Self-planarized quantum-disks-in-nanowires ultraviolet-B emitters utilizing pendeo-epitaxy.

The growth of self-assembled, vertically oriented and uniform nanowires (NWs) has remained a challenge for efficient light-emitting devices. Here, we demonstrate dislocation-free AlGaN NWs with spontaneous coalescence, which are grown by plasma-assisted molecular beam epitaxy on an n-type doped silicon (100) substrate. A high density of NWs (filling factor >95%) was achieved under optimized growth conditions, enabling device fabrication without planarization using ultraviolet (UV)-absorbing polymer materials. UV-B (280-320 nm) light-emitting diodes (LEDs), which emit at ∼303 nm with a narrow full width at half maximum (FWHM) (∼20 nm) of the emission spectrum, are demonstrated using a large active region ("active region/NW length-ratio" ∼50%) embedded with 15 stacks of AlxGa1-xN/AlyGa1-yN quantum-disks (Qdisks). To improve the carrier injection, a graded layer is introduced at the AlGaN/GaN interfaces on both p- and n-type regions. This work demonstrates a viable approach to easily fabricate ultra-thin, efficient UV optoelectronic devices on low-cost and scalable silicon substrates.

Correlates of age at menopause and osteoporosis in Saudi women.

OBJECTIVE: To evaluate the age of menopause among Saudi Arabian women and to predict the local trend in the prevalence of osteoporosis. MATERIAL & METHOD: All menopausal women who had bone mineral density studies at King Khaled University Hospital, Riyadh, Saudi Arabia, between 1999 to 2003. Correspondence and logistic regression analysis were conducted to identify variables that were positively associated with age of menopause. RESULTS: 935 postmenopausal females were included. The mean age of menopause was 48.1 +/- 5.9 years. Early and late onset of menopause were associated with osteoporosis, while normal onset of menopause was associated with osteopenia or remained normal. There was no association between age of menopause and parity or body mass index. CONCLUSION: The age of menopause among Saudi women is lower than in Western countries but similar to other Arabic countries. In addition to cultural differences genetics play a role in determining the age of menopause and the development of osteoporosis.

Measurement of iodine-123 thyroid uptake using a gamma camera with LEAP collimator.

OBJECTIVE: This study compared the 123I thyroid uptake measurements obtained from a gamma camera fitted with a low-energy all-purpose (LEAP) collimator to those obtained from a thyroid uptake probe and gamma camera fitted with a pinhole (PH) collimator. METHODS: Thirty-one patients (27 female and 4 male patients) were studied for comparison between a probe and a gamma camera fitted with LEAP collimators. A different group of 25 patients (20 female and 5 male patients) were studied for comparison between LEAP and PH collimators. The patients were given 7.4-11 MBq (200-300 pCi) 123I capsules orally. Uptake with both the probe and the gamma camera was measured at 5 h and 24 h. The uptake measurements by these 3 methods were compared. RESULTS: Comparison of all the camera uptake values with the probe system correlated well with correlation coefficient values ranging from 0.912-0.988. The probe system yielded uptake ratios slightly higher than those measured by the gamma camera with LEAP collimator. Comparison between LEAP and PH uptake values resulted in a correlation coefficient of 0.979 for 5 h and 0.931 for 24 h uptake. CONCLUSION: Iodine-123 uptake with a gamma camera fitted with a LEAP collimator can accurately and consistantly be used to determine the thyroid uptake of 123I if proper ROIs are applied.

Features of hepatic cavernous hemangioma on planar and SPECT Tc-99m-labeled red blood cell scintigraphy.

