Preoperative imaging protocol for cochlear implant candidates.

OBJECTIVE: To formulate and test a CT imaging protocol for preoperative scanning of the temporal bone in cochlear implant candidates. MATERIAL AND METHODS: A human head was scanned in three CT planes: axial, axiopetrosal and semilongitudinal. Multiplanar reformats (MPRs), based on axial slices, were created and compared with the corresponding images obtained by direct scanning in the respective planes. All scans were analyzed on a viewing workstation. RESULTS: The axial plane image allowed for an overview of the temporal bone. The width of the facial recess and the cochlear nerve canal could be studied on combined axial and axiopetrosal images. Cochlear patency could be evaluated using combined axial and semilongitudinal images. Axiopetrosal and semilongitudinal MPRs were able to replace the images obtained by direct scanning in the respective planes. CONCLUSION: The combination of the axial CT plane image and MPRs was found to be sufficient for preoperative analysis of the temporal bone morphology.

Precision and accuracy of CT-based measurements of masticatory muscles in patients with hemifacial microsomia.

OBJECTIVE: The objective of this study was to quantitatively assess masticatory muscle volumes in patients with hemifacial microsomia. Until recently, this congenital malformation was only studied in terms of restoring bony and skin morphologies. Study of the masticatory muscles, however, adds a new dimension. MATERIALS AND METHODS: Contiguous 1.5 mm CT scans were made using a Philips Tomoscan 350 in six patients with hemifacial microsomia and in one patient without asymmetry. These CT scans were processed by a Cemax 1500X 3D workstation. The volume of the masseter, temporal, and medial and lateral pterygoid muscles was measured from CT scans using three-dimensional (3D) segmentation followed by 3D imaging. The precision and accuracy of measurements of masticatory muscle volumes were investigated. The precision of 3D imaging was assessed by carrying out repeated measurements by two observers. The accuracy of the volume determination technique was assessed by scanning a piece of porcine muscle tissue with a known volume. RESULTS: Intraobserver repeatability was near perfect, with the lowest alpha being 0.96 (for the medial pterygoid muscle). All interobserver correlations were high (>0.99). The accuracy of the method of measurement demonstrated differences ranging from 2.3% to 4.4%. CONCLUSION: Craniofacial soft tissue measurements obtained from CT scans in patients with hemifacial microsomia were accurate and reproducible but time consuming.

Relationship in hypoplasia between the masticatory muscles and the craniofacial skeleton in hemifacial microsomia, as determined by 3-D CT imaging.

The purpose of this study, based on three-dimensional (3-D) computed tomographic (CT) reconstructions, was to evaluate the relation between underdevelopment of masticatory muscles and hypoplasia of the craniofacial skeleton in hemifacial microsomia (HFM). In 25 patients with HFM and 19 control patients the volumes of the masseter, the temporal, and the medial-pterygoid and lateral-pterygoid muscles were measured on the basis of CT scans, using three-dimensional segmentation and voxel addition. The size and shape of the craniofacial structures were classified, using three-dimensional imaging based on CT scans. Contiguous 1.5-mm computed tomography scans were made with a Philips Tomoscan 350 and processed by a Cemax 1500X 3-D workstation. Using the Pearson product moment correlation coefficient, the Pruzansky/Kaban classification system, the new Craniofacial Deformity Scoring System, Cranial Deformity Scoring System, and Mandibular Deformity Scoring System (MDS) demonstrated correlation coefficients with the "masseter muscle percentage" varying from 0.71 to 0.81 (P < 0.05), with the medial pterygoid muscle percentage correlation coefficient varying from 0.43 to 0.56 (P < 0.05), with the lateral pterygoid muscle percentage correlation coefficient varying from 0.55 to 0.61 (P < 0.05), and with the temporal muscle percentage correlation coefficient varying from 0.67 to 0.84 (P < 0.05). The normal right/left difference in volume of the masticatory muscles of the control patients, calculated as a percentage of the total, demonstrated small differences of 3.4% to 4.8%. Bony malformations are associated with underdevelopment of the masseter and the temporal muscles, and demonstrate a tendency toward a clear relationship. The degree of muscular underdevelopment of the different muscles of mastication in one patient could vary widely. The normal right/left difference of the masticatory muscles of the control patients is minimal. The volume of the masticatory muscles of the non-affected side does not demonstrate a compensatory effect in patients with HFM.

CT-based size and shape determination of the craniofacial skeleton: a new scoring system to assess bony deformities in hemifacial microsomia.

