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The developing trend for all medical images to be in digital form raises an important question: should diagnostic interpretations be made directly from a CRT or from some form of hard copy recording of the CRT? This question was studied by having two observers read a series of digital images of the thyroid including both conventional scintigrams and computer-generated tomograms. The CRT images were photographed in a carefully controlled fashion. Images were read once from film and a second time directly from the CRT. No significant difference in performance could be found for either display modality based on an ROC analysis. Although based on uncomplicated images and analysis, this result suggests that the decision to read from film or from the CRT can be made on other grounds than observer performance. This important result needs confirmation with more complex images such as ultrasound or CT.

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PubMedDate not supplied

Can positron emission tomography distinguish tumor recurrence from irradiation sequelae in patients treated for larynx cancer?

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.

Diagnosis, Differential↗