Multinomial Processing Tree Models

Multinomial processing tree (MPT) models have become popular in cognitive psychology in the past two decades. In contrast to general-purpose data analysis techniques, such as log-linear models or other generalized linear models, MPT models are substantively motivated stochastic models for categorical data. They are best described as tools (a) for measuring the cognitive processes that underlie human behavior in various tasks and (b) for testing the psychological assumptions on which these models are based. The present article provides a review of MPT models and their applications in psychology, focusing on recent trends and developments in the past 10 years. Our review is nontechnical in nature and primarily aims at informing readers about the scope and utility of MPT models in different branches of cognitive psychology.

Bacterial ghosts: non-living candidate vaccines

Expression of cloned PhiX174 gene E in bacteria results in lysis of bacteria. It is unique among phage lysis systems as it introduces a transmembrane tunnel structure through the cell envelope complex of Gram-negative bacteria. The resulting bacterial ghosts have intact envelope structures devoid of cytoplasmic contents. E-mediated lysis has been achieved in a variety of Gram-negative bacteria including Escherichia coli, Salmonella typhimurium, Vibrio cholerae, Klebsiella pneumoniae, and Actinobacillus pleuropneumoniae. Such ghosts, derived from human or animal pathogens, have been proposed as non-living candidate vaccines and represent an alternative to heat or chemically inactivated bacteria. In 'recombinant ghosts', foreign proteins (e.g., viral proteins) are inserted into the inner membrane via specific N-, or C-, or N- and C-terminal anchor sequences prior to lysis. Relevant advantages of (recombinant) bacterial ghosts as immunogens include: (i) inactivation procedures that denature relevant immunogenic determinants are not employed in the production of ghosts used as vaccines or as carriers of relevant antigens; (ii) the recombinant proteins are inserted into a highly immune stimulatory environment; (iii) there is no size limitation of the foreign protein moieties: multiple antigenic determinants can be presented simultaneously; (iv) bacterial ghosts can be produced inexpensively in large quantities; (v) (recombinant) ghosts are stable for long periods of time and do not require the cold chain storage system. Intraperitoneal, subcutaneous or intramuscular applications of recombinant ghosts in experimental animals induced specific humoral and cellular immune responses against bacterial and viral components. Initial aerosol vaccinations of swine with ghosts from Actinobacillus pleuropneumoniae showed that protective immunity can be established by this route of application and that the well-preserved surface structures of ghosts obtained by E-mediated lysis are able to target the mucosal immune system.

Indications for surgical treatment of cerebellar haemorrhage and infarction

This report summarizes the outcome of 56 patients with cerebellar lesions of vascular origin, 40 patients with cerebellar infarction, and 16 with spontaneous cerebellar haemorrhage. All patients had computerized tomography: occlusive hydrocephalus was diagnosed in 75% of patients with cerebellar haemorrhage and in 23% with cerebellar infarction. Nine out of 10 patients survived after early surgical evacuation of the haematoma and 4 of them recovered completely. Two patients underwent only external ventricular drainage (EVD), one died after 2 days, and the other recovered with a moderate deficit. Three of 4 medically treated patients died within one week; all had developed occlusive hydrocephalus. The fourth medically treated patient recovered completely; consciousness had never deteriorated nor had occlusive hydrocephalus developed. Among 40 patients with cerebellar infarction, 13 developed progressive deterioration of consciousness; 7 of them underwent decompressive craniectomy of the posterior fossa and survived. One patient had only external ventricular drainage and died. Four out of the 5 medically treated patients died during the acute phase. From these observations and several reports in the literature, it is concluded that both cerebellar haemorrhage and infarction should be operated on as soon as progressive deterioration of consciousness develops. This occurs more frequently in patients with cerebellar haemorrhage than with cerebellar infarction. Individual decision-making in each case necessitates intensive neurosurgical observation.

