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In this issue of RadioGraphics, a symposium consisting of four comprehensive articles prepared by leaders in the field of cardiac positron emission tomography (PET) is presented (1–4). In many ways, 2011 is an appropriate time to focus on this rapidly expanding modality. The medical literature certainly illustrates the growth of scholarly interest in cardiac PET. During the past 5 years, 658 peer-reviewed articles and several dedicated texts on cardiac PET have been published (5). In the previous 5 years, only 184 were found, based on a Google Scholar search. Despite the proliferation of competing technologies, including magnetic resonance (MR) imaging, multidetector computed tomography (CT), and advanced echocardiography, the volume of cardiac PET/CT studies continues to grow exponentially. This interest is partially related to the rapid growth of the use of PET in oncologic diagnosis and posttreatment follow-up examinations (6). In addition, new advances in technology such as the development of increasingly more efficient software and equipment have been introduced. Many of the problems associated with “thoracic drift” and cardiac motion, which leads to image misregistration, have been addressed with image postprocessing corrections and the use of respiratory and electrocardiographic gating (7). Indications for PET/CT have broadened, particularly for the diagnosis of the ischemic myocardium, obstructive coronary artery disease, and large vessel arteritis, in direct competition to using stand-alone CT and MR imaging for these applications. This upward trend in cardiac PET/CT utilization may also be related to a shift in user preference from single photon emission computed tomography (SPECT) to PET for myocardial perfusion imaging because of the recognized clinical advantages of PET and the uncertainty regarding the available supplies of radionuclides used in SPECT studies. In an in-depth article, Di Carli and Murthy (1) from the Brigham and Women’s Hospital, Boston, discuss the advantages of PET imaging, especially in comparison with SPECT imaging, with an emphasis on use of generator-produced rubidium 82, use of optimized protocols, radiation dose reduction, and minimizing image artifacts. Stolzmann and his associates (2) from Massachusetts General Hospital, Boston, compare the value of cardiac PET and CT for characterizing atherosclerotic disease. The authors emphasize the complementary role of CT for exquisite Robert M. Steiner, MD Why Should We Be Interested in Cardiac PET/CT Imaging?1

A 37-year-old white man presented with a productive cough, anorexia, weight loss, and night sweats of 4 months’ duration. He also complained of back pain with stiffness. The back pain was worse at night. He was treated for pneumonia 3 years ago and had a 20 pack-year history of smoking. He was a thin man in no distress. His vital signs were stable and temperature was 38.6°C (101.6°F). Bilateral enlarged firm but nontender axillary and inguinal lymph nodes were noted. Chest wall expansion was limited, but otherwise the thoracic examination was unremarkable. There was kyphosis of the lumbar spine with limited forward bending, The range of motion of the cervical spine was severely limited, and there was no lateral motion of the neck. The pelvis was anteverted, and there was a flexion deformity of both knees. Laboratory findings were as follows: WBC count, 11,300 cells/mL; and erythrocyte sedimentation rate, 30 mm/h. There was a positive human leukocyte antigenB27 antigen. Sputum smears and cultures for acid-fast bacilli were negative. Smears of BAL fluid and bronchial washings revealed rare acid-fast bacilli. The purified protein derivative skin test was negative. A chest radiograph (Fig 1) revealed bilateral upper lobe cavitary lesions. The remainder of the lungs were hyperinflated. There was mild upward retraction of the hilar structures indicating upper lobe volume loss. Contrast-enhanced chest CT (Fig 2) showed distortion of the lung architecture with

A 38-year-old man with Ehlers-Danlos syndrome was examined for abdominal pain and fever. An In-111 leukocyte scan performed to detect the possible source of occult sepsis revealed intense activity above the liver. The presence of the intrathoracic spleen was confirmed on a Tc-99m sulfur colloid scan. Computed tomography showed herniation of the stomach, colon, and spleen through a large diaphragmatic defect into the chest. The mechanism of a wandering spleen in this patient is most likely ligamentous laxity caused by Ehlers-Danlos syndrome, which also accounts for the hiatus hernia.

