Leaf transmission reduction using moving jaws for dynamic MLC IMRT

The aim of this work is to investigate to what extent it is possible to use the secondary collimator jaws to reduce the transmitted radiation through the multileaf collimator (MLC) during an intensity modulated radiation therapy (IMRT). A method is developed and introduced where the jaws follow the open window of the MLC dynamically (dJAW method). With the aid of three academic cases (Closed MLC, Sliding-gap, and Chair) and two clinical cases (prostate and head and neck) the feasibility of the dJAW method and the influence of this method on the applied dose distributions are investigated. For this purpose the treatment planning system Eclipse and the Research-Toolbox were used as well as measurements within a solid water phantom were performed. The transmitted radiation through the closed MLC leads to an inhomogeneous dose distribution. In this case, the measured dose within a plane perpendicular to the central axis differs up to 40% (referring to the maximum dose within this plane) for 6 and 15 MV. The calculated dose with Eclipse is clearly more homogeneous. For the Sliding-gap case this difference is still up to 9%. Among other things, these differences depend on the depth of the measurement within the solid water phantom and on the application method. In the Chair case, the dose in regions where no dose is desired is locally reduced by up to 50% using the dJAW method instead of the conventional method. The dose inside the chair-shaped region decreased up to 4% if the same number of monitor units (MU) as for the conventional method was applied. The undesired dose in the volume body minus the planning target volume in the clinical cases prostate and head and neck decreased up to 1.8% and 1.5%, while the number of the applied MU increased up to 3.1% and 2.8%, respectively. The new dJAW method has the potential to enhance the optimization of the conventional IMRT to a further step.

Comparative dose measurements by spiral tomography for preimplant diagnosis: the Scanora machine versus the Cranex Tome radiography unit

Objective. The purpose of this study was to determine the dose profile of the Cranex Tome radiography unit and compare it with that of the Scanora machine.Study design. The radiation dose delivered by the Cranex Tome radiography unit during the cross-sectional mode was determined. Single tooth gaps in regions 3 (16) and 30 (46) were simulated. Dosimetry was carried out with 2 phantoms, a head and neck phantom and a full-body phantom loaded with 142 thermoluminescent dosimeters (TLD) and 280 TLD, respectively; all locations corresponded to radiosensitive organs or tissues. The recorded local mean organ doses were compared with those measured in another study evaluating the Scanora machine.Results. Generally, dose values from the Cranex Tome radiography unit reached only 50% to 60% of the values measured for the Scanora machine. The effective dose was calculated as 0.061 mSv and 0.04 mSv for tooth regions 3 (16) and 30 (46), respectively. Corresponding values for the Scanora machine were 0.117 mSv and 0.084 mSv.Conclusion. Cross-sectional imaging in the molar region of the upper and the lower jaw can be performed with the Cranex Tome unit, which delivers only approximately half of the dose that the Scanora machine delivers.

An integral conservative gridding--algorithm using Hermitian curve interpolation

The problem of re-sampling spatially distributed data organized into regular or irregular grids to finer or coarser resolution is a common task in data processing. This procedure is known as 'gridding' or 're-binning'. Depending on the quantity the data represents, the gridding-algorithm has to meet different requirements. For example, histogrammed physical quantities such as mass or energy have to be re-binned in order to conserve the overall integral. Moreover, if the quantity is positive definite, negative sampling values should be avoided. The gridding process requires a re-distribution of the original data set to a user-requested grid according to a distribution function. The distribution function can be determined on the basis of the given data by interpolation methods. In general, accurate interpolation with respect to multiple boundary conditions of heavily fluctuating data requires polynomial interpolation functions of second or even higher order. However, this may result in unrealistic deviations (overshoots or undershoots) of the interpolation function from the data. Accordingly, the re-sampled data may overestimate or underestimate the given data by a significant amount. The gridding-algorithm presented in this work was developed in order to overcome these problems. Instead of a straightforward interpolation of the given data using high-order polynomials, a parametrized Hermitian interpolation curve was used to approximate the integrated data set. A single parameter is determined by which the user can control the behavior of the interpolation function, i.e. the amount of overshoot and undershoot. Furthermore, it is shown how the algorithm can be extended to multidimensional grids. The algorithm was compared to commonly used gridding-algorithms using linear and cubic interpolation functions. It is shown that such interpolation functions may overestimate or underestimate the source data by about 10-20%, while the new algorithm can be tuned to significantly reduce these interpolation errors. The accuracy of the new algorithm was tested on a series of x-ray CT-images (head and neck, lung, pelvis). The new algorithm significantly improves the accuracy of the sampled images in terms of the mean square error and a quality index introduced by Wang and Bovik (2002 IEEE Signal Process. Lett. 9 81-4).

