The clinical use of single photon emission computed tomography (SPECT) has grown steadily over the last decade. SPECT is now an essential technique for certain studies such as cerebral blood flow imaging. Many other common nuclear medicine studies give better results when they are performed with SPECT. These include myocardial perfusion imaging with thallium-201 or the new technetium-99m perfusion agents, myocardial infarct imaging with infarct-avid agents, imaging of tumors or infections with agents such as gallium-67 or indium-111 WBC's, and certain cases of bone imaging. Still other studies such as liver/spleen imaging, most brain studies, and perhaps renal imaging may benefit from SPECT even though planar imaging gives satisfactory results. Future developments in 3D display techniques and faster computers may extend the clinical usefulness of SPECT to other areas such as pulmonary perfusion imaging and gated cardiac blood pool imaging.

PURPOSE:A prospective, single institution study was conducted to evaluate the role of positron emission tomography with fluoro-deoxyglucose (FDG) before and after definitive radiation therapy for patients with head-and-neck cancer. Correlation with CT or MRI imaging and pathologic findings at the time of planned neck dissection was made. METHODS AND MATERIALS:Twelve patients with AJCC Stages III-IV cancer of the head and neck received CT or MRI and PET imaging before treatment with definitive radiation therapy. One month after completion of treatment, repeat CT or MRI and PET imaging was obtained. All images were reviewed independently by radiologists who were blind to the results of the other modality. Patients then underwent planned neck dissection. Pathologic correlation with posttreatment scans allowed calculation of the sensitivity, specificity, negative predictive value, and the positive predictive value for both CT/MRI and PET. RESULTS:Comparison of CT/MRI to PET obtained before definitive RT revealed both primary tumor and nodal disease were detected by both modalities in all cases where primary tumor was known. After RT, comparison of CT/MRI imaging to findings of neck dissection revealed a sensitivity of 90%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 50%. Comparison of PET imaging with pathologic findings demonstrated sensitivity of 45%, specificity of 100%, positive predictive value of 100%, and a negative predictive value of 14%. CONCLUSIONS:In this small series of patients, the presence of a positive PET 1 month after RT accurately indicated the presence of residual disease in all cases; however, a negative PET indicated absence of disease in only 14%. Further investigation is warranted before FDG-PET should be used to determine whether post-RT neck dissection should be omitted.

Our aim was to determine if less expensive interictal indices can predict which epilepsy patients may benefit from the more expensive comprehensive pre-surgical evaluation. Surgical treatment was determined based on the results of a comprehensive inpatient continuous video-EEG monitoring. This evaluation included three interictal tests, which were reviewed retrospectively—2 hour-sleep-deprived electroencephalogram (SDEEG), magnetic resonance imaging (MRI), and positron emission tomography (PET). Sixty-nine patients were evaluated with 35 patients having focal resection (33 temporal, two frontal). When two or more interictal tests were positive, 77% (27 /35) went to surgery, but when one test was positive 23% (8 /34) had surgery. When all tests were negative, only a single patient (1 /13 or 7.7%) had surgery, a frontal resection. The positive predictive value for any single interictal test was 68%, while it was higher for any combination of two positive tests (77–83%). PET was the most sensitive (0.86) single interictal test, compared to SDEEG (0.66) and MRI (0.66). The odds ratio for predicting surgical treatment for a positive PET, SDEEG, or MRI was 8.57, 4.01, and 4.01, respectively. MRI was three and PET was six times the cost of a SDEEG. The combination of SDEEG and MRI had the best cost/PPV ratio. Seventy-nine percent (11 /14) of the patients with three positive tests were seizure free following focal resection compared to 43% (9 /21) when less than three tests were positive ( P≤ 0.05). Interictal tests may predict which patients are most likely to benefit from comprehensive pre-surgical evaluation. Two or more positive tests are the most predictive. If all tests are negative, it is unlikely that the patient would qualify for surgical treatment. The combination of SDEEG and MRI may be more cost-effective as outpatient screening tools.