Purpose: The goal of this work was to identify and categorize the spectrum of pulmonary parenchymal and pleural abnormalities identified by CT in patients with acute pulmonary thromboembolism (PE). Method: A review of interpretations from 4,715 consecutive contrast-enhanced thoracic CT studies identified 41 examinations in which the diagnosis of PE was reported. Thirty-four studies were available for review, and two radiologists confirmed intraluminal defects in 31 patients. The number of emboli were counted and localized using bronchopulmonary nomenclature. Associated parenchymal and pleural abnormalities were tabulated. Results: Of the 31 patients, 13 underwent confirmatory or correlative studies including angiography, radionuclide study, or autopsy. In addition, deep venous thrombosis was confirmed by ultrasound or MRI in 13 patients. An average of 7.5 emboli per patient was detected. Pleuroparenchymal findings were as follows: Nine patients (29%) had no acute pulmonary parenchymal or pleural abnormality. In the remaining 22 patients, pleural effusion was the most common abnormality, found in 14 of 31 (45%). Ten patients (32%) had peripheral wedge-shaped parenchymal opacities suggestive of pulmonary infarction. Normally enhancing lobar atelectasis was seen in nine patients (29%). Six patients (19%) demonstrated heterogeneous parenchymal enhancement within nonaerated lung, two of whom had pathologically proven pulmonary infarct. Thirteen of 31 patients underwent high resolution CT; a typical mosaic perfusion pattern was seen in only I patient. Conclusion: Twenty-nine percent of patients with acute PE had no acute lung parenchymal abnormality on CT; thus, the absence of parenchymal abnormality on CT does not exclude PE. High resolution CT mosaic perfusion was not a common feature of acute pulmonary embolism. Regions of decreased enhancement within nonaerated lung, seen in 19%, may prove to be an indicator of pulmonary infarction; however, this is a nonspecific finding. Index Terms: Computed tomography, Spiral-Lungs, abnormalities-Pulmonary embolism.

The value of sonographic guidance during video-assisted thoracoscopic surgery (VATS) was studied in 13 patients with one or more peripheral pulmonary nodules who later underwent wedge resection.After a review of the chest radiographs and CT scans of each patient, sonographic guidance for VATS was requested by the attending surgeon when the nodule or nodules in question were determined to be too small or too deep in the lung parenchyma from the pleural surface for location by VATS. A multifrequency (5.0-, 6.5-, or 7.5-MHz) sonographic probe was introduced through a thoracoscopic port during VATS. The nodule or nodules in question were located by intraoperative sonography or determined by inspection and confirmed by sonography before wedge resection. The size and location of each lesion and the time needed for sonographic guidance were recorded.Sonography revealed a peripheral pulmonary nodule in 12 of the 13 patients. Of these, it confirmed the suspected location of the pulmonary nodule in six. In the remaining six patients, the surgeon was unable to locate the nodule without the use of sonography. The additional operative time required for sonographic guidance during VATS averaged 7.5 min. However, the time commitment of radiology personnel during surgery varied and was sometimes lengthy (maximum, 150 min).Sonographic guidance during thoracoscopy helped to locate lesions and determine their size and proximity to pleural surfaces. Sonographic guidance can be done safely and can be completed expeditiously. Unlike percutaneous hookwire techniques, sonographic guidance does not require an additional invasive procedure to locate the peripheral pulmonary nodule.

Mediastinal lymphadenopathy is frequently associated with interstitial lung disease (ILD) in patients with systemic sclerosis (SSc). This study compared the extent of lymphadenopathy in diffuse and limited SSc with the presence and type of ILD found on CT scans.Seventy-three patients with diffuse and limited SSc underwent thoracic CT. The presence of lymphadenopathy was correlated with the frequency and type of ILD.Fifty-eight percent (18/31) of patients with diffuse cutaneous SSc and 40% (17/42) of patients with limited cutaneous SSc had lymphadenopathy. A significant relationship was found between lymphadenopathy and the presence of interstitial disease (p = .0002). Seventy-two percent (18/25) of patients with a ground-glass parenchymal pattern of interstitial disease and 74% (14/19) of patients with a honeycomb pattern had lymphadenopathy.Lymphadenopathy is prevalent in patients with SSc and ILD regardless of clinical subtype or interstitial pattern. Lymphadenopathy appears to increase as a function of the profusion rather than the morphology of ILD.