Extraosseous langerhans cell histiocytosis in children

Langerhans cell histiocytosis, a rare disease that occurs mainly in children, may produce a broad range of manifestations, from a single osseous lesion to multiple lesions involving more than one organ or system. The clinical course varies widely in relation to the patient's age. Multisystem disease may demonstrate especially aggressive behavior in very young children, with the outcome depending largely on the stage of disease and the degree of related organ dysfunction at the time of diagnosis. Extraosseous manifestations are less commonly seen than osseous ones and may be more difficult to identify. To accurately detect extraosseous Langerhans cell histiocytosis at an early stage, radiologists must recognize the significance of individual clinical and laboratory findings as well as the relevance of imaging features for the differential diagnosis. The pattern and severity of pulmonary, thymic, hepatobiliary, splenic, gastrointestinal, neurologic, mucocutaneous, soft-tissue (head and neck), and salivary involvement in Langerhans cell histiocytosis generally are well depicted with conventional radiography, ultrasonography, computed tomography, and magnetic resonance imaging. However, the imaging features are not pathognomonic, and a biopsy usually is necessary to establish a definitive diagnosis.

[Treatment of lymphangiomas with picibanil in the first year of life]

BACKGROUND: The therapeutic gold standard of cystic hygroma is its complete resection. Because of its growth pattern and its main location in the head and neck region complete resection is not always possible. An alternative is the local injection of Picibanil, but only few cases have been published about its use in infants. PATIENTS/METHOD: We retrospectively analyzed the data of 8 infants (age: 2 weeks-12 months) who got Picibanil therapy because of cystic hygroma in the time period 2002 until 2006. Follow up ranged from 3 months up to 3 years. RESULTS: During the postoperative period all patients had local swelling, in 4 cases accompanied with local inflammation and fever. Tumor reduction of >50% was obtained in 7 of 8 patients. CONCLUSIONS: Local injection of Picibanil in infants with cystic hygroma seems to be a safe alternative to surgical therapy, especially when complete tumor resection means damage of important neighbouring structures. Prospective trials are necessary to confirm the better outcome after therapy with Picibanil compare to primary surgery.

Role of the extraosseus blood supply in osteoarthritic femoral heads

Blood perfusion to the femoral head might be endangered during the surgical approach or the preparation of the femoral head or both in hip resurfacing arthroplasty. The contribution of the intramedullary blood supply to the femoral head in osteoarthritis is questionable. Therefore, the contribution of the extraosseous blood supply to osteoarthritic femoral heads was measured intraoperatively to question if there is measurable blood flow between the epiphysis and metaphysis in osteoarthritic hips in case of extraosseus vessel damage. At defined points during surgery we acquired the epiphyseal and metaphyseal femoral head perfusion by high-energy laser Doppler flowmetry. Complete femoral neck osteotomy sparing the retinacular vessels to simulate intraosseous blood disruption showed unchanged epiphyseal blood flow compared to initial measurement after capsulotomy. The pulsatile signal disappeared after transection of the retinacular vessels. Based on these acute measurements, we conclude intramedullary blood vessels to the femoral head do not provide measurable blood supply to the epiphysis once the medial femoral circumflex artery or the retinacular vessels have been damaged. We recommend the use of a safe surgical approach for hip resurfacing and careful implantation of the femoral component to respect blood supply to the femoral head and neck region in hip resurfacing arthroplasty.

Primary cutaneous CD4+ small-/medium-sized pleomorphic T-cell lymphoma: a cutaneous nodular proliferation of pleomorphic T lymphocytes of undetermined significance? A study of 136 cases

Patients with skin nodules characterized by the infiltrate of pleomorphic small/medium T lymphocytes are currently classified as "primary cutaneous CD4+ small-/medium-sized pleomorphic T-cell lymphoma" (SMPTCL) or as T-cell pseudolymphoma. The distinction is often arbitrary, and patients with similar clinicopathologic features have been included in both groups. We studied 136 patients (male:female = 1:1; median age: 53 years, age range: 3-90 years) with cutaneous lesions that could be classified as small-/medium-sized pleomorphic T-cell lymphoma according to current diagnostic criteria. All but 3 patients presented with solitary nodules located mostly on the head and neck area (75%). Histopathologic features were characterized by nonepidermotropic, nodular, or diffuse infiltrates of small- to medium-sized pleomorphic T lymphocytes. A monoclonal rearrangement of the T-cell receptor-gamma gene was found in 60% of tested cases. Follow-up data available for 45 patients revealed that 41 of them were alive without lymphoma after a median time of 63 months (range: 1-357 months), whereas 4 were alive with cutaneous disease (range: 2-16 months). The incongruity between the indolent clinical course and the worrying histopathologic and molecular features poses difficulties in classifying these cases unambiguously as benign or malignant, and it may be better to refer to them with a descriptive term such as "cutaneous nodular proliferation of pleomorphic T lymphocytes of undetermined significance," rather than forcing them into one or the other category. On the other hand, irrespective of the name given to these equivocal cutaneous lymphoid proliferations, published data support a nonaggressive therapeutic strategy, particularly for patients presenting with solitary lesions.

