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T Sundin

Publications and source records attributed to T Sundin.

At least 19 recordsLinked to original sources
PubMed2001

MR spectroscopy quantitation: a review of time-domain methods.

In this article an overview of time-domain quantitation methods is given. Advantages of processing the data in the measurement domain are discussed. The basic underlying principles of the methods are outlined and from them the situations under which these algorithms perform well are derived. Also an overview of methods to preprocess the data is given. In that respect, signal-to-noise and/or resolution enhancement, the removal of unwanted components and corrections for model imperfections are discussed.

Algorithms↗
PubMed2001

Nonparametric NMR spectroscopy.

The parametric (or model-based) approach to NMR spectroscopy suffers from two general problems: it is sensitive to modeling errors and requires knowledge of the number of resonances present in the compound(s) under analysis. The nonparametric approach has neither of these drawbacks and it may also be computationally simpler than the parametric approach. However, if not applied properly, the nonparametric approach may yield significantly less accurate spectroscopic results than the parametric approach. In this paper we introduce a high-resolution nonparametric methodology for NMR spectroscopy based on the adaptive filter bank approach. The main salient feature of the new approach is that it provides 2D spectra versus both frequency and damping, as opposed to the classical 1D frequency spectra routinely used in NMR spectroscopy. To show the power of our new nonparametric approach we compare its performance with the ultimate performance of the parametric approach. We use both simulated and real NMR signals in our numerical performance study.

Magnetic Resonance Spectroscopy↗
PubMed2000

Frequency-selective quantification of biomedical magnetic resonance spectroscopy data.

In this paper the possibility of obtaining accurate estimates of parameters of selected peaks in the presence of unknown or uninteresting spectral features in biomedical magnetic resonance spectroscopy (MRS) signals is investigated. This problem is denoted by frequency-selective parameter estimation. A new time-domain technique based on maximum-phase finite impulse response (FIR) filters is presented. The proposed method is compared to a number of existing approaches: the application of a weighting function in the time domain, frequency domain fitting using a polynomial baseline, and the time-domain HSVD filter method. The ease of use and low computational complexity of the FIR filter method make it an attractive approach for frequency-selective parameter estimation. The methods are validated using simulations of relevant (13)C and (31)P MRS examples.

Adenosine Triphosphate↗
PubMed2000

Exact ML estimation of spectroscopic parameters

In a paper on spectroscopic imaging published in this journal Spielman et al. (J. Magn. Reson. 79, 66-77 (1988)) made the important point that a priori information about the compounds present can and should be incorporated into the estimation of spectroscopic signal parameters. They proposed using the maximum likelihood (ML) approach for parameter estimation, but failed to incorporate properly the full a priori information that was assumed to be available. Consequently they ended up with a spectroscopic imaging method that is only a suboptimal approximation of the ML method. In this paper we derive the exact ML method, present a computationally efficient implementation of it (which is much faster than the direct implementation suggested by Spielman et al. for their suboptimal method), and illustrate numerically the performance gain that can be achieved over the method of Spielman et al. Copyright 2000 Academic Press.

Journal Article↗
PubMed1999

Accurate quantification of (1)H spectra: from finite impulse response filter design for solvent suppression to parameter estimation.

A scheme for accurate quantification of (1)H spectra is presented. The method uses maximum-phase finite impulse response (FIR) filters for solvent suppression and an iterative nonlinear least-squares (NLLS) algorithm for parameter estimation. The estimation algorithm takes the filter influence on the metabolites of interest into account and can thereby correctly incorporate a large variety of prior knowledge into the estimation phase. The FIR filter is designed in such a way that no distortion of the important initial samples is introduced. The FIR filter method is compared numerically with the HSVD method for water signal removal in a number of examples. The results show that the FIR method, using an automatic filter design scheme, slightly outperforms the HSVD method in most cases. The good performance and ease of use of the FIR filter method combined with its low computational complexity motivate the use of the proposed method.

Algorithms↗
PubMed1995

Delayed management of posterior urethral disruption in children.