Video-assisted thoracic surgery is an important component of modern thoracic surgery, providing a safe, less invasive alternative to open thoracotomy in the evaluation of pleural, mediastinal, and parenchymal pathology. Advancements in endoscopic techniques and video-optics have permitted greater visualization of the thoracic cavity and allowed limited pulmonary resections with significantly reduced postoperative morbidity. Thoracoscopy is indicated for diagnosis of intrathoracic pathology when usual methods of diagnosis, including fine-needle aspiration and transbronchial biopsy, are inconclusive. The diagnostic accuracy of video-assisted thoracic surgery approaches 100%. Increasingly, the indications for thoracoscopy include therapeutic resections of pulmonary nodules in cases of limited lung metastases and bronchogenic carcinoma when pulmonary function is poor. Successful diagnostic and therapeutic resection by thoracoscopy requires intraoperative localization of the lesion within the collapsed lung. The indications and methods of thoracoscopic surgery and preoperative localization are discussed.

A chest radiographic equalization system using lung-shaped templates mounted on filter wheels is under development. Using this technique, 25 lung templates for each lung are available on two computer controlled wheels which are located in close proximity to the x-ray tube. The large magnification factor (> 10X) of the templates assures low-frequency equalization due to the blurring of the focal spot. A low-dose image is acquired without templates using a (generic) digital receptor, the image is analyzed, and the left and right lung fields are automatically identified using software developed for this purpose. The most appropriate left and right lung templates are independently selected and are positioned into the field of view at the proper location under computer control. Once the templates are positioned, acquisition of the equalized radiographic image onto film commences at clinical exposure levels. The templates reduce the exposure to the lung fields by attenuating a fraction of the incident x-ray fluence so that the exposure to the mediastinum and diaphragm areas can be increased without overexposing the lungs. A data base of 824 digitized chest radiographs was used to determine the shape of the specific lung templates, for both left and right lung fields. A second independent data base of 208 images was used to test the performance of the templates using computer simulations. The template shape characteristics derived from the clinical image data base are demonstrated. The detected exposure in the lung fields on conventional chest radiographs was found to be, on average, three times the detected exposure behind the diaphragm and mediastinum.(ABSTRACT TRUNCATED AT 250 WORDS)

Congenital heart disease (CHD) is a major clinical problem in children, occurring in 0.8% of newborns (1). In the past, most patients with CHD died in infancy. With improved surgical and postoperative care, as well as more accurate preoperative evaluation, the overall 10-year survival rate is > 90%. As a result, > 500,000 adults in the United States have surgically treated CHD (2). In addition, at least 150,000 adults are thought to have unrecognized, misdiagnosed, or recognized but untreated CHD (3,4). Diagnostic imaging procedures for the evaluation of CHD include plain film radiology, fluoroscopy, angiocardiography, echocardiography, scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI). Each has unique as well as overlapping abilities to characterize precisely cardiovascular anatomy and pathophysiology. We emphasize those congenital cardiac disorders found predominantly in adults. In addition, conditions that are usually unrecognized in childhood, "slip through the system", and become clinically recognized in adults for the first time, often with an atypical clinical presentation, are discussed (5). The interpreter of the plain film radiograph has a unique opportunity to identify and often characterize the severity of a congenital cardiac disorder that may be unrecognized by the patient's physician. Important clues found on plain film radiographs will suggest either additional studies to pin-point the type of CHD more precisely or that no additional studies are needed because the recognized lesion is incidental and not of clinical significance.

RATIONALE AND OBJECTIVES Ultrafast gradient-recalled-echo techniques for obtaining high-quality pulmonary magnetic resonance angiograms within a single breath-hold were optimized. METHODS Fourteen subjects were imaged with both the body coil and a phased-array surface coil, using three gradient-recalled-echo pulse sequences: 1) two-dimensional sequential; 2) two-dimensional interleaved; and 3) volumetric acquisitions. Image quality was assessed with varied flip angle, receiver bandwidth, slice thickness/number, and matrix size. Cardiac compensation diminished ghost artifacts in the interleaved sequence. Individual sagittal sections and maximum intensity projections were reviewed. RESULTS Pulmonary magnetic resonance angiograms acquired with volumetric and two-dimensional interleaved gradient-recalled-echo pulse sequences benefit greatest from intravenous gadolinium and result in greater pulmonary arterial visualization than traditional time-of-flight techniques. Phased-array coils result in improved vessel detection. CONCLUSIONS High-quality breath-held pulmonary magnetic resonance angiography can be obtained with an intravenous contrast-enhanced gradient-recalled-echo acquisition; however, image quality is dependent on the pulse sequence.