Major bleeding of the upper aerodigestive tract due to oral anticoagulant/antibiotic interactions

INTRODUCTION Although a well-known complication in certain medical specialties, major bleeding due to the interaction between oral anticoagulants and antibiotics has been rarely reported concerning the upper aerodigestive tract. We report three cases of life-threatening bleeding of the upper aerodigestive tract in a context of antibiotic therapy in patients treated with oral anticoagulants. CASE SERIES Three male patients under coumadin anticoagulation therapy presented major bleeding in three different contexts (epistaxis, peritonsillar abscess and postoperative course after total laryngectomy). Surgical intervention for hemostasis was required in all cases, with coagulation correction in two. Complications were severe anemia (2/3) and chronic heart failure (1/3). DISCUSSION/CONCLUSIONS Interactions between two drugs commonly used in otolaryngology can result in major bleeding. The goal of this article is to raise practitioners' awareness of a potentially fatal, although rare, complication. We also review the main preventive strategies.

Assessment of Collimator Jaw Optimization in Reducing Normal Tissue Irradiation with Intensity Modulated Radiation Therapy

Purpose: To evaluate normal tissue dose reduction in step-and-shoot intensity-modulated radiation therapy (IMRT) on the Varian 2100 platform by tracking the multileaf collimator (MLC) apertures with the accelerator jaws. Methods: Clinical radiation treatment plans for 10 thoracic, 3 pediatric and 3 head and neck patients were converted to plans with the jaws tracking each segment’s MLC apertures. Each segment was then renormalized to account for the change in collimator scatter to obtain target coverage within 1% of that in the original plan. The new plans were compared to the original plans in a commercial radiation treatment planning system (TPS). Reduction in normal tissue dose was evaluated in the new plan by using the parameters V5, V10, and V20 in the cumulative dose-volume histogram for the following structures: total lung minus GTV (gross target volume), heart, esophagus, spinal cord, liver, parotids, and brainstem. In order to validate the accuracy of our beam model, MLC transmission measurements were made and compared to those predicted by the TPS. Results: The greatest change between the original plan and new plan occurred at lower dose levels. The reduction in V20 was never more than 6.3% and was typically less than 1% for all patients. The reduction in V5 was 16.7% maximum and was typically less than 3% for all patients. The variation in normal tissue dose reduction was not predictable, and we found no clear parameters that indicated which patients would benefit most from jaw tracking. Our TPS model of MLC transmission agreed with measurements with absolute transmission differences of less than 0.1 % and thus uncertainties in the model did not contribute significantly to the uncertainty in the dose determination. Conclusion: The amount of dose reduction achieved by collimating the jaws around each MLC aperture in step-and-shoot IMRT does not appear to be clinically significant.

