Radiation dose estimation in computed tomography examinations using NRPB-SR250 software in aretrospective analysis of a patient population.

Computed tomography (CT) imaging contributes to a major part of medical radiation exposure. With regard to patients safety, frequent CT examinations (CTEs) performed on the same patient are of particular concern. Tools for tracking the individual patient radiation exposure history and cumulative dose assessment may become important. Here, the applicability of the NRPB-SR250 software was assessed in a retrospective analysis of radiation doses from CTE made consecutively in male patients. Most of the examinations focused on the abdomen or the whole body. The mean number of CTs per patient was 6.8. Significant cumulative effective doses were observed: 76 (66 %) patients received an effective dose higher than 50 mSv, while the maximum was ∼280 mSv. A more than 3-fold effective dose difference was observed between scanners, depending on the scanning protocols. The NRPB-SR250 software proved to be a robust tool for the assessment of organ doses and the effective radiation dose from CT, while challenges were encountered in finding the precise imaging data in retrospective protocols.

Comparison of digital and conventional radiostereometric image analysis in an ankle phantom model.

BACKGROUND AND AIMS: Radiostereometric analysis (RSA) allows accurate three-dimensional measurements of micromotion in skeletal structures. The current RSA techniques are based on the analysis of scanned plain films. This study was undertaken to compare digital filmless RSA technique to conventional scanning technique using a phantom model of the ankle mortise. MATERIAL AND METHODS: In the first experiment, the relative displacement of the markers inserted to the fibula in relation to the markers inserted to the tibia was studied by means of double examinations and the precision of DICOM images were compared to scanned images of printed radiographs. In the second experiment, the film pair of double examination was re-imported or re-scanned and self-compared in order to show merely the error related to the image processing. RESULTS: The precision of RSA using scanned images of printed radiographs was compatible to DICOM images. However, the mean error of rigid body fitting (ME) values were significantly lower in use of DICOM images compared with scanned radiographs, indicating less deformation of rigid body segments in filmless analysis. CONCLUSIONS: Precision of the RSA method was improved under the completely filmless environment. Therefore, this technique can be recommended for clinical studies of radiostereometric analysis.

Auditory evoked potential monitoring with the AAITM-index during spinal surgery: decreased desflurane consumption.

BACKGROUND: The auditory evoked potential (AEP) is sensitive to the depth of anesthesia. The A-line monitor is a novel device that processes the amplitude and latency of the AEP during the mid-latency time window to provide a simple numerical index, the AAItrade mark-index. The hypothesis of the present study was that titration of anesthetic depth (desflurane) by means of the AAItrade mark-index could decrease the consumption of the main anesthetic and shorten emergence times. METHODS: Thirty ASA I-II patients scheduled for elective open spine surgery under general anesthesia were randomly allocated to two groups. Group I (n=15), the main anesthetic, desflurane, was titrated with a target AAItrade mark-index of 20+/-5. Group II (n=15), desflurane was titrated according to routine clinical signs, including heart rate, blood pressure, sweating and tears. No fixed MAC-multiple was sought. The primary study variable was desflurane consumption; and secondary study variables were time to extubation and orientation. RESULTS: All patients had an uncomplicated course and no patients showed signs of awareness or had any recall postoperatively. AAItrade mark-index guidance reduced desflurane consumption by 29% and improved emergence. Time until extubation and orientation and ability to state name and date of birth was significantly shortened among AAItrade mark-index titrated patients. CONCLUSION: Titrating depth of desflurane anesthesia using AAItrade mark-index guidance decreased main anesthetic consumption and improved emergence during spine surgery.

Clinical follow-up method for frontal sinus obliteration with bioactive glass S53P4.

A clinical follow-up method was developed to investigate the behavior of a massive amount of bioactive glass S53P4 (BG) clinically used in frontal sinus obliteration. Two sizes of granules (0.63-0.8 mm or 0.8-1.0 mm) in 16 separate BG amounts, weight 25 g, were tested both in simulated body fluid (SBF) and in a buffer containing tris-hydroxymethyl aminomethane citric acid (TRIS-c.a) in standard conditions. The dissolution of silicon (Si) and phosphate (P) was detected with direct current plasma atom emission spectroscopy (DCP-AES) monthly up to 6 months. The BG masses were scanned both wet in the solutions and dried by computer tomography (CT), and the scans were analyzed by Region of Interest (ROI) technique. Calcium phosphate (CaP)- and silica (Si)-gel-layers were studied by scanning electron microscopy (SEM) at 1, 3, and 6 months. Cumulative loss of Si and P was stronger in TRIS-c.a than in SBF (p < 0.0001), and it was higher with smaller than with larger granules in both solutions (p < 0.0001). This was shown correspondingly by the decrease of Hounsfield units (HUs) in ROI analysis (p < 0.0001). The level of HUs was lower with dried than with wet BG (p < 0.0001). The results were compared for clinical ROI analysis of patients with obliterated frontal sinuses up to 48 months and they were parallel. The follow-up method seems to indirectly reveal the behavior of BG and the healing process in the obliterated cavity.

