[Surgical possibilities in the treatment of diseases and injuries of the spine in patients with manifest osteoporosis ]

In the presence of a vertebral injury or disease, manifest osteoporosis affects preoperative planning. Thus, if surgery is indicated, bone density should be determined in cases of suspected or diagnosed osteoporosis. Instrumentation of the spine is frequently not required in surgical interventions. However, if indicated, instrumentation should be fixed multifocally and the deformity should be corrected with special care. It is absolutely necessary to avoid ending instrumentation within a kyphosis.

Treatment of femoral head necrosis with vascularized iliac crest transplants

The development of microsurgical methods has allowed for the use of vascularized bone transplants in the treatment of femoral head necrosis, particularly for Stages II, III, and IV according to the Association Internationale de Recherche sur la Circulation Osseuse classification system. Eighty patients with avascular necrosis of the femoral head were treated with vascular pedicled iliac crest transplant, perfused by the circumflexed ilium profunda artery between 1988 and 1996. On average, the postoperative followup was 5 years. Evaluation was based on the Harris hip score, and clinical and radiologic examination. Clinical results according to the Harris hip score were good or excellent in 86.6% of the patients. Radiologic appearance during the followup remained stable in 56.1% of the patients according to the classification system of the Association Internationale de Recherche sur la Circulation Osseuse. These findings are compatible with the findings of other studies in which vascularized bone transplants were used and approximately 50% of the patients with Stages II, III, and IV, according to the classification of the Association Internationale de Recherche sur la Circulation Osseuse had an unchanged stage of disease 5 to 6 years after the procedure.

[Virus relevant physicochemical parameters of viscoelastics in cataract operation]

PURPOSE

To define the physicochemical parameters of viscoelastics that are most important for visual acuity after phacoemulsification.

MATERIAL AND METHODS

Eleven commercially available viscoelastics (ophthalmic viscosurgical device, OVD) were used in consecutive cataract operations. In addition to clinical findings, we assessed visual acuity, intraocular pressure, endothelial cell density, and pachymetric data preoperatively and on the first postoperative day.

RESULTS

On the first postoperative day the loss of endothelial cells in all phacoemulsifications was 0.661%, corrected for 1 s phacotime, while corneal thickness increased by 0.2384% and visual acuity by 5.206%, and intraocular pressure decreased by 0.306%. The most important parameters for visual acuity were the concentration of sodium hyaluronate and viscosity (100/s.) of the OVD. Pachymetric data were more relevant for postoperative visual acuity than endothelial cell counts.

CONCLUSION

Early visual rehabilitation after phacoemulsification depends on stable pachymetric data. OVD with a high content of sodium hyaluronate and high viscosity significantly reduces corneal swelling and improves visual acuity after phacoemulsifications on the first postoperative day.

The role of the Drosophila TAK homologue dTAK during development

The TAK kinases belong to the MAPKKK group and have been implicated in a variety of signaling events. Originally described as a TGF-beta activated kinase (TAK) it has, however, subsequently been demonstrated to signal through p38, Jun N-terminal kinase (JNK) and Nemo types of MAP kinases, and the NFkappaB inducing kinase. Despite these multiple proposed functions, the in vivo role of TAK family kinases remains unclear. Here we report the isolation and genetic characterization of the Drosophila TAK homologue (dTAK). By employing overexpression and double-stranded RNA interference (RNAi) techniques we have analyzed its function during embryogenesis and larval development. Overexpression of dTAK in the embryonic epidermis is sufficient to induce the transcription of the JNK target genes decapentaplegic and puckered. Furthermore, overexpression of dominant negative (DN) or wild-type forms of dTAK in wing and eye imaginal discs, respectively, results in defects in thorax closure and ommatidial planar polarity, two well described phenotypes associated with JNK signaling activity. Surprisingly, RNAi and DN-dTAK expression studies in the embryo argue for a differential requirement of dTAK during developmental processes controlled by JNK signaling, and a redundant or minor role of dTAK in dorsal closure. In addition, dTAK-mediated activation of JNK in the Drosophila eye imaginal disc leads to an eye ablation phenotype due to ectopically induced apoptotic cell death. Genetic analyses in the eye indicate that dTAK can also act through the p38 and Nemo kinases in imaginal discs. Our results suggest that dTAK can act as a JNKKK upstream of JNK in multiple contexts and also other MAPKs in the eye. However, the loss-of-function RNAi studies indicate that it is not strictly required and thus either redundant or playing only a minor role in the context of embryonic dorsal closure.