BACKGROUND:A single institution study was undertaken to evaluate the role of positron emission tomography (PET) scans with fluorodeoxyglucose (FDG) prior to radiation and following radiation. METHODS:Forty-five patients with head and neck cancers were evaluated with FDG-PET scans as well as either CT or MRI prior to treatment with definitive radiation (RT). These same scans were obtained following completion of RT at 1 month (36 patients), 4 months (28 patients), 12 months (19 patients), and 24 months (15 patients). Standard uptake values (SUV) normalized for blood glucose and lean body mass were calculated on the initial and 1-month post-treatment PET scans. RESULTS:Fifteen patients are alive without evidence of disease at 24 to 52 months following RT. Initial SUVs were calculated on the primary tumor site and ranged from 2.5 to 28.5. These values did not have any correlation with local control when examined for the entire group, primary site, or T stage. One-month post-RT SUV ranged from 1.8 to 6.24. Of the 36 1-month post-RT PET scans, six were interpreted as positive for residual disease and were confirmed by biopsy. Four of the five scans, which were interpreted as equivocal, were positive on biopsy. Seven of the 25 scans, which were interpreted as negative for tumor, were positive on biopsy. Four-month scans were more accurate for disease with disease noted in 0 of 18 negative scans, 6 of 7 positive scans, and 2 of 3 equivocal scans. CONCLUSIONS:PET is useful for initial imaging of head and neck cancers. SUV does not appear to be useful for predicting outcome following treatment with RT. One-month post-RT scans were inaccurate for predicting the presence of cancer. Four-month post-RT scans were a better predictor for the presence of cancer.

Background: Patients with primary tumors of the head and neck have been reported to have a high rate of synchronous primary tumors of the upper aerodigestive tract. This study was performed to determine whether inclusion of the thorax in the scan volume would be diagnostically useful for positron emission tomography (PET) with [F-18] fluorodeoxy-D-glucose (FDG) in patients with primary tumors of the head and neck.Methods. FDG PET scans from the midcranium to the diaphragm were obtained on 56 patients with a variety of head and neck tumors on initial examination before definitive therapy. PET findings in the chest were correlated with results of all other imaging studies, biopsy results, and clinical follow-up.Results. In nine studies (16%), areas of increased FDG uptake in the chest were seen and were judged to be tumors. Six of these probably were false-positive results, although one of these six may have been unconfirmed true positives. Of the three confirmed true-positive studies, two were obvious from other routine studies. In only one case did the PET study reveal a significant lesion not found by means of routine evaluation, resulting in a case-finding yield of 2%. If the unconfirmed possible true-positive results are included, the case-finding yield increases to 4%.Conclusions. No compelling indication was seen for including the chest in PET studies of patients with head and neck cancer. (C) 2000 John Wiley & Sons, Inc.

Patients who present with squamous cell carcinoma metastatic to cervical lymph nodes and no clinically apparent primary site present a therapeutic dilemma. Positron emission tomography imaging with 2‐[F‐18]fluoro‐2‐deoxy‐D‐glucose (FDG‐PET) has been shown to be useful for the examination of known primary tumors. This study was undertaken to determine whether FDG‐PET imaging improves detection of occult primary tumors in patients with metastatic squamous cell carcinoma in the lymph nodes of the head and neck.

Background. The objective of this study was to review and describe the usage of fluorine-labeled deoxyglucose (FDG) and positron emission tomography (PET) in the diagnosis and management of head and neck cancer.Methods. Several prospective series,-including 159 newly diagnosed and previously untreated and 23 previously irradiated head and neck squamous cell carcinoma patients initially seen at the Wake Forest University Medical Center and evaluated by clinical examination, conventional computed tomography/ magnetic resonance imaging (CT/MRI) scans, PET scans, and histopathologic studies,-were reviewed and the findings summarized for comparison of the correct differentiation of primary and metastatic cancers and for postirradiation tumor clearance in a subsegment of those cases.Results. Position emission tomography scanning using a fluorine-labeled deoxyglucose (FDG) radiotracer proved as reliable as conventional scanning for primary and metastatic tumor identification. Compared with clinical examination, PET was better for identification of nodal metastatic tumors but poorer for small primary tumors. For previously irradiated patients treated at least 4 months before the test, PET scanning was clearly superior to clinical examination and conventional imaging in differentiating tumor recurrence from soft-tissue irradiation effects.Conclusions. Fluorine-labeled deoxyglucose-PET scanning is comparable to conventional imaging of head and neck cancers in detecting primary and metastatic carcinoma. Lack of anatomic detail remains its major drawback. Currently. its greatest role is in the evaluation of the postradiotherapy patient. (C) 1998 John Wiley & Sons. Inc.

