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PubMed2006

Comparison of wavefront reconstructions with Zernike polynomials and Fourier transforms.

PURPOSE: To make a direct comparison between Fourier and Zernike reconstructions of ocular wavefronts using a newly available analytical theory by which Fourier coefficients can be converted to Zernike coefficients and vice versa. METHODS: Noise-free random wavefronts were simulated with up to the 15th order of Zernike polynomials. For each case, 100 random wavefronts were simulated separately. These wavefronts were smoothed with a low-pass Gaussian filter to remove edge effects. Wavefront slopes were calculated, and normally distributed random noise was added within the circular area to simulate realistic Shack-Hartmann spot patterns. Three wavefront reconstruction methods were performed. The wavefront surface error was calculated as the percentage of the input wavefront root mean square. RESULTS: Fourier full reconstruction was more accurate than Zernike reconstruction from the 6th to the 10th orders for low-to-moderate noise levels. Fourier reconstruction was found to be approximately 100 times faster than Zernike reconstruction. Fourier reconstruction always makes optimal use of information. For Zernike reconstruction, however, the optimal number of orders must be chosen manually. The optimal Zernike order for Zernike reconstruction is lower for smaller pupils than larger pupils. CONCLUSIONS: Fourier full reconstruction is faster and more accurate than Zernike reconstruction, makes optimal use of slope information, and better represents ocular aberrations of highly aberrated eyes.

Corneal Topography↗

PubMed1999

Incidence and outcomes of anterior cruciate ligament reconstruction among U.S. Army aviators.

BACKGROUND: The incidence, injury history and aeromedical disposition of anterior cruciate ligament (ACL) reconstruction among Army aviators is unknown. METHODS: The U.S. Army Aviation Epidemiology Data Register was queried for the study period of calendar years 1988-95. Factors considered included age, gender, type and mechanism of injury, prior history of ACL reconstruction, and final aeromedical disposition. The population was divided into two groups: Group I aviators had no history of ACL injury before entering aviation service, while Group II aviators had ACL reconstructions prior to entering aviation service. The data set was analyzed to determine the incidence of ACL reconstruction, to characterize the type and mechanism of injury and to determine the risk of aeromedical termination from service. RESULTS: The ACL reconstruction rate (ACL reconstructions/1000 aviators per year) was 0.52 overall, 0.50 for males and 1.39 for females. Sports accounted for 76% of the injuries requiring ACL reconstruction. The ACL reconstruction rate in Group I was 0.050%, while that of Group II was 63.3%. Among Group I aviators requiring ACL reconstruction, 94.3% returned to aviation service, 2.3% were aeromedically terminated and 3.4% were lost to follow-up. Among Group II aviators requiring revision ACL reconstruction, 60% returned to aviation service and 40% were aeromedically terminated. CONCLUSION: Female aviators and Group II aviators had the greatest risk of requiring ACL surgery. Group II aviators had a greater likelihood of undergoing a revision ACL reconstruction and subsequent aeromedical termination compared with an initial ACL reconstruction for Group I aviators.

Adolescent↗

PubMed1999

Iterative reconstruction based on median root prior in quantification of myocardial blood flow and oxygen metabolism.

