in evaluation of patients with stage III melanoma

BACKGROUND: Metastatic disease is detected infrequently by computed tomography (CT) in early stage melanoma. The diagnostic yield of routine CT for stage III melanoma is less established, despite extensive use in clinical practice. METHODS: Charts from 347 asymptomatic patients with stage III melanoma were reviewed. Findings suggestive of metastatic melanoma identified by head or body CT, chest radiography, bone scan, or liver function studies were confirmed histologically or by progression of disease. RESULTS: Individual CT scans identified 33/788 (4.2%) instances of metastatic melanoma, with 66/788 (8.4%) false positive studies. No metastases were identified among 104 head CT scans. Chest CT had the highest yield in patients with cervical adenopathy (7/35, 20%), and the lowest yield with groin adenopathy (1/50, 2%). Pelvic CT diagnosed metastases in 7/94 (7.4%) patients with groin adenopathy, but no patients with palpable axillary (n = 76) or cervical (n = 21) nodes. Metastatic melanoma was diagnosed in 11/136 (8.1%) patients having complete body CT imaging (chest, abdomen, and pelvis), including six patients (4.4%) identified by CT alone. CONCLUSIONS: Routine CT in patients with clinical stage III melanoma infrequently identifies metastatic disease. Head CT in the asymptomatic patient, chest CT in patients with groin adenopathy, and pelvic CT in the presence of axillary or cervical adenopathy are not indicated. Selective use of chest CT in patients with cervical adenopathy or pelvic CT in the presence of groin disease may be useful.     

Unenhanced helical CT of ureterolithiasis: value of the tissue rim sign

OBJECTIVE: The tissue rim sign-a rim or halo of soft-tissue attenuation seen around the circumference of an intraureteral calculus on unenhanced axial CT-has been described as useful in differentiating ureteral calculi from extraurinary abdominal or pelvic calcifications. The purpose of this study was to determine the prevalence of the tissue rim sign in patients with ureterolithiasis and extraurinary calcifications and to determine the relationship between the tissue rim sign, the size of a calculus, and the degree of urinary obstruction. MATERIALS AND METHODS: Unenhanced helical CT studies followed by excretory urography were obtained in 59 patients with suspected acute ureterolithiasis. Each calcification along the expected course of the ureter seen on axial CT scans was categorized as a ureteral calculus or as an extraurinary calcification. Each categorization was based on CT, urographic, and clinical findings and the presence or absence of a tissue rim sign. When the outer wall of the ureter could not be seen because there was no clear fat plane at the level of the calcification on CT, the sign was categorized as "indeterminate." The size of the calculus was measured on CT, and the degree of urinary obstruction was estimated on the basis of the urograms. RESULTS: Thirty-two patients each had a single ureteral calculus. Of these patients, CT revealed a positive tissue rim sign in 16 patients (50%), was negative in five patients (16%), and was indeterminate in 11 patients (34%). In addition, we saw 57 extraurinary calcifications in 18 patients (11 patients with ureteral calculi and seven patients without ureteral calculi). None of the 57 extraurinary calcifications was associated with a positive tissue rim sign. The tissue rim sign was negative in 39 (68%) of the 57 extraurinary calcifications and indeterminate in the remaining 18 (32%). Ureteral calculi with a negative tissue rim sign were larger than ureteral calculi with a positive tissue rim sign (p < .01). A high degree of obstruction was present in four of five patients with ureteral calculi for which CT showed a negative tissue rim sign. Conversely, six of 16 patients in whom CT revealed a positive tissue rim sign also had a high degree of obstruction. Therefore, no clear relationship was found between the degree of obstruction and the presence of a positive tissue rim sign. CONCLUSION: A positive tissue rim sign is specific for the diagnosis of ureterolithiasis. However, a negative tissue rim sign does not preclude such a diagnosis. The presence or absence of this tissue rim sign correlates with the size of a calculus but not with the degree of urinary obstruction. When CT reveals an indeterminate tissue rim sign, careful inspection for other CT findings, such as ipsilateral ureteral dilatation, perinephric edema, dilatation of the intrarenal collecting system, and renal swelling, is necessary.     

Nodular sarcoidosis of the liver and spleen: analysis of 32 cases

PURPOSE: To describe the computed tomographic (CT) appearance of nodular hepatosplenic sarcoidosis and its association with stage with chest radiography and clinical status. MATERIALS AND METHODS: Thirty-two patients (21 women, 11 men; aged 25-68 years) with nodular hepatosplenic sarcoidosis were evaluated. CT findings were described along with chest radiographic stage, clinical status, and level of angiotensin-converting enzyme (ACE). RESULTS: Nodules were small, multiple, and of low attenuation. Organomegaly was common. Abdominal adenopathy was present in 76% of the patients. Chest radiographs were normal in 25%; 61% had stage 1 or 2 radiographs. Abdominal or systemic symptoms were present in 66%. ACE level was elevated in 10 (91%) of 11 patients tested. No change in chest radiographic stage was noted in 74% of patients with follow-up radiographs. CONCLUSION: Nodular hepatosplenic sarcoidosis is associated with organomegaly, adenopathy, and symptoms. Nodules were not associated with advanced lung disease and did not herald a change in chest radiographic stage. An elevated ACE level may be helpful in diagnosis.     

