单次屏气及自由呼吸TSENSE技术对心功能测量及图像质量的评价

目的:评价TSENSE技术在不同加速因子及自由呼吸状态下测量心功能的准确性及图像质量.方法:15例患者真实稳态自由进动(trueFISP)全心短轴位电影检查.检查序列包括多次屏气trueFISP结合GRAPPA,不同加速因子(2～4)单次屏气TSENSE和自由呼吸TSENSE(R=3).测量并比较各种序列所测心脏射血分数(EF)、舒张末期容积(EDV)和收缩末期容积(ESV).结合乳头肌水平图像的对比噪声比(CNR)对各序列图像质量进行评价.结果:与GRAPPA相比,TSENSE各序列所测心功能指标差异无显著性意义(P＞0.05),两者结果具有一致性.各序列图像均具有诊断性,以GRAPPA和R=2时TSENSE图像质量最佳.结论:单次屏气和自由呼吸TSENSE技术全心扫描能准确评价左心室容积大小,以R=3时TSENSE序列最适合临床运用.     

单次屏气TGRAPPA及TmSENSE技术对左右心功能测量的应用研究

【摘要】目的：对比评价单次屏气TGRAPPA、TmSENSE与多次屏气GRAPPA技术结合true FISP电影在评价左右心室功能中的价值。方法：对37例行心脏MRI检查的患者,进行真实稳态自由进动采集全心短轴位电影检查,检查序列包括多次屏气GRAPPA结合true FISP电影检查及单次屏气TGRAPPA及TmSENSE。测量并比较各种序列的扫描时间、左右心室射血分数（EF）、舒张末期容积指数（EDVI）、收缩末期容积指数（ESVI）及心搏量（SV）。选取乳头肌水平图像进行图像质量评价及CNR分析。结果：多次屏气GRAPPA、单次屏气TGRAPPA及TmSENSE的扫描时间（189±57;17±5;17±5s）具有显著统计学差异（P＜0.01）;测得的左室功能参数EF（53.6±17.1、53.8±17.2、53.7±17.4％）、EDVI（80.4±33.2、79.9±33.4、79.5±33.7mL/m2）、ESVI（41.7±35.8、41.6±36.3、41.1±35.9mL/m2）、SV（38.7±10.2、38.2±10.7、38.3±10.8mL/m2）;右心室功能参数EF（52.0±15.6、52.7±15.7、52.5±15.7％）、EDVI（69.8±23.9、69.1±23.9、69.1±23.5mL/m2）、ESVI（34.9±21.2、34.2±21.5、34.2±21.1mL/m2）、SV（34.9±12.7、34.9±12.6、34.9±12.9mL/m2）;经统计学分析,三种方法的结果差异均无显著性意义（P＞0.05）。从图像质量上评价,相较于传统的多次屏气方法,TGRAPPA、TmSENSE技术的CNR会下降（P＜0.05),但TGRAPPA的CNR及图像质量评分高于TmSENSE。结论：单次屏气TGRAPPA、TmSENSE技术能够完成左右心功能的评价,相较于传统GRAPPA技术,明显缩短了采集时间,达到快速扫描的目的,TGRAPPA图像质量优于TmSENSE。     

MRI对慢性阻塞性肺疾病患者肺动脉血流和右心功能评估的应用价值

目的 探讨MRI在检测慢性阻塞性肺疾病(COPD)患者肺动脉血流与右心功能评估中的应用价值。方法选取我院COPD患者52例,依据患者有无肺动脉高压划分成观察组(存在肺动脉高压) 22例和对照组(无肺动脉高压) 30例,对比两组左右心室功能、肺动脉血流有关指标水平。结果 观察组右心室ESV、EDV、EF、SV、MM及左心室EF、SV和对照组相比差异有统计学意义(P <0.05),观察组右心室ESV、EDV、MM均高于对照组(P <0.05),右心室EF、SV和左心室EF、SV均低于对照组(P <0.05);两组左心室ESV、EDV和MM相比差异无统计学意义(P> 0.05)。观察组主肺动脉的血流量平均值、血流峰值及顺应性和对照组相比差异有统计学意义(P <0.05),观察组主肺动脉的血流量平均值、血流峰值及顺应性均低于对照组(P>0.05)。结论 MRI作为COPD患者右心功能与肺动脉血流检测中的一项无创影像学技术,能为临床提供参考依据。     