2000 Volvo Award winner in biomechanical studies: Monitoring in vivo implant loads with a telemeterized internal spinal fixation device

STUDY DESIGN

Implant loads were measured in 10 patients using telemeterized internal spinal fixation devices.

OBJECTIVE

To determine the postoperative temporal course of implant loads.

SUMMARY OF BACKGROUND DATA

Little information exists regarding the temporal course of loads on internal spinal fixation devices.

METHODS

The telemeterized internal spinal fixator allows the measurement of three force components and three moments acting in the fixator. Implant loads were determined in up to 20 measuring sessions for different activities, including walking, standing, sitting, lying in the supine position, and lifting an extended leg while in the supine position.

RESULTS

Implant loads often increased shortly after anterior interbody fusion was performed. Several patients retained the same high level even after fusion had taken place. This explains the reason why screw breakage sometimes occurs more than half a year after implantation. The time of fusion could not be pinpointed from the loading curves.

CONCLUSIONS

The results show that fixators may be highly loaded even after fusion has occurred. A flexion bending moment acts on the implant even with the body in a relaxed lying position. This means that already shortly after the anterior procedure, the shape of the spine is not neutral and unloaded, but slightly deformed, which loads the fixators. Pedicle screw breakage more than half a year after insertion does not prove that anterior interbody fusion has not occurred.

Depth scanning for a conformal ion beam treatment of deep seated tumours

Only target-conformal treatment allows one to exploit the advantages of ion beams (the increased dose and high biological efficiency at the end of the particle range) to a maximum extent. Up to now, target-conformal treatments such as spot scanning or intensity-controlled raster scanning have used fast magnetic lateral deflection in one or two directions perpendicular to the beam axis and a slow range variation in the longitudinal axis by active or passive energy variation. The present paper describes a new method for conformal irradiation with a fast intensity-controlled longitudinal scan in the beam direction, called 'depth scanning'. Its advantages and disadvantages will be discussed. First experimental results from depth scanning will be presented.

Treatment planning for heavy-ion radiotherapy: physical beam model and dose optimization

We describe a novel code system, TRiP, dedicated to the planning of radiotherapy with energetic ions, in particular 12C. The software is designed to cooperate with three-dimensional active dose shaping devices like the GSI raster scan system. This unique beam delivery system allows us to select any combination from a list of 253 individual beam energies, 7 different beam spot sizes and 15 intensity levels. The software includes a beam model adapted to and verified for carbon ions. Inverse planning techniques are implemented in order to obtain a uniform target dose distribution from clinical input data, i.e. CT images and patient contours. This implies the automatic generation of intensity modulated fields of heavy ions with as many as 40000 raster points, where each point corresponds to a specific beam position, energy and particle fluence. This set of data is directly passed to the beam delivery and control system. The treatment planning code has been in clinical use since the start of the GSI pilot project in December 1997. Forty-eight patients have been successfully planned and treated.

[Assessment of routine mobility in geriatrics using static posturography--a population based study]

In a population-based study of 110 women between 53 and 82 years of age (mean age 64.5 +/- 7.9 years) static posturography data were compared to functional items of gait and balance in common geriatric mobility scales. Posturographic data of double-stance with eyes open and eyes closed (DSEO; DSEC) did not differ from those of a group of healthy women previously tested for intact nervous system function. The total neuromuscular score--roughly corresponding to the well-known Tinetti score--did not correlate to the posturographic measures. DSEC correlated with the items "rapid walking" and "single-stance left leg". Age, vision, and neuropsychologic test results correlated with DSEO, "rapid walking", "single-stance right leg", "single-stance left leg", and "walking a figure eight". Multiple linear regression confirmed the impact of age, vision, DSEO, and DSEC on "rapid walking" with a 34% variance explanation. Posturographic parameters did predict other selected gait and balance items. When used in older women living independently in the community, parameters of static posturography reflect to some extent the functional disabilities of gait and balance.

