Entries Tagged as 'Semin Nucl Med'
Pulmonary embolism: a clinician’s perspective.
Semin Nucl Med. 2008 Nov;38(6):404-11
Authors: Wells PS
Recent advances in the management of patients with suspected pulmonary embolism (PE) have both improved diagnostic accuracy as well as made management algorithms safer and more accessible. Physicians need to more frequently consider PE in patients with chest pain or dyspnea and should be aware of the proper diagnostic approach. Diagnostic strategies should include pretest clinical probability, D-dimer assays, and imaging tests. Although it has been proven that the use of algorithms result in better outcomes, there are patient-specific issues that must be considered. Approaches that use computed tomographic pulmonary angiography or ventilation-perfusion (V/Q) scanning appear equally safe, but each approach has advantages and disadvantages that should be appreciated to provide the best care. Ongoing clinical trials are evaluating whether these diagnostic processes can be made even easier and less expensive. Importantly, patients at low risk with a negative D-dimer can avoid imaging tests and those at moderate risk with a negative high sensitivity D-dimer can have venous thromboembolism excluded without the need for imaging. However, these patients also represent those most likely to have false-positive tests and clinically irrelevant PE. V/Q scanning may be more appropriate in premenopausal women, in those with renal dysfunction or diabetes, in those with known contrast allergies, and perhaps in patients with known family history of breast cancer. As with any illness, there is room for improvement in the management of PE, but it remains unknown whether preventive measures, diagnosis, treatment modalities, or physician or patient education should be the focus.
PMID: 19331834 [PubMed - indexed for MEDLINE]
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The use of leg venous ultrasonography for the diagnosis of pulmonary embolism.
Semin Nucl Med. 2008 Nov;38(6):412-7
Authors: Anderson DR, Barnes D
The role of ultrasonography of the lower extremities for the evaluation of patients with suspected pulmonary embolism has become more clearly defined with time. Ultrasonography is a useful first-line test for pulmonary embolism in clinical circumstances in which radiographic imaging is contraindicated or not readily available (eg, pregnancy). Ultrasonography is likely not required for the evaluation of patients with suspected pulmonary embolism who have a negative computed tomography pulmonary angiography, particularly if there are no symptoms of deep vein thrombosis. Ultrasonography is helpful to exclude a diagnosis of deep vein thrombosis in patients who have nondiagnostic ventilation-perfusion scans. For patients with nondiagnostic ventilation-perfusion scans and negative ultrasonography who are considered clinically highly likely to have pulmonary embolism, it is recommended that computed tomography pulmonary angiography be performed.
PMID: 19331835 [PubMed - indexed for MEDLINE]
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The role of multidetector computed tomography angiography for the diagnosis of pulmonary embolism.
Semin Nucl Med. 2008 Nov;38(6):418-31
Authors: Cronin P, Weg JG, Kazerooni EA
From a radiological point of view, computed tomography pulmonary angiography (CTPA) has effectively become the de-facto first-line imaging test for the evaluation of pulmonary embolism (PE), as patients with a high-quality negative CTPA do not require further examination or treatment for suspected PE. We are likely to see further technical developments in CT technology in the near future. These advances will most likely further improve image quality. Several questions or issues remain, including strategies for further imaging when CT is inconclusive or contraindicated, issues regarding radiation exposure, the prevalence of PE in specific populations, best tests and pathways in specific patient groups, including patients with specific comorbidities such as oncology patients or patients with chronic obstructive pulmonary disease. Also, the question whether all PE patients need anticoagulation, the clinical effect of follow-up imaging, and the accuracy of different clinical prediction rules, remains.
PMID: 19331836 [PubMed - indexed for MEDLINE]
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Enhancing lung scintigraphy with single-photon emission computed tomography.
Semin Nucl Med. 2008 Nov;38(6):441-9
Authors: Roach PJ, Bailey DL, Harris BE
Although widely used for many years in the assessment of pulmonary embolism, planar ventilation-perfusion (V/Q) scintigraphy has well-recognized limitations. Single-photon emission computed tomography (SPECT) imaging, which can be readily performed in most modern nuclear medicine centers equipped with multihead gamma cameras, overcomes many of these limitations through its ability to generate 3-dimensional imaging data. V/Q SPECT has been shown to have a greater sensitivity and specificity than planar imaging and has a lower nondiagnostic rate. For reporting clinicians who may be reluctant to abandon conventional planar V/Q images, planar-like images can also be readily obtained from V/Q SPECT with the use of postacquisition techniques. The use of SPECT can also facilitate advances in V/Q imaging, including the generation of parametric V:Q ratio images, coregistration with computed tomography, respiratory gating, and more accurate quantification of regional lung function. Although direct comparisons in the literature are limited in number, V/Q SPECT appears to have comparable, or greater, sensitivity than multidetector computed tomography pulmonary angiography and is not associated with contrast-related complications such as allergy and nephropathy. It also involves significantly less radiation dose to breast tissue, an important consideration, particularly in young women. For the V/Q scan to remain relevant in the evaluation of patients with suspected pulmonary embolism, it is essential that image data are obtained so as to maximize their accuracy and diagnostic usefulness. V/Q SPECT can achieve this and, furthermore, may have a role in conditions other than pulmonary embolism, including both clinical and research fields.
