Antagonizing effects of haloperidol and bicuculline on inhibition of neurons of the substantia nigra,pars compacta

In rats anesthetized with urethane, effects of intravenously administered haloperidol (HAL; 0.1 mg/kg) and bicuculline (BCL; 0.2 mg/kg) were tested on inhibition of neuronal discharges of the substantia nigra, pars compacta (SNC), induced by single-shock stimulation of the sciatic nerve (SC). In two-thirds of the SNC neurons tested these two drugs antagonized the SC-induced inhibition, independent of the side of stimulation. In the remaining cases the effects of HAL and BCL were asymmetric. With HAL the inhibition from the contralateral SC was antagonized, whereas that from the ipsilateral SC was not antagonized or sometimes slightly potentiated. The asymmetric effect of BCL occurred in the opposite direction to that of HAL.     

Auditory nerve fiber activity influenced by contralateral ear sound stimulation

Modulation of efferent olivo-cochlear bundle activity by heterolateral ear sound stimulation suggests that acoustic stimulation may modify contralateral auditory afferent activity. Therefore, changes in auditory nerve fiber activity elicited by contralateral ear sound stimulation were studied. Low sound intensities prevented cross talk between both ears, while response averaging enabled the demonstration of small effects. Heterolateral tonal stimulation decreased the homolateral sound-evoked activity of about 25% of the units studied. To elicit this effect heterolateral tones had to be at least 20 dB above the threshold for homolateral activation of the unit and had to last more than 100 ms. Frequency-response curves of the decrease in homolateral sound-evoked activity elicited by heterolateral stimulation were in most cases V-shape. Homolateral and contralateral frequency-response curves had similar characteristic frequencies. Occasionally W-shape curves were found. The effect also depended on the characteristics of the homolateral tone, being greater if it was at the characteristic frequency and of low intensity. Heterolateral white noise stimulation elicited an increase in the homolateral responses in about 88% of the units which showed decreased responses with heterolateral tone stimulation; other units were not influenced by low-intensity heterolateral white noise stimulation. Modifications of the “spontaneous” activity by heterolateral tones were observed in about 46% of the units which showed decreased responses with heterolateral tonal stimulation. The degree of contralateral modulation depended on the characteristics of the homolateral and heterolateral sounds. The described effects may act to enhance the perception of differences between sounds stimulating both ears.     

Periaqueductal gray inhibition of trigeminal subnucleus caudalis unitary responses evoked by dentine and nonnoxious facial stimulation

The possible pain inhibitory effects of periaqueductal gray (PAG) stimulation were investigated in cats anesthetized with Nembutal and immobilized with Flaxedil. Unitary responses evoked by electrical stimulation of the upper canine dentine and by cutaneous facial noxious and nonnoxious stimuli were recorded extracellularly from the trigeminal subnucleus caudalis. A bipolar electrode was introduced into the PAG to test the effects of PAG excitation on the trigeminal response to dentine (TRED) and cutaneous nonnoxious stimulation. In some experiments, a similar electrode was lowered into the contralateral posterior thalamus to study the antidromic activation of subnucleus caudalis cells and the effects of thalamic stimulation on the TRED. Dentine stimulation evoked brief (6- to 15-ms) bursts of 1 to 10 spikes with 3- to 25-ms latencies. Most units (88%) were also activated by cutaneous facial stimulation. Stimulation of the posterior thalamus had no effect on the TRED or on responses to cutaneous stimulation, but activated antidromically 10% of the units. In 71% of the units PAG stimulation inhibited the TRED. In some of those cases (12%), the inhibitory effect persisted 30- to 60 s. The PAG stimulation could produce paradoxical effects, potentiating the TRED evoked by threshold intensity and inhibiting the TRED elicited by suprathreshold stimulation. About one-half the PAG points evoked detectable effects. Their location had no clear topographical distribution, although ventral sites were more potent than dorsal sites. Responses evoked by nonnoxious facial stimulation were also inhibited by the PAG.     

