Biomedical subjects
Publications and source records attributed to Todd M Blodgett.
This report describes the case of a parturient with complete coarctation of the aorta that was diagnosed during pregnancy. The use of invasive monitoring and the choice of labor analgesia for vaginal delivery are reviewed. Management of patients with complex cardiac anomalies requires consultation among cardiologist, obstetricians, and anesthesiologists to ensure good outcome for the mother and baby.
Combined positron emission tomography/computed tomography (PET/CT) became FDA-approved for clinical use in late 2001. There are several design advantages of combined PET/CT over PET and CT acquired on separate devices, including more accurate CT and PET data co-registration, improved lesion localization, consolidation of imaging studies, and reduced scan times compared to dedicated PET. There are several protocols that can used to scan patients on combined PET/CT devices. Although there is no single "correct" protocol for performing a PET/CT scan, the use of oral and intravenous contrast media may improve the diagnostic value of the CT component. Whether to utilize contrast media depends on important clinical variables, including the specific type of tumor and the likelihood of encountering viable abdominal and pelvic malignancy. This article discusses various protocols pertinent to PET/CT imaging, including how the CT portion of a PET/CT scan can be performed and optimized, as well as PET/CT interpretation and reporting issues.
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PURPOSE: To prospectively determine whether combined positron emission tomography (PET) and computed tomography (CT) is more accurate than either PET or CT alone in depicting malignant lesions in the head and neck. MATERIALS AND METHODS: Study was approved by the institutional review board, and patient informed consent was waived. Sixty-five consecutive patients (42 men, 23 women; age range, 43-83 years) known to have or suspected of having head and neck cancer were examined with combined PET/CT. CT was performed with intravenous administration of a contrast agent, and the CT data were used for attenuation correction. Each examination was interpreted in three ways: PET images in the absence of CT data, CT images in the absence of PET data, and fused PET/CT images. Probability of malignancy of each lesion was assigned a score by using a five-point scale. Receiver operating characteristic (ROC) analyses were performed by using biopsy, imaging, or clinical follow-up as the reference standard. The minimum follow-up was 6 months (range, 6-12 months). The results were additionally analyzed to assess the degree of radiologist confidence. RESULTS: Follow-up was available for 64 (98%) of 65 patients. ROC analyses demonstrated that PET/CT is significantly superior to PET or CT alone for depiction of malignancy in the head and neck (P < .05). In this series, PET/CT had a sensitivity of 98%, a specificity of 92%, and an accuracy of 94%. Radiologist confidence was substantially higher with the combined modality. CONCLUSION: Combined PET/CT is more accurate than PET or CT alone for the depiction of malignancy in the head and neck. Radiologist confidence is improved with the combined modality.
OBJECTIVE: This article identifies the most commonly encountered issues of combined PET/CT and shows the wide variability in perceived possible solutions to these issues. This article will serve as a catalyst to stimulate discussion between experts in both radiology and nuclear medicine. CONCLUSION: Combining a PET tomography and CT scanner into a single unit amounts to advantages that are not merely additive, but synergistic. Even PET/CT skeptics will embrace the technology after becoming acquainted with the possibilities and will accept the reality that there is no return to PET only.
F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) is used extensively in oncology to diagnose, stage, and restage patients with various malignancies. Many patients treated for malignancies develop neutropenia secondary to marrow suppressive chemotherapy and are subsequently treated with synthetic hematopoietic growth factors (HGF), both granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-colony-stimulating factor (G-CSF). Patients taking HGF can present a diagnostic challenge for those interpreting PET because they can demonstrate diffuse marrow uptake on FDG-PET scans, mimicking diffuse bone marrow metastases. It has not been reported whether bone marrow uptake is affected on PET scans in patients taking erythropoietin, the erythroid-specific cell-line stimulator. We report a case of extensive diffuse bone marrow uptake in a 77-year-old man with a history of colon cancer who began taking erythropoietin 3 weeks before his PET scan. This case demonstrates the need to consider erythropoietin in the differential diagnosis of possible etiologies causing diffuse bone marrow uptake on PET scans.
