18F-FDG PET/CT and PET/MRI fusion imaging for neuroendocrine carcinoma of the tongue: A case report

Neuroendocrine carcinoma (NEC) involving the tongue is a rare and aggressive disease that is more common in middle-aged and elderly males. We report a case of a 56-year-old male who presented to our hospital with sore throat and was found to have a mass in the left root of the tongue. ¹⁸F-FDG PET/CT revealed intense FDG uptake in the mass of the tongue base, as well as different uptake of FDG in the mid-posterior mediastinal mass, right adrenal gland, and enlarged lymph nodes in the neck and mediastinum. Gadolinium-enhanced MRI clearly showed the extent of the tongue lesion, additionally suggesting the presence of brain metastases. ¹⁸F-FDG PET/MRI fusion images of the neck were obtained on the workstation, which may have a higher diagnostic value for tongue NEC. The patient underwent a biopsy of the mass in the left root of the tongue and was pathologically diagnosed with NEC. Whole-body ¹⁸F-FDG PET/CT and regional PET/MRI fusion images have complementary roles in the diagnosis of tongue NEC, and the former is mainly applied to determine the clinical stage of the disease and to guide treatment.     

Intraosseous hemangioma arising in the clavicle

Intraosseous hemangioma (IH) is commonly seen in the vertebral column and skull: however, IH occurring in the appendicular skeleton, including the clavicle, is uncommon. We herein report the case of a 69-year-old female presenting with IH of the left clavicle. The findings of preoperative imaging studies, including radiographs, computed tomography (CT), magnetic resonance imaging, fluorine-18-fludeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT and ultrasonography, are described. In particular, ¹⁸F-FDG PET/CT showed an ill-defined osteolytic lesion with abnormally high FDG uptake. Surgical en bloc resection with preoperative embolization was carried out and a histopathological examination confirmed the presence of an intraosseous cavernous hemangioma in the clavicle.     

Pitfalls and Misinterpretations of Cardiac Findings on PET/CT Imaging: A Careful Look at the Heart in Oncology Patients

Positron emission tomography (PET) computed tomography (CT) with 2-[fluorine-18] fluoro-2-deoxy-d-glucose (FDG) has been established as an effective modality for evaluation of cancer. Interpretations of patterns of physiologic ¹⁸F-FDG uptake by the heart is particularly difficult given the wide normal variations of ¹⁸F-FDG metabolic activity observed. Atypical patterns of focal or diffuse physiologic cardiac ¹⁸F-FDG uptake and post-therapeutic effects after radiation therapy, systemic diseases, or cardiomyopathy may also be confused with malignant disease on ¹⁸F-FDG PET/CT. In this article, we review the variations of normal cardiac ¹⁸F-FDG uptake observed in oncology patients and the appearances of other patterns of pathologic metabolic activity, related or not related to the malignancy being investigated, that may lead to false-negative and false-positive results.     

Disseminated sarcoidosis involving lymph nodes,bone and spleen with progressive cardiac sarcoidosis on 18F-FDG PET/CT and cardiac MRI

A 63-year-old lady with a background of ischemic heart disease was referred for ¹⁸F-FDG PET/CT for multiple lytic bone lesions which showed disseminated FDG avid lesions in the skeleton, nodal stations as well as spleen simulating advanced malignancy such as diffuse lymphomatous disease. A diagnosis of sarcoidosis was pathologically confirmed with bone biopsy. Following treatment, repeat PET/CT revealed significant regression of FDG avid lesions, however prominent uptake in the lateral ventricular wall was suspicious for active cardiac sarcoidosis, particularly given recurrent chest pain. This was confirmed on cardiac MRI and correlation with PET enabled discrimination between ischemic and non-ischemic fibrosis.     

Imaging characteristics of cardiac dominant diffuse large B-cell lymphoma demonstrated with MDCT and PET/CT

Purpose

To investigate the specific imaging findings of multidetector row CT (MDCT) and PET/CT with¹⁸F-FDG in cardiac dominant diffuse large B-cell lymphoma (DLBCL) in comparison with other cardiac tumours.