Pain and orthopaedic and neurologic signs after lumbar discectomy: a 2-year followup.

In a prospective study of 161 consecutive patients with lumbar discectomy, pain, lumbar mobility, and neurologic and root tension signs were followed up for at least 2 years. Sciatica and root tension signs decreased promptly after surgery and remained largely unchanged during followup, which was not the case for neurologic signs. Similarly, pain relief was not associated with neurologic signs but was associated with lumbar mobility and root tension signs. Patients without neurologic symptoms before surgery did not report more sciatica after 2 years than did those with positive neurologic signs before surgery. Positive crossed Lasegue sign and restricted lumbar mobility before surgery predicted better chances for postoperative pain relief. Patients with a ruptured anulus fibrosus at surgery had less sciatica and back pain after surgery than did patients with an intact anulus fibrosus.

Experimental follow-up model for clinical frontal sinus obliteration with bioactive glass (S53P4).

Bioactive glass S53P4 (BG) is an osteoconductive allograft material. Since 1990, BG has been used in the obliteration of frontal sinuses in more than 30 consecutive patients. The patients have been monitored regularly with clinical examinations, computer tomography (CT) scans, laboratory tests and, in a few cases, biopsies have also been obtained. The material has been well tolerated and no loss of volume of obliteration material has been seen in the obliterated sinuses. However, in repeated CT monitoring and with Region of Interest (ROI) analysis, a decrease in the density of the obliteration material inside the frontal sinuses has been seen. In the present study, the clinical conditions after an obliteration operation were simulated and the behaviour of the BG in the obliterated area was observed. The aim was to study whether it is possible indirectly to estimate the resorption of a massive amount of BG with ROI analysis for monitoring the clinical success of the treatment. Thus two sizes of granules (0.63-0.8 mm and 0.8-1.0 mm) in eight separate BG amounts, weight 25 g, were tested in simulated body fluid (SBF) in standard conditions. The dissolution of silicon (Si) and phosphate (P) was detected with direct plasma atom emission spectroscopy (DCP-AES) monthly up to 6 months. The BG amounts were scanned with CT and the slices analysed using the ROI technique at 1, 3 and 6 months. The cumulative loss of Si and P in SBF was significant during the study (p < 0.0001) and it was stronger with smaller than with larger granules (p < 0.0001). This was shown correspondingly by the decrease of Hounsfield units (p < 0.0001) in ROI analysis. The method seems reliably to reveal the resorption of BG for clinical purposes.

In vitro model for frontal sinus obliteration with bioactive glass S53P4.

An in vitro model was used to investigate the behavior of a massive frontal sinus obliteration with bioactive glass S53P4 (BG) for clinical purposes. Two sizes of granules (0.63-0.8 mm or 0.8-1.0 mm) in 16 separate BG amounts, weight 25 g, were tested both in simulated body fluid (SBF) and a buffer containing trishydroxymethyl aminomethane citric acid (TRIS-c.a) in standard conditions. The dissolution of silicon (Si) and phosphate (P) was detected with direct current plasma atom emission spectroscopy (DCP-AES) monthly up to 6 months. The BG masses were scanned by computer tomography (CT) and the scans analyzed by Region of Interest (ROI) technique. Calcium phosphate (CaP)- and silica (Si)-gel-layers were studied by scanning electron microscopy (SEM) at 1, 3, and 6 months. Cumulative loss of Si and P was stronger in TRIS -c.a than in SBF (p < 0.0001), and it was higher with smaller than with larger granules in both solutions (p < 0.0001). This was shown correspondingly by the decrease in Hounsfield units (HU) by ROI analysis (p < 0.0001). In SBF-soaked BG masses, the CaP-layer occurred on the uppermost granules, and in TRIS-c.a at 3-6 months, on the granules in the center and lower parts. The decrease of HU seems to reveal indirectly the resorption of BG.

