Single institution experience with peptide receptor radionuclide therapy (PRRT) in neuroendocrine tumors (NET)

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Background: Neuroendocrine tumors (NETs) are rare but increasing in incidence. The only curative treatment is surgery, which in many cases is not an option due to metastatic disease at diagnosis. The NETTER-1 study showed high efficacy and low toxicity of peptide receptor radionuclide therapy (PRRT) for midgut NETs. Here, we present our initial experience with PRRT in the treatment of patients with NET. Methods: Fifty-two patients (27 males and 25 females; 37 - 81 yo, mean ± SD: 61.8 ± 10.6 years) with documented progressive NET (25 pancreas, 17 small intestine, 1 coecum, 4 unknown primary, 3 paragangliomas, and 2 pheochromocytomas) were referred to undergo PRRT at our institution from July 2018 to September 2019. Laboratory tests were obtained at baseline, 1 week before each cycle and every 3 months following treatment. Progression-free survival (PFS), objective response rate (ORR) and toxicity were assessed. An interim overall survival (OS) analysis was performed. Results, when possible, were compared with the NETTER-1 trial. Lines of therapy were documented. Results: 22/52 (42%) patients completed all 4 cycles of PRRT. 18/52 (34%) patients are currently being treated. 12/52 (23%) patients had to discontinue treatment. Hematotoxicity was the only side effect which can be related to PRRT. The 6-month and 9-month PFS rate was 82.4% and 66.8% respectively vs. 89% and 84% in the NETTER-1 trial. The ORR was 36% vs. 18% in the NETTER-1 trial. In the interim OS analysis, 6 deaths occurred. In contrast to the NETTER-1 study, PRRT in our patient cohort was performed later in the course of treatment (median lines of therapy before PRRT = 4 ±1.3 (range 1-6)). Conclusions: Our preliminary data show overall good results of PRRT in patients with NETs. However, compared to the NETTER-1 trial, PFS is shorter which is most likely due to the extensive pretreatment, but ORR was higher. [Table: see text]

Computer-aided 3-D simulation and prediction of craniofacial surgery: a new approach

BACKGROUND

In plastic and reconstructive craniofacial surgery, careful preoperative planning is essential. In complex cases of craniofacial synostosis, rapid prototyping models are used to simulate the surgery and reduce operating time. Recently, 3-D CT model surgery has been introduced for presurgical planning and prediction of the postoperative result.

OBJECTIVE

For simulation of craniofacial surgery a computer-based system was developed that allows visualization and manipulation of CT-data using computer graphics techniques. Surgical procedures in all areas of the bony skull can be performed interactively.

RESULTS

The case of a child with scaphocephalus is presented. Surgery is planned using the craniofacial surgery simulator described above.

CONCLUSION

The computer-based interactive surgery simulation systems presented here allow precise visualization of craniofacial surgery. The accurate computer-aided 3-D simulation of bone displacements is also the prerequisite for transfer of the simulated surgery using a navigation system for surgery. Thus the preoperatively planned procedure could be transferred directly to the operating table.

3-D simulation of craniofacial surgical procedures

An integrated system for simulating craniofacial surgical procedures is presented. The system computes nonlinear soft-tissue deformation due to bone realignment. It is capable of simulating bone cutting and bone realignment with integrated interactive collision detection. Furthermore, soft-tissue deformation and cutting due to surgical instruments can be visualized. The system has been tested with several individual patient data sets. Simulation processes are based on a 3-D model of a patient's preoperative bone structure of the skull derived from a computer tomography scan and on a 3-D, photorealistic model of the patient's preoperative appearance obtained by a laser range scanner. The multi-layer soft-tissue model is represented by nonlinear springs. Very fast and robust prediction of nonlinear soft-tissue deformation is computed by optimizing a nonlinear cost function.

[Possibilities of computer graphics simulation in orthopedic surgery]

BACKGROUND

In addition to standard X-rays, photographic documentation, cephalometric and model analysis, a computer-aided, three-dimensional (3D) simulation system has been developed in close cooperation with the Institute of Communications of the Friedrich-Alexander-Universität Erlangen-Nürnberg. With this simulation system a photorealistic prediction of the expected soft tissue changes can be made. Prerequisites are a 3D reconstruction of the facial skeleton and a 3D laser scan of the face. After data reduction, the two data sets can be matched. Cutting planes enable the transposition of bony segments. The laser scan of the facial surface is combined with the underlying bone via a five-layered soft tissue model to convert bone movements on the soft tissue cover realistically.

CONCLUSION

Further research is necessary to replace the virtual subcutaneous soft tissue model by correct, topographic tissue anatomy.