Methods

Five patients with DLBCL and 12 patients with other cardiac tumours including pericardial tumours were retrospectively reviewed. Among the patients with other cardiac tumours, seven had metastatic tumours, three had benign tumours, and two had other malignant cardiac tumours. The location of the cardiac mass, the encasement of the coronary artery surrounded by the mass, and pericardial effusion were evaluated using MDCT. The disease activity of the cardiac tumour was also evaluated by PET/CT.

Results

Four of the five DLBCL patients had primarily right-sided cardiac lesions, which was seen significantly more frequently in DLBCL than in other cardiac tumours (p?=?0.028). All cardiac DLBCL lesions were located around the atrioventricular groove and encased the coronary arteries. ECG-gated cardiac MDCT showed that there was no apparent stenosis of the coronary arteries. Large amounts of pericardial effusion were seen in all DLBCL patients. PET/CT revealed significantly higher FDG uptake in DLBCL than in other cardiac malignant tumours, with no overlap (p?=?0.0007).

Conclusion

The combination of a right-sided cardiac mass with a large pericardial effusion and no apparent stenosis of the encased coronary artery revealed by MDCT and a high maximum standard uptake value were the specific findings in cardiac dominant DLBCL.     

Usefulness of <Superscript>18</Superscript>F-FDG PET/CT to Detect Metastatic Mucinous Adenocarcinoma Within an Inguinal Hernia

Metastatic mucinous adenocarcinoma in an inguinal hernia is a rare disease and the image findings of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) are little known. Here, we introduce a 57-year-old man with metastatic mucinous adenocarcinoma in an inguinal hernia. On initial ¹⁸F-FDG PET/CT, hypermetabolism was observed in mucinous adenocarcinoma of the cecum, and adenocarcinomas of the transverse and ascending colon, respectively. Follow-up ¹⁸F-FDG PET/CT revealed newly developed multiple hypermetabolism in peritoneal seeding masses and nodules in the pelvic cavity and scrotum. Peritoneal carcinomatosis in the right pelvic side wall was extended to the incarcerated peritoneum and mesentery in the right inguinoscrotal hernia.¹⁸F-FDG PET/CT was useful to reveal unexpected peritoneal seeding within the inguinal hernia. Also, this case demonstrated that metastatic mucinous adenocarcinomas had variably intense FDG uptake.     

Diuretic 18F-FDG PET/CT imaging for detection and locoregional staging of urinary bladder cancer: prospective evaluation of a novel technique

Purpose

Positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluorodeoxyglucose (FDG) has been used with limited success in the past in primary diagnosis and locoregional staging of urinary bladder cancer, mainly because of the pharmacokinetics of renal excretion of ¹⁸F-FDG. In the present prospective study, we have evaluated the potential application of diuretic ¹⁸F-FDG PET/CT in improving detection and locoregional staging of urinary bladder tumours.

Methods

Twenty-five patients suspected of having primary carcinoma of the urinary bladder were evaluated prospectively for diagnosis and staging. All of these 25 patients underwent conventional contrast-enhanced computed tomography (CECT) of the abdomen/pelvis and whole-body diuretic ¹⁸F-FDG PET/CT. In addition, pelvic PET/CT images were obtained using the special technique of forced diuresis using intravenous furosemide (20–40 mg). Of the 25 patients, 10 underwent radical cystectomy and 15 underwent transurethral resection of the bladder tumour (TURBT). Results of CECT and diuretic ¹⁸F-FDG PET/CT were compared considering histopathology as a reference standard.

Results

Of the 25 patients, CECT detected a primary tumour in 23 (sensitivity 92 %), while ¹⁸F-FDG PET/CT was positive in 24 patients (sensitivity 96 %). Mean size and maximum standardized uptake value of the bladder tumours were 3.33 cm (range 1.6–6.2) and 5.3 (range 1.3–11.7), respectively. Of the 25 patients, only 10 patients underwent radical cystectomy based on disease status on TURBT. Among those ten patients, nine had locoregional metastases. Among the nine patients who had positive lymph nodes for metastasis on histopathology, CECT and PET/CT scan had a sensitivity of 44 and 78 %, respectively. ¹⁸F-FDG PET/CT was found to be superior to CECT in the detection of the primary tumour and locoregional staging (p?<?0.05).