PET/CT offers advantages over PET alone, which is limited by poor anatomic localization and CT alone, which provides morphologic data only. Retrospective fusion of separately acquired PET and CT images allows for potential fusion misregistration in the mobile head and neck between imaging sessions. Indications for PET/CT include recurrent neoplasm, tumor surveillance, and staging. This article will focus on recurrent head and neck neoplasm including, head and neck cancer, thyroid cancer, recurrent skull base tumor. PET/CT may change management in facilitating earlier detection of recurrence than is possible with conventional CT or MR imaging, in guiding biopsy, and in detecting second primary sites and distant metastases. Limitations of PET/CT include physiologic uptake, metabolically active tissue, and muscle contraction during uptake phase. PET/CT, however, is better equipped than is PET alone to mitigate these limitations by precisely localizing FDG uptake to anatomic structures. In addition, small lesions (< 1 cm) may be below scanner resolution and, therefore, a lower SUV (that is < or = 3), may suggest neoplasm. Recent treatment may result in false negative findings, especially when PET is performed within 4 months of radiation therapy. Finally, tumors of low metabolic activity (e.g., salivary gland tumors) may be prone to false negative results. In the future, PET/CT imaging will become more useful in staging head and neck cancer with improved scanner resolution. Development of specific tumor markers may allow for tumor-specific ligands that will increase sensitivity to head and neck neoplasia. Treatment targeting for radiation therapy is an application that is likely to become widely used.
New technology that combines positron tomography with x-ray computed tomography (PET/CT) is available from all major vendors of PET imaging equipment: CTI, Siemens, GE, Philips. Although not all vendors have made the same design choices as those described in this review all have in common that their high performance design places a commercial CT scanner in tandem with a commercial PET scanner. The level of physical integration is actually less than that of the original prototype design where the CT and PET components were mounted on the same rotating support. There will undoubtedly be a demand for PET/CT technology with a greater level of integration, and at a reduced cost. This may be achieved through the design of a scanner specifically for combined anatomical and functional imaging, rather than a design combining separate CT and PET scanners, as in the current approaches. By avoiding the duplication of data acquisition and image reconstruction functions, for example, a more integrated design should also allow cost savings over current commercial PET/CT scanners. The goal is then to design and build a device specifically for imaging the function and anatomy of cancer in the most optimal and effective way, without conceptualizing it as combined PET and CT. The development of devices specifically for imaging a particular disease (eg, cancer) differs from the conventional approach of, for example, an all-purpose anatomical imaging device such as a CT scanner. This new concept targets more of a disease management approach rather than the usual division into the medical specialties of radiology (anatomical imaging) and nuclear medicine (functional imaging).
Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) has been effective for the diagnosis, staging, and restaging of malignancies of the head and neck region. However, lack of anatomic landmarks, variable physiologic uptake, and asymmetric FDG distribution in several altered physiologic states can confound image interpretation. In addition, many benign causes and several artifacts can simulate physiologic or pathologic FDG uptake in the head and neck. Combined PET-computed tomography (CT) is a unique imaging modality that permits anatomic and functional imaging on a single scanner with nearly perfect coregistration. Combined PET-CT provides information that cannot be obtained with PET or CT alone. In particular, PET-CT facilitates the interpretation of FDG uptake in the head and neck, an area that is characterized by dense and complex anatomic structures. An atlas of FDG uptake in this anatomic region was compiled on the basis of combined PET-CT findings in 11,000 patients. In general, patterns of FDG uptake were variable and often reflected patient activity during or immediately preceding the uptake phase. With the growing interest in PET-CT, interpreting radiologists and nuclear medicine physicians must be familiar with the patterns of FDG uptake in the head and neck to avoid misinterpretation or mis-diagnosis.
Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) is effective for monitoring head and neck cancer. However, lack of anatomic landmarks, variable physiologic FDG uptake, and asymmetric FDG distribution in the neck can confound image interpretation. This is particularly true in the treated neck, where distortion of normal tissue planes makes detection of early disease recurrence difficult with conventional computed tomography (CT) and magnetic resonance imaging. Combined PET-CT helps prevent the misinterpretation of FDG PET findings in patients with head and neck cancer. Superior localization of FDG uptake with this technique can improve diagnostic accuracy and help avoid interpretative pitfalls. In the future, development of tumor-specific ligands will enhance the usefulness of PET-CT in the detection of initial tumors and tumor recurrence, in the evaluation of tumors with low FDG avidity, and in treatment targeting. Furthermore, improved scanner resolution will help address the limitations of PET-CT with respect to small lesions and may make this modality more valuable in initial tumor staging.
Patients who have undergone thyroidectomy may have recurrent laryngeal nerve injury; until recently, Teflon injection was commonly used for vocal cord medialization. We present a case of a patient who underwent thyroidectomy who had significantly increased and unilateral (18)F-fluorodeoxyglucose uptake in the neck, which was found to be localized to the left vocal cord by use of combined positron emission tomography (PET) and CT, presumably because of a Teflon-induced granuloma. Knowledge of this potential source of false-positive PET interpretation because of its inability to precisely localize neoplastic lesions, and the use of combined PET and CT imaging, may allow precise diagnosis and prevention of unnecessary interventions.