PURPOSE: To demonstrate the value of ultrasound (US) guidance during flexible bronchoscopic procedures in a series of patients with known or suspected pulmonary neoplasms. MATERIALS AND METHODS: US-guided bronchoscopy was carried out as an adjunct to conventional bronchoscopy for the diagnosis of mediastinal, hilar, or parenchymal neoplasms in 25 patients with masses previously detected with chest radiography or computed tomography. Miniature transducer-containing catheters were inserted through the biopsy port of the flexible bronchoscope, and cross-sectional real-time US scans of tumors, lymph nodes, and blood vessels were obtained. RESULTS: Among six cases of peripheral masses and 19 cases of central masses, additional information was provided in 18 cases (72%). This information was used to choose the optimal site for transmural biopsy. CONCLUSION: These preliminary results suggest that this US procedure may become an important diagnostic tool during bronchoscopy, due to the ability to identify structu...

Pulmonary opacities following orthotopic liver transplantation (OLT) are frequent due to pneumonia, infarction, or pulmonary edema. Metastatic pulmonary calcifications are present as persistent opacities that may mimic these conditions. In a series of 91 patients who underwent OLT, chest radiographs of 77 were reviewed and pulmonary calcinosis was seen in 4 (5.2%). Pulmonary calcinosis may be due to a variety of conditions, including dystrophic calcification in damaged lung and primary or secondary hyperparathyroidism. In this series, patients with pulmonary calcinosis had significantly higher levels of serum phosphate and calcium postoperatively and had received more intraoperative platelets and other blood products containing exogenous calcium than other patients. Pulmonary calcinosis should be considered in patients following OLT when stable, nonspecific pulmonary opacities are present. CT or radionuclide studies will aid in confirming this diagnosis.

This report demonstrates a thymic cyst arising in association with cervical irradiation for laryngeal carcinoma; a process not previously described. Thymic cysts are rare anterior mediastinal masses which have many etiologies, though an increased incidence of thymic cysts in association with Hodgkin's disease has been reported. This association was thought to be related to either mediastinal irradiation or cystic changes within a thymic focus of Hodgkin's disease. This case supports the theory that at least some thymic cysts arise secondary to irradiation.

Parenchymal iron deposition occurs in hemochromatosis, while iron is deposited in reticuloendothelial (RE) cells after blood transfusions or rhabdomyolysis. Magnetic resonance images of patients with decreased liver signal intensity on T2-weighted images at 1.5 T were blindly compared in an effort to distinguish these conditions. In each of five patients with hemochromatosis, the pancreas had low signal intensity, but splenic signal intensity was decreased in only one. In contrast, only three of the 16 patients with RE iron overload had low pancreatic signal intensity, while all of these patients either had low splenic signal intensity (n = 14) or previously underwent splenectomy (n = 2). Distinction among these causes of iron deposition is clinically important because parenchymal iron overload from hemochromatosis may produce significant tissue damage, while the RE iron of transfusions and rhabdomyolysis is of little clinical consequence.

A patient with a history of coronary artery bypass graft surgery underwent computed tomography scanning for evaluation of a lung mass. A heterogeneous mediastinal mass discovered incidentally on computed tomography scanning was shown to be a saphenous vein bypass graft aneurysm.

The purpose of the present study was to investigate the effect of alpha-thalassemia on the prevalence of avascular necrosis in 52 adult patients with sickle cell anemia. alpha-Globin genotypes were determined by restriction endonuclease mapping of genomic DNA extracted from peripheral blood leukocytes. Radiographs of humeral and femoral heads were interpreted by two radiologists who were not aware of the clinical picture and the genotype of the patients in the study. We present data showing that there is a significant positive correlation between alpha-gene deletion and the prevalence and extent of avascular necrosis in our patient population.

