ABSTRACT
PURPOSE: This study analyzes clinical consequences and dosimetric variations after imperfect brachytherapy insertions. It examines treatment decisions after such insertions in patients having difficult anatomy, which leads to good subsequent insertions with acceptable dose volume parameters. MATERIAL AND METHODS: We reviewed images of all insertions performed during last one year and sorted faulty ones out. Clinical outcome was assessed, analyzing original treatment records. Repeat three-dimensional planning using identical dose-optimization-technique compared their dosimetry. Statistical analysis using SPSS®-Statistics-software included Fisher's-exact-test to analyze predisposing factors for faulty insertions and predictive factors for subsequent satisfactory insertion. Friedman test was used to compare dose-volume-effects of normalization. RESULTS: Eighteen of 292 brachytherapy plans revealed imperfect insertions, including thirteen perforations (4.5%). Lack of pre-planning, obstructing mass, narrow vagina, acute anteversion of uterus, and multi-parity were significant (p ≤ 0.05) predisposing factors for atypical insertions. Satisfactory optimization was possible after correcting acute anteflexion or positioning tandem in retroverted direction in uncorrectable retroverted uterus. Dose normalization at point A shifted optimized dose from contoured volume to point of normalization, often undesirably. This difference, however, was statistically not significant (p = 0.121). In patients having obstructing mass, subsequent insertions were perfect, and dose volume parameters were acceptable only when full prescribed dose was delivered to at least 60% volume of the mass after a faulty insertion (p < 0.001). CONCLUSIONS: Pre-planning by imaging is suggested in all cases of brachytherapy. Insertion of adequate length of tandem aligned to uterine axis is warranted for adequate tumor coverage. Whenever detected, acute anteflexion and mobile retroversion should be corrected. Tandem inserted in retroverted direction in uncorrectable retroverted uterus generates acceptable dose volume parameters. In cases with obstructive cervical mass, good subsequent insertion is possible with acceptable dose volume parameters, if planned dose can be delivered to its 60% volume.
ABSTRACT
PURPOSE: This study is intended to compare dose-volume parameters evaluated using different forward planning- optimization techniques, involving two applicator systems in intracavitary brachytherapy for cervical cancer. It looks for the best applicator-optimization combination to fulfill recommended dose-volume objectives in different high-dose-rate (HDR) fractionation schedules. MATERIAL AND METHODS: We used tandem-ring and Fletcher-style tandem-ovoid applicator in same patients in two fractions of brachytherapy. Six plans were generated for each patient utilizing 3 forward optimization techniques for each applicator used: equal dwell weight/times ('no optimization'), 'manual dwell weight/times', and 'graphical'. Plans were normalized to left point A and dose of 8 Gy was prescribed. Dose volume and dose point parameters were compared. RESULTS: Without graphical optimization, maximum width and thickness of volume enclosed by 100% isodose line, dose to 90%, and 100% of clinical target volume (CTV); minimum, maximum, median, and average dose to both rectum and bladder are significantly higher with Fletcher applicator. Even if it is done, dose to both points B, minimum dose to CTV, and treatment time; dose to 2 cc (D2cc) rectum and rectal point etc.; D2cc, minimum, maximum, median, and average dose to sigmoid colon; D2cc of bladder remain significantly higher with this applicator. Dose to bladder point is similar (p > 0.05) between two applicators, after all optimization techniques. CONCLUSIONS: Fletcher applicator generates higher dose to both CTV and organs at risk (2 cc volumes) after all optimization techniques. Dose restriction to rectum is possible using graphical optimization only during selected HDR fractionation schedules. Bladder always receives dose higher than recommended, and 2 cc sigmoid colon always gets permissible dose. Contrarily, graphical optimization with ring applicators fulfills all dose volume objectives in all HDR fractionations practiced.
ABSTRACT
Mycobacterium avium subsp. hominissuis (MAH) is an environmental bacterium causing opportunistic infections. The objective of this study was to identify flexible genome regions in MAH isolated from different sources. By comparing five complete and draft MAH genomes we identified a genomic island conferring additional flexibility to the MAH genomes. The island was absent in one of the five strains and had sizes between 16.37 and 84.85kb in the four other strains. The genes present in the islands differed among strains and included phage- and plasmid-derived genes, integrase genes, hypothetical genes, and virulence-associated genes like mmpL or mce genes.
Subject(s)
Genomic Islands , Genomics , Mycobacterium avium/genetics , Animals , Environment , Humans , Mycobacterium avium/isolation & purification , Species SpecificityABSTRACT
Infections caused by Mycobacterium avium and its subspecies are reported as emerging disease in many countries worldwide. In our study we applied the multilocus sequence typing technology to 98 German M. avium strains originating from different hosts and specimens to examine the degree of the genetic diversity. By MLST, 80% of strains were identified as subspecies 'M. avium hominissuis', and 20% as subspecies M. avium avium/M. avium silvaticum. Distinctly different MLST profiles were identified for both subspecies. Based on the analysis of 4 and 5 loci, 87 and 106 SNPs and 1 codon deletion could be detected, respectively, resulting in 40 different strain profiles. Twelve out of these have recently been described for strains coming from different countries, yet in our study, additional new strain profiles (n=28) were found. The high degree of diversity within 'M. avium subsp. hominissuis' as well as the relatedness of human, porcine and environmental strains could be confirmed by IS1245 RFLP fingerprinting. The detection of ISMav6 and hsp65 code 15 in one adult patient strain being positive for IS901, but displaying 'M. avium subsp. hominissuis' MLST profile revealed that PCR for detection of IS901 is not a definitive proof of M. avium subsp. avium/M. avium subsp. silvaticum.