Computed radiography of the chest in patients with paraesophageal varices: diagnostic accuracy and characteristic findings

OBJECTIVE: The purpose of our study was to determine the diagnostic accuracy of computed radiography of the chest in the detection of paraesophageal varices and to describe the characteristic radiographic findings. SUBJECTS AND METHODS: From June 1995 through May 1997, in 100 consecutive patients, portal hypertension was diagnosed through both clinical and radiologic evidence. Computed radiographs of the chest and hepatic helical CT scans of these 100 patients with portal hypertension and 20 control subjects were analyzed by two chest radiologists and one abdominal radiologist, who were not aware of the results of the other study. RESULTS: On CT, paraesophageal varices were seen in 38 (38%) of 100 patients with portal hypertension. Overall, the sensitivity, specificity, and accuracy of chest computed radiography in the detection of paraesophageal varices were 53% (20/38), 90% (74/82), and 78% (94/120), respectively. In the patients with paraesophageal varices, splenomegaly (29/38, 76%), lateral displacement or obliteration of the inferior portion of the azygoesophageal interface (18/38, 47%), obliteration or nodularity of the inferior portion of the descending thoracic aorta interface (9/38, 24%), lateral displacement of the right inferior paraspinal interface (6/38, 16%), lateral displacement of the left inferior paraspinal interface (4/38, 11%), and varices in the left inferior pulmonary ligament (1/38, 3%) were seen on chest computed radiographs. Paraesophageal varices smaller than the diameter of the descending thoracic aorta (usually <2.5 cm) were not detected. CONCLUSION: Although chest computed radiography is only moderately sensitive for paraesophageal varices, the findings are characteristic when well developed, with a limited differential diagnosis. Splenomegaly, whether detected clinically or radiographically, eliminates most other diagnostic possibilities.     

Conventional and high-resolution CT in asymptomatic asbestos-exposed workers

To compare the value of conventional CT (CCT) and high-resolution CT (HRCT) to detect benign asbestos-related diseases, 159 exposed workers with a normal chest radiography were imaged by both techniques. Pleural plaques were detected in a total of 59 cases (37.1%). Ten cases (16.9%) were detected by CCT only and one case (1.7%) by HRCT only. Pulmonary lesions compatible with parenchymal asbestosis were detected by HRCT in 20 cases, whereas CCT showed abnormalities in 45% of these. Rounded atelectasis was equally recognized by both techniques. The results confirm that in a subject with a normal chest radiography, HRCT is a better diagnostic tool to demonstrate lesions of asbestosis. On the other hand, HRCT is insufficient to exclude the presence of pleural plaques. When HRCT does not reveal pleural abnormalities, CCT should be performed.     

Radiation-induced changes in bone

Radiation therapy has important applications in curative, adjuvant, and palliative therapy for a wide range of malignant conditions. Evidence of radiation therapy may be seen on radiologic images obtained subsequent to therapy. Bone growth disturbances may be observed in the immature axial or appendicular skeleton. Complications in the mature skeleton include osteoradionecrosis, pathologic fracture, and radiation-induced neoplasms. Radiologic features of mandibular osteoradionecrosis include ill-defined cortical destruction without sequestration. In osteoradionecrosis of the ribs, clavicle, scapula, and humerus, radiography may demonstrate osteopenia, disorganization and coarsening of trabecular architecture, and cortical irregularity; computed tomography more clearly depicts subtle fractures, alterations in bone architecture, and dystrophic soft-tissue calcification. In osteoradionecrosis of the spine, hematopoietic cellular elements of the spinal marrow are replaced with fat, which has high signal intensity on T1-weighted magnetic resonance images and intermediate signal intensity on T2-weighted images. Radiation-induced changes in the pelvis include osteopenia, increased bone density, and widening and irregularity of the sacroiliac joints. Radiation-induced osteochondromas are radiographically identical to those that arise spontaneously. Radiographic findings in radiation-induced sarcoma demonstrate an aggressive pattern of bone destruction. Awareness of the varied radiographic manifestations of radiation-induced changes in bone and correlation with clinical features and the radiation field will usually allow distinction of these changes from those associated with other pathologic conditions.     