Repositioning accuracy: comparison of a noninvasive head holder with thermoplastic mask for fractionated radiotherapy and a case report

PURPOSE

To compare accuracy, clinical feasibility, and subjective patient impression between a noninvasive head holder (Vogele Bale Hohner [VBH]; Wellhoefer Dosimetry, Schwarzenbruck, Germany) developed at the University of Innsbruck and the thermoplastic mask fixation system for use in fractionated external radiotherapy. We present a case report of an actual patient fixated in the VBH head holder during radiation therapy.

MATERIALS AND METHODS

The VBH head holder consists of an individualized vacuum dental cast connected to a head plate via two hydraulic arms allowing noninvasive, reproducible head fixation of even uncooperative patients. Accuracy was tested and compared with that of the thermoplastic mask using the Phillips EasyGuide navigation system on five volunteers. Specific external registration points served as landmarks and their positions were compared after each repositioning. System and operator inaccuracy were also taken into account. The times taken for production and repositioning of the respective fixation devices were compared, and subjective impressions were noted.

RESULTS

Mean VBH head holder repositioning accuracy was 1.02 mm while that of the thermoplastic mask was 3.05 mm. 69% of mask repositionings showed a deviation > 2 mm and 41% > 3 mm (as opposed to 8% and 1% respectively for the VBH head holder) Those points located farthest away from the respective plane of fixation showed the largest deviations. Both production and repositioning times were similar between the systems; depending upon the patient, the VBH head holder was generally better tolerated than the mask system.

CONCLUSION

Due to its significantly better repositioning accuracy compared to that of the thermoplastic mask, the VBH head holder is especially suited for external radiation requiring precise repositioning due to critical tissues in immediate surrounding of the area to be irradiated.

Computerized tomography and prognosis in early aneurysm surgery

A study of computerized tomography (CT) scans was performed in a consecutive series of 100 patients with ruptured saccular cerebral aneurysms who were admitted, diagnosed, and operated on within 72 hours after subarachnoid hemorrhage (SAH) and treated with calcium antagonists. The aneurysms were in the anterior portion of the circle of Willis in 95% of patients and in the posterior portion in 5%; 12% had multiple aneurysms. Preoperative neurological grades according to Hunt and Hess were I to III in 74% of patients and IV or V in 26%. Subarachnoid hemorrhage as determined by CT scanning was minor in 20%, moderate in 43%, and severe in 37% of patients. All patients received intraoperative and postoperative administration of the calcium antagonist nimodipine. Three days postoperatively, SAH (as measured by CT) was significantly reduced in the majority of patients but was still moderate in 18%. In the postoperative course, 2% of patients developed delayed ischemic neurological symptoms due to vasospasm. In two additional patients, ischemic symptoms were transient and fully reversible. At the 6-month follow-up interval, a significant prognostic difference was found between two patient groups with different CT scan findings. Among the patients with SAH only, the rate of good outcome (no or minimal deficit) was 93% when the preoperative neurological Grade was I or II; but even with a Grade of III to V, there was a good outcome in 84% of patients. By contrast, in patients with additional intracerebral and/or intraventricular hemorrhage, the good-outcome rate was only 44%. From these data it is concluded that morphological preoperative CT findings are of prognostic value and may even be superior to clinical grading in predicting outcome.

Prognostic value of changes in resting-state functional connectivity patterns in cognitive recovery after stroke: A 3T fMRI pilot study

Resting‐state studies conducted with stroke patients are scarce. First objective was to explore whether patients with good cognitive recovery showed differences in resting‐state functional patterns of brain activity when compared to patients with poor cognitive recovery. Second objective was to determine whether such patterns were correlated with cognitive performance. Third objective was to assess the existence of prognostic factors for cognitive recovery. Eighteen right‐handed stroke patients and eighteen healthy controls were included in the study. Stroke patients were divided into two groups according to their cognitive improvement observed at three months after stroke. Probabilistic independent component analysis was used to identify resting‐state brain activity patterns. The analysis identified six networks: frontal, fronto‐temporal, default mode network, secondary visual, parietal, and basal ganglia. Stroke patients showed significant decrease in brain activity in parietal and basal ganglia networks and a widespread increase in brain activity in the remaining ones when compared with healthy controls. When analyzed separately, patients with poor cognitive recovery (n = 10) showed the same pattern as the whole stroke patient group, while patients with good cognitive recovery (n = 8) showed increased activity only in the default mode network and fronto‐temporal network, and decreased activity in the basal ganglia. We observe negative correlations between basal ganglia network activity and performance in Semantic Fluency test and Part A of the Trail Making Test for patients with poor cognitive recovery. A reverse pattern was observed between frontal network activity and the abovementioned tests for the same group. Hum Brain Mapp 35:3819–3831, 2014. © 2014 The Authors. Human Brain Mapping published by Wiley Periodicals, Inc.