A form of angiitis and granulomatosis principally involving the lung was identified as a variant form of Wegener granulomatosis only 15 years ago. Recent experience indicates that the most common form of pulmonary angiitis and granulomatosis is lymphomatoid granulomatosis. Chest radiographs of 16 patients with this condition were reviewed and the findings compared with those of Wegener granulomatosis. The frequency and distribution of nodular masses, cavitation, and migratory lesions were similar in the two disorders, but reticulonodular infiltrates occurred only in lymphomatoid granulomatosis. The study suggests that lymphomatoid granulomatosis and Wegener granulomatosis occasionally can be distinguished by radiographic criteria. Although radiologic patterns will suggest the diagnosis of pulmonary angiitis and granulomatosis, the specific diagnosis of lymphomatoid granulomatosis must rely on clinical, immunologic, and pathologic evidence. Accurate differentiation is essential since treatment of Wegener granulomatosis with cyclophosphamide is highly effective while treatment of lymphomatoid granulomatosis is infrequently successful.

Computed tomography and magnetic resonance imaging are now commonly performed for a variety of pulmonary and mediastinal lesions. However, some of the lesions that affect these areas also involve the chest wall. These include tumors, infections, trauma, and congenital processes. In such cases, a knowledge of chest wall anatomy combined with careful analysis of cross-sectional images is necessary to make the diagnosis. This article describes the basic cross-sectional anatomy of the chest wall and the principal pathologic chest wall lesions.

Ischemic necrosis of bone is believed to occur exclusively in areas of predominantly fatty marrow. Sickle cell disease is unusual in that marrow infarction occurs in areas of active hematopoiesis. MR images of long bone obtained in ten patients with sickle cell anemia (SCA) were analyzed to correlate the distribution and appearance of marrow infarction with the type of marrow. While the hematopoietic marrow predominated in metaphyseal and diaphyseal regions of femurs and tibias, the fatty or mixed marrow was the most common pattern in epiphyses. Infarcts occurred in fatty as well as hematopoietic marrow. Marrow infarcts were isointense or minimally hyperintense on T1 weighted images with the hematopoietic marrow and therefore difficult to detect. On T2 weighted images, the infarcts showed very high signal. T2 weighted images are essential for detection of marrow infarction. Soft tissue changes seen as low signal on T1 and high signal on T2, may be secondary to intramuscular injections of analgesics or muscle ischemia occurring during sickle crisis.

Computerized tomography (CT) was used in the pretreatment evaluation of 23 patients who had bronchogenic carcinoma and applied to planning radiation therapy treatments. It was used to supplement conventional radiologic and clinical methods. Major changes in radiation therapy treatment were based on CT scans in nine patients, either through demonstration of larger or smaller treatment volumes or additional sites of disease, including distant metastasis. In two patients, CT scans falsely indicated absence of metastasis or benign rather than malignant disease. Changes in treatment techniques, e.g. electron beams for superficial lesions, were made based on CT scans in an additional eight patients. Follow-up studies were obtained at three-month intervals; however, CT scans did not distinguish conclusively between tumor recurrence and radiation fibrosis of the lung, although the possible value of contrast material was noted.

Three patients with uncertain pacemaker electrode position on plain film radiography were studied with fast cine cardiovascular computed tomography (CT) imaging. The value of this new technique in determining the position of pacing electrodes is discussed.

Since considerable expansion of hematopoietic marrow occurs in patients with sickle cell anemia (SCA), magnetic resonance images of 20 hips in 10 patients with known homozygous SCA were reviewed to determine a) if low signal hematopoietic marrow extended into the femoral capital epiphysis and b) if the MR characteristics of avascular necrosis (AVN) differed depending on the type of epiphyseal marrow. Our results revealed variable epiphyseal marrow type; mixed (fatty and hematopoietic) marrow (42%), fatty marrow (32%), hematopoietic marrow (16%) and hemosiderotic marrow (10%). AVN occurred irrespective of the underlying marrow. Segmental areas of low signal intensity in variable shapes (ring, band, crescent or large homogeneous area) was the most consistent MR manifestation of AVN in SCA. A low signal intensity peripheral rim surrounding a central zone, isointense with epiphyseal marrow on T1 and T2 weighted images, was most frequently observed similar to that described in patients without hemoglobinopathy. The notable difference, however, was of segmental areas within the same femoral head that demonstrated variable central zone signal on T2 weighted images. Further, while an increase in hip joint fluid is commonly seen with both early and advanced AVN in patients without hemoglobinopathy; it was increased in only one hip in patients with SCA. The observed differences in MR characteristics may be due to different pathophysiology of AVN in patients with SCA.

