Response of diamond detectors in ultra-high dose-per-pulse electron beams for dosimetry at FLASH radiotherapy.

Objective.With increasing investigation of the so-called FLASH effect, the need for accurate real time dosimetry for ultra-high dose rates is also growing. Considering the ultra-high dose-per-pulse (DPP) necessary to produce the ultra-high dose rates for investigations of the FLASH effect, real time dosimetry is a major challenge. In particular, vented ionization chambers, as used for dosimetry in conventional radiotherapy, show significant deviations from linearity with increasing DPP. This is due to recombination losses in the sensitive air volume. Solid state detectors could be an alternative. Due to their good stability of the response with regard to the accumulated dose, diamond detectors such as the microDiamond could be suitable here. The aims of this work are to investigate the response of microDiamond and adapted microDiamond prototypes in ultra-high DPP electron beams, to understand the underlying effects and to draw conclusions for further detector developments.Approach.For the study, an electron beam with a DPP up to 6.5 Gy and a pulse duration of 2.5µs was used to fulfill the conditions under which the FLASH effect was observed. As a dose rate-independent reference, alanine dosimeters were used.Main Results.It has been shown that the commercially available microDiamond detectors have limitations in terms of linearity at ultra-high DPP. But this is not an intrinsic limitation of the detector principle. The deviations from linearity were correlated with the series resistance and the sensitivity. It could be shown that the linear range can be extended towards ultra-high DPP range by reducing the sensitivity in combination with a low series resistance of the detectors.Significance.The work shows that synthetic single crystal diamond detectors working as Schottky photodiodes are in principle suitable for FLASH-RT dosimetry at electron linear accelerators.

[Periodic fever and pancytopenia in a 35-year-old patient]. / Periodisches Fieber und Panzytopenie bei einem 35­jährigen Patienten.

MEDICAL HISTORY AND INITIAL PRESENTATION: A 35-year-old patient with a previous history of persistent episodic fever, sore throat, myalgia, and cephalgia presented for evaluation of pancytopenia. He had no recent travel history, except for a stay in Italy 1 year prior to admission and in Spain several years in the past. DIAGNOSTIC WORKUP: Laboratory evaluation confirmed pancytopenia, agranulocytosis, and elevated infection parameters without indicative serological results en par with lymphadenitis colli. Computed tomography scanning revealed cervical lymphadenopathy, hepatosplenomegaly, and colitis with occult perforation of the sigmoid colon. Bone marrow biopsy showed an infiltration of polyclonal plasma cells. Lymph node biopsy was compatible with necrotizing lymphadenitis. DIAGNOSIS: Polymerase chain reaction analysis of a lymph node specimen confirmed the presence of Leishmania species, thereby enabling the diagnosis of visceral Leishmania. THERAPY COURSE: Treatment with liposomal amphotericin B was initiated. Both fever and lymphadenopathy quickly resolved. CONCLUSION: VL is a clinically pleiotropic, severe disease with fatal outcome if left untreated. It often presents with distinct similarities to hematologic malignancies. Exacerbation can occasionally occur as fulminant macrophage activation syndrome. Disease incidence is globally increasing and has not peaked as yet. A complex interplay between pathogen and the immune system is the key pathophysiological mechanism.

Response of the alanine/ESR dosimeter to radiation from an Ir-192 HDR brachytherapy source.

The response of the alanine dosimeter to radiation from an Ir-192 source with respect to the absorbed dose to water, relative to Co-60 radiation, was determined experimentally as well as by Monte Carlo simulations. The experimental and Monte Carlo results for the response agree well within the limits of uncertainty. The relative response decreases with an increasing distance between the measurement volume and the source from approximately 98% at a 1 cm distance to 96% at 5 cm. The present data are more accurate, but agree well with data published by Schaeken et al (2011 Phys. Med. Biol. 56 6625-34). The decrease of the relative response with an increasing distance that had already been observed by these authors is confirmed. In the appendix, the properties of the alanine dosimeter with respect to volume and sensitivity corrections are investigated. The inhomogeneous distribution of the detection probability that was taken into account for the analysis was determined experimentally.

[Prevalence of carbapenemase-producing bacteria in hospitals in Saxony, Germany]. / Prävalenzerhebung zum Vorkommen von Carbapenemase-Bildnern in sächsischen Kliniken.

The presence of pathogenic bacteria with acquired carbapenem resistance constitutes an increasing problem for infection control and infectious disease management. Prompted by an outbreak of infections with Klebsiella pneumoniae producing the carbapenemase KPC-2 at a hospital in Saxony, the Saxon State Ministry of Social Affairs and Consumer Protection (SMS) initiated a point-prevalence survey for carbapenemase-producing gram-negative bacteria. Wards at 53 hospitals in Saxony, mainly intensive care units, were investigated between October 2012 and February 2013. Stool samples and rectal swabs of 1,037 patients were analyzed for the presence of bacteria with resistance against four major groups of antibiotics (4MRGN). Carbapenemase producers were detected in 3 patients [0.3% CI95 (0.0596; 0.843)] and carbapenem-resistant bacteria without carbapenemases were detected in 9 patients [0.9% CI95 (0.397; 1.64)]. Furthermore, antimicrobial susceptibility testing revealed 166 patients [16.0% CI95 (13.82; 18.38)] with extended-spectrum beta-lactamase (ESBL)-producing bacteria. At the time of investigation, K. pneumoniae producing the carbapenemase KPC-2 was diagnosed in 2 patients at one hospital. Moreover, it is necessary to remain vigilant towards other types of carbapenemase producers, as demonstrated by the finding of a Pseudomonas aeruginosa strain harbouring the carbapenemase VIM-1 in another hospital.