PURPOSE: To determine the value and diagnostic accuracy of planar and SPECT Tc-99m-labeled red blood cell (Tc-99m RBC) scintigraphy in the investigation of suspected hepatic cavernous hemangioma as found on ultrasound. PATIENTS AND METHODS: One hundred patients, 89 women (89%) and 11 men (11%), between 22 and 67 years old (mean age, 38 years) were evaluated for liver masses found on abdominal ultrasound. All the patients had previous Tc-99m RBC scintigraphy. The size of the lesions ranged from 1 to 9 cm. The final diagnosis was reached through cytologic biopsy, or histopathologic tests (or all of these). RESULTS: One hundred thirty lesions were found. With regard to the distribution of the lesions, 116 (89%) were single; 14 (3%) were multiple, with 118 (91%) in the right lobe and 12 (9%) in the left lobe; 83 (64%) were posterior; and 47 (36%) were anterior. With respect to the pattern of radioactivity fill-in, 86 (66%) lesions were typical and 44 (34%) were atypical. The results of Tc-99m RBC scintigraphy showed sensitivity, specificity, and positive and negative predictive and accuracy values of 97%, 83%, 98%, 77%, and 96% respectively. The use of SPECT improved the sensitivity value by 11% for lesions of 1 to 2 cm. CONCLUSIONS: Tc-99m RBC scintigraphy is the noninvasive technique most helpful in the diagnosis of hepatic hemangioma, especially in those at risk for lesion rupture or bleeding. SPECT should be performed whenever planar imaging fails to show the lesion by 2 hours. The use of ultrasound should precede scintigraphy for two important reasons: the size and the location of the lesion. Location of the lesion (anterior or posterior) is important for optimal gamma camera acquisition parameters. Lesions less than 1 cm are cannot be detected because they are beyond the limit of spatial resolution of the gamma camera we used.

Familial occurrence of congenital hypothyroidism due to lingual thyroid gland.

Two sisters who presented with midline neck masses proved to be biochemically hypothyroid. Thyroid scintigraphy supplemented with perchlorate discharge testing showed lingual thyroid glands and ruled out the expected autosomal recessive organification defect. The related literature is reviewed.

Measurement of bone mineral density of the lumbar spine and femur in normal Saudi children and adolescents using dual x-ray absorptiometry.

Full text is available as a scanned copy of the original print version.

Osteoporosis in postmenopausal Saudi women using dual X-ray bone densitometry.

Full text is available as a scanned copy of the original print version.

Radionuclide esophageal transit time for the assessment of pneumatic dilation in patients with achalasia.

OBJECTIVE: The aim of this study was to assess the value of radionuclide esophageal transit time (RET) in prediction of the results of pneumatic dilation in patients with achalasia. PATIENTS AND METHODS: Thirty patients (13 males) with a mean age of 37 +/- 15.6 years (range 17-73 years) were included in the study. All patients were diagnosed to have idiopathic achalasia of the cardia and selected for pneumatic dilation. Each patient had three RET, two the same day of dilation (pre-and postdilation) and a third follow up one within three months of dilation (4 patients failed to come for follow up and were excluded). RESULTS: Several parameters were derived from RET studies, T/50: time required for 50% of activity in the esophagus to be cleared, T/10 : time required for 90% of activity in the esophagus to be cleared and percentage clearance at 10 min. These parameters were compared to response of dysphagia to dilation. It was evident that the higher the esophageal clearance postdilation, the better the outcome. When immediate post dilation clearance was 85% or more the success rate was 83.3% whereas when it was 20-50% the success rate was only 21.4%. No relation was found between T/50, T/10 and dysphagia response. CONCLUSION: RET appears to be a useful quantitative procedure in the assessment of pneumatic dilation outcome in achalasia patients.

TC-99m-labeled red blood cell scintigraphy in the investigation of patients with hepatic cavernous hemangioma.

OBJECTIVE: To evaluate the diagnostic accuracy of 99mTc-red blood cell scintigraphy in the diagnosis of hepatic cavernous hemangiomas. PATIENTS AND METHODS: Sixty three patients, 56 females (89%) and 7 males (1 I%), with ages between 22 and 54 years (median 33 years) were investigated for liver masses found on ultrasonography of the abdomen. All the patients had undergone 99mTc-liver-spleen scan followed by 99mTc-red blood cells scintigraphy. The size of the lesions ranged between 3 and 9 cm. The final diagnosis was reached through cytology, and/or histopathology or follow up for more than 3 years. RESULTS: A total of 70 lesions were found as a single lesion in 60 patients and multiple (i.e. total of 10 lesions) in the other 3 patients. The results of 99mTc-red blood cells scintigraphy, compared to the results of the final diagnosis, showed sensitivity and specificity rates of 100% and 89% respectively, positive and negative predictive values of 98% and 100% respectively, and accuracy rate of 98.6%. A single false positive case was a hepatocellular carcinoma. CONCLUSION: 99mTc- red blood cell scintigraphy is highly accurate in the diagnosis of liver cavernous hemangioma and should characterize liver mass found on ultrasonography and suspected for hemangioma.