UNLABELLED: The aim of this study was to compare reproducibility and accuracy of two reconstruction methods in quantification of myocardial blood flow and oxygen metabolism with 15O-labeled tracers and PET. A new iterative Bayesian reconstruction method based on median root prior (MRP) was compared with filtered backprojection (FBP) reconstruction method, which is traditionally used for image reconstruction in PET studies. METHODS: Regional myocardial blood flow (rMBF), oxygen extraction fraction (rOEF) and myocardial metabolic rate of oxygen consumption (rMMRO2) were quantified from images reconstructed in 27 subjects using both MRP and FBP methods. For each subject, regions of interest (ROIs) were drawn on the lateral, anterior and septal regions on four planes. To test reproducibility, the ROI drawing procedure was repeated. By using two sets of ROIs, variability was evaluated from images reconstructed with the MRP and the FBP methods. RESULTS: Correlation coefficients of mean values of rMBF, rOEF and rMMRO2 were significantly higher in the images reconstructed with the MRP reconstruction method compared with the images reconstructed with the FBP method (rMBF: MRP r = 0.896 versus FBP r = 0.737, P < 0.001; rOEF: 0.915 versus 0.855, P < 0.001; rMMRO2: 0.954 versus 0.885, P < 0.001). Coefficient of variation for each parameter was significantly lower in MRP images than in FBP images (rMBF: MRP 23.5% +/- 11.3% versus FBP 30.1% +/- 14.7%, P < 0.001; rOEF: 21.0% +/- 11.1% versus 32.1% +/- 19.8%, P < 0.001; rMMRO2: 23.1% +/- 13.2% versus 30.3% +/- 19.1%, P < 0.001). CONCLUSION: The MRP reconstruction method provides higher reproducibility and lower variability in the quantitative myocardial parameters when compared with the FBP method. This study shows that the new MRP reconstruction method improves accuracy and stability of clinical quantification of myocardial blood flow and oxygen metabolism with 15O and PET.

Adult↗

PubMed2001

DIEP flap breast reconstruction--new experience.

One of the important microsurgical procedures in our department is breast reconstruction after ablations. For many years, the standard method was reconstruction with autologous tissues--a free TRAM flap with a recipient vessels vasa mammaria. We are convinced that this give very satisfactory results with microsurgical safety of operations. We use this method of reconstruction in 17-20 patients per year. The standard time of unilateral reconstruction is 2.5-4 hours, of bilateral reconstruction 4-6 hours. Postoperative morbidity in the abdominal region is, as a rule, associated with a weakening of the abdominal wall and the development of hemias (Galli et al., 1992); a perforator flap in which neither muscle nor fasciae are used creates the prerequisite condition for markedly reduced the morbidity associated with the site of flap collection. Although we used a perforator flap three times for reconstructions of the extremities as early as three years ago, we began to use it for breast reconstruction from the beginning of 2000. No doubt this late use of a large skin flap supplied by 1-2 perforators was due to a lack of trust in the provision of adequate blood perfusion for the large amount of tissue of the flap. From the beginning of 2000, in the course of five months, nine DIEP flaps were used for breast reconstructions, in two cases for bilateral reconstruction. In two instances sensory nerves of the flap were sutured to the branch of the intercostal nerves at the site of insertion. Seven flaps healed p.p.i; in two instances we were faced with the complication of postoperative venostasis, calling for revision and connection of the superficial venous system of the flap to the circulation. Subsequent healing was without complications. Preparation of the flap appears to be relatively easy, and the only pitfall is the selection of a suitable perforator. The operation is longer by half an hour than the classical free TRAM; when the sensory nerve of the flap is sutured, it is ca 1 hour longer. We like to use the DIEP flap for breast reconstruction, and it is a reliable method even for the reconstruction of large pendulous breasts. The donor site morbidity is significantly lower.

Abdominal Muscles↗

PubMed2003

The effect of ovarian steroid deficiency on regeneration of oviductal mucosa following reconstructive surgery.

