Sumeet G Dua

Therapeutic Response to Radiofrequency Ablation of Neoplastic Lesions: FDG PET/CT Findings

Ablation of neoplastic lesions by using radiofrequency energy is gaining popularity in clinical practice because of the minimally invasive nature of radiofrequency ablation (RFA). Primary and secondary tumors of the liver and lung are treated with RFA when surgery is precluded because of comorbidity. Benign bone tumors are also treated with RFA to relieve pain and prevent further tumor growth. Differentiation between postablation tissue changes and residual disease is difficult with morphologic imaging modalities such as ultrasonography, computed tomography (CT), and magnetic resonance (MR) imaging, thus limiting the use of these modalities to detection of residual disease early after RFA. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is a functional imaging modality that can be used to study the effects and efficacy of RFA. Lesions that show increased FDG uptake at PET become completely photopenic immediately after RFA, a finding that is suggestive of the completeness of ablation. Focal areas of increased FDG uptake within the ablated zone are suggestive of residual disease. Reactive tissue changes such as inflammation are depicted in the periphery of the ablated lesion and show a uniform low-grade FDG uptake, which can be differentiated from the focal, nodular intense uptake in areas of residual disease. Use of combined FDG PET/CT to detect residual disease early after RFA allows ablation to be repeated, if necessary, to obtain the maximum therapeutic benefit. Note that FDG uptake in the complications sometimes associated with RFA can be a cause of potential false-positive PET results.

Imaging findings in a rare case of extra-articular chondrocalcinosis.

We report the imaging findings in extra-articular chondrocalcinosis in a 53-year-old man with swelling and pain in right scapular area for 1 year. Plain radiography showed a right scapular area calcific mass. The clinical suspicion was of a soft tissue sarcoma. As a part of diagnostic workup, a bone scan and a PET/CT scan were done. Bone scan revealed intense MDP uptake in the right scapular area. FDG PET/CT revealed intense FDG uptake in the mass. The biopsy revealed chondrocalcinosis. This is an addition to our long list of causes of extraosseous uptake of MDP.

F-18 fluoride PET/CT in the detection of radiation-induced pelvic insufficiency fractures.

Abstract:Radiotherapy for gynecologic malignancies puts the pelvic bones and the sacrum at risk for insufficiency fractures. Symptoms of sacral insufficiency fractures are nonspecific and can be mimicked by degenerative diseases and metastasis; the diagnosis thus is essentially based on imaging. We

Pulmonary artery and femoral vein tumour thromboembolism in a patient with osteogenic sarcoma demonstrated by FDG PET/CT

FDG PET/CT is frequently used in staging and restaging of sarcomas. A 35-year-old man who had undergone an abovethe-knee amputation for an osteosarcoma of the right tibia presented with localized swelling and progressive dyspnoea whileonfollowup.TheMIPimage(a) from a restaging PET/ CT study revealed linear tracer uptake (arrow) in the right thigh along with hypermetabolic branching foci in the chest. A contrast-enhanced CT scan of the chest (b )r evealed nonocclusive branching intraluminal filling defects (arrow) in both pulmonary arteries. The fusion PET/CT image (c) showed moderate to high-grade FDG uptake (SUV 7.8) corresponding to the linear filling defects in the pulmonary arteries (arrow) suggesting the diagnosis of pulmonary tumour emboli. The linear uptake in the thigh was confirmed by ultrasonography as a deep femoral vein thrombus. Metastases and infection are frequent causes of respiratory symptoms in patients with osteosarcoma. Rarely the tumour cells can permeate the major veins and give rise to pulmonary tumour emboli [1]. The diagnosis is then unsuspected as the symptoms are nonspecific [2]. Pulmonary artery filling defects showing significant tracer uptake on fusion images in such a patient serve as indirect evidence for tumour embolism, proof of which is obtained from embolectomy [3] or autopsy [4] specimens. We demonstrate the characteristic FDG PET/CT findings of pulmonary artery and femoral vein tumour thrombi, a rare consequence of osteosarcoma, not previously described on FDG PET/CT imaging.