Conclusion

Diuretic ¹⁸F-FDG PET/CT is highly sensitive and specific and plays an important role in improving detection of the primary tumour and locoregional staging of urinary bladder tumours. Diuretic ¹⁸F-FDG PET/CT demonstrated a higher diagnostic value when compared with CECT in these patients.     

18F-FDG PET/CT in detection of gynecomastia in patients with hepatocellular carcinoma

ObjectiveWe retrospectively investigate the prevalence of gynecomastia as false-positive 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) imaging in patients with hepatocellular carcinoma (HCC).MethodsAmong the 127 male HCC patients who underwent ¹⁸F-FDG PET/CT scan, the ¹⁸FDG uptakes at the bilateral breasts in 9 patients with gynecomastia were recorded as standard uptake value (SUVmax) and the visual interpretation in both early and delayed images.ResultsThe mean early SUVmax was 1.58/1.57 (right/left breast) in nine gynecomastia patients. The three patients with early visual score of 3 had higher early SUVmaxs.ConclusionGynecomastia is a possible cause of false-positive uptake on ¹⁸F-FDG PET/CT images.     

Role of 18F-FDG PET/CT in the prediction of gastric cancer recurrence after curative surgical resection

Purpose

The study evaluated the role of preoperative ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the prediction of recurrent gastric cancer after curative surgical resection.

Methods

A total of 271 patients with gastric cancer who underwent ¹⁸F-FDG PET/CT and subsequent curative surgical resection were enrolled. All patients underwent follow-up for cancer recurrence with a mean duration of 24?±?12?months. ¹⁸F-FDG PET/CT images were visually assessed and, in patients with positive ¹⁸F-FDG cancer uptake, the maximum standardized uptake value (SUV_max) of cancer lesions was measured. ¹⁸F-FDG PET/CT findings were tested as prognostic factors for cancer recurrence and compared with conventional prognostic factors. Furthermore, ¹⁸F-FDG PET/CT findings were assessed as prognostic factors according to histopathological subtypes.

Results

Of 271 patients, 47 (17?%) had a recurrent event. Positive ¹⁸F-FDG cancer uptake was shown in 149 patients (55?%). Tumour size, depth of invasion, presence of lymph node metastasis, positive ¹⁸F-FDG uptake and SUV_max were significantly associated with tumour recurrence in univariate analysis, while only depth of invasion, positive ¹⁸F-FDG uptake and SUV_max had significance in multivariate analysis. The 24-month recurrence-free survival rate was significantly higher in patients with negative ¹⁸F-FDG uptake (95?%) than in those with positive ¹⁸F-FDG uptake (74?%; p?18F-FDG uptake was a significant prognostic factor in patients with tubular adenocarcinoma (p?=?0.003) or poorly differentiated adenocarcinoma (p?=?0.0001). However, only marginal significance was shown in patients with signet-ring cell carcinoma and mucinous carcinoma (p?=?0.05).

Conclusion

¹⁸F-FDG uptake of gastric cancer is an independent and significant prognostic factor for tumour recurrence. ¹⁸F-FDG PET/CT could provide effective information on the prognosis after surgical resection of gastric cancer, especially in tubular adenocarcinoma and poorly differentiated adenocarcinoma.     

Incidentally Detected Small Intestine Intussusception Caused by Primary Small Intestine Carcinoma on <Superscript>18</Superscript>F-FDG PET/CT

Small intestine intussusception in adults is a rare condition mainly caused by primary or metastatic small intestine malignancy. Here, we present a 72-year-old male patient who was diagnosed with small intestine cancer that was presented as small intestine intussusception on hybrid ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT). The patient was initially referred for an abnormality on a chest radiography and severe anemia. FDG PET/CT showed the lung lesion in the right upper lobe of lung as a high FDG uptake mass. Accidentally, FDG PET demonstrated another intense hypermetabolic intraluminal lesion in the small intestine accompanied with intussusception shown as a circumferential hypermetabolic wall. By pathologic examination, the patient was diagnosed as primary small intestine cancer with lung metastasis. This case highlights usefulness of hybrid FDG PET/CT to identify unexpected malignancy.     