Pain and pathology in lumbar disc hernia.

The authors analyzed pain drawings of patients having lumbar disc surgery and tried to correlate pain pattern to disc pathology and level. Preoperatively, patients having spinal surgery were asked to draw on a standardized form the localization, postural variation, and modality of their pain. In this study, 185 consecutive patients with unilateral and unisegmental L4-L5 and L5-S1 hernias were analyzed. The pain drawings were coded and read blindly; each drawing was divided operationally into anatomic areas, and the type of pain symbol in each pixel was recorded, digitized, and analyzed by stepwise discriminant analysis. For predicting the level of the lesion, the most important variables were pain on the anterolateral aspect of the leg (L4-L5) and pain radiating to the posterior aspect of the foot (L5-S1). For predicting the grade of herniation, the most discriminative factors were pain radiating to the foot (sequestrated hernia) and bilateral back pain (protruded hernia). Pain drawing facilities communication and documentation. In addition, it is an aid to diagnose the level and degree of the hernia, and therefore is useful for selecting patients who might benefit from disc surgery. For scientific purposes, data are digitized easily, allowing analyses of large populations.

The effect of weight-bearing pressure on the plantar circulation in diabetes mellitus.

Patients with diabetic neuropathy are prone to ulceration on the sole of the foot, especially in areas with high weight-bearing pressure. The relationship between weight-bearing pressure and nutritive skin circulation in the plantar region was studied. Gait analysis was performed with the EMED Gait Analysis System and the skin circulation was measured by fluorescein flowmetry in ten neuropathic diabetic patients and in eight healthy controls. The critical plantar foot pressure above which nutritional blood flow in the skin was arrested was 3 N cm-2 or more in both diabetic and control subjects. Below 3 N cm-2 the blood flow was independent of weight-bearing pressure both in diabetic and control subjects (correlation coefficient r = -0.01 and -0.19, respectively). Thus, our results indicate that the nutritional blood flow in the plantar region is not decreased in patients with diabetic neuropathy.

Skin circulation in the nipple after reduction mammaplasty with a bipedicle vertical dermal flap.

Necrosis of the nipple after a reduction mammaplasty with transposition of the nipple is a serious complication. A study was undertaken to measure the skin circulation in the nipple before, during and after this operation. In 16 patients undergoing reduction mammaplasty according to the method of McKissock, the skin circulation was measured in both breasts by laser Doppler flowmetry (LDF) and fluorescein flowmetry (FF). LDF showed that the skin circulation increased after de-epithelialization to 245.7 +/- 39.3% of the preoperative blood flow (100%) (mean +/- SEM, p less than 0.01). When 40 ml of 0.25% adrenaline was injected into the incision lines, the corresponding increase in blood flow was 153.4 +/- 15.6% (p less than 0.01). After the medical and lateral glandular resections the blood flow in the nipple of the vertical dermal pedicle was 125.6 +/- 21.2% of the preoperative blood flow and when adrenaline was given the corresponding value was 79.3 +/- 6.5%. After the skin had been sutured, the blood flow was 128.4 +/- 25.9% of the preoperative value and in the breast in which adrenaline was injected it was 177 +/- 96.9%. One to four days postoperatively the blood flow was 123.1 +/- 19.9% of the preoperative value and in the breast that received adrenaline 130 +/- 24%. At FF homogeneous fluorescence was observed in the nipple postoperatively in all patients but one; in this patient avascular necrosis later developed. Our results thus show that the circulation in the nipple after reduction mammaplasty by the McKissock method is adequate.

MR imaging of experimental intramuscular hemorrhage at 0.02 T. Contrast enhancement with Gd-DOTA.

Intramuscular hemorrhage was induced by injecting autologous blood into the paraspinal muscle of 8 rabbits. In order to evaluate the time-dependent changes of hemorrhage observed on MRI, the animals were imaged at different stages of blood resolution at 0.02 tesla (T), and control examined with ultrasound using a 7.5 MHz linear transducer. Six inversion recovery sequences (TR = 1,000 ms. TE = 30 ms, and TI = 18, 48, 148, 201, 302, and 398 ms) were used for the in vivo calculation of T1 relaxation times. IR 1,000 (398)/30 imaging was performed before and after the Gd-DOTA administration. The hemorrhage was evident on MR images throughout the study, especially on the T2 weighted (SE 1,000/100) images. MRI showed the healing lesion longer than ultrasound. The T1 relaxation time increased during the time of resolution. Lesions on days 4 to 7 enhanced in intensity after the injection of Gd-DOTA.