Pulmonary hydatid cyst detected on FDG PET-CT.

A 40-year-old man on follow-up for treated tongue cancer was evaluated with a chest radiograph for cough of recent onset. The radiograph revealed a lung mass which was diagnosed as hydatid cyst after surgical resection. Tapeworms of the genus Echinococcus cause hydatid disease in humans, which most commonly involves the liver. Pulmonary hydatid cysts may, however, be seen in isolation. These have varied imaging appearances and can often be mistaken for a lung mass or masses of more sinister origins. We describe the positron emission tomography-computed tomography appearance of a lung hydatid cyst.

Fibrodysplasia ossificans progressiva detected on FDG PET/CT.

Abstract: Fibrodysplasia ossificans progressiva (FOP) is a genetic disorder of the skeletal system which, due to its rarity, is frequently misdiagnosed for a malignancy (Kitterman et al. Pediatrics. 2005;116:e654–e661). Consequently, these patients are subjected to multiple invasive diagnostic and therapeutic procedures which instead can aggravate the disease (Kitterman et al. Pediatrics. 2005;116:e654–e661). Recognition of the computed tomography appearance of FOP is thus vital, as these patients are likely to be referred for a positron emission tomography/computed tomography (PET/CT) to stage a misdiagnosed cancer. In this study, the PET/CT features of FOP are demonstrated in a child who was referred for staging of an erroneously diagnosed lymphoma.

Incidental detection of high-riding innominate artery and bilateral retropharyngeal carotid arteries: radiological findings and clinical relevance

Variations in the branching pattern of the arch of the aorta are well recognized; however, a high-riding innominate artery reaching as far superiorly in the neck as the thyroid gland has only rarely been reported in literature. Also, retropharyngeal transposition of bilateral common carotid arteries is an uncommon anatomic variant. Both these variations, though rare, have far-reaching clinical implications. While the former is associated with haemorrhagic complications during surgical procedures in the neck, such as tracheostomy, retropharyngeal carotid arteries can complicate endotracheal intubation and pharyngeal surgery. The incidental detection of both these aberrations at preoperative contrast-enhanced computed tomography (CT) in a patient with a solitary fibrous tumour of the pleura is reported and the relevance of documenting these findings to the surgical management are discussed.

Bone infarct-associated sarcoma detected on FDG PET/CT.

Secondary sarcomas arising on the background of a bone infarct are extremely uncommon. Based on the knowledge of classic imaging patterns, however, lesions like bone infarcts can be recognized during positron emission tomography/computed tomography studies, which are now being performed increasingly in cancer patients. We demonstrate the detection of this rare entity on positron emission tomography/computed tomography and its correlation on magnetic resonance imaging in a 56-year-old man with asymptomatic multifocal osteonecrosis secondary to steroid treatment for polymyositis.

Isolated mandibular condylar metastases: an uncommon manifestation of recurrent cervical cancer.

Bone metastases from recurrent cervical cancer is a rare scenario, with commonly involved sites being lumbar spine and pelvic bones report an extremely rare manifestation of cervical cancer recurrence presenting as a painful jaw swelling due to metastasis to the mandibular condyle.

Unusual lower limb skeletal metastases from carcinoma of the cervix: detection by F-18 FDG PET/CT.

Osseous metastases from carcinoma of the cervix are often associated with locoregional and nodal recurrence, and bear an adverse correlation with survival. The lumbar spine is the commonest site and metastases to the distal appendicular and sacral bones are an infrequent finding. Positron emission tomography/computed tomography (PET/CT) using fluorodeoxyglucose as tracer (FDG) is being increasingly used in staging and follow-up of patients treated for carcinoma of the cervix. We report rare osseous sites of metastatic recurrence in the tibia, patella, and the intermediate cuneiform detected on FDG PET/CT in a patient treated for cervical cancer, findings hitherto undescribed.