In patients with distal tubal occlusion a microsurgical oviductal reconstruction is, apart from the in vitro fertilization, the only treatment option. Unfortunately, the results of reconstructive surgery are often unsatisfactory. The effects of sex steroids on the regeneration process after reconstructive surgery have not been well investigated. This study was aimed to evaluate the effect of decreased concentrations of ovarian sex steroids (castration) on regeneration of the oviduct mucosa after the reconstructive surgery of distally occluded oviducts. The study was performed on 32 female rabbits that underwent unilateral oviduct ligature and resection of fimbriae. The occlusion lasted six (group I) or twelve weeks (group II). After this time the animals were re-operated, and allocated into 4 groups: castration with reconstructive surgery (IA, IIA), reconstructive surgery only (IB, IIB). After next six or twelve weeks the fallopian tubes were examined under light, scanning and transmission electron microscopes. An immunohistochemical reaction for Ki-67 proliferative antigen was also performed. Ovarian steroid levels were evaluated by radioimmunoassays. The castrated animals had significantly lower levels of estradiol, progesterone and 17-hydroxyprogesterone than the control groups. Long lasting tubal occlusion caused pronounced histological changes of tubal mucous membrane (group II). In the rabbits with preserved ovaries and twelve-week long oviductal occlusion (group IIB), the regeneration of the distal end and restoration of fimbria were not complete twelve weeks after microsurgical reconstruction. In castrated animals with long-lasting occlusion (group IIA) the destructive changes, found in the mucosa of tubal ampullas of occluded oviducts before reconstruction, were still present and even intensified twelve weeks following reconstructive surgery. The castration hampered proliferation of the mucosa cells, thus no fimbriae were restored. Low levels of ovarian steroids were found to have adverse effect on fallopian tube regeneration following reconstructive surgery. The effect was noted even in cases with minor preoperative fallopian tube damage. Therefore, the treatment of concomitant endometriosis or uterine fibroids with GnRH analogues should not be recommended simultaneously with microsurgical tubal reconstruction.

17-alpha-Hydroxyprogesterone↗

PubMed1990

Reasons why mastectomy patients do not have breast reconstruction.

Breast reconstruction after mastectomy is valuable, yet only a small percentage of eligible patients ever have reconstruction. Little has been done to determine why so few patients proceed with reconstructive surgery. A homogeneous population of mastectomy patients, some of whom underwent breast reconstruction while others did not, were surveyed regarding their attitudes about breast reconstruction. A total of 245 women were surveyed. One-hundred and fifty-eight (64 percent) responded, 71 of whom had been reconstructed while 87 had not. Comparison of the responses of the two groups suggests factors that play a role in determining whether the mastectomy patient will accept or decline the option of breast reconstruction. Considerations that made it less likely that a woman would pursue reconstruction included advanced age at the time of mastectomy, concern about complications from further surgery, uncertainty about outcome, and fear about the effect of reconstruction on future problems with breast cancer. Marital status, receiving chemotherapy, or knowing a patient who had a bad result from reconstruction did not affect the decision. An awareness and understanding of these factors may be helpful to physicians in counseling patients and in increasing the number of women who enjoy the benefits of breast reconstruction.

Adult↗

PubMed1990

Regional flaps in facial reconstruction.

Soft-tissue defects of the head and neck that are too extensive to be reconstructed with local flaps without excessive impairment of either form or function usually require repair by some type of regional flap. Selection of a specific regional flap depends on the type of defect, i.e., its size and location, and on the intrinsic properties of the regional flap. Single pedicle peninsular or island axial pattern flaps are usually selected because of their improved blood supply compared with random flaps. For most skin defects of the face and neck requiring reconstruction with a regional flap, a medially based deltopectoral flap is usually preferable to musculocutaneous flaps because it is less bulky and produces less donor-site functional impairments. Likewise, for large defects of the upper or lower lip, a deltopectoral flap in most instances is the regional flap of choice for reconstruction. Nasal defects that require regional flaps for repair are reconstructed with various types of forehead flaps. The median flap remains the most useful because the donor site can be closed primarily, leaving a thin midline scar that is camouflaged relatively easily. For nasal defects that require a longer flap that can be provided by a median flap, the oblique forehead flap provides additional length sufficient to reach the base of the columella. Larger defects of the oral cavity and oral pharynx usually require regional or microsurgical flaps for reconstruction of soft-tissue deficits. In addition, mandibular reconstruction may be necessary. The pectoralis major musculocutaneous flap is the author's preferred choice of a regional flap for reconstruction of such defects. The flap readily reaches the oral cavity and oral pharynx and the muscle provides good coverage of the carotid artery when neck dissection has been accomplished. A great advantage of the flap is the ability to achieve reconstruction in one stage without the need for a controlled salivary fistula. Although the deltopectoral flap is the author's preferred regional flap for reconstruction of major defects of the hypopharynx, the pectoralis major musculocutaneous flap is the regional flap of choice when patients are severely malnourished or cachetic. Both flaps provide a source of nonirradiated skin and provide sufficient tissue for total reconstruction of the hypopharynx and cervical esophagus. Both methods of reconstruction, however, have a relatively high rate of stenosis of the distal anastomoses.

