Intra-fraction motion of the prostate during treatment with helical tomotherapy

Background and purpose

To measure the geometric uncertainty resulting from intra-fraction motion and intra-observer image matching, for patients having image-guided prostate radiotherapy on TomoTherapy.

Material and methods

All patients had already been selected for prostate radiotherapy on TomoTherapy, with daily MV-CT imaging. The study involved performing an additional MV-CT image at the end of treatment, on 5 occasions during the course of 37 treatments. 54 patients were recruited to the study. A new formula was derived to calculate the PTV margin for intra-fraction motion.

Results

The mean values of the intra-fraction differences were 0.0 mm, 0.5 mm, 0.5 mm and 0.0° for LR, SI, AP and roll, respectively. The corresponding standard deviations were 1.1 mm, 0.8 mm, 0.8 mm and 0.6° for systematic uncertainties (Σ), 1.3 mm, 2.0 mm, 2.2 mm and 0.3° for random uncertainties (σ). This intra-fraction motion requires margins of 2.2 mm in LR, 2.1 mm in SI and 2.1 mm in AP directions. Inclusion of estimates of the effect of rotations and matching errors increases these margins to approximately 4 mm in LR and 5 mm in SI and AP directions.

Conclusions

A new margin recipe has been developed to calculate margins for intra-fraction motion. This recipe is applicable to any measurement technique that is based on the difference between images taken before and after treatment.     

Accuracy of a relocatable stereotactic radiotherapy head frame evaluated by use of a depth helmet

In high precision radiotherapy, the more accurately the patient can be relocated, the smaller the clinical to planning target volume margin can be, with reduction in the volume of normal tissue irradiated. The Gill-Thomas-Cosman (GTC) relocatable stereotactic head frame provides immobilization of the patient which is highly reproducible. A depth helmet and measuring probe were used to confirm the accuracy of relocation of 31 patients treated in the GTC frame. The measurements were processed in a spreadsheet developed to calculate the size of the patient's displacement as a vector. Twenty-seven patients received fractionated stereotactically-guided conformal radiotherapy, and 4 single fraction stereotactic radiosurgery, amounting to 564 measurement episodes. The accuracy was extremely good, and considerably more accurate than standard thermoplastic head shells. Ninety-two percent of the displacement vectors were less than 2 mm, and 97% less than 2.5 mm. Considering each dimension separately, the largest mean displacement was 0.4 mm in the superior-inferior direction. Accuracy was constant through a fractionated course for most patients, but prediction based on measurements from the first few fractions was not reliable. Results were dependent on patient selection, with worse reproducibility in patients with neurological deficits, or difficulty cooperating. The depth helmet measurements detected a loosened mouth bite in one patient and allowed repositioning to be verified without the need for the simulator. Total treatment time, including use of the depth helmet to verify treatment position, is quicker (mean 15.7 min) than using portal films. The depth helmet, used in conjunction with the vector displacement spreadsheet, provides a simple way to define the CTV-PTV margin. For fractionated stereotactic radiotherapy we use a 3 mm CTV-PTV margin. This system could assist technology transfer to centres starting stereotactic radiotherapy using the GTC frame.     

Gas in the cranium: an unusual case of delayed pneumocephalus following craniotomy

We present the case history of a 23-year-old man who underwent frontal craniotomy followed by radiotherapy for a Grade III anaplastic glioma. Magnetic resonance imaging (MRI) at the 3-month follow-up showed significant tumour response. He became unwell some weeks after the MRI with an upper respiratory tract infection, severe headache and mild right-sided weakness. A computed tomographic (CT) scan showed a very large volume of intracranial gas, thought to have entered via a defect in the frontal air sinus after craniotomy and brought to light by blowing his nose. Intracranial air is frequently present after craniotomy, but it is normally absorbed within 34 weeks. The presence of pneumocephalus on a delayed postoperative CT scan should raise the possibility of a cerebrospinal fluid (CSF) fistula, or infection with a gas-forming organism. Many CSF fistulae require surgical closure in order to prevent potentially life-threatening central nervous system infection and tension pneumocephalitis. Immediate neurosurgical review is advisable.     