Excitatory synaptic potentials in spastic human motoneurons have a short rise-time

This study assessed whether changes in size or time-course of excitatory postsynaptic potentials (EPSPs) in motoneurons innervating spastic muscle could induce a greater synaptic response, and thereby contribute to reflex hyperexcitability. We compared motor unit (MU) firing patterns elicited by tendon taps applied to both spastic and contralateral (nonspastic) biceps brachii muscle in hemiparetic stroke subjects. Based on recordings of 115 MUs, significantly shortened EPSP rise times were present on the spastic side, but with no significant differences in estimated EPSP amplitude. These changes may contribute to hyperexcitable reflex responses at short latency, but the EPSP amplitude changes appear insufficient to account for global differences in reflex excitability.     

Quantitative magnetization transfer mapping of bound protons in multiple sclerosis

Quantitative analysis of magnetization transfer images has the potential to allow a more thorough characterization of the protons, both bound and free, in a tissue by extracting a number of parameters relating to the NMR properties of the protons and their local environment. This work develops previously presented techniques to produce estimates of parameters such as the bound proton fraction, f, and the transverse relaxation time of the bound pool, T(2B), for the whole brain in a clinically acceptable imaging time. This is achieved by limiting the number of data collected (typically to 10); to collect 28 5-mm slices with a reconstructed resolution of 0.94 x 0.94 mm. The protocol takes 82 sec per data point. The fitting technique is assessed against previous work and for fitting failures. Maps and analysis are presented from a group of seven controls and 20 multiple sclerosis patients. The maps show that the parameters are sensitive to tissue-specific differences and can detect pathological change within lesions. Statistically significant differences in parameters such as T(2B) and f are seen between normal-appearing white matter, multiple sclerosis lesions, and control white matter. Whole-brain histograms of these parameters are also presented, showing differences between patients and controls.     

Radiography-based treatment planning compared with computed tomography (CT)-based treatment planning for intracavitary brachytherapy in cancer of the cervix: analysis of dose-volume histograms

PURPOSE: To analyze the dose-volume histograms (DVHs) of the tumor volume and organs at risk by CT-based treatment planning compared with conventional radiography-based treatment planning for intracavitary brachytherapy in cancer of the cervix. METHODS AND MATERIALS: Fifteen consecutive patients with cancer of the cervix (1 IB1, 3 IB2, 7 IIB, 4 IIIB) were treated with plastic CT-compatible HDR intracavitary applicators and underwent postimplant pelvic CT scans with applicators in place. CT-images were transferred to the PLATO treatment planning system. The gross tumor volume (GTV) and organs at risk were digitized. Dwell positions in the uterine tandem and colpostats were identified and registered for each patient. All patients were treated with 6 Gy per fraction to Point A using radiography-based planning. For the CT-based planning, DVHs were performed for the GTV, bladder, rectum, sigmoid colon, and small bowel in the pelvis. The dose delivered to 3% volume of the organs at risk (D3%) was compared with the respective ICRU reference doses. RESULTS: For stage IB(I), IB2, IIB, and IIIB disease the mean GTV was 20.5 cc, 56.6 cc (54.2-57.2), 63.7 cc (55.4-118.9), and 77.6 cc (49.4-102.9), respectively. The 6 Gy pear-shaped volume (PSV) encompassed an average GTV of 98.5%, 89.5%, 79.5%, and 59.5% for stages IBI, IB2, IIB, and IIIB, respectively. The mean dose for the ICRU bladder point and D3% was 3.72 Gy (1.51-5.53) and 4.74 Gy (1.70-10.10), respectively. The mean dose for the ICRU rectal point and D3% was 3.97 Gy (2.09-5.37) and 3.52 Gy (2.05-4.08), respectively. The D3% for the sigmoid colon was highest (3.88 Gy), followed by the rectum (3.52 Gy), and the small bowel (3.36 Gy). CONCLUSION: Radiography-based conventional treatment planning overestimates tumor dose, especially those with more advanced tumors. To correlate DVHs for tumor control, improved tumor imaging is necessary.     