心脏磁共振单次屏气三维容积电影成像在心脏功能评价中的应用

【摘要】目的：探讨单次屏气三维（3D）平衡式稳态自由进动（bSSFP）心脏电影成像评估心脏功能方面的可行性。方法：对20例入选的心脏疾病患者进行常规心脏各切面的2D bSSFP序列和单次屏气心脏全容积3D bSSFP序列的电影成像。采集的MRI图像由2名经验丰富的放射科医师采用双盲法进行分析。采用四分法对图像的总体质量进行等级评分（1分为最差,4分为最优）,然后利用两种序列的图像,分别测量左心室舒张末容积（EDV）、收缩末容积（ESV）、每搏输出量（SV）、射血分数（EF）、心排量（CO）和心指数（CI）。依据数据的正态性分布情况,采用配对t检验或秩和检验比较两种序列的图像质量评分和心功能各项参数值,并进行Pearson相关分析或Spearman相关分析。结果：20例患者均成功完成两种序列的电影成像。3D序列扫描时间［(23.0±2.7)s］明显短于2D序列总成像时间［(488.8±27.0)s］,3D和2D序列的图像质量评分分别为（2.90±0.31）和（3.55±0.60）分,差异具有统计学意义（Z=3.357,P=0.001）。剔除3例2D或3D图像质量较差有可能影响诊断的患者,对余下的17例患者进行心功能评价,2D和3D序列的心功能参数比较结果显示,EDV（t=2.519,P=0.023）和ESV（t=2.804,P=0.013）在两者间差异具有统计学意义;而SV（Z=1.254,P=0.210）、EF（t=1.728,P=0.103）、CO（Z=1.250,P=0.211）和CI（Z=0.995,P=0.320）在两者间差异无统计学意义。相关性分析显示2D和3D序列的EDV、ESV、SV、EF、CO和CI结果均高度相关（相关系数r分别为0.992、0.995、0.981、 0.999、0.985和0.965,P均<0.01）。结论：相对于常规2D bSSFP序列,单次屏气3D bSSFP序列电影成像的图像质量虽略低,但在保证左心室功能评估的准确性的同时,大大节约CMR成像的时间成本。     

MRI心功能参数对陈旧性心肌梗死左心室重塑的评估价值

目的：观察陈旧性心肌梗死后心室形态和心功能参数的变化,探讨MRI测量心功能参数对心室重塑的评估价值。方法：纳入33例陈旧性心肌梗死患者为病变组,12例健康志愿者为对照组。病变组及对照组成员均行MRI检查。MRI测量参数包括：舒张末期客积（EDV）、收缩末期容积（ESV）、每搏输出量（SV）、左心室射血分数（LVEF）、射血率峰值（PER）、充盈率峰值（PFR）。同时测量梗死心肌面积所占的百分比,以24％为分界值,分为无重塑组（≤24％）和重塑组（〉24％）,分析各组间的心功能参数的差异,进行受试者操作特征（ROC）曲线分析,筛选能独立评估心室重塑的心功能指标。结果：病变组的EDV、ESV、SV均高于对照组,病变组的LVEF、PER和PFR低于对照组。ESV随EDV的增加而增加（P〈0．001）,PER、PFR及LVEF均随EDV的增加而下降（P〈0．05）,而SV与各参数均无相关性。PFR、EDV和ESV的ROC分析曲线下面积分别为0．725、0．741、0．764,分界值分别为2．27EDV／sec、140．23ml和79．12ml（P值分别为0．036、0．021和0．032）。结论：MRI可以从收缩和舒张功能的不同角度全面地评估心功能变化。MRI心功能指标对评估心室重塑有重要作用。PFR、EDV、ESV可以作为独立因子评估心室重塑,其中以PFR的评估效能更高。     

冠状动脉SYNTAX评分与左心功能指数间相关性研究

目的 分析冠心病患者冠状动脉病变复杂程度与左心功能指数间的相关性.方法 69例冠心病患者根据冠状动脉CT血管成像(CTA) SYNTAX评分分为低危组(27例)、中危组(23例)、高危组(19例).使用SPSS16软件,采用ANOVA分析比较3组左心功能的差异,采用Spearman秩相关分析SYNTAX评分与左心功能指标间的相关性.结果 低、中、高危3组患者间左心室舒张末期容积(EDV)、收缩末期容积(ESV)、每搏输出量(SV)、射血分数(EF)、心肌质量(MM)差异有统计学意义(F值分别为7.254、9.181、13.004、7.544、5.276,P均<0.05).冠状动脉SYNTAX评分与左心室EF呈显著负相关(r=-0.702,P<0.05),与MM呈显著正相关(r=0.638,P<0.05).结论 冠状动脉SYNTAX评分与左心室EF呈显著负相关,与左心室MM呈显著正相关.     