[Aortoduodenal fistula as a cause of gastrointestinal bleeding--difficulties in endoscopic diagnosis]. / Aortoduodenale Fistel als Ursache der gastrointestinalen Blutung - eine endoskopisch schwierige Differenzialdiagnose.

We report on three patients with severe gastrointestinal bleeding arising from aortoenteric fistula. Two patients presented with a secondary aortoduodenal fistula. In the first case bleeding occurred 8 months after aortobifemoral graft implantation. In the second patient aortobiliacal graft implantation was performed 22 years before. In the third case the aortoenteric fistula was primary and was caused by an abdominal aortic aneurysm without prior vascular intervention. In the first case diagnosis was made by urgent endoscopy visualizing ongoing bleeding from the duodenal fistula. In the two other patients urgent endoscopy and CT as well could not demonstrate the bleeding source. Aortoenteric fistula was diagnosed endoscopically during severe rebleeding some hours later. Two patients underwent surgery with implantation of an axillobifemoral bypass; the third patient declined further intervention and died. The course shows that aortoduodenal fistula can present with severe but intermittent gastrointestinal bleeding making the diagnosis in the non-bleeding interval difficult. In patients with severe gastrointestinal bleeding and a history of aortic disease (aneurysm, prior aortic graft repair or stenting) an aortoduodenal fistula should be suspected and the indication for surgical intervention should be considered early in spite of negative results of endoscopy and CT.

[Unenhanced spiral computerized tomography in acute diagnosis of flank pain. Examination in contraindications for contrast medium administration]. / Native Spiral-Computertomographie in der Akutdiagnostik von Flankenschmerzen. Untersuchung bei Kontraindikationen zur Kontrastmittelgabe.

The diagnostic value of unenhanced helical computed tomography was investigated in a prospective study. In 53 patients (aged 35 to 82 years) with acute flank pain tomography was performed in addition to abdominal plain film and ultrasound examination. All 53 patients had a contraindication for intravenous administration of contrast medium. Ureteral calculi were either confirmed or excluded by retrograde ureteropyelography in 44 cases, in 9 patients by asservation of calculi and clinical follow-up. Helical computed tomography was able to precisely identify all of the 34 ureteral calculi, whereas abdominal plain films led to 6 false positive and 17 false negative findings. In 1 patient with retroperitoneal lymphoma (diagnosed by CT) false positive findings occurred. Unenhanced helical computed tomography reaches a distinctively increased diagnostic value (sensitivity 100%, specificity 95%, accuracy 97%) in the evaluation of acute flank pain as compared to conventional radiologic imaging and ultrasound. This non-invasive procedure is to be considered method of choice for patients with contraindications for the application of radiopaque material.

Unenhanced helical computed tomography in the evaluation of acute flank pain.

OBJECTIVE: The diagnostic value of unenhanced helical computed tomography (CT) for the evaluation of acute flank pain is investigated in a prospective study. PATIENTS AND METHODS: In 125 patients aged 18-86 years, we performed unenhanced helical CT in addition to abdominal plain film, abdominal ultrasound and urinalysis as a diagnostic measure for acute flank pain. Ureteral calculi were confirmed or, respectively, excluded by retrograde ureteropyelography in 80 cases. In the other cases, diagnosis was verified by clinical course and/or stone asservation. RESULTS: In 91 of 125 patients the flank pain was caused by a ureteral calculus. In 67 of 91 patients with urolithiasis, stones could be collected for analysis. Helical CT was able to precisely identify 90 ureteral calculi. Abdominal plain films led to 8 false-positive and 48 false-negative findings. Thus, sensitivity of plain radiography, ultrasound and urinalysis was 47, 11 and 84% with a specificity 76, 97 and 32%, respectively. CONCLUSIONS: Unenhanced helical CT reaches a distinctively increased diagnostic value (sensitivity 99%, specificity 97%) in the evaluation of acute flank pain as compared to plain radiography, ultrasound and urinalysis.

Gas formation after renal artery embolisation: genesis and clinical relevance.

Preoperative embolisation of renal carcinomas has several pros and cons for the patient. The negative aspects can be summarized as 'post-infarction' syndrome'. Radiologically, intrarenal gas formation is always evident. As sterile breakdown products of tumor cell necrosis these have to be interpreted as regular postinterventional findings and not as indicators for infection or even sepsis. Tumor embolisation as a means to reduce surgical difficulties in large hypervascularized renal carcinomas and also as a palliative measure in marked macrohematuria and/or tumor-induced flank pain is thus very conceivable. The best time for the tumor-nephrectomy is the day of embolisation or the first postinterventional day. This makes the nephrectomy easier and prevents the postinfarction syndrome for the patient.