Comparison of dynamic and step-and-shoot intensity-modulated radiation therapy planning and delivery.

Intensity-modulated radiation therapy (IMRT) is commonly delivered using the dynamic or segmental mode of multileaf collimators (DMLC or SMLC). Both methods are designed to deliver intensity-modulated beams as determined by inverse planning software. In this study, we have used the Helios IMRT planning system to generate ideal treatment plans for 10 cases of 2 common treatment sites (prostate and head and neck) and have investigated the actual treatment fluence distributions generated for each of the MLC leaf motion choices. The 2 dose delivery techniques were dosimetrically compared to each other and to the treatment plans. For each technique, point doses were measured in a water phantom using ionization chambers. Also for each technique, 2-dimensional dose distributions at a selected depth in a plastic phantom were obtained, using extended range film. The total delivery time and the number of monitor units (MU) delivered by each method were also compared. Our results indicate that the 2 delivery methods produce comparable results dosimetrically. For the cases reviewed, the delivery time was an average of 15% longer for SMLC deliveries, while the number of MUs (beam-on time) required by SMLC was an average of 15% fewer, than that for the DMLC. In the interest of simplicity, lower beam-on time, and potentially fewer mechanically-related problems, we think that the SMLC delivery technique may be the better choice when Helios is used for planning and Varian linear accelerators are used for delivery.     

Effects of inferior colliculus lesions on the acoustic startle response

"Nonspecific" electrolytic lesions (with respect to subdivision) of the mouse inferior colliculus (IC) resulted in the attenuation of acoustic startle response (ASR) amplitudes on the 1st post-operative day, but ASR amplitudes increased to above baseline levels 1 week later. Lesions of the IC central nucleus (CN) also attenuated ASR amplitudes on the 1st postsurgery day, but startle amplitudes recovered to baseline levels 1 week after surgery. Lesions of the IC lateral nucleus (LN) or dorsal cortex (DC) resulted in elevation of startle amplitudes above baseline 7 days after surgery and produced enhanced ASR amplitudes to repeated stimuli. Fourteen days after the surgery, lesion effects on startle amplitudes remained the same as those on Day 7 for each lesion condition. The present findings implicate the ICLN and the ICDC as inhibitory modulators of the ASR, but indicate only a minor role for the ICCN.     

Expression of the 5.1 H11 antigen, a fetal muscle surface antigen, in normal and neoplastic tissue

The monoclonal antibody 5.1 H11 recognizes an antigen on human fetal muscle and on rhabdomyosarcoma cell lines and xenografts that has been shown to be homologous to the neural cell adhesion molecule. To evaluate its range of expression, we used immunoperoxidase staining of fresh frozen-tissue sections to determine monoclonal antibody 5.1 H11 reactivity in normal and neoplastic tissue. Among normal tissue specimens, intense antibody staining was seen in brain and peripheral nerve, and weaker staining in ganglionic elements of colon. In addition to 26 of 29 rhabdomyosarcoma specimens, 5.1 H11 antibody showed reactivity to 9 of 10 Wilms' tumors, 6 of 6 neural tumors, and 4 of 4 gliomas, and with single specimens of ectomesenchymoma, clear-cell sarcoma of kidney, undifferentiated sarcoma of liver, ovarian fibroma, and neurofibroma. We conclude that the monoclonal antibody 5.1 H11 recognizes an antigen present not only on fetal muscle but on normal brain and nerve as well. In addition to rhabdomyosarcoma, a variety of other tumors, most of which have been previously shown to express neural cell adhesion molecule, also appear to express the antigen recognized by 5.1 H11. Our results thus offer additional confirmatory evidence that an epitope of neural cell adhesion molecule is the antigen for 5.1 H11.     

Morphometric analysis of breast carcinoma: association with survival.

In a retrospective study of 126 cases of infiltrating ductal adenocarcinoma of the breast the percentage area of sections of each neoplasm occupied by malignant cells was assessed by morphometry. The duration of postoperative survival was related to the area occupied by tumour cells within a neoplasm; the greater the tumour cell area to stroma the more prolonged the survival. This variable seemed to be independent of histological grade and was of greater prognostic importance than the diameter of the neoplasm. Furthermore, combination of percentage of tumour area with histological grade provided greater information on the survival characteristics of these patients. Extensive tumour necrosis was a particularly poor prognostic feature.     

Measurement of the dose deposition characteristics of x-ray fluoroscopy beams in water

The purpose of this study was to characterize the x-ray dose distribution of fluoroscopy beams by measuring their percent depth dose curves and lateral dose profiles in a water phantom. Percent depth dose curves were measured near the surface with an Attix parallel plate chamber and deep within the water phantom with a Farmer-type cylindrical chamber. Percent depth dose curves were compared to published data where applicable. Lateral dose profiles were measured at depths of 2, 5, 10, and 15 cm in phantom with a Farmer chamber. Pulsed, 50 mA x-ray beams with peak tube potentials of 60, 80, 100, and 120 kV and half value layers of 1.89, 2.52, 3.20, and 4.09 mm Al, respectively, were investigated.     