Head and neck tumors: fractionated frameless stereotactic interstitial brachytherapy-initial experience

The authors used a frameless stereotactic navigation system, the Vogele-Bale-Hohner head holder, and a targeting device to reproducibly position brachytherapy needles for fractionated interstitial brachytherapy in 12 patients with inoperable cancers of the head and neck. In all cases, deviations of the needle relative to the planned position were within 1-15 mm depending on the location of the tumor.

Laser Doppler imaging of axial and random pattern flaps in the maxillo-facial area. A preliminary report

Objective, non-invasive examination, techniques in addition to clinical parameters, are required to follow-up the wound healing of flaps. With the new laser Doppler Scanner (LDI DIM 1.0 Lisca Development AB, Sweden) it is possible, for the first time, to measure and image the microcirculation continuously, non-invasively and without contact with the wound, in an area of 12 cm square maximum. We performed measurements and simultaneous two-dimensional imaging of the microcirculation 24, 48, 72 h and 5 and 14 days postoperatively in 20 patients, who had had reconstruction procedures performed using random or axial pattern flaps. The perfusion diagrams were correlated to the clinical appearance. Necrotic areas, venous stasis and normal course of wound healing can be clearly visualized and differentiated from one another. The new laser Doppler imaging system seems to be an excellent aid for following up and planning of flaps in plastic and reconstructive surgery.

[3D navigation for interstitial stereotaxic brachytherapy]

AIM

The aim of this paper is to describe the adaption of 3D-navigation for interstitial brachytherapy. The new method leads to prospective and therefore improved planning of the therapy (position of the needle and dose distribution) and to the possibility of a virtual simulation (control if vessels or nerves are on the pathway of the needle).

MATERIAL AND METHODS

The EasyGuide Neuro navigation system (Philips) was adapted in the way, that needles for interstitial brachytherapy were made connectable to the pointer and correctly displayed on the screen. To determine the positioning accuracy, several attempts were performed to hit defined targets on phantoms. Two methods were used: "free navigation", where the needle was under control of the navigation system, and the "guided navigation" where an aligned template was used additionally to lead the needle to the target. In addition a mask system was tested, whether it met the requirements of stable and reproducible positioning. The potential of applying this method in clinical practice was tested with an anatomical specimen.

RESULTS

About 91% of all attempts lied within 5 mm. There were even better results on the more rigid table (94% < 4 mm). No difference could be seen between both application methods ("free navigation" and "navigation with template"), they showed the same accuracy.

CONCLUSIONS

The accuracy of the phantom experiments and the confirmation by the experiment with the anatomical specimen showed that excellent results can be expected in clinical practice using rigid tables and patient supporting systems.

Two-dimensional blood flow determinations in allergic reactions using laser Doppler scanning