Face↗

PubMed1995

Psychological evaluation of patients undergoing breast reconstruction using two different methods: autologous tissues versus prostheses.

Breast reconstruction has become an available option for most patients undergoing mastectomy. In fact, many authors agree that breast reconstruction does not interfere with possible therapies and improves the women's quality of life. The aim of this study was to evaluate the psychological adjustment of patients who had immediate or delayed reconstruction using two different methods: implants and autologous tissues. Specifically, it was explored whether the different methods of breast reconstruction have caused significant changes in psychological functioning. The study population (102 patients) was derived from patients who underwent breast reconstruction in the period January 1988 to December 1991 at the Department of Plastic and Reconstructive Surgery of the National Institute for Cancer Research in Genoa, Italy. Fifty-two patients underwent breast reconstruction using implants and 50 using the transverse rectus abdominis myocutaneous (TRAM) flap. Demographic information was gathered from each patient. The psychological instruments consisted of three standardized self-administered questionnaires: Psychological Distress Inventory, State Trait Anxiety Inventory, Form Y, and the Eysenck Personality Inventory. To better assess the changes in body image after breast reconstruction, three more specific questions about sexual desire, physical image, and social relationships were added. The 102 patients assessed in this study indicated a low incidence of psychological distress. Impairment was reported regarding body image by patients who underwent delayed reconstruction; these patients also showed higher distress scores. The type of breast reconstruction also seems to influence body image, showing in the patients with TRAM flap reconstruction more relevant psychological discomfort.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Psychological↗

PubMed1997

Intraoperative autologous transfusion during elective infrarenal aortic reconstruction: a decision analysis model.

PURPOSE: The use of intraoperative autologous transfusion devices expanded during the last decade as a result of the increased awareness of transfusion-associated complications. This study was designed to determine whether routine use of an intraoperative autologous transfusion device (Haemonetics Cell Saver [CS]) during elective infrarenal aortic reconstructions is cost-effective ($50,000/QALYs threshold). METHODS: A decision analysis tree was constructed to model all of the complications that are associated with red blood cell replacement during aortic reconstructions for both abdominal aortic aneurysm (AAA) and aortoiliac occlusive disease (AIOD). It was assumed that a unit of CS return (CSR; 250 ml/unit) equaled a unit of packed red blood cells (PRBCs) and that all CS transfusions were necessary. Transfusion requirements (AAA:PRBC = 2.8 +/- 3.2 units, CSB = 3.7 +/- 3.2 units; AIOD:PRBC = 3.1 +/- 3.0 units, CSR = 2.1 +/- 1.7 units) were determined from retrospective review of all elective aortic reconstructions (AAA, N = 63; AIOD, N = 75) from Jan. 1991 to June 1995 in which the CS was used (82.1% of all reconstructions). Risk of allogenic transfusion-related complications (transfusion reaction, hepatitis B, hepatitis C, human immunodeficiency virus, human T-cell lymphotropic virus types I and II) and their associated treatment costs (expressed in dollars and quality-adjusted life years (QALYs) were obtained from the medical literature, institutional audit, and a consensus of physicians. RESULTS: Routine use of the CS during elective infrarenal aortic reconstructions was not cost-effective in our practice. Use during reconstructions for AAA repairs cost $263.75 but added only 0.00218 QALYs, for a rate of $120,794/QALY. Use during reconstructions for AIOD was even more costly at $356.68 and provided even less benefit at 0.00062 QALYs, for a rate of $578,275/QALY. The sensitivity analyses determined that the routine use of the CS would be cost-effective in our practice only for AAA repairs if the incidence of hepatitis C were tenfold greater than the baseline assumption. The model determined that CS was cost-effective if the CSR exceed 5 units during reconstructions for AAA and 6 units during reconstructions for AIOD. CONCLUSIONS: The routine use of the CS during elective infrarenal aortic reconstructions is not cost-effective. The use of the device should be reserved for a select group of aortic reconstructions, including those in which cost-effective salvage volumes are anticipated. Alternatively, the CS should be used as a reservoir and activated as a salvage device if significant bleeding is encountered.