The purpose of this study was to design a better craniofacial classification system for bony deformities in patients with hemifacial microsomia than the existing ones. It was meant to incorporate the deformity of the craniofacial skeleton other than that of the mandible. The "Mandibular Deformity Scoring" System (MDS), the "Cranial Deformity Scoring" System (CDS), the the "Craniofacial Deformity Scoring" System (CFDS) are three newly developed classification systems, which are based on three-dimensional computed tomography (3-D CT) reconstructions. The size and shape of the craniofacial structures of 34 children, 25 with hemifacial microsomia and 9 with minimal dysplasia or trauma, were determined from CT scans, using 3-D image segmentation and rendering. Contiguous 1.5-mm CT scans were made using a Philips Tomoscan 350 and were processed using a Cemax 1500X 3-D workstation. The precision of the 3-D imaging was assessed by repeated determinations carried out by two observers (intra- and interreliability). Accuracy of the bone determination technique was assessed by comparing the interpretations of the craniofacial skeleton by 3-D CT reconstructions of laser-stereolithographic 3-D models. Correlations of the Pruzansky/Kaban classification system and the newly developed classification systems were demonstrated by the use of the Pearson product moment correlation coefficients. The new CFDS (= CDS + MDS) provides an adequate basis for assessment of bony structures using three-dimensional imaging and demonstrates a high correlation with the known Pruzansky/Kaban classification system. This new scoring system can handle the wide variety of individual variation of the deformity seen in patients with hemifacial microsomia better than the existing scoring systems.

The usefulness of quantitative orbital magnetic resonance imaging in Graves' ophthalmopathy.

BACKGROUND: Two-thirds of patients with Graves' ophthalmopathy (GO) respond to immunosuppressive treatment (prednisone or orbital irradiation), but one-third do not respond. Responders are likely to be in the active, oedematous stage of the eye disease, nonresponders in the inactive fibrotic stage. Clinical distinction between the two stages can be difficult. Quantitative magnetic resonance imaging (MRI) might be helpful in this respect, as T2 relaxation times are longer in oedematous than in fibrotic tissues. STUDY DESIGN: Prospective study on quantitative orbital MRI in healthy subjects and patients with moderately severe GO, evaluating T2 relaxation time of extraocular muscles (EOM): (a) in patients vs. controls, and (b) in patients, as a predictor of outcome to orbital irradiation. SUBJECTS AND MEASUREMENTS: Nine healthy volunteers and 64 consecutive patients with moderately severe untreated GO, who were euthyroid for > or = 2 months and qualified for orbital irradiation. T2 relaxation times were measured at the site of the largest diameter in all eight EOM of each subject. Baseline T2 values in patients were related to outcome of radiotherapy, as assessed by an independent observer 6 months later according to predefined criteria. RESULTS: T2 relaxation times of the eight EOM were longer in GO patients than in controls: median [range] 126 [52--250] vs. 88 [50--126] msec; P = 0.003. Per subject the single eye muscle with the longest T2 time was selected to represent active inflammation (excluding the lateral muscles for technical reasons). Again patients were different from controls: 160 [68--250] vs. 103 [86--115] msec, P < 0.001. In the group of 34 responders to subsequent radiotherapy, these T2 times tended to be longer than in the 30 nonresponding patients: 168 [108--250] vs. 138 [68--216] msec, P = 0.07. Using a cut-off value of 130 msec (derived from a receiver-operator-characteristics curve) a positive predictive value of 64% and a negative predictive value of 92% for the outcome of radiotherapy was calculated. CONCLUSION: Quantitative orbital magnetic resonance imaging was found to be less accurate in predicting successful outcome of radiotherapy than expected. It seems more useful in detecting the fibrotic end-stage than the active stage of Graves' ophthalmopathy. It is therefore of limited use in the decision whether or not to apply immunosuppression in patients with moderately severe Graves' ophthalmopathy.

[Long-term results of secondary orbital implants]. / Langzeitergebnisse sekundärer Orbitaimplantate.

BACKGROUND: Secondary orbital implants are used for the correction of the post-enucleation socket syndrome (PESS). This study evaluates retrospectively the post-operative course, complications, additional surgery, long-term cosmetic and functional results, and patient's satisfaction after secondary orbital implants. PATIENTS: Nineteen out of 24 patients who underwent secondary baseball implant insertion between 1986 and 1989 for the correction of PESS were re-examined. RESULTS: Five patients had complications, 11 patients (58%) further surgery. After a mean follow-up of 8.6 years, 17 patients (89%) showed findings better than preoperatively. Two patients were unchanged. The static overall impression, assessing particularly volume deficit and symmetry, using a scale of 1 to 5, was improved from 4.5 preoperatively to 2.5. CONCLUSIONS: Secondary orbital implants improve symptoms of PESS and patient's satisfaction in a high proportion of cases also in the long term. Complications are not rare, and frequently more than one operation is necessary. There is no significant risk of long-term side effects and no reduction of the positive effect with time.