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HomeRadiologyVol. 204, No. 1 PreviousNext LettersPET Data Analysis of Pulmonary AbnormalitiesJohn W. Keyes, JrJohn W. Keyes, JrAuthor AffiliationsPET Center, Bowman Gray School of Medicine, Winston-Salem, NC 27157John W. Keyes, JrPublished Online:Jul 1 1997https://doi.org/10.1148/radiology.204.1.282-bMoreSectionsPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In Article HistoryPublished in print: July 1997 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 204, No. 1 Metrics Altmetric Score PDF download

PURPOSE Distinguishing persistent or recurrent tumor from post-radiation edema or soft-tissue/cartilage necrosis in patients treated for carcinoma of the larynx can be difficult. Because recurrent tumor is often submucosal, multiple deep biopsies may be necessary before a diagnosis can be established. Positron emission tomography with F-18 fluorodeoxyglucose was studied for its ability to aid in this problem. PATIENTS AND METHODS FDG PET scans were performed on 31 patients who were suspected of having persistent or recurrent tumor after radiation treatment for carcinoma of the larynx. Patients underwent thorough history and physical examinations, scans with computed tomography (23 patients), and pathological evaluation when indicated. PET scans were interpreted by each of the two radiologists, who were blinded to patient outcome and the other's report. RESULTS The time between completion of radiation treatment and positron emission tomography examination ranged from 2 to 61 months with a median of 6 months. Fifteen patients had pathological evidence of tumor in the larynx, while 16 have remained without evidence of disease. The overall sensitivity and specificity of the positron emission tomography interpretations were 80% and 81%, respectively. The sensitivity and specificity of the computed tomography scan interpretations were 58% and 100%, respectively. Of the 23 patients with computed tomography scans, eight patients acquired useful information from the positron emission tomography, three patients had incorrect positron emission tomography interpretations and correct computed tomography interpretations, and one patient had positive tumor despite a negative positron emission tomography and computed tomography. DISCUSSION Positron emission tomography is useful in distinguishing benign from malignant changes in the larynx after radiation treatment. This noninvasive technique can supplement information provided by computed tomography scans. It is reasonable to delay biopsy, which could traumatize radiation-damaged tissues and precipitate necrosis, for those patients with negative positron emission tomography scans who have clinical signs and symptoms associated with recurrence.

In our extensive experience with FDG PET imaging in head and neck cancer, we have found the technique to be of high accuracy but of limited usefulness. This seeming paradox arises from several causes. Competing techniques such as CT, MR imaging, and even clinical examination already have good accuracy. In addition, high-resolution studies such as CT and MR imaging provide information required for treatment planning that is unavailable from FDG PET images. The high cost of FDG PET militates against its use in this setting, in which only a small marginal gain can be expected. In the special problem areas in which FDG PET might be expected to offer unique advantages, such as screening for second primary lesions, searching for unknown primary lesions, or differentiating benign salivary rumors from malignant lesions, the results of FDG PET have been disappointedly poor. Of these special problem areas, only the question of accuracy in finding occult primary lesions appears unresolved and in need of further study. The single application in which FDG PET appears to be advantageous is the posttherapy setting. In this setting, the technique is definitely superior to alternative methods of determining tumor recurrence and differentiating posttherapy sequelae such as radiation necrosis from tumor recurrence. We believe that considerable opportunity remains for further research on the use of FDG PET in head and neck cancer. Other agents such as 11C-methionine for example, might improve the diagnostic accuracy of FDG PET in some of the problem areas that we have identified, such as the early postirradiation period. We currently have such a study under way. Also, because FDG PET offers a unique way to measure tumor metabolism, further investigation of the use of FDG PET tracers to evaluate various biologic parameters such as proliferation rates or tumor hypoxia are needed. Such studies could provide a noninvasive technique to identify which fractionation schemes or combinations of therapy might be useful for individual patients. A final caveat is in order. Although our findings of the usefulness (and lack thereof) of FDG PET in head and neck cancer may be disappointing to many, these results should not be generalized to other applications of FDG PET in oncology. Each tumor type and setting presents its own specific problems, and in some instances FDG PET offers unique advantages over other imaging techniques. A good example is the setting of primary lung cancer, in which FDG PET appears clearly superior to all other methods of pretherapy screening [19-20].