Three-dimensional BANG gel dosimetry in conformal carbon ion radiotherapy

In this study we applied BANG polymer-gel dosimetry using magnetic resonance imaging (MRI) to densely ionizing radiation such as carbon ion beams. BANG polymer gels were irradiated with a quadratic field of monoenergetic 12C ions at different beam energies in the range of 135 MeV u(-1) to 410 MeV u(-1). They were irradiated at the radiotherapy facility of the GSI, Darmstadt, Germany. Our object was to examine the saturation effect for densely ionizing radiation that occurs at high values of linear energy transfer (LET). The examination yielded the first effectiveness values that will be discussed in the following sections. A solid sphere and a hollow sphere were both irradiated with a horizontal pencil beam from the raster scanning facility at energies of 268 MeV u(-1) (solid sphere) and 304 MeV u(-1) (hollow sphere) respectively. MR dosimetry measurements were compared with data from a planning system. As far as quality is concerned, there is good agreement between the measured dose distributions of both samples and the dose maps from the planning software. The measured MR signals cannot be converted into absolute dose, since the relative efficiency is still unknown for mixed radiation fields of primary carbon ions and it is known only to a limited extent for nuclear fragments with different energies from highly energetic photon radiation. Model calculations are in progress in order to facilitate conversions of measured MR signals into dose.

Feasibility and safety of inducing modest hypothermia in awake patients with acute stroke through surface cooling: A case-control study: the Copenhagen Stroke Study

BACKGROUND AND PURPOSE

Hypothermia reduces neuronal damage in animal stroke models. Whether hypothermia is neuroprotective in patients with acute stroke remains to be clarified. In this case-control study, we evaluated the feasibility and safety of inducing modest hypothermia by a surface cooling method in awake patients with acute stroke.

METHODS

We prospectively included 17 patients (cases) with stroke admitted within 12 hours from stoke onset (mean 3.25 hours). They were given hypothermic treatment for 6 hours by the "forced air" method, a surface cooling method that uses a cooling blanket with a flow of cool air (10 degrees C). Pethidine was given to treat compensatory shivering. Cases were compared with 56 patients (controls) from the Copenhagen Stroke Study matched for age, gender, initial stroke severity, body temperature on admission, and time from stroke onset to admission. Blood cytology, biochemistry, ECGs, and body temperature were monitored during hypothermic treatment. Multiple regression analyses on outcome were performed to examine the safety of hypothermic therapy.

RESULTS

Body temperature decreased from t(0)=36.8 degrees C to t(6)=35.5 degrees C (P:<0.001), and hypothermia was present until 4 hours after therapy (t(0)=36.8 degrees C versus t(10)=36.5 degrees C; P:=0.01). Mortality at 6 months after stroke was 12% in cases versus 23% in controls (P:=0. 50). Final neurological impairment (Scandinavian Stroke Scale score at 6 months) was mean 42.4 points in cases versus 47.9 in controls (P:=0.21). Hypothermic therapy was not a predictor of poor outcome in the multivariate analyses.

CONCLUSIONS

Modest hypothermia can be achieved in awake patients with acute stroke by surface cooling with the "forced air" method, in combination with pethidine to treat shivering. It was not associated with a poor outcome. We suggest a large, randomized clinical trial to test the possible beneficial effect of induced modest hypothermia in unselected patients with stroke.

Nuclear signaling by Rac and Rho GTPases is required in the establishment of epithelial planar polarity in the Drosophila eye

BACKGROUND

The small GTPases Rac and Rho act as cellular switches in many important biological processes. In the fruit fly Drosophila, RhoA participates in the establishment of planar polarity, a process mediated by the receptor Frizzled (Fz). Thus far, analysis of Rac in this process has not been possible because of the absence of mutant Rac alleles. Here, we have investigated the role of Rac and Rho in establishing the polarity of ommatidia in the Drosophila eye.

RESULTS

By expressing a dominant negative or a constitutively activated form of Rac1, we interfered specifically with Rac signaling and disrupted ommatidial polarity. The resulting defects were similar to the loss/gain-of-function phenotypes typical of tissue-polarity genes. Through genetic interaction and rescue experiments involving a polarity-specific, loss-of-function dishevelled (dsh) allele, we found that Rac1 acts downstream of Dsh in the Fz signaling pathway, but upstream of, or in parallel to, RhoA. Rac signaled to the nucleus through the Jun N-terminal kinase (JNK) cascade in this process. By generating point mutations in the effector loop of RhoA, we found that RhoA also signals to the nucleus during the establishment of ommatidial polarity. Nevertheless, Rac and RhoA activated transcription of distinct target genes.