Perirenal 18F-FDG Uptake in a Patient with a Pheochromocytoma

Increased ¹⁸F-fluorodeoxyglucose (FDG) uptake of brown fat on ¹⁸F-FDG positron emission tomography (PET) originating from physiological activation is a common incidental finding and is usually located in the neck, shoulder, and supraclavicular areas. We present a case of an incidental pheochromocytoma showing diffusely increased ¹⁸F-FDG uptake in bilateral perirenal fat tissue as well as supraclavicular and paravertebral fat tissue on ¹⁸F-FDG PET/CT. The patient had no clinical symptoms except hypertension, and a pheochromocytoma was confirmed in a postsurgical specimen. A pheochromocytoma should be considered a cause in cases of increased ¹⁸F-FDG uptake of perirenal brown fat.     

18F-FDG PET/CT Findings in a Breast Cancer Patient with Concomitant Tuberculous Axillary Lymphadenitis

Although ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) is a sensitive modality for detecting a malignant lesion, increased ¹⁸F-FDG uptake is also seen in infected or inflammatory processes. Here, we report the case of a breast cancer patient with concomitant tuberculous axillary lymphadenitis that showed increased ¹⁸F-FDG uptake. A 39-year-old woman underwent preoperative ¹⁸F-FDG PET/computed tomography (CT) as a part of the work-up for right breast cancer. ¹⁸F-FDG PET/CT images showed a malignant lesion in the right breast with moderate ¹⁸F-FDG uptake, and multiple enlarged right axillary lymph nodes with intense ¹⁸F-FDG uptake. Subsequently, the patient underwent right mastectomy and right axillary lymph node dissection. Histopathological examination confirmed breast cancer and tuberculous lymphadenitis, and the patient was treated concomitantly with anti-tuberculous therapy.     

Giant Cell Tumor with Secondary Aneurysmal Bone Cyst Shows Heterogeneous Metabolic Pattern on <Superscript>18</Superscript>F-FDG PET/CT: A Case Report

Giant cell tumor (GCT) is a generally benign bone tumor accounting for approximately 5 % of all primary bone neoplasms. Cystic components in GCTs that indicate secondary aneurysmal bone cysts (ABCs) are reported in 14 % of GCTs. Although both of them have been described separately in previous reports that may show considerable fluorodeoxyglucose (FDG) uptake despite their benign nature, the findings of GCT with secondary ABC on ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) have not been well-known. We report a case of GCT with secondary ABC in a 26-year-old woman. ¹⁸F-FDG PET/CT revealed a heterogeneous hypermetabolic lesion in the left proximal femur with the maximum standardized uptake value of 4.7. The solid components of the tumor showed higher FDG uptake than the cystic components. These observations suggest that the ABC components in GCTs show heterogeneous metabolic patterns on ¹⁸F-FDG PET/CT.     

Imaging spectrum and pitfalls of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in patients with tuberculosis

Mycobacterium tuberculosis (TB) is one of the most prominant diseases frequently causing false positive lesions in oncologic surveys using ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT), since TB granulomas are composed of activated macrophages and lymphocytes with high affinity for glucose. These pitfalls of ¹⁸F-FDG PET/CT are important for radiologists. Being familiar with ¹⁸F-FDG images of TB could assist in preventing unfavorable clinical results based on misdiagnoses. In addition, ¹⁸F-FDG PET/CT has the advantage of being able to screen the whole body, and can clearly detect harboring TB lesions as high uptake foci. This article details the spectrum and pitfalls of ¹⁸F-FDG PET/CT imaging in TB.     

Pseudomesotheliomatous lung cancer mimicking mesothelioma on 18F-FDG PET/CT images: report of 2 cases

The authors report two cases of pseudomesotheliomatous lung cancer (PLC) detected by ¹⁸F-FDG PET/CT scan. ¹⁸F-FDG PET/CT clearly revealed the extent of the disease in both cases, a case of adenocarcinoma of the lung and a case of squamous cell carcinoma of the lung. Intense ¹⁸F-FDG uptake by the diffusely thickened pleurae and primary lesion was observed in both cases, and increased ¹⁸F-FDG uptake by a pelvic bone metastasis was observed in the case of squamous cell carcinoma. Although PLC is indistinguishable from malignant pleural mesothelioma on ¹⁸F-FDG PET/CT scans, ¹⁸F-FDG PET/CT was helpful in identifying the primary focus of the PLCs and in staging the disease. Diagnostic image interpreters should be familiar with the ¹⁸F-FDG PET/CT findings in PLC.     