A prospective study was conducted to compare the accuracy of clinical examination, computed tomography (CT), and positron emission tomography (PET) in identifying head and neck squamous cell carcinoma metastatic to cervical lymph nodes. The findings in the necks of 49 patients evaluated by clinical examination and CT were compared to the findings in the same necks by PET, a newly available metabolic imaging modality. Pathology specimens were available for 45 of the necks. The findings of PET and CT correlated in 84% of cases. In the cases that did not correlate, CT proved correct in four of five cases. PET (82%) and CT (84%) were comparable and were both better than clinical examination (71%) in correctly identifying the presence or absence of metastatic disease.

Digital clubbing is a classic cutaneous manifestation of pulmonary disease, but its mechanism is unknown. We describe a patient with lung cancer and clubbing in whom positron emission tomography (PET) demonstrated, for the first time, that increased glucose metabolism occurs at the nailbed. PET may contribute to future investigations of digital clubbing.

Objective: Proper alignment of the transmission and emission images in PET is crucial for appropriate attenuation correction and other uses, such as registration of the PET emission data with data from another modality. The patient may be removed from the table after the transmission scan and later repositioned for the emission scan using a laser beam projected onto fiducial marks on the patient. Repositioning the patient introduces the possibility of misalignment between the transmission and emission scans. The purpose of this investigation was to determine the magnitude of any transmission-emission scan misalignment. Methods: An immediate postemission transmission scan was obtained on 17 patients. The usual preinjection transmission image was registered to the postemission transmission image using a surface-matching algorithm. The rotations and translations necessary to register the two data sets are a measure of patient repositioning error. Results: The average X, Y and Z translations were 2.32 mm (range 0.54–4.66 mm), 1.35 mm (0.11–4.33 mm) and 4.6 mm (0.66–16.61 mm), respectively. The average X, Y and Z rotations were 1.32° (0.07–4.79°), 0.84° (0.10–2.12°) and 2.67° (0.01–13.03°), respectively. Conclusion: We conclude that while our transmission and emission data are generally repositioned within acceptable limits for the purpose of attenuation correction, significant errors are most likely to occur in the Z axis repositioning.

Quantification has always held a pervasive allure for nuclear medicine. There is a sense that anything that can be quantified should be. Once we have the numbers in hand, there is a mysterious tendency to accord them special value. Why this should be the case is unclear. Perhaps it is because of the functional nature of nuclear medicine studies, which seem as if they should be quantified. Perhaps it is because it is so easy to extract numbers from our studies. Whatever the cause, the phenomenon has been particularly strong in PET, in which we hear at every turn that PET is {open_quotes}quantitative.{close_quotes} DiChiro and Brooks commented on this phenomenon years ago, noting that, in many applications, subjective interpretation of PET images is actually superior to the use of quantitative data. Undaunted, however, the field has continued to lean heavily toward numbers as the final arbiter of correctness. 15 refs., 2 tabs.