CONCLUSIONS

Rac is specifically required downstream of Dsh in the Fz pathway. It functions upstream or in parallel to RhoA and both signal to the nucleus, through distinct effectors, to establish planar polarity in the Drosophila eye.

Jun mediates Frizzled-induced R3/R4 cell fate distinction and planar polarity determination in the Drosophila eye

Jun acts as a signal-regulated transcription factor in many cellular decisions, ranging from stress response to proliferation control and cell fate induction. Genetic interaction studies have suggested that Jun and JNK signaling are involved in Frizzled (Fz)-mediated planar polarity generation in the Drosophila eye. However, simple loss-of-function analysis of JNK signaling components did not show comparable planar polarity defects. To address the role of Jun and JNK in Fz signaling, we have used a combination of loss- and gain-of-function studies. Like Fz, Jun affects the bias between the R3/R4 photoreceptor pair that is critical for ommatidial polarity establishment. Detailed analysis of jun(−) clones reveals defects in R3 induction and planar polarity determination, whereas gain of Jun function induces the R3 fate and associated polarity phenotypes. We find also that affecting the levels of JNK signaling by either reduction or overexpression leads to planar polarity defects. Similarly, hypomorphic allelic combinations and overexpression of the negative JNK regulator Puckered causes planar polarity eye phenotypes, establishing that JNK acts in planar polarity signaling. The observation that Dl transcription in the early R3/R4 precursor cells is deregulated by Jun or Hep/JNKK activation, reminiscent of the effects seen with Fz overexpression, suggests that Jun is one of the transcription factors that mediates the effects of fz in planar polarity generation.

[Ventrodorsal correction and instrumentation in idiopathic scoliosis]

A number of different procedures are used for the surgical treatment of King II scoliosis. One reason for the controversial discussion in this context is that the term King II scoliosis is usually inadequate, because there are partly marked clinical and radiological differences in this type of curvature. From January 1996 to December 1997, a total of 26 patients with rigid King II scoliosis were submitted to a ventrodorsal procedure. Twenty-three patients were included in the study. The indication for this procedure was established in cases with a secondary lumbar curvature of at least 50 degrees as well as unsatisfactory straightening of the primary and secondary curvature in the bendings and inadequate horizontal positioning of the caudal end vertebra of not less than 10 degrees. Ventral Derotation-Spondylodesis (VDS) and Dorsal correction-Spondylodesis (DKS) led to a thoracic and lumbar straightening from 68.4 degrees to 13.2 degrees and from 61.4 degrees to 17.8 degrees, respectively. The tilt of the vertebra instrumented farthest caudally was corrected from 21.2 degrees to 4.9 degrees. The thoracic hypokyphosis was improved from 16.6 degrees to 25.1 degrees. In 11 patients, the dorsal instrumentation was extended to the caudal end vertebra, in another 11 patients, instrumentation was achieved up to a vertebra cranial from the end vertebra. The correction loss and complication rate was extremely low. Based on the surgical goals discussed further down, combined application of VDS and DKS is efficient and suitable in conjunction with the indication described. The complication rate is quite low. The different types of King II scoliosis have to be differentiated preoperatively.

Minor role of Cl- secretion in non-cystic fibrosis and cystic fibrosis human nasal epithelium

Na+ and Cl- currents were studied in primary cultures of human nasal epithelium derived from non-cystic fibrosis (non-CF) and cystic fibrosis (CF) patients. We found that Na+ absorption dominates transepithelial transport and the Na+ current contains an amiloride-sensitive and amiloride-insensitive component. In non-CF tissue both components contribute about equally to the entire short-circuit current (ISC), whereas in CF tissues the major part of the current is amiloride-sensitive. Na+ removal reduced ISC to values close to zero. Several Cl- channel blockers were used to identify the remaining tiny Na+-independent current. Under unstimulated, physiological conditions in the presence of Cl- on both sides and amiloride on the apical side of the epithelium diphenylamine-2-carboxic acid (DPC), 4,4'-diisothiocyanatostilbene-2, 2'- disulfonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) failed to induce clearcut inhibition of ISC. cAMP as well as ATP did not affect ISC either in CF or in non-CF epithelia. Reduction of apical Cl- increased ISC and depolarized transepithelial potential; however, the observed increase was insensitive to DIDS, DPC and NPPB. From these data we conclude that Cl- conductances in primary cultures of human nasal epithelium derived from CF patients as well as from non-CF patients are present only in low numbers or do not contribute significantly to transepithelial ion transport.

