Re-evaluation of optimal dose of contrast medium for vascular enhancement in CT of the head and neck

Evaluation of suspected local recurrence in head and neck cancer: a comparison between PET and PET/CT for biopsy proven lesions

BACKGROUND

(18)F-FDG PET has a high accuracy for re-staging of head and neck cancer. The purpose of this study was to determine whether the diagnostic accuracy can be further improved with integrated PET/CT.

MATERIALS AND METHODS

Forty-nine patients with a mean age of 59+/-18 years were studied retrospectively. Histo-pathological verification was available either from complete tumor resection with or without lymph node dissection (n=27) or direct endoscopic biopsy (n=16) or ultrasound guided biopsy (n=6). Two reviewers blinded to the pathological findings read all PET images in consensus. An experienced radiologist was added for the interpretation of the PET/CT images.

RESULTS

Tissue verification was available for 110 lesions in 49 patients. Sixty-seven lesions (61%) were biopsy positive and 43 (39%) were negative for malignant disease. PET and PET/CT showed an overall accuracy for cancer detection of 84 and 88% (p=0.06), respectively. Sensitivity and specificity for PET were 78 and 93% versus 84 (p=NS) and 95% (p=NS) with PET/CT. A patient-by-patient analysis yielded a sensitivity, specificity and accuracy for PET of 80, 56 and 76%, compared to 88% (p=NS), 78% (p=NS) and 86% (p=0.06) for PET/CT.

CONCLUSION

The results of this study indicate that PET/CT does not significantly improve the detection of recurrence of head and neck cancer. However, a trend towards improved accuracy was observed (p=0.06).

Single-bolus technique for spiral CT of laryngopharyngeal squamous cell carcinoma: comparison of different contrast material volumes, flow rates, and start delays

PURPOSE

To evaluate different contrast material volumes, flow rates, and start delays for contrast material enhancement of neck structures and squamous cell carcinoma to determine the most effective examination protocol.

MATERIALS AND METHODS

Seventy patients with squamous cell carcinoma were prospectively randomized into four groups for examination with different protocols (125 mL of contrast material administered at a flow rate of 2.5 mL/sec, 100 mL at 2.0 mL/sec, 90 mL at 1.5 mL/sec, or 70 mL at 1.0 mL/sec). Dynamic series were performed on the tumors and relevant anatomic structures to obtain time-attenuation curves. The protocols were compared (analysis of variance and Tukey-Kramer tests) with regard to time and level of maximum tumor enhancement and carotid arterial enhancement of more than 150 HU. One selected protocol was tested in 30 additional routine examinations with start delays of 40 seconds (for laryngeal and/or hypopharyngeal tumors, 3-mm collimation) and 45 seconds (for oropharyngeal tumors, 5-mm collimation).

RESULTS

Except for the 70-mL bolus administered at 1.0 mL/sec, the other protocols performed similarly well, yielding comparable maximum tumor enhancement at 52 seconds and later. In spite of a smaller volume of 90 mL, due to the prolonged flow time at 1.5 mL/sec, carotid arterial enhancement of more than 150 HU was prolonged (when compared with that in 100- or 125-mL protocols). As a result of these circumstances, injection of 90 mL at 1.5 mL/sec was considered more effective, providing no significant differences in tumor (P =.39) or carotid arterial (P =.52) enhancement between routine examinations and dynamic series.

CONCLUSION

A single bolus of 90 mL administered at 1.5 mL/sec appears to be the most desirable protocol for contrast enhancement.

Contrast-Enhanced Helical CT of the Head and Neck

OBJECTIVE

We evaluated the impact of delayed scans on the conspicuity of squamous cell carcinoma in helical CT of the head and neck.

SUBJECTS AND METHODS

Twenty-seven patients with biopsy-proven squamous cell carcinoma of the head and neck underwent dual-phase helical CT examinations using 100 mL of nonionic contrast material. In all patients, the early phase started 30 sec after the commencement of injection. The patients were assigned to one of two groups in which the delayed phase started either 180 sec (group A, n = 13) or 300 sec (group B, n = 14) after the start of injection. The overall image quality, including vascular opacification and the quality of lesion conspicuity, was determined according to a three-point scoring system.

RESULTS

Overall image quality scored better on the early scans (score, 1.4 +/- 0.5) than on the late scans with a 180-sec (score, 1.6 +/- 0.6; p = 0.03) or a 300-sec delay (score, 2.4 +/- 0.5; p = 0.002). Tumor conspicuity scored better on scans with a 180-sec delay (score, 1.4 +/- 0.5) than on the scans with a 30-sec delay (score, 2.3 +/- 0.7; p = 0.02) or the scans with a 300-sec delay (score, 2.3 +/- 0.7; p = 0.03). In eight (62%) of 13 patients in group A and in six (43%) of 14 patients in group B, the tumor was better delineated on the late scans than on the early scans.

CONCLUSION

Although early scans provide optimal vascular enhancement and are therefore necessary for helical CT studies of the head and neck, additional delayed scans may improve lesion detection in patients with squamous cell carcinoma of the head and neck.