With the goal of improving training programs for residents and fellows in cardiac and pulmonary radiology, a committee of the Society of Thoracic Radiology undertook this survey of radiology departments with residency programs to evaluate the current nature and content of cardiac and pulmonary radiology training. The responses to a comprehensive questionnaire were analyzed and used to form the basis for this report.

Eleven patients with homozygous sickle cell anemia (SCA) undergoing painful crisis were studied with magnetic resonance (MR) imaging. The signal intensity of bone marrow was diffusely decreased in the axial and peripheral skeleton on short repetition time (TR)/echo time (TE) images and long TR/TE images, which suggested hematopoietic marrow hyperplasia and was confirmed by isotope marrow scans in five patients. Focal areas of further decrease in signal intensity were seen on short TR/TE images in 12 of the 14 (86%) painful joints and three of the five (60%) painless joints. In the painful joints, these focal areas converted to high signal intensity on long TR/TE images, presumably due to edema, which suggested acute marrow infarction. In the painless joints, these low-intensity focal areas remained as low signal on long TR/TE images, which suggested absence of edema and thus areas of old infarction or fibrosis. These results indicate that MR imaging may enable differentiation between acute and chronic marrow infarcts in patients with SCA and serve as a useful guide in monitoring and directing therapy.

Pulmonary disease caused by Mycobacterium avium complex usually occurs in patients with chronic lung disease or deficient cellular immunity, and its prevalence is increasing. We describe 21 patients (mean age, 66 years) with such infection without the usual predisposing factors, representing 18 percent of the 119 patients surveyed. Seventeen women and 4 men were given a diagnosis of M. avium complex from 1978 to 1987, with a stable incidence over the decade, on the basis of pulmonary symptoms, abnormalities on chest films, positive cultures, and in 14, biopsy evidence of invasive disease. Most of the patients (86 percent) presented with persistent cough and purulent sputum, usually without fever or weight loss. The cough was present for a mean of 25 weeks before the correct diagnosis was made. Radiographic patterns of slowly progressive nodular opacities predominated (71 percent); only five patients had cavitary disease at presentation. All patients responded initially to antimycobacterial therapy, but eight eventually relapsed when it was stopped. Four patients died of progressive pulmonary infection caused by M. avium complex. The extent of the initial pulmonary involvement was greater in patients with progressive disease than in those whose condition improved. We conclude that pulmonary disease caused by the M. avium complex can affect persons without predisposing conditions, particularly elderly women, and that recognition of this disease is often delayed because of its indolent nature.

Thirty-four patients who had received radiotherapy for Hodgkin's disease had repeat lymphangiography eleven to forty months after initial treatment to follow the abdominal and pelvic nodes when contrast material from the initial lymphangiogram was inapparent. Thirteen were in remission; in the remainder, signs or symptoms of abdominal or systemic disease had developed. The yield of positive second lymphangiography in asymptomatic patients was small. Fewer than half with signs or symptoms suggesting recurrent disease showed positive lymphangiograms. Suggestive changes on postlymphangiographic follow-up correlated well with positive repeat studies and served to define the extent of disease.

A 67 year old white woman presented with the clinical findings of cardiac tamponade, heart murmur and a history of recurrent carcinoma of the rectosigmoid. Radioisotopic angiography performed after injection of an intravenous bolus of 99m technetium pertechnetate substantiated the presence of pericardial effusion and also showed a large filling defect in the right ventricle. The presence of the defect was confirmed by selective contrast angiography, and a diagnosis of right ventricular tumor was made. Subsequently, over a period of 5 weeks, radioisotopic angiocardiography was used 3 times to assess any change in tumor size resulting from megavoltage radiation therapy. Postmortem examination confirmed the presence of a large malignant intracavitary tumor, histologically of colonic origin, involving the right ventricle. The endocardium, myocardium and the pericardium were involved.