Effects of the 5-HT3 antagonist cilansetron vs placebo on phasic sigmoid colonic motility in healthy man: a double-blind crossover trial

AIMS

5-hydroxytryptamine3 receptor antagonists act antiemetically and slow colonic transit. This study evaluated effects of the high-affinity 5-HT3 antagonist, cilansetron, on fasting, meal-and anticholinesterase-stimulated phasic contractile activity of the human sigmoid colon as well as on bowel habits and stool consistency.

METHODS

Five female and seven male healthy volunteers received, during three 7 day periods separated by 7 day wash-out periods, 4 mg cilansetron, 8 mg cilansetron or placebo three times daily orally under random, double-blind, crossover conditions. On day 8 of each treatment period, motility 20-40 cm from the anal verge was recorded using five pressure sensors spaced at 5 cm intervals. After a basal 30 min, subjects swallowed a further dose of the scheduled treatment; 60 min later, blood was taken for the determination of plasma cilansetron levels. Thereafter, subjects ingested a 4200 kJ meal and 250 ml sweetened mallow tea (166 kJ); 90 min after meal onset, 1 mg neostigmine was administered intramuscularly and motility recording was continued for 60 min

RESULTS

Phasic contractile activity and intraluminal base-line pressure increased postprandially and more so after neostigmine. With cilansetron, the area under the pressure curve as the primary outcome variable and the number of contractions were significantly greater than with placebo (P = 0.005), amplitude and duration of contractions and base-line pressure were not affected. The effects of the two cilansetron dosages did not differ. With cilansetron, stool tended to become firmer. No adverse effects were observed. Plasma levels were highest with 8 mg cilansetron.

CONCLUSIONS

Cilansetron slightly augments meal-stimulated and markedly neostigmine-stimulated phasic motility of the sigmoid colon. When administered over 7 days, it tends to increase stool consistency and is well tolerated.

Changes in the loads on an internal spinal fixator after iliac-crest autograft

Spines are often stabilised posteriorly by internal fixation and anteriorly by a bone graft. The effect of an autologous bone graft from the iliac crest on implant loads is unknown. We used an internal spinal fixation device with telemetry to measure implant loads for several body positions and activities in nine patients before and after anterior interbody fusion. With the body upright, implant loads were often higher after than before fusion using a bone graft. Distraction of the bridged region led to high implant loads in patients with a fractured vertebra and to marked changes in load in those with degenerative instability. Leaving the lower of the bridged intervertebral discs intact led to only small changes in fixator load after anterior interbody fusion. A bone graft alone does not guarantee a reduction of implant loads.

Changes in the loads on an internal spinal fixator after iliac-crest autograft

Spines are often stabilised posteriorly by internal fixation and anteriorly by a bone graft. The effect of an autologous bone graft from the iliac crest on implant loads is unknown. We used an internal spinal fixation device with telemetry to measure implant loads for several body positions and activities in nine patients before and after anterior interbody fusion. With the body upright, implant loads were often higher after than before fusion using a bone graft. Distraction of the bridged region led to high implant loads in patients with a fractured vertebra and to marked changes in load in those with degenerative instability. Leaving the lower of the bridged intervertebral discs intact led to only small changes in fixator load after anterior interbody fusion. A bone graft alone does not guarantee a reduction of implant loads.

Sequence and expression of the kettin gene in Drosophila melanogaster and Caenorhabditis elegans

Kettin is a large modular protein associated with thin filaments in the Z-disc region of insect muscles. The sequence of a 21.3 kb contig of the Drosophila gene has been determined. The corresponding protein sequence has 35 immunoglobulin-like (Ig) domains which are separated by shorter linker sequences, except near the N and C termini of the molecule where linker sequences are short or missing. This confirms a model in which each Ig domain binds to an actin protomer. The Drosophila kettin gene is at 62C 1-3 on the third chromosome. Two P-element insertions, l(3)j1D7 and l(3)rL182 are in the kettin gene, and complementation tests showed that existing l(3)dre8 mutations are in the same gene. The RNA was detected in wild-type Drosophila embryos at stage 11, first in the gut invagination region of the mesoderm, and by stage 13 in both visceral and somatic mesoderm. Somatic mesoderm expression became segmental at stage 13. RNA expression was greatly reduced in embryos of P-element homozygotes but normal in heterozygotes. The structure of the flight muscle in all the heterozygous mutants was normal, including the myofibril-cuticle connections, and they were able to fly. Kettin sequence homologous to the Drosophila protein, was identified in the Caenorhabditis elegans genome database. The RNA was detected in pharyngeal, body wall and anal depressor muscles of larvae and adult worms, as well as in the male gonad. Antibody to insect kettin labelled the pharyngeal, body wall, anal depressor and proximal gonadal muscles in adult worms. Body wall muscles were labelled in an obliquely striated pattern consistent with the Z-disc localisation in insect muscle. The relationship of kettin to D-titin, which has been assigned to the same chromosomal locus in Drosophila, is discussed.