Osteopetrosis in children.

Over a 10-year period, 28 Arab children with autosomal recessive osteopetrosis were seen in two hospitals in Riyadh, Saudi Arabia. Eighteen (64%) had osteopetrosis associated with metabolic acidosis probably due to a renal tubular defect; nine (32%) had a malignant infantile form of osteopetrosis and one had a mild form with delayed onset. Parental consanguinity was 56% and 40% among patients with and without acidosis respectively. Somatic and psychomotor retardation and recurrent bone fractures were common in both groups. Dental caries, cerebral calcification and optic atrophy were more frequent in patients with acidosis, while anaemia, hepatosplenomegaly and deafness were more common in patients without acidosis. To guarantee optimal rehabilitation, children with this progressive disease require an early multiteam approach.

Hepatobiliary scintigraphy in the distinction between biliary hypoplasia and biliary atresia.

The aim of this work is to see whether distinction between biliary atresia and biliary hypoplasia is possible or not and to present the value and usefulness of hepatobiliary scintigraphy in the investigation of infants with persistent hyperbilirubinemia. Seventy-seven patients of the age between five days and six months (average 62 days), 43 females and 34 males of which 65 Saudi, and 12 non-Saudis were investigated. Laboratory tests, abdominal ultrasound, hepatobiliary scintigraphy, liver biopsy, explorative laparatomy and intraoperative cholangiography were performed whenever indicated. The findings on hepatobiliary scintigraphy of nonvisualization of the gallbladder and no activity in the bowel upto 24 hours post injection were considered consistent with the diagnosis of biliary atresia. Minimal bowel activity, or visualization of the gallbladder where consistent with biliary hypoplasia. In addition, the liver in the two entities appeared in a different shape and can be used as an additional distinctive feature. Thirty-four infants were diagnosed by hepatobiliary scintigraphy as having biliary atresia. Only 3 of the 34 were false positives as compared to cholangiogram and liver biopsy results. Five cases were biliary hypoplasia. Hepatobiliary scintigraphy in infants with persistent hyperbilirubinemia can be distinguished between BA and BH in a simple and noninvasive approach.

Hemiconvulsion-hemiplegia-epilepsy syndrome. A clinical, electroencephalographic and neuroradiological study.

Six patients (4 boys and 2 girls) with hemiconvulsion-hemiplegia-epilepsy (HHE) syndrome are described. They had prolonged seizures, lasting from 30 min to 12 h, at ages 1-4 years. These took the form of hemiconvulsion in three of the children and generalized tonic-clonic seizures in the others, being preceded by hemifacial twitching or head and eye deviation in two. They were followed by hemiplegia, which cleared with time in five patients, apart from subtle pyramidal tract signs. One child had spastic quadriparesis, choreiform movements, contracture deformities and severe mental retardation following repeated status epilepticus. Subsequent epilepsy developed in five patients and was satisfactorily controlled with carbamazepine and/or phenobarbitone. Cerebral hemiatrophy was documented in all patients by cranial computed tomography and/or magnetic resonance imaging. Single photon emission computed tomography (done in 4 patients) showed ipsilateral hypoperfusion (of the damaged hemisphere). Electroencephalography showed ipsilateral slowing and low voltage of background activity. Epileptiform discharges were found on the ipsilateral side in two cases and the contralateral side (the undamaged hemisphere) in one.

Bone mineral density and bone scintigraphy in children and adolescents with osteomalacia.