PMID: 19331838 [PubMed - indexed for MEDLINE]
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The current and continuing important role of ventilation-perfusion scintigraphy in evaluating patients with suspected pulmonary embolism.
Semin Nucl Med. 2008 Nov;38(6):432-40
Authors: Freeman LM, Stein EG, Sprayregen S, Chamarthy M, Haramati LB
After the publication of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study in 1990, there was considerable controversy concerning the ventilation-perfusion (V/Q) study in regard to its low sensitivity and high number of nondiagnostic examinations when used in patients with suspected pulmonary embolism (PE). Many lessons have been learned from the PIOPED database that have greatly improved our interpretive skills in the 2 decades since the study was performed. One of the key problems negatively impacting interpretation was the predominantly inpatient population that was studied. Inpatients generally are sicker patients with abnormal chest x-rays. This factor significantly degrades V/Q interpretation. A normal chest x-ray greatly facilitates accurate interpretation of the lung scan. The emergence of computed tomography angiography (CTA) in the early to mid-1990s provided a superb new means of imaging patients with suspected PE. As this technology became more sophisticated with multidetector units, it became the procedure of choice in the great majority of medical centers. CT scanners located in or proximal to many emergency departments as well as its 24/7 availability supported this preference. Within the past 2 to 3 years, the publication of the PIOPED II study as well as some other prospective and retrospective studies have confirmed similar diagnostic accuracy for CTA and V/Q studies. Additionally, there have been several recent publications cautioning physicians about the large radiation dose associated with CTA, particularly to the female breast. Considering the great benefits of both techniques as well as their limitations, it is prudent for both clinicians and imaging physicians to develop an appropriate approach to studying patients with suspected PE. Considerations such as objective clinical assessment, D-dimer assay and the chest x-ray appearance all play significant roles in this decision-making process.
PMID: 19331837 [PubMed - indexed for MEDLINE]
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Fever of unknown origin.
Semin Nucl Med. 2009 Mar;39(2):81-7
Authors: Bleeker-Rovers CP, van der Meer JW, Oyen WJ
Fever of unknown origin (FUO) often is defined as a fever greater than 38.3 degrees C on several occasions during at least 3 weeks with uncertain diagnosis after a number of obligatory tests. In general, infection accounts for approximately one-fourth of cases of FUO, followed by neoplasm and noninfectious inflammatory diseases. No diagnosis is reached in up to 50% of cases. Scintigraphic methods, such as (67)Ga-citrate, labeled leukocytes, and (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET), are often used in the diagnosis of FUO. In FUO, FDG-PET appears to be of great advantage because malignancy, inflammation, and infection can be detected. FDG-PET does not seem to contribute to a final diagnosis in patients with normal erythrocyte sedimentation rate and C-reactive protein. Image fusion combining PET and computed tomography facilitates anatomical localization of increased FDG uptake and better guiding for further diagnostic tests to achieve a final diagnosis. In conclusion, the body of evidence on the utility of FDG-PET in patients with FUO is growing and FDG-PET will probably become the preferred diagnostic procedure, especially when a definite diagnosis cannot easily be achieved. Because of favorable characteristics of FDG-PET, conventional scintigraphic techniques may be replaced by FDG-PET in institutions in which PET is available.
PMID: 19187801 [PubMed - indexed for MEDLINE]
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Positron emission tomography as a diagnostic tool in infection: present role and future possibilities.
Semin Nucl Med. 2009 Jan;39(1):36-51
Authors: Basu S, Chryssikos T, Moghadam-Kia S, Zhuang H, Torigian DA, Alavi A
The past decade has witnessed the emergence of yet another promising application of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in the detection and management of patients with infection and inflammatory disorders. This phenomenon is quite evident when the peer-reviewed scientific literature is searched for on this topic. Among these scientific communications, the 6 conditions in which FDG-PET has demonstrated its greatest utility include (1) chronic osteomyelitis, (2) complicated lower-limb prostheses, (3) complicated diabetic foot, (4) fever of unknown origin, (5) acquired immunodeficiency syndrome (ie, AIDS), and (6) vascular graft infection and fistula. On the basis of published literature, orthopedic infections, particularly those related to implanted prostheses and osteomyelitis (including that occurring in the setting of a complicated diabetic foot), can be detected successfully by the use of FDG-PET and, therefore, this modality has great promise for becoming the study of choice in these complex settings. Increasingly, this technique is being used to detect infection in soft tissues, including those representing the sources of fever of unknown origin. The ability of FDG-PET to diagnose vascular graft infection and fistula, even when the anatomical imaging modalities are inconclusive, is of considerable interest to practitioners of vascular surgery. Combined PET/computed tomography (CT) imaging has the potential to determine the sites of infection or inflammation with high precision. The data on the role of PET/CT imaging in the assessment of infection and inflammation is sparse, but this combined modality approach may prove to be the study of choice in foreseeable future for precise localization of involved sites. However, the role of PET/CT may be limited in the presence of metallic artifacts (such as those caused by prostheses) adjacent to the sites of infection.