Method dependence of proton spin-lattice relaxation analysis in biologic tissues.

Spin-lattice proton relaxation times (T1) in several biologic and phantom samples have been measured and analysed by using standard inversion recovery (IR) and spin echo (SE) sequences at 0.02 T. The average T1 of the sample was measured with the two-data point method. In the case of bi-exponential relaxation the value of a single T1 is strongly dependent on the TI and TR selected. With short TI the T1 value obtained by using the two point method is approximately equal to the weighted average of the two relaxation time components (T1s and T1l), while at long inversion times TI the single T1 is more dependent on the long component T1l. The more the true short and long relaxation time components T1s and T1l of the bi-exponential relaxation differ from each other, the greater is the potential error, provided that the weights ws and wl do not differ very much. When two-data point analyzing method is used, the possible multi-exponential behaviour of the relaxation in tissues will be missed. For more reliable T1 values a series of images with as many values of TI as possible should be taken. Knowledge of true multi-exponential relaxation parameters helps in optimizing the sequence parameters and the image contrast between the various tissues.

The utility of contrast media in MRI at 0.02 T. A preliminary report.

The effect of 0.1 mmol gadolinium-DTPA on ultralow field magnetic resonance (MR) images of intracranial neoplasms was studied on 20 patients. Tumors that characteristically were enhanced markedly on computed tomography (CT) (meningiomas, acoustic neuromas) demonstrated moderate to marked contrast enhancement with inversion recovery sequences and with saturation recovery sequences with a short repetition time. Standard spin-echo sequences failed to show any contrast effect. The enhancement of gliomas and metastases was weak and often absent. Contrast enhancement, when present, was helpful in delineating the tumor from surrounding edema but the differentiation of living from necrotic tumor was not successful because of low signal intensity. The low effect of gadolinium-DTPA at 0.02 T may be due to a relatively higher T2 weighting of available pulse sequences. The relaxing effect of macromolecules may also change the proportional effect of paramagnetic substances in an ultralow magnetic field.

Paramagnetic contrast enhancement at 0.02 T: an experimental study using Gd-DOTA in normal and hydronephrotic kidneys.

Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd-DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd-DOTA injection. The enhancement pattern was similar in 1- and 3-week-old hydronephrosis. The effect of Gd-DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd-DOTA injection (0.1 mmol/kg) the T1 times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd-DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fields (greater than 0.15 T).

Examination of infant brain maturation using ultra low field MRI.

The brains of 42 newborn infants were examined with MRI at 0.02 T field, and regional variations of T1 relaxation time were measured from the images. There were three groups: 1. full term infants (9), 2. preterm infants (10) and 3. SGA (= small for gestational age) infants (20). Relaxation times showed a correlation to myelination of the brain. The brain of SGA infants showed a large variation in their T1 values.

Skin circulation in the nipple after reduction mammaplasty by upper and lower glandular resections.

Avascular necrosis of the nipple is a serious complication of reduction mammaplasty with nipple transposition. A study was undertaken to measure the skin circulation in the nipple before, during and after this operation. In 14 patients undergoing a reduction mammaplasty according to the method of Strömbeck, the skin circulation was measured in 25 breasts with laser doppler flowmetry (LDF) and fluorescein flowmetry (FF). LDF showed that the skin circulation increased after de-epithelialization to 204.4 +/- 31.0% of the preoperative value (100%) (mean +/- SEM, p less than 0.01). After the upper and lower glandular resection the circulation was reduced to 90.7 +/- 12.3% of the preoperative value. The division of the lateral pedicle did not affect the circulation. After the skin had been sutured, the circulation was 71.5 +/- 9.1% of the preoperative value (p less than 0.01). One to four days postoperatively the circulation was 100.3 +/- 13.2% of the preoperative value. At FF uniform fluorescence was observed in the nipple postoperatively in all patients but two, in whom avascular necrosis later developed. Our results thus show that the circulation in the nipple after reduction mammaplasty by the Strömbeck method is adequate and that it is safe to divide the lateral dermal pedicle.

Laser iridotomy in post-traumatic and post-surgical pupillary block: a report of five cases.

In five cases of aphakic pupillary block after trauma or surgery we found laser iridotomy to be a simple, effective, non-invasive alternative to operation in relieving pupillary block where medical management had failed.