IMRT in a Pregnant Patient: How to Reduce the Fetal Dose?

The purpose of our study was to find a solution for fetal dose reduction during head-and-neck intensity modulated radiation therapy (IMRT) of a pregnant patient. The first step was optimization of the IMRT treatment plan with as few monitor units (MUs) as possible, while maintaining an acceptable dose distribution. The peripheral dose originating from the final IMRT plan was measured at distances reaching from the most proximal to the most distal fetal position, along the accelerator's longitudinal axis, using an anthropomorphic phantom extended with water-equivalent plastic. The measured peripheral dose was divided into leakage, and internal and collimator scatter, to find the degree to which each component influences the peripheral dose to build an appropriate shield. Collimator scatter was the greatest contributor to the peripheral dose throughout the range of the growing fetus. A shield was built and placed beneath the accelerator head, extending caudally from the field edge, to function as an extra collimator jaw. This shield reduced the fetal dose by a factor of 3.5. The peripheral dose components were also measured for simple rectangular fields and also here the collimator scatter was the greatest contributor to the peripheral dose. Therefore, the shielding used for the IMRT treatment of our patient could also be used when shielding in conventional radiotherapy. It is important for a radiation therapy department to be prepared for treatment of a pregnant patient to shield the fetus efficiently.     

How valid is the determination of hematocrit values to detect blood manipulations?

The aim of this paper is a critical reflection of the practice in competitive cycling to use the hematocrit value (Hct) as an indirect control measure for doping with erythropoietin. To demonstrate the individual physiological variation of Hct values, five different studies were performed: 1) Eight subjects were observed (i) during 23 h after a 1 h lasting bout of cycle exercise at 60% of maximum performance and (ii) during 24h under control conditions. 2) Seven subjects were exposed to a 20 min period of -7 head down tilt (HDT), which was followed by 15 min in sitting position. 3) From four subjects blood samples were taken in a sitting position up to 60 min after they had ingested 1 liter isotonic saline solution. 4) Ten subjects performed a vita maxima test on a cycle ergometer, starting at 100W and increasing the workload by 17W every minute. 5) Four elite cyclists participated in a 10 days competition (1,700 km). RESULTS: 1) During the 24h observation period Hct decreased during the night from 45.3+/-3.1 % to 42.9+/-1.5% and returned to the initial values in the morning. This diurnal variation was even more pronounced after submaximal exercise (-4.1 %). 2) Due to fluid shifts from the interstitial into the intravasal compartment, HDT was accompanied by a 3.1+/-0.5% lower Hct. 3) Drinking of the isotonic saline solution also reduced the hematocrit by 3.3+/-0.5% after one hour. 4) Maximum cycle exercise increased the Hct from 46.8+/-2.4 % to 51.3+/-1.9% which was due to a 15 % decrease in plasma volume. 5) Repeated bouts of cycle-exercise reduced the Hct from 46.4+/-1.5% to 41.3+/-1.6%. CONCLUSIONS: All experiments demonstrate that the Hct is not a constant value but can be considerably changed by physiological measures. Clinical studies show that brain oxygen supply decreases with increasing Hct-values, which are also associated with a higher risk of stroke accidents. We therefore recommend to use a Hct-limit solely under strongly controlled standardized conditions to protect professional cyclists from hazardous manoeuvre until more appropriate methods to detect EPO-doping are developed.     

Rotator cuff disorders: How to write a surgically relevant magnetic resonance imaging report?

Evaluation of rotator cuff is a common indication for magnetic resonance imaging (MRI) scanning of the shoulder. Conventional MRI is the most commonly used technique, while magnetic resonance (MR) arthrography is reserved for certain cases. Rotator cuff disorders are thought to be caused by a combination of internal and external mechanisms. A well-structured MRI report should comment on the relevant anatomic structures including the acromial type and orientation, the presence of os acromiale, acromio-clavicular degenerative spurs and fluid in the subacromial subdeltoid bursa. In addition, specific injuries of the rotator cuff tendons and the condition of the long head of biceps should be accurately reported. The size and extent of tendon tears, tendon retraction and fatty degeneration or atrophy of the muscles are all essential components of a surgically relevant MRI report.     