Aged↗

PubMed1997

[The use of Holmstrom's flap in breast reconstruction].

The authors consider 12 cases of breast-reconstruction after mastectomy, made with the Holmstrom's flap, to verify the validity and the real utility of this way of reconstruction. It has been made a follow-up of 4 years, to verify, in course of time, the characteristics of the reconstructed breasts. All the patients have been operated in a general surgery department. The Holmstrom's flap has been prevalently used in patients, during immediate reconstruction. The breast reconstruction, made with this fascio-cutaneous transposition flap, requires the use of prosthesis. The operating time has a very short duration. The breast reconstruction, made with this method, requires a very short staying in hospital. The nipple-areola complex reconstruction has been made in a second time, few months later. The patients have been examined periodically, to verify, immediately, the result of the flap and, later, the quality of the new breast's shape and the occurrence of capsular contracture. The results achieved with this reconstructive method are a good shape and ptosis as to confer great naturalness to the new breast. The authors conclude that, even if they use the TRAM-flap as first choice in breast-reconstruction, the Holmstrom's flap is a reconstructive technique of great utility in immediate breast reconstruction, that is able to give very good aesthetic results.

Breast Neoplasms↗

PubMed1997

Cutaneous nasal malignancies: is primary reconstruction safe?

BACKGROUND: The nose is particularly vulnerable to cutaneous malignancies, making it the most common location for presentation. Recurrence of these cutaneous lesions is not uncommon, often compromising the timing of nasal restoration. It is the purpose of this report to reexamine the safety of primary nasal reconstruction in selected patients. METHODS: Seventy-one patients who underwent nasal reconstruction at The University of Texas M. D. Anderson Cancer Center between 1987 and 1995 were retrospectively reviewed. There were 35 men and 36 women with an average age of 60 years. All nasal reconstructions were performed for defects secondary to malignancies. Basal cell carcinoma was the most common lesion (n = 49), followed by squamous cell carcinoma (n = 10) and melanoma (n = 7), with five additional variable malignancies. The most common location of the cutaneous lesions was the nasal dorsum, and the forehead flap was the most common adjacent tissue used for reconstruction. Immediate reconstruction was performed for 42 of the basal cell carcinomas, 6 of the squamous cell carcinomas, 6 melanomas, and 3 other lesions. Delayed restoration was performed for 7 basal cell carcinomas, 4 squamous cell carcinomas, 1 melanoma, and 2 additional lesions. The average time between surgical extirpation and the start of nasal reconstruction was 8.2 months for basal cell carcinoma, 29 months for squamous cell carcinoma, and 10 months for melanoma. RESULTS: Twenty-six recurrent lesions were identified at an average of 36 months after extirpation. Despite these numbers, only three recurred after nasal reconstruction at our institution. Follow-up averaged 41 months, with none less than 1 year. Seventy patients are still alive with no evidence of disease. CONCLUSION: Primary reconstruction is safe in selected patients. Surgical delay in reconstruction should be considered if margins are questionable, the pathology is determined to be aggressive, if there is perineural or deep bony invasion, or if postoperative radiotherapy is to be initiated. Nasal reconstruction ultimately is based upon a complex series of issues but can be performed with few complications in an effort to restore self-image.