OBJECTIVE: To review the results of delayed operative treatment of total disruption of the posterior urethra in children. PATIENTS AND METHODS: Twelve boys (3-12 years, mean 7.5) with a suprapubic catheter were referred after primary management in other hospitals. All but one had been involved in road traffic accidents. In addition to their urethral injury, they all had pelvic fractures and the majority also had other major associated injuries. Six to 14 months after injury, abdominoperineal transpubic urethroplasty was performed in 11 patients according to Turner-Warwick. In one case a perineal anastomotic urethroplasty was performed. RESULTS: After the operation, voiding cysto-urethrography showed a wide anastomosis in all cases. After 3 to 45 months follow-up, there were no strictures. Eight boys were continent, two were totally incontinent, two had stress incontinence and one nocturnal enuresis. All patients with confirmed erections after injury also had erections after their operation. CONCLUSION: Primary suprapubic cystostomy and delayed repair can be used successfully for the treatment of posterior urethral disruption in children.

Accidents, Traffic↗
PubMed1995

Augmentation cystoplasty after cesarean hysterectomy for placenta previa-percreta.

We report a case of a 38-year old woman with placenta previa-percreta and urinary bladder invasion. Resection of the bladder wall during cesarean hysterectomy was complicated by a postoperative vesico-vaginal fistula and small-capacity bladder. A reconstructive augmentation cystoplasty utilizing the ileum was successful in improving the bladder capacity. To our knowledge, this is the first report of a placenta previa-percreta with bladder wall invasion which required reconstructive augmentation cystoplasty after cesarean hysterectomy. The obstetrician-gynecologist should be aware of reports of complications related to augmentation procedures, including late malignancy which may develop in the bowel segment used for cystoplasty.

Adult↗
PubMed1994

Ureteral injury secondary to laparoscopic CO2 laser.

A case of a 32-year-old nulligravida who underwent a carbon dioxide laser-laparoscopy for endometriosis is reported. Ureteral injury was complicated by a postoperative 'urinoma'. Injury occurred despite utilizing the hydrodissection technique destined to create a bed of water beneath the peritoneum to prevent laser beam penetration to adjacent normal tissue. This case illustrates that the hydrodissection technique may be less effective in the presence of severe endometriotic adhesions and fibrosis.

Adult↗
PubMed1993

The valved S-shaped rectosigmoid pouch for continent urinary diversion.

Continent urinary diversion to the valved S-shaped rectosigmoid pouch was performed in 9 female and 6 male patients 12 to 65 years old (mean age 51 years). The pouch was constructed by detubularization and S-shaped reconfiguration of 30 cm. of the intact rectum and sigmoid colon. The ureters were reimplanted into the pouch using antireflux techniques. Reflux of urine from the pouch to the proximal colon was prevented by fashioning an intussusception valve. The construction was protected by a transverse colostomy for 6 to 8 weeks. With a followup of 3 to 24 months (mean 11 months), all patients are continent during the day and also at night with evacuation intervals of 3 to 6 hours. There have been no cases of symptomatic urinary tract infection. Only 1 patient had mild hyperchloremic acidosis. No patient complained of abdominal distention or constipation. Contrast study via the anus (radiography of the pouch) showed that the intussusception valve was competent in all but 1 patient in whom reflux to the proximal colon was noted due to sliding of the nipple valve, which was revised successfully. Urodynamic studies (cystometry of the pouch) showed a capacity of 400 to 900 ml. (mean 600) with an intraluminal pressure of 22 cm. water (range 10 to 34) at maximal filling. The valved S-shaped rectosigmoid pouch is a faster and simpler surgical procedure compared with the modified rectal bladder (valved rectum augmented with ileum). It also results in a smooth postoperative course, since an intestinal anastomosis proximal to the colostomy is avoided.

Adolescent↗
PubMed1993

Placenta percreta with bladder invasion: report of three cases.