The new technique of laser Doppler scanning (LDS) provides a 2-dimensional pattern of cutaneous microcirculation, which offers a visual image and can quantify the intensity and expansion of perfusion. With the help of this technique, we examined the microcirculatory pattern of Type IV reactions to recall antigens, which were applied using a test stamp (Multitest Merieux). The measurements were performed before application of the test stamp as well as 10 min, 24, 48 and 72 h afterwards. The inflammatory hyperemia was evaluated using LDS and unidimensional laser Doppler fluxmetry. The diameter of the inflammatory infiltrate was quantified by means of palpation, the thickness by means of high-resolution 20 MHz sonography. The clinically visible erythema was measured planimetrically. An unspecific hyperemia resulting from the trauma of the stamp revealed no evident infiltrate under sonography 10 min after the test application. Depending of the individual reaction, the mean flux and the expansion of the hyperemia were at their peak after 48 h. The flux values were at a maximum in the center of the inflammatory reaction and dropped continuously toward the periphery. The area of the hyperemia seen in the LDS image was significantly larger than the expansion of the erythema measured planimetrically, but there was a significant correlation. The perfusion correlated significantly with the infiltration diameter (24 h, 48 h, 72 h) and the infiltration thickness 48 h after testing. All in all, it was possible to measure directly and without touching the skin and to quantify a subclinical pattern of skin perfusion as a response to and inflammatory reaction on a 2-dimensional display.

Selective amplification of RNA utilizing the nucleotide analog dITP and Thermus thermophilus DNA polymerase

The ability to selectively amplify RNA in the presence of genomic DNA of analogous sequence is cumbersome and requires implementation of critical controls for genes lacking introns. The convenient approaches of either designing oligonucleotide primers at the splice junction or differentiating the target sequence based on the size difference obtained by the presence of the intron are not possible. Our strategy for the selective amplification of RNA targets is based on the enzymology of a single thermostable DNA polymerase and the ability to modulate the strand separation temperature requirements for PCR amplification. Following reverse transcription of the RNA by recombinant Thermus thermophilus DNA polymerase (rTth pol), the resulting RNAxDNA hybrid is digested by the RNase H activity of rTth pol, allowing the PCR primer to hybridize and initiate second-strand cDNA synthesis. Substitution of one or more conventional nucleotides with nucleotide analogs that decrease base stacking interactions and/or hydrogen bonding (e.g. hydroxymethyldUTP or dITP) during the first- and second-strand cDNA synthesis step reduces the strand separation temperature of the resultant DNAxDNA duplex. Alteration of the thermal cycling parameters of the subsequent PCR amplification, such that the strand separation temperature is below that required for denaturation of genomic duplex DNA composed of standard nucleotides, prevents the genomic DNA from being denatured and therefore amplified.

Evaluation of the efficacy of H1 blockers by noninvasive measurement techniques

BACKGROUND

Evaluation techniques for determining the strength of action and the onset of activity of H1 receptor blockers have not yet been sufficiently standardized.

OBJECTIVE

The clinical efficacy of the H1 receptor blocker loratadine was to be measured upon a wheal response subsequent to an intracutaneous injection of 0.1 ml histamine (0.1%).

METHODS

In a pilot study, 10 patients were treated with the H1 receptor blocker loratadine for a period of 7 days. Various noninvasive measurement techniques, i.e. 20-MHz sonography, laser-Doppler flowmetry, chromatometry using the Lab* system and computer-assisted planimetry, were applied to provide a quantitative evaluation of the wheal and the marginal erythema. Using these quantification methods, the development of the urticarial reaction 20 min after injection and its decline were evaluated.

RESULTS

The urticarial reaction was reduced substantially under treatment with 10 mg loratadine over a period of 7 days. The methods we used could accurately quantify different aspects of the urticarial reaction noninvasively.

CONCLUSIONS

All of the chosen measurement techniques are widely recognized. For objective assessment of the urticarial reaction with high-frequency ultrasound, we recommend the measurement of the distance between skin entrance echo and fascia since the demarcation of the wheal is often impossible by ultrasound. In order to improve comparison of results of various workgroups in the future, we therefore suggest the use of the selected combination of noninvasive procedures as a standard for evaluating the efficacy of H1 receptor blockers.

