Dynamic CT of the neck

Prognostic factors of glottic carcinomas treated with radiation therapy: value of the adjacent sign on radiological examinations in the sixth edition of the UICC TNM staging system

PURPOSE

To evaluate the predictive value of the adjacent sign, the tumor adjacent to the thyroid cartilage on radiologic examinations, in the new sixth edition of the International Union Against Cancer (UICC) staging system of glottic carcinoma.

METHODS AND MATERIALS

Between 1989 and 1998, 130 patients with T1-2N0 glottic squamous cell carcinoma, classified according to the fifth edition of the UICC staging system and evaluated by computed tomography or magnetic resonance imaging, were treated with radiation therapy (RT). Factor analysis included clinical, radiologic, and treatment characteristics. Tumors with the adjacent sign, considered representative of paraglottic space invasion with or without minor thyroid cartilage erosion, were retrospectively classified as T3-stage tumors by the UICC sixth edition.

RESULTS

The 5-year local control rate after RT was 76%. Univariate analysis showed that the T stage according to the UICC fifth edition, supraglottic extension, subglottic extension, tumor size, adjacent sign, total dose, fraction size, field size, and overall treatment time were significant factors for the local control rate. Multivariate analysis confirmed the adjacent sign as the only independent predictor. According to the UICC sixth edition, the 5-year local control, laryngeal preservation, cause-specific survival, and overall survival rates of the T3 (adjacent sign-positive) vs. T1 and T2 (adjacent sign-negative) lesions were 37% vs. 87% (p < 0.0001), 47% vs. 95% (p < 0.0001), 75% vs. 99% (p < 0.0001), and 54% vs. 81% (p = 0.0180), respectively.

CONCLUSION

Factor analysis confirmed the adjacent sign as an independent prognostic factor. The UICC sixth edition appears to identify correctly patients with T3 lesions as a high-risk group.

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.

Radiologic evaluation of neck metastases: the otolaryngologist's perspective

Imaging of the neck for the assessment of nodal metastases can be used to detect occult metastases or to assess operability of palpable metastases. The detection of small occult metastases has limitations, as micrometastases cannot be depicted. However, imaging can diminish the risk of occult metastases and thus influence management; for this purpose a very sensitive technique is necessary. The currently used radiologic criteria are not sensitive enough to accomplish enough reduction in the risk of occult metastases. Therefore, more sensitive CT and MRI criteria, but especially ultrasound guided aspiration, should be used to assess the clinically negative neck.

Helical CT for the diagnosis of extracranial internal carotid artery dissection

BACKGROUND AND PURPOSE

We attempted to evaluate the sensitivity of helical CT for the diagnosis of extracranial internal carotid artery (ICA) dissection.

METHODS

Sixteen consecutive patients with 18 angiographically confirmed extracranial ICA dissections were studied with a helical CT protocol with large-volume acquisition and thin axial slice reconstructions. A control group including normal and atherosclerotic ICAs was formed for comparison, and a blind interpretation of CT images was made by two observers. We evaluated the presence of stenosis, eccentric lumen, mural thickening, aneurysm, occlusion, and annular contrast enhancement. When the artery seemed to be occluded, we measured the external diameter of the ICA (1) on the occluded side, at its upper portion and most enlarged level, (2) at its lower portion, beyond the bulb, and (3) on the contralateral side, at is upper portion.

RESULTS

Interobserver agreement was good except for the presence of annular contrast enhancement. In the stenotic dissection group (n=12), the presence of a narrowed eccentric lumen at the upper portion of the ICA on axial CT images was classified correctly in all cases (sensitivity, 100%; specificity, 100%). An arterial wall thickening was seen in all cases of dissection but also in three cases of the control group. In the occlusive dissection group (n=6), the enlargement of the dissected artery was the best criterion (sensitivity, 100%, specificity, 100%) for occlusive dissection.