In order to demonstrate the role of bone mineral density (BMD) measurement and bone scans in the management of patients with osteomalacia, radioisotope bone scintigraphy using technetium-99m methylene diphosphonate (MDP) and BMD measurements of the lumbar spine and femur by means of dual X-ray absorptiometry (DXA) were performed at the time of diagnosis and 6 months after therapy in 26 Saudi patients (17 females and nine males). Their mean age was 13.5 years (range, 5-16). BMD measurements were compared with those of normal Saudi subjects matched for age and sex. Bone scan showed an increase in tracer uptake throughout the skeleton ("superscan") in all children and demonstrated multiple stress fractures in eight. The mean BMD for the lumbar spine was 0.53 g/cm2 (Z-score, -3.1) and for the femoral neck 0.55 g/cm2 (Z-score, -2.8). Repeated bone scan and BMD after 6 months of therapy with oral vitamin D, calcium and proper sun exposure demonstrated a significant increase (P<0.001) in BMD and healing of pseudofractures. In conclusion, as a non-invasive method with minimal radiation exposure, measurements of BMD in children with osteomalacia are to be recommended in the initial assessment of the severity of osteopenia and in the follow-up to monitor the response to therapy. Bone scintigraphy is valuable in demonstrating the site and severity of stress fractures.

Congenital anomalies in infants with congenital hypothyroidism: is it a coincidental or an associated finding?

During the period between December 1988 and February 1995, a total of 279,482 newborn infants were screened in the regional neonatal screening program for congenital hypothyroidism (CH) in Riyadh province, Saudi Arabia. Eighty-one infants were confirmed to have CH giving an incidence of 1 in 3,450. Variable congenital anomalies, other than those of the thyroid gland, were present in 16 (19.8%). The anomalies most frequently encountered were congenital heart defects (7), unclassified multiple congenital anomalies (5) and Down's syndrome (2). The results of our study confirm this association, and emphasize the need to search for such anomalies in infants born with CH. Nationwide studies, however, on birth defects in the general population and those associated with CH are still needed to help us understanding the role of local genetic and environmental factors.

Transient iodine organification defect in infants with ectopic thyroid glands.

BACKGROUND: Thyroid gland ectopy is the most common cause in infants with congenital hypothyroidism (CH). Its association with iodine organification defect, as suggested by positive perchlorate discharge test (PDT) has been reported. However, whether such an association represents a true or transient defect has not yet been determined. This finding has an important clinical, epidemiological, and genetic implications. OBJECTIVE: To determine the natural history of iodine organification defect in patients with CH caused by thyroid ectopy detected by neonatal screening. DESIGN: Prospective longitudinal study. SETTING: King Khalid University Hospital, Riyadh, Saudi Arabia. PATIENTS AND METHODS: PDT was performed, at the time of diagnosis and follow-up, in infants who showed an enlarged ectopic thyroid gland with a Tc-99m pertechnetate uptake of 2% or more. RESULTS: Of 115 neonates with ectopic thyroid glands, 19 showed an enlarged gland with Tc-99m uptake ranging from 2 to 3.2%. Perchlorate discharge test was performed in 13 of these and was consistent with iodine organification defect in nine. Repeated PDT in seven patients showed normal values. CONCLUSION: The results of the authors' study indicate the transient nature of the iodine organification defect and suggest that a delay in the developmental of synthetic mechanisms occur in the dysgenetic glands.

Hepatobiliary scintigraphy in the diagnosis of choledochal cysts in children.

The objective is to present the usefulness of hepatobiliary scintigraphy in the investigation of children with suspected choledochal cysts through our experience in King Khalid University Hospital at King Saud University, Riyadh. Seven patients aged between I and 10 years (average 4.8 yrs) comprising six females and one male were investigated. Laboratory tests, abdominal Ultrasound and/or CT, and cholangiography were performed whenever indicated. Persistent activity in a dilated common bile duct, with or without dilatation of intrahepatic bile ducts, was considered a positive indicator for choledochal cyst disease. Four children with cystic dilatation (type I) were diagnosed by hepatobiliary scintigraphy, one saccular (type II), and two cases of Caroli's disease (type V). The diagnosis of choledochal cyst was proven by surgery with histological confirmation. Visualization of the gallbladder occurred in one case only. The common bile duct was seen in four cases. Late activity in the bowel was noted in two cases.

Congenital hypothyroidism: increased incidence in Najran province, Saudi Arabia.