[Botulinum toxin type A treatment of cosmetically disturbing masseteric hypertrophy]. / De toepassing van botuline A toxine bij cosmetisch storende M.-masseterhypertrofie.

Two patients, a woman aged 21 and a man aged 29, with asymmetrical swellings of both mandibular angles and a painful, heavy sensation in the masticatory muscles (and in the woman also round the maxillary joint), were diagnosed as having hypertrophy of the masseter muscles. Both had the habit of jaw clenching and tooth grinding. Treatment consisted not of the traditional surgical debulking which also allows correction of overdeveloped osseous mandibular angles, but of injections with botulinum toxin type A. Injection of 40-60 IU (product: Botox) per muscle was followed by some atrophy; cosmetically satisfactory results were achieved after repetition of the treatment a few months later. Reduction of muscle volume was confirmed by a quantitative volumetric assessment of MRI scans. In the female patient, the pain also abated.

Single-step fronto-orbital resection and reconstruction with individual resection template and corresponding titanium implant: a new method of computer-aided surgery.

In the cranio-maxillofacial field, computer-aided surgery based on computed tomography (CT) data is becoming more and more important. Navigation systems, which allow the precise intraoperative orientation of surgical instruments, can be used for greater accuracy in determining resection margins of tumours. These techniques support ablative procedures very well, but defect reconstruction still remains a problem. In contrast, computer-aided design (CAD) and computer-aided manufacturing (CAM) systems allow the construction and fabrication of individual templates for bone resection based on coherent numerical 3-D models. The template determines the exact pathway of an oscillating saw so that the planned extent of the resection and, if necessary, also the orientation of the cutting plane are verified. An individual titanium implant is prefabricated with a geometry fitting to that of the template. This implant closes the bone defect so that the contour is reconstructed precisely and individually. This new method was used for the first time for a single-step resection of a meningioma and defect-reconstruction. The tumour which had infiltrated the frontal bone resulting in a protrusion. Fronto-orbital resection and insertion of the titanium implant worked precisely as planned, so that this method offers promising new applications in the field of computer-aided surgery.

High-resolution MR imaging anatomy of the orbit. Correlation with comparative cryosectional anatomy.

High resolution MR imaging of the orbit enables visualization of anatomic details in the orbit, including important blood vessels, muscles, nerves and connective tissue structures. The best resolution of anatomic details currently is obtained by using surface coils and T1-weighted spin echo sequences. Some examples of clinical applications demonstrate that a detailed knowledge of orbital imaging anatomy is a prerequisite for successful interpretation of clinical MR images. Additionally, this noninvasive diagnostic technique may be used for anatomical in vivo studies.

Three-dimensional imaging of congenital disorders involving the orbit.

Three-dimensional imaging of the orbit and its adnexa provides an excellent topographic visualization of the deformity or tumor extent. This helps comprehension, communication, education, and documentation in the process of treating the patient. This article briefly describes the technique of three-dimensional imaging and classifies congenital orbital deformities which are extensively illustrated with relevant case material.

The role of bone centers in the pathogenesis of craniosynostosis: an embryologic approach using CT measurements in isolated craniosynostosis and Apert and Crouzon syndromes.

This paper describes the role of the displacement of bone centers, i.e., the tubers, in the pathogenesis of craniosynostosis. This displacement was studied in 54 patients with isolated or syndromic craniosynostosis in the form of CT scans as well as in two dry neonate skulls with Apert syndrome. For comparison, 49 fetal and 8 normal infant dry skulls were studied. Our investigation was restricted to the coronal and metopic sutures. The results showed a significantly more occipital localization of the frontal bone center and a more frontal localization of the parietal bone center at the side of a synostotic coronal suture in the isolated form as well as in Apert syndrome. In contrast, this was not the case in Crouzon syndrome, thus showing that these two syndromes have a different pathogenesis. For trigonocephaly, a more anteromedial localization of the frontal bone centers was found.

[The use of 3-dimensional models in craniofacial surgery]. / Het gebruik van driedimensionale modellen in de craniofaciale chirurgie.