Efficiency analysis of multihypothesis motion-compensated prediction for video coding

Overlapped block motion compensation or B-frames are examples of multihypothesis motion compensation where several motion-compensated signals are superimposed to reduce the bit-rate of a video codec. This paper extends the wide-sense stationary theory of motion-compensated prediction (MCP) for hybrid video codecs to multihypothesis motion compensation. The power spectrum of the prediction error is related to the displacement error probability density functions (pdfs) of an arbitrary number of hypotheses in a closed-form expression. We then study the influence of motion compensation accuracy on the efficiency of multihypothesis motion compensation as well as the influence of the residual noise level and the gain from optimal combination of N hypotheses. For the noise-free limiting case, doubling the number of (equally good) hypotheses can yield a gain of up to 1/2 bits/sample, while doubling the accuracy of motion compensation can additionally reduce the bit-rate by up to 1 bit/sample independent of N. For realistic noise levels, it is shown that the introduction of B-frames or overlapped block motion compensation can provide larger gains than doubling motion compensation accuracy. Spatial filtering of the motion-compensated candidate signals becomes less important if more hypotheses are combined. The critical accuracy beyond which the gain due to more accurate motion compensation is small moves to larger displacement error variances with increasing noise and increasing number of hypotheses N. Hence, sub-pel accurate motion compensation becomes less important with multihypothesis MCP. The theoretical insights are confirmed by experimental results for overlapped block motion compensation, B-frames, and multiframe motion-compensated prediction with up to eight hypotheses from ten previous frames.

Deformable modeling of facial tissue for craniofacial surgery simulation

While deformable object modeling has been studied by computer graphics specialists for more than two decades, only a few applications in the field of surgical simulation have been developed which provide both real-time and physically realistic modeling of complex, nonlinear tissue deformations. Particularly in craniofacial surgery, the prediction of soft-tissue changes--which result from alterations in the underlying bone structure--is critical to the surgical outcome. The prediction these tissue changes and, therefore, the prognosis of the postoperative appearance of the patient, is still based on empirical studies of the relationship between bone and tissue movements: There exists no physical model which takes into account the individual patient anatomy to simulate the resulting tissue changes during craniofacial surgery. In this article we present two different deformable tissue models which are intergrated in an interactive surgical simulation test bed. Both techniques allow precise preoperative simulation of the resulting soft tissue changes during craniofacial surgery and visualization of the patient's postoperative appearance. The different deformable models are described in detail and both are applied to the same craniofacial case study. The simulation results are shown and compared with regard to the speed and accuracy of the prediction of the patient's postoperative appearance.

Advances in interactive craniofacial surgery planning by 3D simulation and visualization

In craniofacial surgery careful preoperative planning is essential. Traditional preoperative work-up consists of cast model surgery, cephalometric prediction tracing and analysis of photographs. Recently, we introduced 3-dimensional (3D) computed tomography (CT) model surgery in our preoperative work-up and presurgical prediction of the postoperative result. However, only limited information can be extracted concerning soft tissue changes which are most important for the patients' postoperative appearance. We propose a new system which will allow a precise preoperative visualization of not only bony structures but also the soft tissue surfaces. 3D CT data of the skull are integrated with 3D surface data acquired by laser scanning. Based on the 3D CT data the bony structures are segmented automatically and processed interactively to simulate the planned surgical procedure. Afterwards, the 3D soft tissue changes resulting from the shifting of bony segments are computed. The postoperative appearance of the patient is visualized using computer animation techniques.

Vector quantization for entropy coding of image subbands

Vector quantization for entropy coding of image subbands is investigated. Rate distortion curves are computed with mean square error as a distortion criterion. The authors show that full-search entropy-constrained vector quantization of image subbands results in the best performance, but is computationally expensive. Lattice quantizers yield a coding efficiency almost indistinguishable from optimum full-search entropy-constrained vector quantization. Orthogonal lattice quantizers were found to perform almost as well as lattice quantizers derived from dense sphere packings. An optimum bit allocation rule based on a Lagrange multiplier formulation is applied to subband coding. Coding results are shown for a still image.

The fascicular structure of the lingual nerve and the chorda tympani: an anatomic study

Damage of the lingual nerve is one of the most common problems in oral surgery, especially during removal of the third molar. After microsurgery of the lingual nerve, there is a lack of regeneration of the gustatory fibers in comparison with the sensory fibers. The histologic investigation of ten human lingual nerve preparations showed that the chorda tympani fibers distribute widely in the fascicles of the lingual nerve. Therefore, after microsurgical reconstruction of the lingual nerve in the third molar region, the chance of the gustatory fibers meeting and regenerating is very low.

[Common variable hypogammaglobulinemia. Apropos of a new case]

The authors report the case of a 17 year-old girl who presented with typical clinical features (pneumonia, sinusitis, otitis and diarrhoea) of Variable Primary Hypogammaglobulinemia for over 15 years. Immunodeficiency investigations showed a defective antibody response with a panhypogammaglobulinemia but normal cell-mediated immunity. Serum protein electrophoresis and detection of natural and acquired antibodies in the blood are the basic biological tests to run for a quick diagnosis. The main long term complication consists of the risk of neoplasia. The patient recovered a good clinical status after she was treated by IgG infusions every 2,5 weeks and antibiotics in case of superimposed infection.