Postoperative pulmonary complications after preoperative chemoradiation for esophageal carcinoma: correlation with pulmonary dose-volume histogram parameters

PURPOSE: To clarify the relationship between the percentage of lung receiving low radiation doses with concurrent chemotherapy and the occurrence of postoperative pulmonary complications in the treatment of esophageal carcinoma. METHODS: From 117 patients who underwent preoperative chemoradiation for esophageal cancer at our institution between 1998 and 2002, we selected 61 patients for whom complete pulmonary dose-volume histogram (DVH) data were available and analyzed the incidence of pneumonia and acute respiratory distress syndrome (ARDS) in this group. All patients received concurrent chemoradiation therapy, and 39 patients also received induction chemotherapy before concurrent chemoradiation. The median age was 62 years, and the median radiotherapy dose was 45 Gy. The percentage of lung volume receiving at least 10 Gy (V10), 15 Gy (V15), and 20 Gy (V20) were recorded from each pulmonary DVH. RESULTS: Eleven (18%) of the 61 patients had pulmonary complications, 2 of whom died after progression of pneumonia. Pulmonary complications were noted more often (35% vs. 8%, p = 0.014) when the pulmonary V10 was > or =40% vs. <40% and when the V15 was > or /=30% vs. < 30% (33% vs. 10%, p = 0.036). An apparent increase in pulmonary complication rate when V20 was > or =20% vs. <20% (32% vs. 10%, p = 0.079) was not significant. None of the other factors analyzed (surgical procedure, tumor location, use of induction chemotherapy, use of concurrent taxane-based chemoradiation, or smoking history) was associated with the occurrence of pulmonary complications. The median hospital stay was 17 days for patients who had pulmonary complications vs. 12 days for patients who did not (p = 0.08). CONCLUSIONS: The use of multimodality therapy may require minimization of lung volume irradiation to levels lower than previously expected. Radiotherapy techniques that decrease the volume of lung receiving low radiation doses may significantly reduce the risk of this potentially life-threatening complication.     

Treatment plan evaluation using dose-volume histogram (DVH) and spatial dose-volume histogram (zDVH)

Objective: The dose–volume histogram (DVH) has been accepted as a tool for treatment-plan evaluation. However, DVH lacks spatial information. A new concept, the z-dependent dose–volume histogram (zDVH), is presented as a supplement to the DVH in three-dimensional (3D) treatment planning to provide the spatial variation, as well as the size and magnitude of the different dose regions within a region of interest.

Materials and Methods: Three-dimensional dose calculations were carried out with various plans for three disease sites: lung, breast, and prostate. DVHs were calculated for the entire volume. A zDVH is defined as a differential dose–volume histogram with respect to a computed tomographic (CT) slice position. In this study, zDVHs were calculated for each CT slice in the treatment field. DVHs and zDVHs were compared.

Results: In the irradiation of lung, DVH calculation indicated that the treatment plan satisfied the dose–volume constraint placed on the lung and zDVH of the lung revealed that a sizable fraction of the lung centered about the central axis (CAX) received a significant dose, a situation that warranted a modification of the treatment plan due to the removal of one lung. In the irradiation of breast with tangential fields, the DVH showed that about 7% of the breast volume received at least 110% of the prescribed dose (PD) and about 11% of the breast received less than 98% PD. However, the zDVHs of the breast volume in each of seven planes showed the existence of high-dose regions of 34% and 15%, respectively, of the volume in the two caudal-most planes and cold spots of about 40% in the two cephalic planes. In the treatment planning of prostate, DVHs showed that about 15% of the bladder and 40% of the rectum received 102% PD, whereas about 30% of the bladder and 50% of the rectum received the full dose. Taking into account the hollow structure of both the bladder and the rectum, the dose–surface histograms (DSH) showed larger hot-spot volume, about 37% of the bladder wall and 43% of the rectal wall. The zDVHs of the bladder revealed that the hot-spot region was superior to the central axis. The zDVHs of the rectum showed that the high-dose region was an 8-cm segment mostly superior to the central axis. The serial array-like of the rectum warrants a closer attention with regard to the complication probability of the organ.

Conclusions: Although DVH provides an averaged dose–volume information, zDVH provides differential dose–volume information with respect to the CT slice position. zDVH is a 2D analog of a 3D DVH and, in some situations, more superior. It provides additional information on plan evaluation that otherwise could not be appreciated. The zDVH may be used along with DVH for plan evaluation and for the correlation of radiation outcome.     

B型超声图像直方图的原理及临床应用

本文叙述了声像图的直方图形成原理及其分析方法。介绍了三种直方图取样方法,即:①点分析取样;②线分析取样;③面分析取样。描述了用以分析的谱线宽度、高次谱位、谱线包络线及统计数据等参数。 本法有助于鉴别各种液性、实质性、纤维化、钙化或结石及混合性病变。本法对超声诊断的量化分析具有十分重要的意义。