双源CT在主动脉瓣置换术前左心功能评价中的应用

目的:以磁共振成像(MRI)为金标准,用双源CT(DSCT)定量评价左心功能,探讨DSCT在主动脉瓣置换术前左心功能评价中的应用价值.方法:选取临床诊断主动脉瓣病变欲行主动脉瓣置换术的患者21例,全部病例均行DSCT和MRI心功能分析检查.由有经验的2位放射科医生独立进行,结果以均数士标准差表示.两种仪器间测量值应用配对样本t检验及相关分析检验,同一仪器测量值的差异相互关系用组内相关系数描述,P ＜0.05为有统计学意义.结果:DSCT和MRI两种方法测量的心功能指标差异无统计学意义,舒张末期容积(EDV)、收缩末期容积(ESV)、每搏输出量(SV)、左室射血分数(EF)相关性高,r值(EDV)=0.93,r值(ESV)=0.94,r值(SV)=0.89,r值(EF)=0.85.EDV均值:DSCT＞ MRI;ESV均值:DSCT＞ MRI;SV均值:DSCT＞ MRI; EF均值:DSCT＞ MRI.同一仪器三次测量值的差异相互关系(ICC值):MRI测量的EDV、ESV、SV、EF值的ICC值在0.8～1之间;DSCT测量的EDV、ESV、SV、EF值的ICC值在0.6～0.75之间.结论:DSCT在左心室收缩功能定量评价方面准确、可靠,重复性好,并可在不增加放射剂量的前提下,一次DSCT冠状动脉造影检查同时评估冠状动脉狭窄情况和左心室收缩功能,能够为临床主动脉瓣置换术前评估及制订手术方案提供更多重要的参考信息.     

MSCT、超声心动图与MRI评价左心功能的比较研究

目的以磁共振成像(MRI)为对照标准,应用64层螺旋CT(MSCT),定量评价左心功能,探讨MSCT和MRI心功能评价指标的相关性及MSCT在冠心病左心功能评价中的应用价值;比较同组病例的超声心动图和心脏MRI的左心功能指标,探讨两种方法心功能指标的相关性。资料与方法临床拟诊冠心病的患者32例(均自愿参加),均行心脏MSCT、MRI和超声心动图检查。结果MSCT和MRI两种方法的心功能指标差异无统计学意义,舒张末期容积(EDV)、收缩末期容积(ESV)、每搏输出量(SV)、左室射血分数(EF)、心肌质量(MM)相关性高(r值=0.78~0.92);超声心动图和MRI两种方法的心功能指标差异亦无统计学意义,EDV和SV相关性高(r值分别为0.63和0.69);ESV和EF值相关性中等或低(r值分别为0.41和0.34)。EDV、ESV均值:MSCT>MRI>超声心动图;SV均值:MSCT>MRI和超声心动图;EF均值:超声心动图>MRI>MSCT。结论MSCT在左心功能定量评价方面准确、可靠,一次MSCT冠状动脉造影检查可以同时评估冠状动脉狭窄情况和左心室功能。超声心动图也具有重要的临床应用价值,但是MSCT用于定量评价左心功能较超声心动图更准确。     

时间-空间相关成像技术评估宫内生长受限胎儿心功能的研究

目的 :探讨时间-空间相关成像技术评估孕晚期宫内生长受限(IUGR)胎儿的心功能变化。方法 :选择孕晚期30例IUGR胎儿和50例正常胎儿,分别作为研究组和对照组。在孕29~36周,通过时间-空间相关成像技术分别采集2组胎儿左心室收缩末期容积(ESV)和舒张末期容积(EDV),计算2组胎儿左心室每搏输出量(SV)、心输出量(CO)和射血分数(EF),并行统计学分析。结果:2组胎儿随着生长发育,SV和CO逐渐增加组间比较差异均有统计学意义(均P0.05),且均与孕龄呈正相关(均P0.05);EF则相对恒定(均P0.05)。结论 :时间-空间相关成像技术可较简便、准确地测量胎儿的心室ESV和EDV,IUGR组SV和CO明显低于正常组,EF评估胎儿心功能不够完善。     