DUAL ENERGY COMPUTED TOMOGRAPHY FOR PROTON THERAPY TREATMENT PLANNING

Proton radiation therapy is gaining popularity because of the unique characteristics of its dose distribution, e.g., high dose-gradient at the distal end of the percentage-depth-dose curve (known as the Bragg peak). The high dose-gradient offers the possibility of delivering high dose to the target while still sparing critical organs distal to the target. However, the high dose-gradient is a double-edged sword: a small shift of the highly conformal high-dose area can cause the target to be substantially under-dosed or the critical organs to be substantially over-dosed. Because of that, large margins are required in treatment planning to ensure adequate dose coverage of the target, which prevents us from realizing the full potential of proton beams. Therefore, it is critical to reduce uncertainties in the proton radiation therapy. One major uncertainty in a proton treatment is the range uncertainty related to the estimation of proton stopping power ratio (SPR) distribution inside a patient. The SPR distribution inside a patient is required to account for tissue heterogeneities when calculating dose distribution inside the patient. In current clinical practice, the SPR distribution inside a patient is estimated from the patient’s treatment planning computed tomography (CT) images based on the CT number-to-SPR calibration curve. The SPR derived from a single CT number carries large uncertainties in the presence of human tissue composition variations, which is the major drawback of the current SPR estimation method. We propose to solve this problem by using dual energy CT (DECT) and hypothesize that the range uncertainty can be reduced by a factor of two from currently used value of 3.5%. A MATLAB program was developed to calculate the electron density ratio (EDR) and effective atomic number (EAN) from two CT measurements of the same object. An empirical relationship was discovered between mean excitation energies and EANs existing in human body tissues. With the MATLAB program and the empirical relationship, a DECT-based method was successfully developed to derive SPRs for human body tissues (the DECT method). The DECT method is more robust against the uncertainties in human tissues compositions than the current single-CT-based method, because the DECT method incorporated both density and elemental composition information in the SPR estimation. Furthermore, we studied practical limitations of the DECT method. We found that the accuracy of the DECT method using conventional kV-kV x-ray pair is susceptible to CT number variations, which compromises the theoretical advantage of the DECT method. Our solution to this problem is to use a different x-ray pair for the DECT. The accuracy of the DECT method using different combinations of x-ray energies, i.e., the kV-kV, kV-MV and MV-MV pair, was compared using the measured imaging uncertainties for each case. The kV-MV DECT was found to be the most robust against CT number variations. In addition, we studied how uncertainties propagate through the DECT calculation, and found general principles of selecting x-ray pairs for the DECT method to minimize its sensitivity to CT number variations. The uncertainties in SPRs estimated using the kV-MV DECT were analyzed further and compared to those using the stoichiometric method. The uncertainties in SPR estimation can be divided into five categories according to their origins: the inherent uncertainty, the DECT modeling uncertainty, the CT imaging uncertainty, the uncertainty in the mean excitation energy, and SPR variation with proton energy. Additionally, human body tissues were divided into three tissue groups – low density (lung) tissues, soft tissues and bone tissues. The uncertainties were estimated separately because their uncertainties were different under each condition. An estimate of the composite range uncertainty (2s) was determined for three tumor sites – prostate, lung, and head-and-neck, by combining the uncertainty estimates of all three tissue groups, weighted by their proportions along typical beam path for each treatment site. In conclusion, the DECT method holds theoretical advantages in estimating SPRs for human tissues over the current single-CT-based method. Using existing imaging techniques, the kV-MV DECT approach was capable of reducing the range uncertainty from the currently used value of 3.5% to 1.9%-2.3%, but it is short to reach our original goal of reducing the range uncertainty by a factor of two. The dominant source of uncertainties in the kV-MV DECT was the uncertainties in CT imaging, especially in MV CT imaging. Further reduction in beam hardening effect, the impact of scatter, out-of-field object etc. would reduce the Hounsfeld Unit variations in CT imaging. The kV-MV DECT still has the potential to reduce the range uncertainty further.

Radiolabeled human monoclonal IgM for intracompartmental cancer therapy

Radioimmunotherapy (RIT) with i.v. administered radiolabeled IgG can selectively irradiate tumor cells in vivo. However, it only provides effective therapy for lymphomas. Intracompartmental RIT with radiolabeled human monoclonal IgM may allow curative treatment of solid tumors by increasing tumor deposition of radioactivity, reducing systemic toxicity and allowing repeated administration. This hypothesis was tested in nude mouse models with IgM radiolabeled with indium-111 $\rm(\sp{111}In)$ or yttrium-90 $\rm(\sp{90}Y).$ The use of two radioisotopes, $\rm\sp{111}In$ for imaging and $\rm\sp{90}Y$ for therapy, allow for more quantitative and cautious development of RIT.^ Radiolabled 2B12, an IgM reactive with human ovarian carcinomas was tested by i.v. and intraperitoneal (i.p.) administration in nude mice bearing i.p. nodules of a human ovarian carcinoma cell line (SKOV3 NMP2). Radiolabeled CR4E8, an IgM reactive with human squamous cell carcinomas was tested by i.v. and intralesional (i.l.) administration in nude mice bearing subcutaneous tumors of a human head and neck squamous cell carcinoma cell line (886). These two models were selected to test proof of concept. Radiolabeled irrelevant IgM (CH-1B9), and $\rm\sp{90}Y$-aggregate served as specificity controls. Biodistribution was performed by excising, weighing and then measuring the radioactivity of tumor and normal organs. Therapy was conducted with i.p. $\rm\sp{90}Y$-labeled 2B12 using both single and fractionated administration and with i.l. $\rm\sp{90}Y$-labeled CR4E8 using single administration. Mice were monitored for tumor response, survival and systemic toxicity.^ Intracompartmental administration of radiolabeled IgM produced immediate high and prolonged tumor deposition of radioactivity with low normal tissue uptake. In contrast, i.v. administration resulted in low tumor, but high liver and spleen uptake. Similar biodistributions were demonstrated for $\rm\sp{111}In$- and $\rm\sp{90}Y$-labeled IgM. Intraperitoneal therapy with $\rm\sp{90}Y$-labeled 2B12 increased survival by approximately 12 days for every 100 $\rm\mu Ci$ of activity without significant toxicity for single (0-300 $\rm\mu Ci)$ and fractionated (150-510 $\rm\mu Ci)$ administration. Intralesional therapy with $\rm\sp{90}Y$-labeled CR4E8 (150-400 $\rm\mu Ci)$ induced prolonged complete regressions. Significant local or systemic toxicity was not observed.^ Intracompartmental RIT with radiolabeled tumor-reactive human monoclonal IgM can selectively irradiate tumor cells. Intracompartmental radiolabled IgM can significantly extend the survival of treated mice with minimal toxicity. It deserves further development as a new cancer therapy. ^