开通闭塞冠状动脉策略的全球性研究 GUSTO—Ⅱb（亚组研究）

病人资料 3 289例因急性冠脉综合征而接受溶栓治疗的患者,2274例接受t－PA治疗,1015例接受链激酶治疗。     

Reproducibility of quantitative CT perfusion imaging.

The ability to demonstrate regions of abnormal cerebral blood flow in the setting of acute stroke is of diagnostic and prognostic importance. It may also influence therapeutic strategies. The advantage of CT perfusion imaging is its ability to give quantifiable measurements of cerebral blood flow on any modern CT machine without the need to buy specialized equipment. The aim was to assess day-to-day variability of values of cerebral blood volume obtained with this technique. Seven patients with cerebral gliomas were studied using dynamic CT perfusion imaging on two occasions, approximately 24 h apart to reduce variability from diurnal variations. Regions of interest were produced in predominately middle cerebral artery locations in both hemispheres on the first and second CT perfusion studies. Absolute values for cerebral blood flow were produced for these regions and were correlated with flows obtained in the same regions of interest on the follow-up study. The Pearson correlation coefficient obtained was 0.884. CT perfusion imaging is easily performed on conventional modern CT equipment and demonstrates little variability in measures of absolute cerebral blood flow within individuals when studied on two occasions within 24 h.     

The importance of injury as a cause of death in sub-Saharan Africa: results of a community-based study in Tanzania

This paper describes rates and causes of injury deaths among community members in three districts of the United Republic of Tanzania. A population-based study was carried out in two rural districts and one urban area in Tanzania. Deaths occurring in the study areas were monitored prospectively during a period of six years. Censuses were conducted annually in the rural areas and biannually in the urban area to determine the denominator populations. Cause-specific death rates and Years of Life Lost (YLL) due to injury were calculated for the three study areas. During a 6 year period (1992-1998), 5047 deaths were recorded in Dar es Salaam, 9339 in Hai District and 11 155 in Morogoro Rural District. Among all ages, deaths due to injuries accounted for 5% of all deaths in Dar es Salaam, 8% in Hai and 5% in Morogoro. The age-standardised injury death rates among men were approximately three times higher than among women in all study areas. Transport accidents were the commonest cause of mortality in all injury-related deaths in the three project areas, except for females in Hai District, where it ranked second after intentional self-harm. We conclude that injury deaths impose a considerable burden in Tanzania. Strategies should be strengthened in the prevention and control of avoidable premature deaths due to injuries.     

Targeting sodium/iodide symporter gene expression for estrogen-regulated imaging and therapy in breast cancer

Expression of the sodium iodide symporter (hNIS) has been detected in breast cancer tissue, but frequently, not at the levels necessary to mediate (131)I accumulation. Transducing the hNIS gene into breast cancer cells with adenovirus could be a tractable strategy to render breast cancer susceptible to radioiodide therapy. We constructed the replication-incompetent virus, AdSERE, in which an estrogen-responsive promoter directs the expression of hNIS. In vitro, we demonstrate that AdSERE mediates hNIS expression and iodide uptake in ER+ breast cancer cells. In vivo, we show that AdSERE-infected ER+ tumors can be imaged due to tracer accumulation; in addition, AdSERE in combination with therapeutic doses of (131)I suppresses tumor growth.     

Hepatic amebic abscess: cholescintigraphic rim enhancement

Cholescintigrams of 17 amebic liver abscesses (ALAs) in 13 patients were studied retrospectively. Rim enhancement around a photopenic defect was seen in nine (53%) of 17 abscesses. Most of the ALAs were solitary, in the right lobe, and ovoid. All were contiguous with the liver capsule. Ultrasonograms, obtained in 11 of 13 patients, showed the ALAs to be predominantly hypoechoic, with low-level echoes on high-gain settings. No sonographic finding could be identified to correlate with rim enhancement. Cholescintigraphic rim enhancement may allow early diagnosis of ALA in patients with right-upper-quadrant pain, facilitating early institution of specific therapy while definitive serologic confirmation of ALA is awaited.