屏气电影法MRI评价左心室功能的价值

目的：探讨MR屏气电影成像技术评价左室功能的价值。方法：应用屏气电影法MRI对18例健康成年志愿者和36例心脏病患者进行检查，并对左室容量和心肌质量进行测量，将屏气电影法MRI的结果与传统电影法MRI及超声心动图进行比较。结果：（1）屏气电影法与传统电影法MRI及超声心动图所得舒张末期容量（EDV）、收缩末期容量（ESV）、射血分数（EF）相关性良好，相关系数为0．52－0．96，3种方法所测各指标的均值间比较差异无显著性意义（P＞0．05）。（2）3种方法所测舒张末期心肌质量（EDM），收缩末期心肌质量（ESM）相关系数较前3个指标低，且MRI与超声心动图所测ESM的均值差异有显著性意义（P＜0．05），MRI与超声心动图ESM测量的一致性欠佳。结论：屏气电影法MRI与传统电影法MRI、超声心动图比较，各心功能指标测量准确，相关性好，且成像时间短，无呼吸运动伪影，是1种临床实用价值很高的技术。     

Nasopharyngeal carcinoma radiotherapy with hybrid technique

The aim of the study was to investigate the effect of the Hybrid technique which was created by combining of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) for the treatment of nasopharyngeal cancer (NPC) patients. 7 to 9 field IMRT, triple arc VMAT, and Hybrid plans were generated for 10 advanced stage NPC patients. The homogeneity index (HI) and the conformity index (CI) of planning target volumes (PTVs) were calculated for each technique to evaluate the plan quality. The techniques were compared in terms of plan quality, sparing of organs at risk (OARs), monitor units (MUs), and delivery time. Hybrid technique significantly improved the target dose homogeneity and the conformity for PTV70 and PTV60 compared to IMRT and VMAT. Hybrid plans significantly reduced the maximum dose of the brainstem sparing compared to the VMAT plans and also improved the sparing of spinal cord compared to IMRT and VMAT. The MUs and the delivery time of Hybrid plans were found to be between values for IMRT and VMAT plans. Hybrid technique can be useful when IMRT and VMAT techniques are not adequate alone in the treatment of NPC patients.     

MR-cholangiography with a double contrast technique

The combination of superparamagnetic particles (SPP) as a 'negative' contrast agent for the liver parenchyma and Cr-HIDA as a 'positive' one for the bile ducts was tested in dogs. The maximum effect of SPP was present about 30 minutes after injection with a reduction of the image intensity of the liver close to the background noise level at the highest dosages. This effect lasted for about 4 to 5 hours and it had disappeared after 24 hours. Before any contrast administration or after Cr-HIDA the bile ducts were not discernible, but a high signal in the gallbladder was present 15 to 30 minutes after injection of Cr-HIDA. After SPP the wider bile ducts were discernible because of the lowering of the signal intensity in the liver. When SPP were followed by Cr-HIDA, the bile had a higher signal intensity, and even tiny bile ducts were visible. After cholecystokinin visualization of the choledochus duct was achieved as well as contrast filling of the duodenum. The blood, urine, and liver function tests were found normal during the experiments. The combination of superparamagnetic particles and Cr-HIDA seems to be a promising method for MR-cholangiography. An evaluation of the anatomic structures of the liver should be possible with this method in different pathologies.     

不翻瓣技术在上颌前牙区种植中的应用效果

 目的 探讨不翻瓣技术在上颌前牙区种植中的应用效果。方法 选取2018年4-10月在武警北京总队医院进行上颌前牙区种植的32例患者,随机分为不翻瓣组(采用不翻瓣技术种植)和翻瓣组(采用翻瓣技术),每组16例。比较两组手术情况和种植手术后的效果;种植后3和6个月进行随访,比较种植体周围牙槽骨骨吸收程度。结果 不翻瓣组的手术时间(18.87±4.34)min,翻瓣组的手术时间为(37.27±5.35)min,两组差异有统计学意义(P<0.05);不翻瓣组的术后肿痛时间和抗生素应用时间分别为(0.85±0.33)d和(1.84±0.75)d,翻瓣组的术后肿痛时间和抗生素应用时间分别为(2.61±0.74)d和(4.22±1.36)d,两组对比差异均有统计学意义(P<0.05)。不翻瓣组种植后3个月和6个月时的种植体周围牙槽骨吸收分别为(0.29±0.05)mm和(0.36±0.07)mm,翻瓣组种植后3个月和6个月分别为(0.55±0.06)mm和(0.65±0.05)mm,两组差异有统计学意义(P<0.05)。结论 口腔种植采用不翻瓣技术,能缩短手术时间和手术后肿痛时间,减少抗生素使用,降低牙槽骨吸收。     

