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Biomedical subjects

M Hatt

Publications and source records attributed to M Hatt.

At least 19 recordsLinked to original sources
PubMed2006

A multiresolution image based approach for correction of partial volume effects in emission tomography.

Partial volume effects (PVEs) are consequences of the limited spatial resolution in emission tomography. They lead to a loss of signal in tissues of size similar to the point spread function and induce activity spillover between regions. Although PVE can be corrected for by using algorithms that provide the correct radioactivity concentration in a series of regions of interest (ROIs), so far little attention has been given to the possibility of creating improved images as a result of PVE correction. Potential advantages of PVE-corrected images include the ability to accurately delineate functional volumes as well as improving tumour-to-background ratio, resulting in an associated improvement in the analysis of response to therapy studies and diagnostic examinations, respectively. The objective of our study was therefore to develop a methodology for PVE correction not only to enable the accurate recuperation of activity concentrations, but also to generate PVE-corrected images. In the multiresolution analysis that we define here, details of a high-resolution image H (MRI or CT) are extracted, transformed and integrated in a low-resolution image L (PET or SPECT). A discrete wavelet transform of both H and L images is performed by using the "à trous" algorithm, which allows the spatial frequencies (details, edges, textures) to be obtained easily at a level of resolution common to H and L. A model is then inferred to build the lacking details of L from the high-frequency details in H. The process was successfully tested on synthetic and simulated data, proving the ability to obtain accurately corrected images. Quantitative PVE correction was found to be comparable with a method considered as a reference but limited to ROI analyses. Visual improvement and quantitative correction were also obtained in two examples of clinical images, the first using a combined PET/CT scanner with a lymphoma patient and the second using a FDG brain PET and corresponding T1-weighted MRI in an epileptic patient.

Algorithms↗
PubMed1998

[Infantile myofibromatosis--a case report].

A four months old child was referred for a rapidly growing recurrency of a tumor of the left eyebrow. The tumor was excised completely. The pathologic examination revealed an infantile myofibromatosis, most probably of the solitary type. The term "infantile myofibromatosis" summarizes a heterogenous group of rare fibromatoses in childhood, characterized by the proliferation of myofibroblasts. Isolated tumors have a fair prognosis after complete excision.

Eye Neoplasms↗
PubMed1996

[Langerhans cell histiocytosis of the orbits].

Langerhans cell Histiocytosis is an infrequent disease of the orbit in little children. It is sometimes recognized in a rather late stage. We present three cases and discuss the manifestations and the treatment.

Diagnosis, Differential↗
PubMed1995

[Automated perimetry in ptosis and blepharochalasis].

BACKGROUND: First, we were looking if a correlation between the extent of ptosis and superior visual field defect exists. In a second step visual fields in blepharochalasis were compared with those in ptosis. PATIENTS AND METHODS: Pre- and postoperative visual fields in 20 patients with blepharochalasis, 6 patients with congenital and 9 with acquired ptosis were tested using program 7 of Octopus 500 automated perimeter. The degree of ptosis was separated in mild, medium and severe. According to the extent of visual field defect the same parameters as in ptosis were used also grading blepharochalasis in mild, medium and severe. RESULTS: We found that the amount of upper visual field defect clearly correlated with the extent of ptosis. In addition, patients with congenital ptosis showed less visual field defect compared to those with acquired ptosis. Comparable to ptosis surgery blepharoplasty also lead in severe and medium cases to a clear gain of upper visual field. CONCLUSION: Using perimetry and the same grading system as for ptosis makes it possible to study the functional defect occurring to the blepharochalasis patient.

Adolescent↗
PubMed1994

[Recurrent polychondritis (von Meyenburg-Altherr-Uehlinger syndrome].

UNLABELLED: Relapsing polychondritis is a rare systemic disease. Main symptoms are recurrent inflammations of the cartilage tissues, the eyes, and the cardiovascular system. Etiology and pathogenesis are obscure, there are hints for an immunologic disorder. PATIENT: Our patient has suffered from the disease since the age of 12 years. The patient has experienced recurrent keratitis with spontaneous ulcerations for 15 years.

Adult↗
PubMed1992

[Orbitoplasty in patients with artificial eyes].

The typical signs of the postenucleation socket syndrome consist of enopthalmos, shallow lower fornix, lower lid laxity and entropion, and ptosis. It causes discomfort and can render the bearing of a prosthesis uncomfortable or impossible. The signs must be corrected in single or combined procedures. The lower fornix and the lids can be corrected with good success, enophthalmos is difficult to correct, however.

Adolescent↗
PubMed1992

[Unilateral eyebrow suspension in severe unilateral congenital ptosis].

The result of unilateral brow suspension in severe unilateral ptosis is said to be cosmetically and functionally not satisfactory. For the reason of symmetry, the myectomy of the levator muscle on the healthy side and the bilateral brow suspension have been recommended (Beard's law). However, we have successfully operated the affected side only in several patients without this far-reaching supplement.

Blepharoptosis↗
PubMed1992

[Cosmetic lower eyelid blepharoplasties].

Between April 1988 and December 1991 42 patients underwent a bilateral lower eyelid blepharoplasty. Depending on the etiology either a skin-muscle-flap or a skin-flap technique was used. When the lid was lax, it was shortened by a wedge-resection to prevent postoperative ectropion. The results were satisfactory with either technique.

Adipose Tissue↗
PubMed1992

Treatment of the paradoxic inversion of the lashes in ectropion.

Ectropion leads to chronic inflammation of the exposed conjunctiva. This inflammation can lead to shrinkage and to a cicatricial paradoxic inversion of the lashes. When the lid margin is surgically brought into its correct position, these lashes may become trichiatic. The surgical eversion of the lid margin at the time of the ectropion operation can prevent this complication.

Aged↗
PubMed1991

[Use of autologous ear cartilage in eyelid surgery].

Autologous ear cartilage is relatively easy to procure in suitable form and sufficient quantity. At the donor site, there are, as a rule, no complications to be expected. Autologous ear cartilage without conjunctival coverage is of good use for replacing and lengthening the inner layer of an eyelid, not only to reconstruct large eyelid-defects, but also to give additional support and length. The cartilage graft will grow on well, provided the wound is well vascularized. This must not be expected with scarring or poor blood perfusion. The brittleness of the cartilage demands an adapted technique. Precautions to protect the cornea and to prevent adhesions in the fornix are to be taken.

Adolescent↗
PubMed1991

[Ptosis operations with silicone suspension at the eyebrow].

In severe ptosis with minimal or absent levator muscle function the lid can be connected with the frontalis muscle by means of silicone material. In our 18 patients (21 ptotic lids) the silastic rods arranged as a double sling to Crawford gave better results than the thinner silastic tube single slings.

Adolescent↗
PubMed1990

[Intraocular lens implantation with subconjunctival local anesthesia].

Between April 1988 and May 1989 extracapsular cataract extraction with intraocular lens implantation was performed on 66 (63 patients) with only subconjunctival local anesthesia (lidocaine/carbostesin with adrenaline 1.5 ml). Anesthesia was excellent, and movements of the globe and lids hardly interfered with the procedure. Subconjunctival anesthesia is less dangerous and more comfortable for the patient. The intraoperative hypotension of the globe is remarkable.

Aged↗
PubMed1990

[Bilateral angle block glaucoma in spontaneous choroid detachment].

A 66 years old patient suffered from a bilateral acute glaucoma attack, provoked by a spontaneous bilateral choroidal detachment. After Nd-YAG iridotomies and local steroid treatment the detachments resumed, the anterior chamber angles deepened, and the intraocular pressures returned to normal.

Acute Disease↗