Right ventricular 18F-FDG uptake is an important indicator for cardiac involvement in patients with suspected cardiac sarcoidosis

Purpose

Cardiac sarcoidosis is most commonly found in the left ventricular (LV) free wall. Presence in the right ventricle (RV) is less common but might be useful for detecting cardiac involvement of sarcoidosis. ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET has been used to detect LV regions with cardiac sarcoidosis. However, the same has not been done for RV involvement. The aims of the current study were to evaluate RV ¹⁸F-FDG uptake and its relationship to the distribution of LV wall ¹⁸F-FDG-positive segments in the LV, and to evaluate whether patients with positive RV ¹⁸F-FDG uptake met the 1993 diagnostic criteria of the Japanese Ministry of Health and Welfare (JMHW) guidelines regarding sarcoidosis with suspected cardiac involvement.

Method

Fifty-nine biopsy-proven extra-cardiac sarcoidosis patients (age 56.1 ± 14.7 years) with suspected cardiac involvement based on abnormal electrocardiography or echocardiography findings underwent fasting ¹⁸F-FDG PET or PET/CT. The LV wall was divided into 17 segments and RV uptake was also evaluated.

Result

Among 59 patients, 35 (59.3 %) showed some abnormal ¹⁸F-FDG uptake in the RV and/or LV wall. With respect to the RV wall, 13 (22.0 %) showed abnormal ¹⁸F-FDG uptake. The number of LV-involved segments was 4.8 ± 2.4 in the patients with RV ¹⁸F-FDG uptake, which was significantly higher than in the patients without RV uptake, 1.8 ± 2.2 (P < 0.0001). Patients with RV uptake more frequently met the diagnostic criteria of the 1993 JMHW guidelines (n = 27), than did those without RV uptake (84.6 vs. 34.8 %, P = 0.0033).

Conclusion

¹⁸F-FDG PET identified RV involvement less frequently than LV involvement in this study population. However, patients who had RV uptake showed a greater number of LV-involved segments and met the JMHW diagnostic criteria more frequently. Although RV uptake is less frequent, ¹⁸F-FDG RV uptake may be useful in diagnosing cardiac involvement in sarcoidosis.

Clinical trial registration

UMIN000006533.     

Update on advances in molecular PET in urological oncology

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) has emerged as a powerful tool for the combined metabolic and anatomic evaluation of many cancers. In urological oncology, however, the use of ¹⁸F-FDG has been limited by a generally low tumor uptake, and physiological excretion of FDG through the urinary system. ¹⁸F-FDG PET/CT is useful when applied to specific indications in selected patients with urological malignancy. New radiotracers and positron emission tomography/magnetic resonance imaging (PET/MRI) are expected to further improve the performance of PET in uro-oncology.     

Role of 68Ga-DOTATOC PET/CT in initial evaluation of patients with suspected bronchopulmonary carcinoid

Purpose

The objective of this study was to evaluate the role of ⁶⁸Ga-DOTATOC positron emission tomography (PET)/CT scan in patients with suspected pulmonary carcinoid tumour and to compare its results with ¹⁸F-fluorodeoxyglucose (FDG) PET/CT scan.

Methods

In this prospective study, 32 patients (age 34.22?±?12.03 years; 53.1 % female) with clinical suspicion of bronchopulmonary carcinoid were evaluated with ⁶⁸Ga-DOTATOC PET/CT and ¹⁸F-FDG PET/CT. The two imaging modalities were compared, considering the tissue diagnosis as the reference standard.

Results

Based on the reference standard 26 cases were carcinoid tumours [21 typical carcinoids (TC) and 5 atypical carcinoids (AC)] and 6 cases were non-carcinoid tumours. The sensitivity, specificity and accuracy of ⁶⁸Ga-DOTATOC PET/CT in the diagnosis of pulmonary carcinoid tumour were 96.15, 100 and 96.87 % respectively, whereas those of ¹⁸F-FDG PET/CT were 78.26, 11.1 and 59.37 % respectively. The maximum standardised uptake value (SUV_max) of TC on ⁶⁸Ga-DOTATOC PET/CT scan ranged from 3.58 to 55, while that of AC ranged from 1.1 to 32.5. ¹⁸F-FDG PET/CT was true-positive in all cases of AC and false-negative in eight cases of TC (sensitivity for TC 61.9 % and for AC 100 %).