Riding the Escalator: How Dangerous is it Really?

INTRODUCTION About 10,000 escalator-related injuries per year result in emergency department treatment in the United States. Since the 1990s, a steady increase has been reported, but few statistics on escalator-related injuries have been published worldwide. We have therefore analyzed escalator accident statistics in admissions to our hospital in Switzerland since 2000. METHODS Using retrospective electronic patient chart analysis, we included in our study patients >16 years treated over an 11-year period. We categorized patients in terms of gender, age and associated risk factors, and classified accidents according to day, time, location and cause. Resulting trauma was categorized according to type and location. We divided post-admission treatment into surgical and conservative, and into treatment as an outpatient, in a short-stay unit, or as a hospital admission. Women and men were compared using Fisher's exact test. RESULTS We identified 173 patients with 285 discrete injuries. Of these, 87 patients (50%) were women. Fifty-three (61%) of the women and 38 (44%) of the men were >60 years old (P = 0.033). Fifty percent of the men (43/86) of the men, but only 7% (6/87) of the women showed signs of alcohol intoxication (P < 0.0001). Accidents in women occurred predominantly on Tuesdays (19/87; 22%) between 12pm and 6pm (35/87; 40%), and in men on Saturdays (16/86; 19%) between 6pm and 12am (29/86; 34%; P = 0.0097). Sixty-two percent (44/71) of the accidents were in public transport facilities and 30% (21/71) in shopping centers. The majority of injuries in women were to the lower extremities (49/87; 56%), while most accidents in men were to the head and neck (51/86; 59%; P = 0.0052). About half (90; 52%) of the patients were treated conservatively. Almost half of all patients (76, 44%) required hospital admission. Of those, 45% left the hospital within 24 hours of admission (short stay unit) and 55% stayed longer than 24 hours. CONCLUSION Escalator accidents can result in severe trauma. Significant gender differences in escalator accidents have been observed. Alcohol intoxication and age are significant risk factors in escalator-related accidents and might be possible targets for preventive measures.

Essentials of forensic post-mortem MR imaging in adults

Post-mortem MR (PMMR) imaging is a powerful diagnostic tool with a wide scope in forensic radiology. In the past 20 years, PMMR has been used as both an adjunct and an alternative to autopsy. The role of PMMR in forensic death investigations largely depends on the rules and habits of local jurisdictions, availability of experts, financial resources, and individual case circumstances. PMMR images are affected by post-mortem changes, including position-dependent sedimentation, variable body temperature and decomposition. Investigators must be familiar with the appearance of normal findings on PMMR to distinguish them from disease or injury. Coronal whole-body images provide a comprehensive overview. Notably, short tau inversion–recovery (STIR) images enable investigators to screen for pathological fluid accumulation, to which we refer as “forensic sentinel sign”. If scan time is short, subsequent PMMR imaging may be focussed on regions with a positive forensic sentinel sign. PMMR offers excellent anatomical detail and is especially useful to visualize pathologies of the brain, heart, subcutaneous fat tissue and abdominal organs. PMMR may also be used to document skeletal injury. Cardiovascular imaging is a core area of PMMR imaging and growing evidence indicates that PMMR is able to detect ischaemic injury at an earlier stage than traditional autopsy and routine histology. The aim of this review is to present an overview of normal findings on forensic PMMR, provide general advice on the application of PMMR and summarise the current literature on PMMR imaging of the head and neck, cardiovascular system, abdomen and musculoskeletal system.