PMID: 19038599 [PubMed - indexed for MEDLINE]
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Nuclear medicine and diabetic foot infections.
Semin Nucl Med. 2009 Jan;39(1):52-65
Authors: Palestro CJ, Love C
Up to 25% of the diabetic population is at risk for developing a pedal ulcer. These ulcers serve as a portal of entry for osteomyelitis and overlie more than 90% of diabetic pedal osteomyelitis cases. The diagnosis of osteomyelitis often is overlooked, and imaging studies are an essential part of the evaluation. The most commonly performed radionuclide tests are bone and labeled leukocyte imaging. Focal hyperperfusion, focal hyperemia, and focal bony uptake on the 3-phase bone scan comprise the usual presentation of osteomyelitis. Many conditions to which the diabetic population with foot problems is prone, however, mimic osteomyelitis, and the test is sensitive but not specific. Consequently, the bone scan often is used as a screening test or to facilitate localization of activity on labeled leukocyte images. Because of its high sensitivity and prevalence of positive results, its value as a screening test is questionable. Investigations comparing labeled leukocyte imaging alone to labeled leukocyte plus bone imaging, demonstrate only marginal improvement for the combined study. Thus, it is time to reevaluate the role of the bone scan in diabetic foot infections. Labeled leukocyte imaging is the radionuclide procedure of choice for evaluating diabetic pedal osteomyelitis. Sensitivity and specificity range between 72% and 100%, and 67% and 98%, respectively. Although intraindividual comparisons are few, the accuracy of the test is similar, whether the leukocytes are labeled with (99m)Tc or (111)In. Labeled leukocytes accumulate in uninfected neuropathic joints, and marrow scintigraphy may be needed to determine whether infection is present. Alternatives to labeled leukocyte imaging include in vivo methods of labeling leukocytes, radiolabeled polyclonal IgG, and radiolabeled antibiotics. The results obtained have been variable and none of these agents is available in the United States. There are few data available on single-photon emission computed tomography/computed tomography. It probably will be useful in the mid and hind foot; in the distal forefoot, given the small size of the structures, its value is less certain. Data on (18)F-fluorodeoxyglucose positron emission tomography and positron emission tomography/computed tomography are limited and inconclusive, and further investigation is needed.
PMID: 19038600 [PubMed - indexed for MEDLINE]
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Positron emission tomography/computed tomography.
Semin Nucl Med. 2008 May;38(3):152-66
Authors: Townsend DW
Accurate anatomical localization of functional abnormalities obtained with the use of positron emission tomography (PET) is known to be problematic. Although tracers such as (18)F-fluorodeoxyglucose ((18)F-FDG) visualize certain normal anatomical structures, the spatial resolution is generally inadequate for accurate anatomic localization of pathology. Combining PET with a high-resolution anatomical imaging modality such as computed tomography (CT) can resolve the localization issue as long as the images from the two modalities are accurately coregistered. However, software-based registration techniques have difficulty accounting for differences in patient positioning and involuntary movement of internal organs, often necessitating labor-intensive nonlinear mapping that may not converge to a satisfactory result. Acquiring both CT and PET images in the same scanner obviates the need for software registration and routinely provides accurately aligned images of anatomy and function in a single scan. A CT scanner positioned in line with a PET scanner and with a common patient couch and operating console has provided a practical solution to anatomical and functional image registration. Axial translation of the couch between the 2 modalities enables both CT and PET data to be acquired during a single imaging session. In addition, the CT images can be used to generate essentially noiseless attenuation correction factors for the PET emission data. By minimizing patient movement between the CT and PET scans and accounting for the axial separation of the two modalities, accurately registered anatomical and functional images can be obtained. Since the introduction of the first PET/CT prototype more than 6 years ago, numerous patients with cancer have been scanned on commercial PET/CT devices worldwide. The commercial designs feature multidetector spiral CT and high-performance PET components. Experience has demonstrated an increased level of accuracy and confidence in the interpretation of the combined study as compared with studies acquired separately, particularly in distinguishing pathology from normal, physiologic tracer uptake and precisely localizing abnormal foci. Combined PET/CT scanners represent an important evolution in technology that has helped to bring molecular imaging to the forefront in cancer diagnosis, staging and therapy monitoring.
PMID: 18396176 [PubMed - indexed for MEDLINE]
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