Three cases are reported of placenta percreta with urinary bladder wall invasion. All three patients had complete placenta previa and each had five previous cesarean sections. Placental invasion caused a giant vesicouterine fistula in the first case. The second patient had a cesarean hysterectomy and the placental portion that penetrated the bladder wall was left to absorb spontaneously. The third patient underwent a cesarean supracervical hysterectomy during which the bladder invasion was left undisturbed. She received intraoperative methotrexate, and pelvic packing and bilateral hypogastric ligation were helpful in hemorrhage control.

Adult↗
PubMed1992

Spontaneous bladder rupture after colocystoplasty. Case report.

An 18-year-old girl had bladder extrophy managed by sigmoid cystoplasty with clean intermittent catheterization. Spontaneous bladder rupture occurred 12 months after reconstructive surgery. The diagnosis was made by ultrasound with abdominal tapping and cystography under fluoroscopy. Management included intravenous antibiotics, laparotomy and closure of the perforation. The diagnosis was delayed and postoperative intraperitoneal abscess formation occurred.

Adolescent↗
PubMed1987

Balloon dilatation of bilharzial ureteric strictures.

Balloon dilatation was performed in nine patients with bilharzial ureteric strictures. In six patients a percutaneous, antegrade approach was used and in three a balloon catheter was introduced into the ureter via a cystoscope. In another four patients, negotiation of the strictured area with a guide wire failed. In all dilated patients, symptomatic and urographic relief of the obstruction was obtained during follow-up periods of 3 to 38 months (mean 19). One patient was re-dilated after 24 months and has remained symptom-free for a further 18 months. Balloon dilatation seems to be a promising method of treating this condition.

Adult↗
PubMed1986

Studies on renal damage from percutaneous nephrolitholapaxy.

To study in detail the effects of percutaneous nephrolitholapaxy on renal function, a consecutive series of 11 patients were investigated preoperatively by excretory urography, gamma camera renography for determination of individual renal function and computerized tomography of the kidneys. Postoperatively, gamma camera examination, computerized tomography, antegrade nephrostography, renal angiography and excretory urography were performed. With 2 exceptions, percutaneous nephrostomy, dilation of the tract and stone removal were done in 1 stage with the patient under continuous epidural anesthesia. Nephrostomy tract dilation was done with an Olbert type balloon catheter or Alken metallic dilators. Thickening of Gerota's fascia was demonstrated by computerized tomography in most cases, and small to moderate perirenal hematomas were found in several. At gamma camera examination decrease of renal function was noted regularly on postoperative day 1 and returned to near initial levels 2 weeks postoperatively in most cases. Angiography in 10 patients showed discrete parenchymal scarring in some and a peripheral arteriovenous fistula in 1. We conclude that percutaneous renal stone surgery usually is tolerated well by the kidney.

Adult↗
PubMed1986

Cardiovascular complications of estrogen therapy for nondisseminated prostatic carcinoma. A preliminary report from a randomized multicenter study.

In a prospective multicenter study, 244 men with highly or moderately differentiated prostatic cancer in stage I, II or III (VACURG) were consecutively randomized to three groups of treatment: Group A (77 patients) received polyestradiol phosphate (Estradurin, Leo) 80 mg i.m. every fourth week + ethinyl estradiol (Etivex, Leo) 150 micrograms daily, group B (72 patients) estramustine phosphate (Estracyt, Leo) 280 mg twice daily, and group C (76 patients) no therapy. Only men without current or previous other malignancy and without cardiovascular disease were admitted to the study. After 4 1/2 years 125 of the 244 patients had left the study, 9 because of cancer progression (stage IV, VACURG). The most serious complications were cardiovascular, including ischemic heart disease, cardiac decompensation, cerebral ischemia and venous thromboembolism, which occurred in 24 patients from group A and 9 from group B as compared to only one patient in group C. The subgroup superficial or deep venous thrombosis comprised 11 group A and 2 group B patients. Estrogens (E + e) offered as palliative treatment to patients with non-generalized prostatic carcinoma is burdened with a high incidence of serious cardiovascular complications.

Aged↗