Rapid, sensitive high-performance liquid chromatographic method for the determination of cyclosporin A and its metabolites M1, M17 and M21

Cyclosporin A (CyA) and its metabolites seem to have nephro-, hepato- and neurotoxic side effects. Immunosuppressive therapy is a narrow path between the risk of rejection by underimmunosuppression and toxic organ damage by overdosage. Thus CyA dosage must be calculated to avoid the risks of organ rejection through underdosage and toxic organ damage through overdosage or accumulation of metabolites. In routine monitoring of CyA therapy, it can be important to measure not only the parent drug but also the metabolites. We describe a rapid and isocratic high-performance liquid chromatographic method for measurement of CyA and its metabolites M1, M17 and M21 in whole blood. CyA was detected by ultraviolet absorption at 212 nm with a CN analytical column maintained at 50 degrees C and recycling of hexane-isopropanol as mobile phase for improved long-term column stability and efficiency. The minimum detectable concentration of CyA and the three metabolites was 10 ng/ml blood. Our modified HPLC method for the determination of CyA and its metabolites is a simple (isocratic), rapid (the retention times were 7.1 min for CYD, internal standard, 8.9 min for CyA, 11.0 min for M21, 12.9 min for M17 and 16.3 min for M1) and economical method suitable for measuring the concentration of the major metabolite, M17, and for routine monitoring of CyA-treated patients.

Properties of the 5'-->3' exonuclease/ribonuclease H activity of Thermus thermophilus DNA polymerase

The recombinant 94 kDa Thermus thermophilus DNA polymerase (rTth pol) was found to release [33P]UMP when incubated with a RNA.DNA hybrid containing a [33P]UMP-labeled RNA strand. The RNase H activity was optimally active in the presence of low monovalent salt concentrations and when Mn2+ was used as the divalent cation activator. RNase H activity also was observed when Mg2+ replaced the Mn2+, but to a much lesser extent. A 60 nucleotide long, 5'- or 3'-radiolabeled RNA or DNA oligomer hybridized to a complementary DNA oligomer was used to determine the mode of digestion. The radiolabeled RNA.DNA hybrid or DNA.DNA duplex was incubated with rTth pol using various metal ion conditions and different incubation times. The DNA.DNA duplex showed very little enzymatic cleavage by rTth pol regardless of the Mn2+ or Mg2+ concentration. However, nearly complete digestion of the RNA.DNA hybrid was observed over a wide Mn2+ concentration range, thus demonstrating a preferential degradation of the RNA.DNA hybrid vs the DNA.DNA duplex. Time course reactions of the enzymatic digestion of the 3'-labeled RNA.DNA hybrid or DNA.DNA duplex by rTth pol indicated that digestion of the substrates occurred exonucleolytically in the 5'-->3' direction.

Comparing abundance distributions and range maps in spatial conservation planning for migratory species

Most spatial conservation planning for wide-ranging or migratory species is constrained by poor knowledge of species' spatiotemporal dynamics and is only based on static species' ranges. However, species have substantial variation in abundance across their range and migratory species have important spatiotemporal population dynamics. With growing ecological data and advancing analytics, both of these can be estimated and incorporated into spatial conservation planning. However, there is limited information on the degree to which including this information affects conservation planning. We compared the performance of systematic conservation prioritizations for different scenarios based on varying the input species' distributions by ecological metric (abundance distributions versus range maps) and temporal sampling resolution (weekly, monthly, or quarterly). We used the example of a community of 41 species of migratory shorebirds that breed in North America, and we used eBird data to produce weekly estimates of species' abundances and ranges. Abundance distributions at a monthly or weekly resolution led to prioritizations that most efficiently protected species throughout the full annual cycle. Conversely, spatial prioritizations based on species' ranges required more sites and left most species insufficiently protected for at least part of their annual cycle. Prioritizations with only quarterly species ranges were very inefficient as they needed to target 40% of species' ranges to include 10% of populations. We highlight the high value of abundance information for spatial conservation planning, which leads to more efficient and effective spatial prioritization for conservation. Overall, we provide evidence that spatial conservation planning for wide-ranging migratory species is most robust and efficient when informed by species' abundance information from the full annual cycle.

Feasibility of Ultrasound-Guided Sacroiliac Joint Injections in Children Presenting with Sacroiliitis

PURPOSE

To evaluate the feasibility and effectiveness of US-guided sacroiliac joint injection in the treatment of sacroiliitis in children.