Adolescent↗

PubMed1994

Major mandibular reconstruction with vascularized bone grafts: indications and selection of donor tissue.

Free vascularized bones have been shown by many specialists to exhibit specific capabilities of reconstructing a major mandibular defect and can solve problems that may be insoluble by other methods. Nevertheless, absolute indications for using vascularized bone for major mandibular reconstructions have not been sufficiently well delineated to convince people of always considering vascularized bone for major mandibular reconstructions as a first option. Based on our experience with 55 major mandibular reconstructions, we might delineate the absolute indications for using free vascularized bone for major mandibular reconstructions explicitly: 1) osteoradionecrosis of mandible or on irradiated tissue bed; 2) hemimandibular reconstruction with a free end facing the glenoid fossa; 3) long segment mandibular defect, especially across the symphysis; 4) inadequate skin or mucosal lining; 5) defects demanding sandwich reconstruction; 6) inability to obtain secure immobilization on the reconstructed unit; 7) failure of reconstruction by other methods; 8) near total mandibular reconstruction. Selection of donor tissue should be according to 1) the amount of tissue deficiencies, 2) composition of the defect, 3) design and placement of the flap, 4) irradiation on the recipient site or not, 5) which vessels to be used, 6) which flap has the appropriate vessel length 7) skin color and texture of the donor tissue, 8) how many osteotomies required to stimulate the curvature of the resected mandible 9) speed of bony union, 10) feasibility of future osseointegration. We have used three kinds of vascularized bones (iliac bone, fibula, scapula). Iliac bone was most frequently used, and has always been our first choice, since it can carry good quality bone, a large skin flap, and ample soft tissue. The fibula has the merit of being less bulky and good for simultaneous intraoral lining, but the contour is more rigid and the bony height is insufficient. The scapula bone is rarely used at present because of its relative inconvenience.

Adult↗

PubMed2002

Iterative versus filtered backprojection reconstruction for statistical parametric mapping of PET activation measurements: a comparative case study.

The significance of task-induced cerebral blood flow responses, assessed using statistical parametric mapping, depends, among other things, on the signal-to-noise ratio (SNR) of these responses. Generally, positron emission tomography sinograms of H(2)(15)O activation studies are reconstructed using filtered backprojection (FBP). Alternatively, the acquired data can be reconstructed using an iterative reconstruction procedure. It has been demonstrated that the application of iterative reconstruction methods improves image SNR as compared with FBP. The aim of this study was to compare FBP with iterative reconstruction, to assess the statistical power of H(2)(15)O-PET activation studies using statistical parametric mapping. For this case study, PET data originating from a bimanual motor task were reconstructed using both FBP and maximum likelihood expectation maximization (ML-EM), an iterative algorithm. Both resulting data sets were statistically analyzed using statistical parametric mapping. It was found, with this dataset, that the statistical analysis of the iteratively reconstructed data confirm the a priori expected physiological response. In addition, increased Z scores were obtained in the iteratively reconstructed data. In particular, for the expected task-related response, activation of the posterior border of the left angular gyrus, the Z score increased from 3.00 to 3.96. Furthermore, the number of statistically significant clusters doubled while their volume increased by more than 50%. In conclusion, iterative reconstruction has the potential to increase the statistical power in H(2)(15)O-PET activation studies as compared with FBP reconstruction.

Brain Mapping↗

PubMed1996

A new iterative reconstruction technique for attenuation correction in high-resolution positron emission tomography.