A case of a recurrent submandibular pleomorphic adenoma with metastasis in which both the primary tumor and metastasis were histologically benign is reported and the literature reviewed.

A 14-year-old girl with a posterior mediastinal chordoma is described. Computed tomography is helpful in defining the extent of the soft tissue mass. Osseous changes related to the presence of the chordoma are described. A review of the pertinent literature is presented.

THE USE of permanent cardiac pacemakers is now a well-established procedure. It is estimated that more than 150,000 units have been employed since Chardack et al1introduced the first self-contained, fixedrate implantable pacemaker in 1960. Since that time, remarkable progress has been made in developing longerlived power resources, durable electrode and generator components, and more versatile pacing modes. The role of the radiologist is important in aiding the surgeon and the cardiologist during the initial examination of the patient and during the immediate and late postimplantation follow-up period. Pacemaker Implantation Following insertion of the pacemaker, films in the posteroanterior and lateral projections should be exposed as soon as possible. This may be done in the operating room, where an overhead tube assembly or a portable roentgenographic machine should be available. Lateral films of the chest are exposed using the horizontal beam with the patient in the supine position. If

Plain films of the abdomen in advanced states of schistosomiasis reveal massive splenomegaly without evidence of splenic calcification. The liver may be enlarged in the early stages but ultimately decreases and becomes small. Ascites is evident in far advanced disease. Chest films are negative in the early stages, but in advanced disease, dilated pulmonary arteries, right ventricular enlargement, and dilatation of the azygous vein may be recognized. Granulomata are seen as multiple small rounded densities scattered throughout both lung fields. The routine barium swallow will reveal unsuspected esophageal varices. Nine patients were studied preoperatively by panhepatic angiography and 14 post-operatively following splenorenal shunt. Thrombosis of the shunt and hepatic encephalopathy were common postoperative complications.

Since Harken et al. in 1959 and Starr and Edwards in 1960 successfully implanted the first caged-ball valve prostheses in the aortic valve, continuous and dramatic improvement in operative mortality, the quality of the prosthetic devices, and the rate of postoperative complications has been achieved. At the present time, late deaths related to prosthetic valve implantation occur in approximately 10% of patients. Death is due in large part to intrinsic cardiac problems, such as myocardial infarction and arrhythmias, and also to complications directly related to the prosthesis itself. Life-threatening complications associated with cardiac valve implantation include thromboembolism, hemolysis, paravalvular or valvular insufficiency, infection, and those of anticoagulation (1).

Seven patients with iatrogenic esophageal-pleural fistulas are described, and the differences in radiographic and physical findings in these patients and in patients with esophageal perforation with mediastinitis are emphasized. Radiographic findings in patients with esophageal pleural fistulas are pneumothorax, hydropneumothorax and localized pneumonitis. These fistulas can mimic other inflammatory supradiaphragmatic or infradiaphragmatic processes. Clinical and radiographic signs may be subtle, and active investigation is needed to establish the diagnosis of esophageal-pleural fistula in patients who have undergone esophageal manipulation.

Reaction of the lung to inhalation of dust depends on several factors, including the chemical nature of the dust, the size and concentration of the dust particles, the duration of exposure, and individual susceptibility. These factors are important in themselves and in combination, as they may be interdependent.1

The radiographic findings associated with the complications of valve implantation are presented. Complementary roles of echocardiography and cine fluoroscopy in the recognition of complications associated with this procedure are emphasized. Identification of prosthetic valves and the knowledge of the modes of action of the various types of valves are stressed.

The effects of an ionic contrast agent (meglumine iothalamate) and a nonionic contrast medium (iopamidol) on the sickling phenomenon were studied in vitro. The findings indicate that, at the same concentration of contrast agent in the blood, iopamidol causes significantly less sickling than meglumine iothalamate. This indicates that nonionic contrast agents are preferable for diagnostic studies in patients with sickle cell anemia.