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Purpose: This paper intends to demonstrate the possibilities of two- and three-dimensional visualisation methods from spiral-CT data sets in the head and neck region and demonstrates their value based on various studies., Material and Methods: The scanner was a Somatom PLUS 4 (Siemens, Forchheim/Germany). The patients were scanned using a slice thickness of 3 mm and a table feed of 5 mm (pitch 1,6). The images were reconstructed with an increment of 1 mm. Contrast agent (150 ml) was applied intravenously with a flow of 2.5 ml/s and a start delay of 80 s. In one study the start delay was 20 s in order to visualise the carotid arteries (extracranial aneurysm). Volumetric data sets were postprocessed with 'Vitrea' and 'VoxelView' (Vital Images) volume rendering software on a Silicon Graphics O2 workstation (virtual laryngoscopy). Multiplanar reformation and colour-coded 3D-reconstruction were done on a Prominence workstation (Siemens/Forchheim/Germany)., Results: In every region of the head and neck MPRs are useful as additional planes (with the exception of the hypopharynx and the larynx), SSDs are always useful if there is extensive bony destruction (skull, spine, skeleton larynx). Colour-coded three-dimensional reformations may be done for extensive tumours and before multi-specialty surgery. Perspective volume rendering is already in use for virtual endoscopy of the paranasal sinuses and the virtual laryngoscopy. In temporal bone evaluation, perspective volume rendering is a new and promising method of the future to assess the inner ear., Summary: Two- and three-dimensional displays are used to visualise pathological findings in their topographic relation to anatomical leading structures. Thus, the radiologist can point out to the clinician the pathological findings by some essential images without having to demonstrate all axial slices.

Spiral-CT is standard for imaging neck tumors. In correspondence with other groups we routinely use spiral-CT with thin slices (3 mm), a pitch of 1.3-1.5 and an overlapping reconstruction increment (2-3 mm). In patients with dental fillings a short additional spiral parallel to the corpus of the mandible reduces artifacts behind the dental arches and improves the diagnostic value of CT. For the assessment of the base of the skull, the orbital floor, the palate and paranasal sinuses an additional examination in the coronal plane is helpful. Secondary coronal reconstructions of axial scans are helpful in the evaluation of the crossing of the midline by small tumors of the tongue base or palate. For an optimal vascular or tissue contrast a sufficient volume of contrast medium and a start delay greater than 70-80 s are necessary. In our opinion the best results can be achieved with a volume of 150 ml, a flow of 2.5 ml/s and a start delay of 80 s. Dynamic enhanced CT is only necessary in some special cases. There is clear indication for dynamic enhanced CT where a glomus tumor is suspected. Additional functional CT imaging during i-phonation and/or Valsalva's maneuver are of great importance to prove vocal cords mobility. Therefore, imaging during i-phonation is an elemental part of every thorough examination of the hypopharynx and larynx region. Multislice-spiral-CT allows almost isotropic imaging of the head and neck region and improves the assessment of tumor spread and lymph node metastases in arbitrary oblique planes. Thin structures (the base of the skull, the orbital floor, the hard palate) as well as the floor of the mouth can be evaluated sufficiently with multiplanar reformations. Usually, additional coronal scanning is not necessary with multislice-spiral-CT. Multislice-spiral-CT is especially advantageous in defining the critical relationships of tumor and lymph node metastases and for functional imaging of the hypopharynx and larynx not only in the transverse plane but also in the coronal plane.

MRI has become the imaging method of choice in special regions of the head and neck (e.g. nasopharynx, oropharynx, oral cavity, floor of the mouth). Superconducting MR-equipment with field strengths of 1.0-1.5 T are appropriate for the evaluation of the head and neck region. Signal acquisition is optimal with circular polarized head coils or with specially designed surface coils; the body coil is insufficient.When imaging tumors we need T1 contrast, T2 contrast and contrast medium information (enhancement information). For the T1 contrast T1-spin-echo is and remains the best sequence. For T2-contast T2 turbo-spin-echo with fat suppression has replaced the T2 spin-echo sequences because it is faster and shows good contrast between tumor and saturated fat tissue. Fat saturated T1 turbo-spin-echo enables best tissue contrast after Gd-DTPA application.