Positron emission tomography (PET) is a relatively new radiologic imaging technique based on glucose analog uptake and metabolism in tumor tissue. In this study, PET was used in evaluating 38 patients with laryngeal cancer. Twenty-five patients were examined with PET prior to treatment to study the reliability of PET in identifying the primary tumor and assessing regional nodal status; 13 patients who had previously received irradiation with curative intent and who represented differential diagnostic problems were imaged to differentiate between irradiation effects and recurrent or residual cancer. Findings for both groups were compared to results of clinical evaluation and those of computed tomography (CT) and magnetic resonance imaging (MRI). The PET results were essentially identical to those of CT, MRI, and clinical evaluation in identifying metastatic lesions (82% correct), and were as reliable as CT and MRI for correctly identifying primary tumors (88%). Positron emission tomography was most helpful in differentiating recurrent tumor from postirradiation tissue sequelae. However, its lack of anatomic detail made PET less valuable for primary staging and therapeutic planning. It may enhance the diagnostic accuracy of CT and MRI where anatomic distortions occur or where diagnostic criteria for CT and MRI are ambiguous.

BACKGROUND:Positron emission tomography (PET) with labeled fluorodeoxyglucose (FDG) demonstrates increased tracer uptake in many neoplasms. This study was undertaken to define the patterns of FDG uptake in head and neck neoplasms before and after high dose irradiation.METHODS:Twenty-five patients were evaluated prospectively with PET and standard clinical and radiographic techniques before and after irradiation.RESULTS:Twenty-seven primary sites were confirmed pathologically in 23 patients and included the nasopharynx (four lesions), oropharynx (14 lesions), larynx (five lesions), oral cavity (two lesions), and paranasal sinuses (two lesions). Two patients had unknown primary sites. Twenty-four of 27 primary sites correlated with areas of increased tracer uptake on PET scans. Five patients had increased uptake in cervical lymph nodes that were uninvolved by radiographic or clinical criteria. Positron emission tomography seemed to be able to differentiate tumor activity from fluid-filled sinuses in two patients with paranasal sinus tumors. In two patients with unknown primary sites, increased uptake in the base of tongue after PET suggested occult primary sites. Positron emission tomography scans obtained 1 month after high dose irradiation (RT) indicated decreased levels of FDG uptake in all patients' tumors. However, these scans did not accurately reflect the status of disease in these patients. Scans obtained 4 months after RT were believed to assess more accurately the presence of malignancy.CONCLUSIONS:Positron emission tomography is a new modality that may be useful in defining tumor activity in clinically negative areas. Appropriately timed posttreatment PET may be useful in predicting outcome after definitive RT and in distinguishing viable tumors from normal tissue changes after RT in patients with head and neck carcinomas.

PURPOSE:To determine whether positron emission tomography (PET) can help differentiate benign from malignant lesions of the salivary glands before surgery.MATERIALS AND METHODS:Masses of the salivary glands were examined in 26 patients by means of computed tomography, magnetic resonance imaging, PET, biopsy (n = 18), and surgery. Contiguous PET scans were obtained from the midcranium to the lower chest 45 minutes after administration of 370 MBq (10 mCi) of fluorine-18 fluorodeoxyglucose (FDG). Standard uptake values (SUVs) were determined for all suspect lesions and for normal parotid glands and cerebellum.RESULTS:All lesions were visualized, and all but two showed some increase in FDG uptake. PET findings helped correctly differentiate benign from malignant masses in 18 (69%) but were false-positive for malignancy in eight (31%). SUV analysis, lesion-to-normal SUV ratios, and lesion-to-cerebellar SUV ratios also failed to differentiate the lesions.CONCLUSION:FDG PET is not useful in classifying salivary gland tumors as benign or malignant.

Stress 201Tl myocardial perfusion studies are useful in differentiating viable, reversibly ischemic from infarcted myocardium. A perfusion defect that shows redistribution 2 to 4 h after 201Tl injection is diagnostic of ischemia, while a fixed defect suggests infarction. However, occasional patients with a fixed defect at 4 h have redistribution at 24 h. This study evaluates the frequency and significance of this delayed redistribution with SPECT 201Tl. Patients with either no or incomplete redistribution at 4 h had repeat imaging 18 to 48 h later. Delayed redistribution was seen in 8/26 (31 percent). Four had incomplete and four had no redistribution at 4 h. Delayed redistribution with SPECT 201Tl is more common than generally appreciated, and we recommend delayed images in patients with fixed perfusion defects or incomplete redistribution at 4-h imaging, particularly in patients with previous infarctions for whom a revascularization procedure is being considered.