CONCLUSIONS

Helical CT seems to be a reliable method for evaluating extracranial ICA dissection. The analysis of the residual arterial lumen and the measurement of the external diameter of the carotid artery were the best criteria for the diagnosis. Further studies with larger groups are required to determine whether ICA dissections might be diagnosed using helical CT as a first procedure.

An optimized examination protocol for contrast-enhanced cervical and mediastinal CT

We compared an optimized contrast-enhanced CT technique for the neck and upper mediastinum with a conventional technique and with nonenhanced images, using densitometric measurements. The optimized protocol included slice thickness, infusion rate, postural maneuvers, and manipulation of the gantry tilt. Densitometric evaluation showed significantly higher enhancement values in vessels and metastases with the optimized protocol than with conventional technique, without significant enhancement in muscle. Semiquantitative assessment demonstrated significantly better image quality with the optimized protocol. The optimized technique has been implemented into routine use.

Magnetic resonance imaging and dynamic CT scan in cervical artery dissections

BACKGROUND AND PURPOSE

The typical magnetic resonance imaging picture of arterial dissection, namely, a narrowed eccentric signal void surrounded by a semilunar signal hyper-intensity (corresponding to the mural hematoma) on T1- and T2-weighted images, has been repeatedly reported, but the sensitivity of magnetic resonance imaging for the diagnosis of cervical dissection is poorly known. Another technique, dynamic computed tomography, may provide evidence of mural hematoma, but there has been no systematic evaluation of this technique. The aims of this study were to assess both the sensitivity of routine 0.5-T magnetic resonance imaging for the detection of a typical picture of cervical artery dissection and the value of dynamic computed tomographic scans to provide evidence of dissecting hematoma.

METHODS

Fifteen consecutive patients with angiographically confirmed extracranial internal carotid (n = 9) or vertebral (n = 10) dissections were studied using a standardized 0.5-T spin-echo magnetic resonance imaging protocol with axial slices. Twelve of these patients had dynamic computed tomographic scans at the site of the dissection suggested by angiography.

RESULTS

A typical magnetic resonance imaging picture of cervical artery dissection was observed in 12 of 15 (80%) patients and in 13 of 19 (68%) dissected vessels. The sensitivity of magnetic resonance imaging was higher in internal carotid (78%) than in vertebral (60%) dissections and in stenotic-type dissections (85%) than in occlusive or aneurysmal-type dissections. The dynamic computed tomographic scan showed the mural hematoma in 11 of the 12 (92%) patients and in 12 of 15 (80%) dissected vessels.

CONCLUSIONS

Routine 0.5-T magnetic resonance imaging with axial slices is a sensitive technique for the diagnosis of dissection, but in about 20% of patients with cervical artery dissection magnetic resonance imaging will demonstrate no typical abnormality. Dynamic computed tomographic scans are a sensitive neuroimaging procedure to confirm the presence of the mural hematoma, but it needs to be directed by prior angiography.

Spiral versus conventional CT in soft tissue diagnosis

Spiral volumetric computed tomography (SVCT) has been predicted to improve vascular and organ enhancement with little effect on image quality. To see if this was the case, we studied 100 patients referred for computed tomography where we would normally have performed dynamic incremental computed tomography (DICT). Patients were randomly allocated to undergo either standard DICT or SVCT. The resulting images were analysed for overall quality, the degree of contrast medium enhancement and the extent of artefacts associated with the technique. No statistically significant difference in overall image quality between SVCT and DICT was found, apart from images of the hepatic parenchyma where the quality was significantly worse on SVCT (P < 0.05) due to the low mA permissible. Contrast enhancement was better with SVCT, although only for the thorax (P < 0.01) and the group taken as a whole (P < 0.01) did this improvement reach statistical significance. There was no statistically significant difference between the extent of artefacts observed in the two techniques. As expected, all acquisition times were shorter using SVCT. The benefits of SVCT have been well described and include the absolute contiguity of the reconstructed images and the ability to obtain many images at peak contrast enhancement. We have confirmed the latter effect. We are now also satisfied that there is no appreciable loss of overall image quality except where large volumes of solid tissue are being examined (e.g. liver).