Objective: To evaluate criteria for detection of tumor recurrence and post-treatment changes in patients with head and neck malignancies in computed tomography (CT) and magnetic resonance imaging (MRI)., Methods and Materials: Thirty-nine patients with head and neck carcinoma receiving radiochemotherapy were examined before, during and after therapy with MRI. Changes in signal intensity were correlated to histology or clinical course. Three hundred and thirty-one patients with head and neck malignancies were examined with CT after therapy. CT diagnoses were correlated with histology or clinical course., Results: Main criteria for recurrent/residual tumor in MRI was infiltrative mass with high signal intensity in T2-weighted images and enhancement after Gd-DTPA in T1-weighted images. Radiation-induced changes led to false positive diagnosis in 46% in the interval up to 3 months after therapy and in 58% in the interval 3-6 months after therapy. The combination of a circumscribed, infiltrative mass with contrast enhancement in CT had a sensitivity of 86% and a specificity of 80%., Conclusion: CT could accurately demonstrate postoperative changes and tumor recurrence. MRI had advantages in differentiation of tumor and scar, but edema after radiation therapy can spoil diagnosis.

Purpose: To evaluate the improvement of multislice-spiral CT in the assessment of head and neck tumors., Material and Methods: 80 patients with suspected tumor in the head and neck region were examined with MSCT (Somatom Plus 4 VZ) after the administration of i.v. contrast material. Slice collimation was 4 x 1 mm with a pitch factor of 6. Additional multiplanar reformations were calculated in each case., Results: The specific anatomy and pathways of tumor spread is difficult to demonstrate in cross-sectional imaging. Tumor infiltration of the base of the skull or the palate could be depicted or excluded on coronal MPR, additional coronal scanning was not necessary. The detection of pathologic lymph nodes was improved with MPR in 7 patients., Discussion: The exact determination of tumor margins is mandatory for modern therapy concepts of limited surgery. High resolution datasets are basis for reformations in arbitrary planes, making additional coronal scanning not necessary. Functional imaging of the larynx and hypopharynx improve the diagnostic accuracy of CT, a short scan time is necessary to reduce motion artifacts. Conclusive assessment of tumor infiltration, lymphatic spread and functional alterations is improved with MSCT.

544 CT studies of 231 patients were evaluated retrospectively to assess the role of CT in posttherapeutic monitoring of patients with head and neck tumours. CT (80%) was inferior to clinical evaluation (87%) in diagnosing recurrent malignancy due to a lack of specificity (76 vs. 92%). With CT small recurrencies were missed. Occasionally evaluation of the oral cavity was impaired by metal artifacts (dental fillings). However with larger recurrent tumours, CT offered important additional information regarding extent, infiltration of deeper compartments and bony destruction in 51% of the cases. CT (95%) was superior to clinical evaluation (80%) in diagnosing recurrent lymph node metastases. A baseline CT study at about 6-8 weeks after the end of therapy is of great importance for follow-up studies.

Diagnostic procedures currently utilized for determining nodal status in patients with head and neck primary carcinomas are reviewed. Diagnostic procedures include clinical palpation, computed tomography, magnetic resonance imaging and ultrasound. Each technique is discussed on the basis of clinical experience at the Technical University of Munich.

Computed tomography is considered as the method of choice concerning N-staging in patients with known malignant tumours of the head and neck region. The application of an intravenous contrast medium (50 ml as a bolus, 100 ml as a fast infusion) is obligatory. In lesions of the neck with unknown histology the plain CT scan is important followed by the application of contrast medium, optional in form of a dynamic sequential CT. Calcifications, the densities pre and post contrast medium application, the curve of enhancement and the structure of the lesion are the important criteria of differential diagnosis.

Basing on an analyses of pretherapeutic CT examinations of 333 patients suffering from squamous cell carcinomas of the head and neck region (206 of these had lymph node metastases), the clinical diagnostic value of CT for lymph node staging was determined. CT criteria for metastatic infestation of the lymph nodes were the lymph node size (greater than 15 mm) and structural characteristics (inhomogenity, central hypdensity with rim enhancement), and it became evident that CT with its 93% sensitivity and 89% accuracy was superior to clinical palpation, where the sensitivity was only 64% and the accuracy 72%. It can be concluded from these results that CT provides a reliable basis for a therapeutic approach.