With the aid of axial CT scanning a polyurethane or resin copy of bony tissue of the craniofacial region of interest can be manufactured. 3-dimensional models are used in planning of osteotomies of the midface and forehead, where complex bone transpositions are to be performed, and in manufacturing complex implants. Different preoperative steps in several patients are demonstrated and the postoperative results are shown. Patient A was a 9-year-old girl who had radiotherapy as a baby for retinoblastoma which destroyed a large part of her face. In patient B, a 46-year-old woman, the whole zygomatic bone and three-quarters of the floor of the orbit were among other things resected for a low-grade osteosarcoma. Patient C had Goldenhar's syndrome (oculoauriculovertebral dysplasia). In all 3 patients reconstructive surgery was prepared with 3-dimensional cut models.

Lenticular system: full-color, limited-angle, autostereoscopic alternative to holography.

The microlenticular system is a method of hard copy imaging that provides stereoscopic cues without the use of special glasses or viewing devices. Therefore, it is called an autostereoscopic technique. The microlenticular system consists of a layer of cylindric lenses combined with a photographic emulsion that carries three to seven different two-dimensional views of the same three-dimensional (3D) scene. Since each of the observer's eyes sees a different view, the resulting image is perceived as being 3D. The microlenticular system technique can be traced back to 1908 but was recently revived because of inventions that allow automatic photographic printing of this type of hard copy. The technique has been applied to visualization of medical 3D images obtained with the following modalities: computed tomography (CT), magnetic resonance imaging, single photon emission CT, ultrasound, scanning electron microscopy, laser scanning, and confocal laser microscopy. Use of this technique results in images suitable for planning complex surgery and for simplifying the communication of complex geometries in science and education.

Quantification of orbital and mid-facial growth retardation after megavoltage external beam irradiation in children with retinoblastoma.

PURPOSE: The late side effects of external beam irradiation in patients with retinoblastoma such as orbital bony growth retardation, are a serious problem in adolescence. Therefore, a quantitative study was performed to investigate the late effects of irradiation on orbital growth in patients with retinoblastoma. METHODS: The orbits of 68 patients with retinoblastoma, 52 bilateral and 16 unilateral, were divided into two treatment groups: radiotherapy alone, 77 orbits; and radiotherapy + enucleation, 43 orbits. Follow-up time was 12 to 240 months (mean, 95 months) in group 1 and 27 to 216 months (mean, 97 months) in group 2. These groups were subdivided further into age groups at which radiotherapy was given. The morphometric measurements of these groups were compared. RESULTS: The authors showed that irradiation causes a significant growth retardation when compared with the growth of nonirradiated orbits (P<0.001). They also demonstrated that radiotherapy in children younger than 6 months of age is more damaging to the orbital growth than at an older age (P<0.01). Finally, the authors showed that secondary enucleation does not have an additive growth-retarding effect. CONCLUSION: Orbital growth retardation in patients with retinoblastoma after radiotherapy is influenced mainly by the age at which irradiation is given and is defined at 6 months. Theoretically, it would be desirable to postpone irradiation in children until they are older than 6 months of age if possible. The irradiation effect on these orbits is not enhanced by enucleation.

A three-dimensional smooth surface analysis of untreated Crouzon's syndrome in the adult.

This study compares the three-dimensional smooth surface shape of five adult patients with Crouzon's disease with nine normal skulls. A new analysis method is described which is based on smooth surface curvature. Surface samples are subdivided by a common ridge curve structure. Three-dimensional images of an average normal and an average Crouzon skull are illustrated. Comparisons between groups are performed on landmarks, as well as ridge curve and surface patch midpoints. There was as much discriminant information in the ridge curves and surface patches between landmarks as there was at the landmarks themselves. When compared with normal samples, the Crouzon's syndrome sample exhibits the following major characteristics: The midface is concave and wide, with the piriform aperture in the center more recessed than the perifery of the midface. The forehead is recessed above a frontal sinus bulge. The orbits are shallow, wide, concave, and tilted inferiorly with a mild hypertelorism. These data suggest that advancement of large, one-piece osteotomy segments will not produce a normal face, and a multisegment approach should be considered.

Dehiscence of the jugular bulb in Crouzon's disease.

Patients with Crouzon's disease have a distorted nasopharynx, which frequently leads to retained middle ear secretions and necessitates myringotomy. A review of the computed tomographic (CT) scans of 21 ears in 11 patients with Crouzon's disease found that 12 jugular bulbs were protruding or dehiscent. The relationship between the jugular bulb and the middle ear space was normal bilaterally in only 2 of the 11 patients. Consequently, patients with Crouzon's disease are at risk for inadvertent puncture of the jugular bulb during myringotomy. CT scans obtained prior to myringotomy can be helpful in detecting dehiscent or protruding jugular bulbs.