MR angiography with oblique gradient-recalled echo technique

Magnetic resonance (MR) angiography with use of an oblique gradient-recalled echo sequence is discussed. The technique was developed for the efficient acquisition of angiographic data when the desired projection direction is already known. The raw data set is acquired directly at the projection angle; thus, a high-resolution projection is created, despite a decrease in the number of phase-encoding views acquired per axial image. Excessive reduction in the number of views acquired causes a loss of contrast in the projection images rather than a loss of resolution. High-resolution, high-contrast MR projection angiograms can be obtained in 2 1/2 minutes, with 50 3-mm sections and 48 phase encodings per section, a repetition time of 50 msec, an echo time of 15 msec, and a flip angle of 45 degrees. This represents one-fifth the time required for a conventional angiographic image. Venous blood is successfully saturated when the saturation band is placed at a fixed distance from the current imaging section. The method is demonstrated in the imaging of the carotid bifurcation in healthy volunteers and of a patient who had undergone carotid endarterectomy.     

Percutaneous pulmonary valvuloplasty with a double-balloon technique

Percutaneous pulmonary valvuloplasty with a double-balloon technique was used in eight patients, aged 10-40 years, in whom valvuloplasty with a single 20-mm balloon resulted in inadequate dilatation of the stenosis. The diameters of the additional balloon varied from 10 to 20 mm. Balloons were inflated manually at about 30-45 psi (206.7-310.1 kPa) and deflated immediately after disappearance of the balloon waist. The mean peak systolic pressure gradient was 85 mm Hg +/- 37 before valvuloplasty, and it decreased to 38 mm Hg +/- 28 afterward (P less than .05). Double-balloon dilation and simultaneous computed tomography were done in two cardiac specimens from adult cadavers. At inflations at 30 and 45 psi (206.7 and 310.1 kPa), the outflow tract was elongated, and the balloons also deformed into ovoid shape at the lower pressure. The double-balloon technique appears to be safe and effective for relief of pulmonary valvular stenosis in those cases in which single-balloon technique is inadequate, especially in older children and adults.     

Three-dimensional magnetic resonance imaging technique for myocardial-delayed hyperenhancement: a comparison with the two-dimensional technique

PURPOSE: To compare two-dimensional and three-dimensional techniques in the detection of myocardial infarction (MI) and in the grading transmural extent (TE). MATERIALS AND METHODS: Twelve patients with clinically proven MI were examined using two-dimensional and three-dimensional techniques with cardiac-gated, breath-hold, T1-weighted gradient echo sequence with an inversion recovery pulse following gadopentetate dimeglumine (Gd-DTPA) at 0.2 mmol/kg. Contrast-to-noise, signal-to-noise, and signal intensity ratios (CNR, SNR, and SIR, respectively) were derived and compared for each technique. RESULTS: From two-dimensional to three-dimensional, statistical significant difference was found in the mean CNR (11.65 vs. 56.59; P = 0.002), SNR (18.03 vs. 76.90; P < 0.001), and SIR (3.6 vs. 6.36; P = 0.05). Intraobserver agreement (kappa) between two-dimensional and three-dimensional were R1 = 74% and R2 = 90%. Interobserver agreements between the readers were two-dimensional = 77% and three-dimensional = 79%. CONCLUSION: Mean CNR, SNR, and SIR are significantly increased in the three-dimensional technique compared to the conventional two-dimensional technique.     