MATERIALS AND METHODS

This study was approved by the institutional review board and informed oral and written consent was obtained from the patients and their parents. In 13 patients (7 females and 6 males), 9 - 16 years (mean +/- std 11.39 +/-1.98), 18 sacroiliac joint (SI joint) injections were performed under US guidance. All patients suffered from severe sacroiliitis. US scanning was performed using a linear-array transducer operating at 5 - 18 MHz. Rating of the patients pain using a 0 - 10 dolorimetry scale on a visual analog score (VAS) was recorded before, immediately after and 3 months after injection to monitor severity and therapeutic response.

RESULTS

Injection could be performed in all patients without complication and showed good response immediately and 3 months after the injection with a decrease of the VAS (from mean +/- std 9.44 +/- 1.097 to 3.89 +/- 3.82, p < 0.001 and to 0.56 +/- 1.097, p < 0.05, respectively).

CONCLUSION

US-guided SI joint injection was feasible in all children, relatively quick and easy to perform and appeared effective in the treatment of children with sacroiliitis.

The Four-States Model of Memory Retrieval Experiences

Abstract. A memory measurement model is presented that accounts for judgments of remembering, knowing, and guessing in old-new recognition tasks by assuming four disjoint latent memory states: recollection, familiarity, uncertainty, and rejection. This four-states model can be applied to both Tulving's (1985) remember-know procedure (RK version) and Gardiner and coworker's ( Gardiner, Java, & Richardson-Klavehn, 1996 ; Gardiner, Richardson-Klavehn, & Ramponi, 1997 ) remember-know-guess procedure (RKG version). It is shown that the RK version of the model fits remember-know data approximately as well as the one-dimensional signal detection model does. In contrast, the RKG version of the four-states model outperforms the corresponding detection model even if unequal variances for old and new items are allowed for.We show empirically that the two versions of the four-statesmodelmeasure the same state probabilities. However, the RKG version, requiring remember-know-guess judgments, provides parameter estimates with smaller standard errors and is therefore recommended for routine use.

VBH head holder to improve frameless stereotactic brachytherapy of cranial tumors

Precise target localization is essential for brachytherapy. We have adapted the VBH (Vogele-Bale-Hohner) head holder (Wellhoefer Dosimetry, Schwarzenbruck, Germany), originally developed at the University of Innsbruck, for frameless stereotactic surgery, for use in brachytherapy of cranial tumors. The VBH head holder allows for rigid, noninvasive head fixation by means of an individualized upper dental cast. Registration rods, rigidly attached to the dental cast, provide stable external points of reference. The dental cast is sucked against the upper palate by vacuum, and then the fixated patient is scanned. During simulation, the targeting device can be positioned with respect to the virtual patient using the ISG Viewing Wand. Following simulation, the real patient is repositioned under vacuum control, the targeting device repositioned as well, and the actual brachytherapy initiated. The VBH head holder is well tolerated by patients and simple to use, and various studies have confirmed submillimeter accuracy. The modified head holder in combination with a new targeting device allows for precise and well-planned insertion of hollow needles into a tumor using frameless stereotactic systems as well as being compatible for uses in other fields.

[100 MHz ultrasound of psoriasis vulgaris plaque]

PURPOSE

20 MHz sonography of inflammatory diseases has concentrated on the evaluation of the echo-poor area in the upper dermis. With regard to higher resolution, this study focuses on the alterations of the epidermis and upper dermis skin using 100 MHz sonography.

METHOD

70 fully developed psoriasis vulgaris plaques of 20 patients were examined using our 100 MHz ultrasound equipment after application of salicylic acid in petrolatum for 24 h. After informing the patient about the aims of the study, a small knife biopsy was taken from 11 plaques.