Daily running promotes spatial learning and memory in rats.

Previous studies on exercise have shown that physical activity improves learning and memory. Present study was performed to determine the effects of acute, chronic and continuous exercise with different periods on spatial learning and memory recorded as the latency and length of swim path in the Morris water maze testing in subsequent 8 days. Four rat groups were included as follows: (1) group C, controls which did not exercise; (2) group A, 30 days treadmill running before and 8 days during the Morris water maze testing period; (3) group B, 30 days exercise before the Morris water maze testing period only; (4) group D, 8 days exercise only during the Morris water maze testing period. The results showed that chronic (30 days) and continuous (during 8 days of Morris water maze testing days) treadmill training produced a significant enhancement in spatial learning and memory which was indicated by decreases in path length and latency to reach the platform in the Morris water maze test (p<0.05). The benefits in these tests were lost in 3 days, if the daily running session was abandoned. In group D with acute treadmill running (8 days exercise only) the difference between the group A disappeared in 1 week and benefit seemed to be obtained in comparison with the controls without running program. In conclusion the chronic and daily running exercises promoted learning and memory in Morris water maze, but the benefits were lost in few days without daily running sessions in adult rats.     

Lumbar degenerative spondylolisthesis: factors associated with the decision to fuse

BACKGROUND CONTEXTThe indication to perform a fusion and decompression surgery as opposed to decompression alone for lumbar degenerative spondylolisthesis (LDS) remains controversial. A variety of factors are considered when deciding on whether to fuse, including patient demographics, radiographic parameters, and symptom presentation. Likely surgeon preference has an important influence as well.PURPOSEThe aim of this study was to assess factors associated with the decision of a Canadian academic spine surgeon to perform a fusion for LDS.STUDY DESIGN/SETTINGThis study is a retrospective analysis of patients prospectively enrolled in a multicenter Canadian study that was designed to evaluate the assessment and surgical management of LDS.PATIENT SAMPLEInclusion criteria were patients with: radiographic evidence of LDS and neurogenic claudication or radicular pain, undergoing posterior decompression alone or posterior decompression and fusion, performed in one of seven, participating academic centers from 2015 to 2019.OUTCOME MEASURESPatient demographics, patient-rated outcome measures (Oswestry Disability Index [ODI], numberical rating scale back pain and leg pain, SF-12), and imaging parameters were recorded in the Canadian Spine Outcomes Research Network (CSORN) database. Surgeon factors were retrieved by survey of each participating surgeon and then linked to their specific patients within the database.METHODSUnivariate analysis was used to compare patient characteristics, imaging measures, and surgeon variables between those that had a fusion and those that had decompression alone. Multivariate backward logistic regression was used to identify the best combination of factors associated with the decision to perform a fusion.RESULTSThis study includes 241 consecutively enrolled patients receiving surgery from 11 surgeons at 7 sites. Patients that had a fusion were younger (65.3±8.3 vs. 68.6±9.7 years, p=.012), had worse ODI scores (45.9±14.7 vs. 40.2±13.5, p=.007), a smaller average disc height (6.1±2.7 vs. 8.0±7.3 mm, p=.005), were more likely to have grade II spondylolisthesis (31% vs. 14%, p=.008), facet distraction (34% vs. 60%, p=.034), and a nonlordotic disc angle (26% vs. 17%, p=.038). The rate of fusion varied by individual surgeon and practice location (p<.001, respectively). Surgeons that were fellowship trained in Canada more frequently fused than those who fellowship trained outside of Canada (76% vs. 57%, p=.027). Surgeons on salary fused more frequently than surgeons remunerated by fee-for-service (80% vs. 64%, p=.004). In the multivariate analysis the clinical factors associated with an increased odds of fusion were decreasing age, decreasing disc height, and increasing ODI score; the radiographic factors were grade II spondylolisthesis and neutral or kyphotic standing disc type; and the surgeon factors were fellowship location, renumeration type and practice region. The odds of having a fusion surgery was more than two times greater for patients with a grade II spondylolisthesis or neutral and/or kyphotic standing disc type (opposed to lordotic standing disc type). Patients whose surgeon completed their fellowship in Canada, or whose surgeon was salaried (opposed to fee-for-service), or whose surgeon practiced in western Canada had twice the odds of having fusion surgery.CONCLUSIONSThe decision to perform a fusion in addition to decompression for LDS is multifactorial. Although patient and radiographic parameters are important in the decision-making process, multiple surgeon factors are associated with the preference of a Canadian spine surgeon to perform a fusion for LDS. Future work is necessary to decrease treatment variability between surgeons and help facilitate the implementation of evidence-based decision making.