Coronary MR angiography with steady-state free precession: individually adapted breath-hold technique versus free-breathing technique

PURPOSE: To compare image quality and coronary artery stenosis detection with breath-hold (BH) and free-breathing navigator-gated (NAV) coronary magnetic resonance (MR) angiography performed with the same imaging sequence (steady-state free precession) and identical spatial resolution in patients suspected of having coronary artery disease. MATERIALS AND METHODS: Forty consecutive patients suspected of having coronary artery disease underwent steady-state free precession MR imaging of the left or the right coronary artery twice. Correction of breathing motion was performed once with NAV and again with BH. Maximal BH duration and coronary artery rest period were individually determined, and duration of data acquisition was adapted (parallel imaging with different sensitivity encoding factors was used). Quantitative analysis of coronary MR angiography data was performed with multiplanar reformatting software to determine visual score for image quality, vessel sharpness, visible vessel length, and number of visible side branches. Diagnostic accuracy for detection of coronary stenosis of 50% or greater was determined in comparison with results of conventional invasive angiography. The two techniques were compared regarding differences in angiographic parameters with paired Student t testing. chi(2) or Fisher exact testing was used when appropriate. RESULTS: More coronary artery segments were assessable with NAV than with BH MR angiography (254 [79.4%] vs 143 [44.7%] of 320 segments). Overall sensitivity and specificity with NAV were 72% (26 of 36 segments) and 91.7% (200 of 218 segments), versus 63% (12 of 19 segments) and 82.3% (102 of 124 segments) with BH; NAV enabled correct diagnosis in 13% more segments. BH yielded nondiagnostic images in 14 patients, while NAV yielded diagnostic images in all patients. When these 14 patients were excluded, there was a significant increase in visual score for left (3.0 vs 2.4, P <.01) and right (3.3 vs 3.0, P <.05) coronary arteries and no significant difference in vessel sharpness but significant improvement in visible vessel length in left coronary artery (85.9 vs 71.4 mm, P =.003) and number of visible side branches in left (4.9 vs 3.9, P =.04) and right (2.8 vs 2.4, P =.04) coronary arteries on NAV images as compared with BH images. CONCLUSION: Free-breathing NAV was superior to BH coronary MR angiography in terms of image quality and diagnostic accuracy of stenosis detection.     

Masquelet技术对于创伤性骨缺损的治疗研究

目的探讨Masquelet技术在修复创伤或感染造成的大段骨缺损中的临床应用及疗效。方法笔者选取高州市中医院骨科2009年1月~2012年1月应用Masquelet技术修复创伤或感染造成的大段骨缺损的9例患者,男性7例,女性2例;年龄27~79岁,平均53岁。分为2期,一期为彻底清创后抗生素骨水泥填充骨缺损,目的为刺激诱导膜的产生;6~8周后诱导膜产生,行二期手术取出骨水泥,置入自体松质骨。结果对接受手术的9例患者进行平均时间为7个月的随访,所有患者的长骨愈合情况良好。结论 Masquelet技术为创伤后骨缺损治疗提供了满意的治疗效果,值得推广。     

A fast spin echo technique with circular sampling

This paper presents a fast spin echo (FSE) imaging method that employs circular sampling of Jr-space. The technique has been implemented on a 2 Tesla imaging system and validated on both phantoms and living animals. Experimental studies have shown that circular sampling can produce artifact-free FSE images without the need of phase correction. Although not fully explored, preliminary results also show that circular sampling may have advantages over the conventional rectilinear FSE in signal-to-noise ratio and imaging efficiency. A major disadvantage is the increased sensitivity to off-resonance effects. The authors expect that the FSE technique with circular sampling will find its applications in magnetic resonance microscopy, neuro-functional imaging, and real-time dynamic studies.     

Indoor radon measurement with The Lucas cell technique

Rn-222 is the most important source of natural radiation and is responsible for approximately half of the received dose from all sources. Most of this dose is from inhalation of the Rn-222 progeny, especially in closed atmospheres. A Lucas cell technique, using a portable device, “PRASSI” (SILENA mod. 5S), for Rn-222 measurements inside the Centre for Radiation Protection and Radioecology (ZSR), Hannover University was used. The portable radon monitor PRASSI is suitable for radon gas continuous or grab sampling measurements with the scintillation cell technique. In recognition of the wide periodic variations in concentration, measurements were made daily for extended periods. At the same time, meteorological variables, such as temperature and humidity were observed so that their influence on radon levels could be evaluated. The radon average concentration during the year was about 55.9 Bq/m³ which gives rise to an annual effective dose 2.2 mSv y⁻¹. The radon concentration is within the limits prescribed by the International Commission for Radiation Protection. A detailed analysis of radon distribution with seasonal variation is presented.