Neonatal screening for congenital hypothyroidism using cord serum thyroid-stimulating hormone (TSH) was initiated in Najran health region in September 1990. A total of 30810 newborn infants were screened by April 1995. Of the 24 infants with abnormal thyroid function tests on recall, 22 had permanent primary congenital hypothyroidism (incidence; 1:1400) and in two male siblings transient congenital hypothyroidism (incidence; 1:15400) was proved on follow-up. There was a significantly higher incidence of dyshormonogenesis. Eight (57 per cent) of the 14 infants who were adequately studied thyroid scan revealed ectopic glands with increased 99mTc uptake, while thyroid ectopy and aplasia were present only in three (22 per cent) infants each. Furthermore, goiter was evident clinically in two other patients.

Neonatal screening for congenital hypothyroidism in Riyadh: Analysis of six year's experience.

The regional screening program for congenital hypothyroidism (CH) in Riyadh Province was started as a pilot study in December 1988. By September 1990, the program covered all deliveries at the Ministry of Health (MOH) and King Saud University hospitals. The program utilizes cord serum thyroid-stimulating hormone (TSH) with a low recall rate of 0.1%. The average cost per specimen was SR 12 (US$ 3.20). Among 283,647 infants screened, 83 infants were confirmed to have CH (incidence 1:3417). In 17 infants, however, the diagnosis was not confirmed due to difficulties in recall. Eleven infants with cord serum TSH of more than 100 mU/L proved to be clinically and biochemically euthyroid at recall. Three of these were secondary to maternal proplthiouracil (PTU) therapy. The female to male ratio was 1.5:1. The majority of infants lacked clinical symptoms and signs of hypothyroidism. Thyroid scans showed the most common etiology to be thyroid ectopy (50%), followed by dyshormonogenesis (26%) and athyrosis (24%). Although there was no significant difference in the mean cord T4 values among the different groups, the mean T4 value at recall in the athyrotic group was significantly (P <0.001) lower than the cord results (14.8 versus 62.7) and that is of recall for the ectopic and dyshormonogenesis groups (14.8 versus 47.0 and 51.3 respectively0. There was bo significant difference in the mean TSH among the different groups in the cord and recall samples. Skeletal maturation was more delayed in the athyrotic group. The mean age at the time of recall was 16.4 days (range 4 to 64), and the mean age at the start of therapy was 17.8 days (range 5-64).

Bone scintigraphy and densitometry in children with osteopetrosis.

Bone scintigraphy and dual x-ray absorptiometry were performed in 18 children (8 males, 10 females) with clinical and radiologic diagnoses of osteopetrosis in order to demonstrate the scintigraphic features of this rare disorder and to measure the bone mineral density. Their mean age was 9 years (range, 3-16 years). Bone scintigraphy demonstrated characteristic features of a widened metaphysis of all long bones that showed increased tracer uptake, particularly in the distal femur and proximal tibia. Dual x-ray absorptiometry of the lumbar spine, three femoral sites, and total body showed a marked increase in bone mineral density. The mean values for bone density of the lumbar spine and greater trochanter were markedly elevated than were other sites. Compared with a normal group matched for age and gender, the increase in bone mineral density was 181% for the lumbar spine and 193% for the greater trochanter. The authors concluded that bone imaging and bone densitometry are useful in establishing the diagnosis of osteopetrosis by demonstrating increase tracer uptake in the widened metaphysis and increased bone density. Bone densitometry may be of prognostic value in follow-up, especially in monitoring the response to therapy.

Thyroid scintigraphy and perchlorate discharge test in the diagnosis of congenital hypothyroidism.

Quantitative thyroid scanning using low doses of technetium-99m sodium pertechnetate was performed on 147 infants (55 males and 92 females) with congenital hypothyroidism detected through the national neonatal screening programme. Thirty-two (21.8%) were athyrotic, while 62 (42.2%) had an ectopic thyroid and 53 (36%) had a eutopic gland with increased 99mTc uptake (mean 17%; range, 5%-38%). The perchlorate discharge test (PDT) was performed in nine of the infants with ectopic glands and 15 with eutopic glands; the findings were consistent with an organification defect in 22 cases (seven ectopic and 15 eutopic). Thyroid scintigraphy and PDT can add useful aetiological, genetic and prognostic information in the clinical evaluation of infants with congenital hypothyroidism detected by neonatal screening.