Variability of Normal Pressure Hydrocephalus Imaging Biomarkers with Respect to Section Plane Angulation: How Wrong a Radiologist Can Be?

BACKGROUND AND PURPOSE:Systematic analysis of angulation-related variability of idiopathic normal pressure hydrocephalus imaging biomarkers has not been published yet. Our aim was to evaluate the variability of these radiologic biomarkers with respect to imaging plane angulation.MATERIALS AND METHODS:Eighty subjects (35 with clinically confirmed idiopathic normal pressure hydrocephalus and 45 age- and sex-matched healthy controls) were prospectively enrolled in a 3T brain MR imaging study. Two independent readers assessed 12 radiologic idiopathic normal pressure hydrocephalus biomarkers on sections aligned parallel or perpendicular to the bicallosal, bicommissural, hypophysis-fastigium, and brain stem vertical lines, respectively.RESULTS:Disproportionately enlarged subarachnoid space hydrocephalus, simplified callosal angle, frontal horn diameter, z-Evans Index, and cella media vertical width did not show significant systematic differences in any of 6 section plane combinations studied. The remaining 7 biomarkers (including the Evans Index and callosal angle) showed significant differences in up to 4 of 6 mutually compared section plane combinations. The values obtained from sections aligned with the brain stem vertical line (parallel to the posterior brain stem margin) showed the most deviating results from other section angulations.CONCLUSIONS:Seven of 12 idiopathic normal pressure hydrocephalus biomarkers including the frequently used Evans Index and callosal angle showed statistically significant deviations when measured on sections whose angulations differed or did not comply with the proper section definition published in the original literature. Strict adherence to the methodology of idiopathic normal pressure hydrocephalus biomarker assessment is, therefore, essential to avoid an incorrect diagnosis. Increased radiologic and clinical attention should be paid to the biomarkers showing low angulation–related variability yet high specificity for idiopathic normal pressure hydrocephalus–related morphologic changes such as the z-Evans Index, frontal horn diameter, or disproportionately enlarged subarachnoid space hydrocephalus.

The prevalence of idiopathic normal pressure hydrocephalus (iNPH) may be as high as 0.5% in the population older than 65 years of age, and iNPH has emerged as a significant health issue for the aging population in developed countries. The symptoms include gait disturbance, memory impairment, and urinary incontinence. Underdiagnosed iNPH entails missed opportunities for successful ventricular shunt treatment.^1,2Numerous linear, angular, and volumetric measurements; relative indexes; CSF flow studies; as well as visual semiquantitative or qualitative parameters have been proposed as radiologic biomarkers of iNPH.^3-15 Most of the iNPH imaging biomarkers have originally been defined by their authors using arbitrary or proprietary settings in terms of defining section planes and/or measurement techniques, which, in many cases, do not comply with the routines of daily radiologic practice. This issue particularly applies to the use of the bicommissural plane, which is rarely used in routine practice because the anatomic landmarks are subtle and, therefore, difficult to apply.Various institutions have been using different definitions of standard imaging planes for decades. For example, a “standard” transverse CT or MR imaging plane can be angulated according to at least 5 different section definitions. Such interinstitutional differences may lead to different outcomes of iNPH imaging studies.The frequently used Evans Index (EI, originally defined on pneumoencephalograms in 1942) was not initially intended for use with cross-sectional imaging.¹⁶ The Evans Index was secondarily adopted for transverse CT sections aligned parallel to orbitomeatal line in 1976 and subsequently transferred into MR imaging, without a particular respect for the transverse plane definition.¹⁷ Even recently published studies often do not precisely define anatomic landmarks used for angulation of transverse or coronal sections in the methodology section. Such methodologic inconsistencies might have contributed to widely differing diagnostic performances of iNPH biomarkers reported by various authors.^3-5,8-12A systematic evaluation of the variability of iNPH biomarkers related to imaging plane definition (bicallosal, bicommissural, hypophysis-fastigium [Hy-Fa], brain stem vertical line, and so forth) has not been published so far. The aim of this study was to assess the variability of individual iNPH cross-sectional imaging biomarkers with respect to different imaging plane angulations.