Standardisation of the examination method is imperative to guarantee reproducible and valid assessability of the cervical lymph node status. To this end, update high-resolution CT equipment of the third generation will be suitable, provided it meets certain minimum requirements, such as: 120 kV, 280 mAs, 480 projections over 360 degrees, 4-5 mm slice thickness, continuous tomography. If a primary tumour is known to exist, no plain examination is needed. The decisive examination is effected after intravenous administration of contrast medium in a dosage of 2.0-2.5 ml contrast medium/kg body weight (assuming a body weight of 70 kg, this would amount to 150 ml = 45 g iodine), one-third of the total dosage to be given as bolus and two-thirds as a rapid infusion. This procedure ensures sharp definition of lymph nodes against vessels and musculature over the entire period of examination. If tumour anamnesis has been established the size of the lymph node is significant for assessing the lymph node status. Even lymph node metastases less than 15 mm can be properly identified if the structure of the lymph nodes is known and employed as a criterion (central hypodensity with rim enhancement, inhomogeneity).

Pre-treatment CT examinations of 333 patients with squamous carcinomas in the head and neck region have been analysed. Two hundred and six patients had lymph-node metastases and lymph-node staging was ascertained. The criteria for metastatic involvement were lymph node size greater than 15 mm. and changes in structure (inhomogeneity, central hypodensity and ring enhancement). CT had a sensitivity of 93% and accuracy of 89%. This was better than palpation (sensitivity 64%, accuracy 72%). CT can be regarded as a reliable basis for treatment planning.

Magnetic resonance tomography (MRI = magnetic resonance imaging) can provide sectional images of the petrous bones in all planes. It is complementary to computed tomography (CT) and can demonstrate inflammatory changes in the petrous bones and mastoids, and cholesteatomas, with accuracy and without artifacts. MRI is inferior to CT for the demonstration of bone destruction and this this limits its use in the diagnosis of glomus tumours. The use of special surface coils combined with thin sections and a gradient-zoom technique provides high resolution images which approach the quality of modern CT examinations. This opens new possibilities for the diagnosis of small acoustic neuromas; because of the excellent tissue contrast, they can be well demonstrated without using intravenous contrast media or intrathecal air (CT-air meatography).

CT is very suitable for showing cervical lymphatic spread in malignant tumors of the head and neck. The regional lymph-node areas of 123 patients with histologically proven malignant tumours of the oral cavity, hypopharynx and larynx were evaluated in a prospective study. Clinical examination, CT-findings and pathological work up of the surgical specimens were comparatively analysed in 53 patients. The proportion of false negative lymph-nodes on palpation was 21%. This error could be reduced by the use of CT to 7.5%.

A comparative study between MRI and CT was done with particular reference to the head and neck regions. Compared with CT, MRI offered better tissue contrast, vascular visualization without the need for iodinated contrast media, direct coronal scanning, and a special surface coil for high spatial resolution. MRI is a promising modality for this region despite its difficulty in visualizing bone and its slightly poorer spatial resolution.

The lymphatic spread in 123 patients with biopsy-proven malignant head and neck tumors was evaluated by CT in a prospective study. In 53 cases, clinical examination, CT and pathological-histological work-up of the surgical specimens were comparatively analysed. The fraction of false-negative judged lymph nodes by palpation was 21%. This high error in judgement could be diminished to 7.5% by the use of CT. 83% of squamous cell metastases showed a central decrease in density due to necrosis after intravenous infusion of contrast material.

The clinical role of contrast-enhanced CT for pre-operative T-staging of oro-facial tumours was evaluated in 174 patients. During stages T1 and T2, clinical examination is 90% accurate and has a significantly higher sensitivity than CT, with an accuracy of only 53%. The clinical diagnosis of T1 and T2 is, however, made with undue frequency; CT makes it possible to obtain correct staging. Combination of CT and clinical examination can improve correct staging from 46% to 81%. During stages T3 and T4. CT has sensitivity of 91% and is markedly superior to clinical examination, with a sensitivity of 34%. Combined clinical and CT examination improves the predictive value from 52% to 92%. Combination of clinical and CT staging, when the higher stage is accepted as being correct, has a sensitivity and reliability of over 90%. It can be used as a firm basis for treatment planning, judging the prognosis and the effects of treatment.