RESULTS

All psoriasis plaques exhibited, in comparison with normal skin, a significant widening of the skin entry echo (p < 0.001). Focally, this echo-rich line broke up into two thinner lines. Correlating histology exhibited in these areas an orthohyperkeratosis and focal parakeratosis. The upper dermis showed an echo-poor, band-shaped area which corresponded histologically to an acanthosis, elongation of rete ridges, and widening of the stratum papillare. The mean grey level of the echo-poor area and of the dermis beneath was significantly lower (p < 0.001) than the normal adjacent dermis. The thickness of the echo-poor area correlated with the thickness of the sum of the acanthosis and the inflammatory infiltrate in the histological sections (r = 0.94).

CONCLUSION

Using 100 MHz sonography changes of the skin entry echo and the upper dermis can be visualized and quantified.

Subsecond spin relaxation times in quantum dots at zero applied magnetic field due to a strong electron-nuclear interaction

A key to ultralong electron spin memory in quantum dots (QDs) at zero magnetic field is the polarization of the nuclei, such that the electron spin is stabilized along the average nuclear magnetic field. We demonstrate that spin-polarized electrons in n-doped (In,Ga)As/GaAs QDs align the nuclear field via the hyperfine interaction. A feedback onto the electrons occurs, leading to stabilization of their polarization due to formation of a nuclear spin polaron [I. A. Merkulov, Phys. Solid State 40, 930 (1998)]. Spin depolarization of both systems is consequently greatly reduced, and spin memory of the coupled electron-nuclear spin system is retained over 0.3 sec at temperature of 2 K.

[Noninvasive head fixation for external irradiation of tumors of the head-neck area]

PURPOSE

To fully utilize the technical capabilities of radiation diagnostics and planning, a precise and reproducible method of head fixation is a prerequisite.

METHOD

We have adapted the Vogele-Bale-Hohner (VBH) head holder (Wellhöfer Dosimetrie, Schwarzenbruck, Germany), originally designed for frameless stereotactic operations, to the requirements of external beam radiotherapy. A precise and reproducible head fixation is attained by an individualized vacuum upper-dental cast which is connected over 2 hydraulic arms to an adjustable head- and rigid base-plate. Radiation field and patient alignment lasers are marked on a relocatable clear PVC localization box.

RESULTS

The possibility of craniocaudal adjustment of the head plate on the base plate allows the system to adapt to the actual position of the patient on the radiotherapy couch granting tensionless repositioning. The VBH head holder has proven itself to be a precise yet practicable method of head fixation. Duration of mouthpiece production and daily repositioning is comparable to that of the thermoplastic mask.

CONCLUSION

The new head holder is in routine use at our hospital and quite suitable for external beam radiation of patients with tumors of the head and neck.

[First experiences with computer-assisted frameless stereotactic interstitial brachytherapy (CASIB)]

PURPOSE

To reach an optimal treatment result and to avoid damage to critical structures a homogeneous dose distribution in the tumor volume with a rapid decreasing dose to the surrounding structures is necessary. Fractionated interstitial brachytherapy of tumors in the ENT region employing needles depends on exact localization of the target volume during all fractions. Therefore reproducibility of positioning of the needle(s) plays an important role.

MATERIAL AND METHODS

We used the ISG Viewing Wand system in combination with the Vogele-Bale-Hohner (VBH) head holder and a new targeting device. Point of entrance, pathway, and target point of the needle were planned and insertion of the needle simulated in advance. To date we have treated 7 patients with inoperable tumors in the ENT region. The actual position of the needle in the control CT was compared to the planned position.

RESULTS

The accuracy of positioning of the needle depended on the location of the tumor. In a patient with a recurrent retroorbital adenocarcinoma the mean accuracy was 1 mm. Due to soft tissue displacement in the neck region and the resulting necessity to readjust the targeting device the needle was placed with a mean deviation of 15 mm between the planned and the actual position.

CONCLUSIONS

Computer-assisted frameless stereotactic interstitial brachytherapy allows for precise, reproducible and preplanned insertion of hollow needles into target structures closely adherent to the surrounding tissue, thus avoiding damage of neighbouring structures. This technique is of great advantage in treating deeply seated tumors which are fixed to bony structures, especially at the skull base. Inaccuracy in the neck region caused by soft tissue shift requires improvement of the immobilization in this region.