Computed tomography in injuries to the respiratory system in children. The correlation with adults

INTRODUCTION: Diagnostic imaging in emergency rooms may be inadequate and delayed, which makes chest traumas in children more severe and difficult to treat. We carried out a retrospective study on adults and children who had survived major chest traumas involving the respiratory tract to assess the differences between the two age groups and the role of emergency CT. MATERIAL AND METHODS: Our series consisted of fourteen children admitted to the emergency department for various accidents. Home accidents prevailed (9/14 = 64.3%). On admission, chest radiography was performed in most cases (11/14 = 78.6%); CT was carried out in 21.4% (3/14 patients). RESULTS: Trauma involved more organs in pediatric patients (11/14 = 78.6%) and lung involvement was always associated with other types of injury, namely contusion (14/14 = 100%), pneumothorax (11/14 = 78.6%), hemothorax (10/14 = 71.4%), tear (4/14 = 28.6%). CT corrected or integrated the radiographic findings of contusion focus in 67% (8/14) and that of pneumothorax in 63.6%; both patterns cannot be demonstrated otherwise. DISCUSSION: Mixed and multiple posterior parenchymal injuries with no rib fractures prevail in young subjects because their bones and ligaments are more elastic, which may lead to trauma underestimation. Tracheobronchial ruptures and pneumomediastinum are much more severe in children than in adults. Chest plain film is often the only diagnostic tool used, despite its major technical and interpretative limitations, also because skull and abdomen are the most investigated regions. Executive limitations are stronger in childhood, increasing the margin of error and the risk of delayed treatment. CT is as cost-effective as radiography and shows even the injuries missed or poorly depicted on conventional images; CT also gives accurate information on damage severity and nature. CONCLUSIONS: Traumatic injuries are more severe in pediatric patients due to their build and to biomechanical, clinical and management factors. Spiral CT should be considered the examination of choice to be performed in the emergency department equipped also for pediatric re-animation.     

Computerized tomography of osteochondral diseases of the talus dome

The definition "osteochondritis dissecans" of the talus improperly includes a variety of diseases involving the chondral surface of the talus dome and the relative subchondral bone. To investigate the CT diagnostic potentials in the study of these conditions, 35 patients complaining of a "painful ankle" were examined with plain radiography and axial and direct paracoronal CT over a 2-year period. Twelve patients were then examined with double contrast CT arthrography with air and iodated contrast agents. CT diagnostic accuracy was assessed evaluating the following parameters: the presence and extent of the subchondral bone fragment, the presence of residual bone fragment attachment at the lesion base or its intraarticular dislocation, the presence of subchondral bone cysts, of chondral surface lesions and, finally, of capsular and ligamentous damage. All the patients with CT findings of osteochondral conditions of the talus dome were submitted to arthroscopic examination/treatment and/or surgical arthrotomy. Baseline CT exams accurately depicted all the lesions, except for early (grade I) lesions. Moreover, the administration of intraarticular contrast agent (CT arthrography) increased the diagnostic accuracy in articular cartilage studies. Therefore, the authors believe baseline CT on the orthogonal planes to represent an effective tool for the staging of osteochondral talar lesions and for accurate treatment planning.     

Guidelines for the selective ordering of admission chest radiography in adult obstructive airway disease

STUDY OBJECTIVE: To validate previously developed guidelines for the selective use of chest radiography in adults admitted for exacerbation of obstructive airway disease. DESIGN: Prospective, observational cohort study using criteria developed in a previous retrospective study. PARTICIPANTS: Unselected convenience sample of 128 adults with obstructive airway disease who did not respond to standard emergency department treatment and required admission. SETTING: Municipal hospital ED and inpatient medical service. INTERVENTIONS: Patients were categorized as "complicated" or "uncomplicated" according to previously developed criteria. Management was recorded as altered if the patient's physician answered the question, "Did the chest radiography alter your management of this patient?" affirmatively. RESULTS: Of 27 patients whose management was altered by the chest radiography, 26 were classified as complicated, for a sensitivity of 96% (95% confidence interval [CI], 81, 100). One of 44 admissions classified as uncomplicated had management altered by the chest radiography (negative predictive value, 98%, 95% CI, 88, 100). This chest radiography was later reread as normal. Classification as an uncomplicated patient with obstructive airway disease was strongly associated with either a normal chest radiography or a radiographic finding that was clinically unimportant (P = .0002). CONCLUSION: Patients with acute exacerbation of obstructive airway disease who are otherwise uncomplicated do not benefit from routine admission chest radiography. The use of this simple clinical strategy would safely reduce the number of chest radiographs by about one-third in this and similar patient populations, decreasing both health care costs and exposure to ionizing radiation.