CT and MRI in severe hypophosphataemia with central nervous system involvement

We report a 38-year-old woman with extreme hypophosphataemia in whom CT and MRI disclosed bilateral lesions within the basal ganglia, thalamus and occipital lobes. After adequate substitution of phosphate the lesions grossly resolved and the patient recovered. This case is the first to demonstrate that profound changes of serum phosphate may be associated with reversible brain lesions.

[Drug adverse effects in the elderly hospitalized with acute pathologies]

OBJECTIVES

Data of Literature suggest that age is not an independent risk factor for adverse drug reactions (ADR), while there is evidence of a positive correlation between ADR and the number of drug taken. To investigate if that is true, we have examined the occurrence of ADR in elderly patients admitted to our Geriatric Department in the first nine months of 1999 for acute illness.

MATERIALS AND METHODS

We have evaluated the occurrence of ADR in 510 patients more than 65 years of age (80 +/- 7.35 years). The adverse drug effect was worth considering when symptomatical or caused a change in the management of the patient (suspension or change of therapy, prolongation of staying in hospital). We used the algorithm of Naranjo (19) to estimate the probability that a drug caused an ADR.

RESULTS AND CONCLUSIONS

In our study the frequency of ADR was 12.5%. Furosemide was responsible for 50% and digoxin for 8% of ADR. Among the patients taking furosemide, 12.5% had an ADR (generally low potassium). The frequency of ADR was correlated neither with the age of the subjects nor with the number of drug taken. It can be possible that the main cause of ADR is the type of drugs assumed by elderly.

Sec61beta, a subunit of the protein translocation channel, is required during Drosophila development

We have identified and isolated mutations in the first Drosophila gene encoding a subunit of the Sec61 protein translocation channel, DSec61beta. While neither the Saccharomyces cerevisiae Sec61beta nor its functional Escherichia coli homologue are essential for viability or for protein translocation, we show that DSec61beta is essential for embryonic development. Homozygous mutant embryos die at the end of embryogenesis and are impaired in the secretion of cuticle proteins from the epidermis. DSec61beta germ line clones, result in defects in dorso-ventral patterning of the egg and are consistent with affected secretion of the protein Gurken from the oocyte to the follicle cells. Clonal analyses in the imaginal discs reveal defects in adult structures, including rhabdomere morphogenesis and a reduction of the size of tarsal segments in the leg. This is the first in vivo study of a component of the protein translocation machinery in higher eukaryotes, and illustrates how a protein that has an inessential, kinetic function in single-cell organisms can become critical for the complex development of a multicellular organism.

Design and construction of a ripple filter for a smoothed depth dose distribution in conformal particle therapy

The ripple filter was designed to broaden the Bragg maximum of carbon beams for the raster-scan technique, a special type of tumour-conformal ion beam treatment. In this technique the target volume is divided into individual layers that are treated sequentially by varying the energy from the accelerator stepwise. Because the unmodified Bragg maximum has a small half-width, below 1 mm for small energies (< 160 MeV u(-1)), homogeneous irradiation at small penetration depths of 2-6 cm can only be obtained by using a large number of energy steps. If the energy step is too large, ripples are produced in the superimposed depth dose distribution. The ripple filter widens a Bragg peak to a Gaussian peak with a half-width of more than 2 mm. This helps to smooth the extended Bragg peak and to reduce the number of energy steps required by a factor of two to three, leading to significantly shorter overall irradiation times and a higher particle fluence per layer. The ripple filter consists of a 2 mm thick Plexiglass (PMMA) plate with a periodic structure of fine grooves. It can be mounted 60 cm upstream of the patient as a stationary device, because the fine structure of the grooves is completely washed out by the lateral scattering of the beam.