Conclusion

⁶⁸Ga-DOTATOC PET/CT is a useful imaging investigation for the evaluation of pulmonary carcinoids. ¹⁸F-FDG PET/CT scan suffers from low sensitivity and specificity in differentiating the pulmonary carcinoids from other tumours.     

Detection of internal mammary lymph node metastasis with 18F-fluorodeoxyglucose positron emission tomography/computed tomography in patients with stage III breast cancer

Purpose

The present study assessed the positive predictive value (PPV) of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the detection of internal mammary node (IMN) metastasis in patients with clinical stage III breast cancer.

Methods

Patients who were diagnosed with clinical stage III breast cancer and underwent pretreatment ¹⁸F-FDG PET/CT were retrospectively analyzed. The ¹⁸F-FDG PET/CT scans were prospectively reviewed by two board-certified nuclear medicine physicians in a blinded manner. The intensities of IMNs were graded into four categories (no activity and lower, similar, and higher activities than that of the mediastinal blood pool). IMNs were measured from the combined CT (largest diameter of the short axis). Histologic data of the IMNs were obtained by ultrasonography-guided fine-needle aspiration biopsy or surgical excision. The PPV was calculated for pathologically confirmed IMNs. Visual grade, maximum standardized uptake values (SUV_max), and sizes were analyzed according to the pathology results.

Results

There were 249 clinical stage III breast cancer patients (age 48.0?±?10.1 years, range 26–79 years) who had undergone initial ¹⁸F-FDG PET/CT prior to treatment. Excluding 33 cases of stage IV breast cancer, 62 of 216 patients had visible IMNs on ¹⁸F-FDG PET/CT, and histologic confirmation was obtained in 31 patients. There were 27 metastatic and four nonmetastatic nodes (PPV 87.1 %). Metastatic nodes mostly presented with visual grade 3 (83.9 %), and SUV_max and size were 3.5?±?4.3 and 5.6?±?2.0 mm, respectively.

Conclusion

¹⁸F-FDG PET/CT has a high PPV for IMN metastasis in clinical stage III breast cancer, indicating the possibility of metastasis in IMNs with FDG uptake similar to/lower than that of the blood pool or small-sized nodes.     

Preoperative assessment of cervical lymph nodes in head and neck cancer with fluorine-18 fluorodeoxyglucose using a dual-head coincidence camera: a pilot study

The aim of this study was to investigate whether in patients with head and neck cancer, staging is possible with fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) using a dual-head positron emission tomography (PET) camera. Twenty patients (ten men, ten women; mean age: 60 years) were studied using 185 MBq (5 mCi) ¹⁸F-FDG. Two of these patients who were suspected of having recurrence in the neck were restaged 19 and 12 months, respectively, after the resection of the primary tumour. The images were visually analyzed and the results were correlated with computed tomography (CT) (n = 18), ultrasonography (n = 17) and pathological findings. With respect to the primary tumour, FDG dual-head PET and CT revealed a sensitivity of 100% and 59%, respectively (P<0.001). In seven patients lymph node metastases were found in the neck specimen. Two of them had bilateral metastases. FDG dual-head PET correctly identified all nine pathological neck sides whereas CT and ultrasonography depicted eight of nine and seven of eight pathological sides, respectively. In three patients, false-positive FDG uptake was seen, which was due to a preceding biopsy in two cases. The sensitivity of FDG dual-head PET, CT and ultrasonography in the identification of pathological neck sides was 100%, 89% and 87%, respectively, and the specificity was 90%, 93% and 50%, respectively. With knowledge of the preceding biopsies, the specificity of FDG dual-head PET would have been 97%. The smallest lymph node metastasis detected by FDG dual-head PET that was missed by CT had a diameter of 0.6 cm. Measurement of ¹⁸F-FDG with a dual-head PET camera is very sensitive in the detection of primary head and neck cancers and accurate in the preoperative assessment of lymph node metastases. The results justify a prospective study on the identification of metastases in patients with head and neck cancer. In addition, it is justified to start a study on the detection of unknown primary tumours in patients with cervical metastases. Received 19 October and in revised form 18 December 1998