A new iterative reconstruction technique (NIRT) for positron emission computed tomography (PET), which uses transmission data for nonuniform attenuation correction, is described. Utilizing the general inverse problem theory, a cost functional which includes a noise term was derived. The cost functional was minimized using a weighted-least-square maximum a posteriori conjugate gradient (CG) method. The procedure involves a change in the Hessian of the cost function by adding an additional term. Two phantoms were used in a real data acquisition. The first was a cylinder phantom filled with uniformly distributed activity of 74 MBq of fluorine-18. Two different inserts were placed in the phantom. The second was a Hoffman brain phantom filled with uniformly distributed activity of 7.4 MBq of 18F. Resulting reconstructed images were used to test and compare a new iterative reconstruction technique with a standard filtered backprojection (FBP) method. The results confirmed that NIRT, based on the conjugate gradient method, converges rapidly and provides good reconstructed images. In comparison with standard results obtained by the FBP method, the images reconstructed by NIRT showed better noise properties. The noise was measured as rms% noise and was less, by a factor of 1.75, in images reconstructed by NIRT than in the same images reconstructed by FBP. The distance between the Hoffman brain slice reconstructed by FBP and the perfect PET Hoffman brain slice created from the MRI image was 0.526, while the same distance for the Hoffman brain slice reconstructed by NIRT was 0.328. The NIRT method suppressed the propagation of the noise without visible loss of resolution in the reconstructed PET images.

Algorithms↗

PubMedDate not supplied

Breast reconstruction: progress in the past decade.

There have been numerous advances in breast reconstruction techniques of the past decade. The disappearance of the radical mastectomy along with the increased frequency of smaller tumor detection have contributed significantly to these changes. Furthermore, reliable studies have shown that breast reconstruction does not interfere with extirpative surgery or delay postoperative adjuvant therapy if indicated. Studies such as these have led increasing numbers of women to elect immediate breast reconstruction as opposed to delaying that reconstruction for months or even years after the tumor extirpation. The advent of successful breast reconstruction using autogenous tissue provided the most radical change to reconstructive techniques over the past 10 years. The TRAM (transverse rectus abdominis myocutaneous) flap was the first of these techniques to be introduced and has rapidly assumed a position of prominence among those techniques chosen for breast reconstruction. The LTTF (lateral transverse thigh flap) and the buttock flap, while requiring microsurgical technique, are important alternatives for those patients who choose autogenous tissue breast reconstruction and should be presented to women during the discussion of alternatives for breast reconstruction. Implant technology has continued to improve with the introduction of the tissue expander, the most important addition in the past decade. Investigations are currently underway to provide a long-term tissue expander that does not have to be removed and replaced by a permanent implant. The ultimate end result would be to create a more normal breast shape without firmness. And the use of stacked or directional expanders may allow more freedom in creation of the new breast shape to conform to the opposite side. Finally, nipple areola reconstruction has improved significantly as the tissues of the breast mound itself are used for the new nipple and areola, thereby avoiding the transfer of grafts from distant sites which do not generally maintain their size or projection over time.

Adult↗

PubMed2003

Do segmented reconstruction algorithms for cardiac multi-slice computed tomography improve image quality?

PURPOSE: To evaluate segmented reconstruction algorithms for spiral multi-slice computed tomography (MSCT) that use data from two cardiac cycles to improve temporal resolution (tau) for imaging of the heart. MATERIALS AND METHODS: An initial group of 78 cardiac patients (heart rates [HR] = 63-167 beats per minute [bpm]) were imaged on a 4-slice, 500 ms gantry rotation time scanner (scanner 1). Images were reconstructed with a single-segment algorithm using data from one cardiac cycle with a reconstruction window of fixed length (tau = 250 ms). Images were also reconstructed with two variants of a multi-segment algorithm using data from two cardiac cycles where only one end of the reconstruction window was fixed and the other end was freely moveable to allow adjustment of tau according to HR: (1) "2-segment fixed start" with fixed start of reconstruction, (2) "2-segment fixed end" with fixed end of reconstruction (for both, tau = 125-250 ms). The resulting image sets were ranked from best to worst (1-3, respectively) in a side-by-side, blinded comparison by two independent readers. A second group of 26 patients (HR = 74-90 bpm) were imaged on a 12-slice, 420 ms gantry rotation time scanner (scanner 2). Data were reconstructed with a single-segment algorithm (tau = 210 ms) and a "2-segment fixed start" algorithm (tau = 105-210 ms) and image sets were ranked from best to worst (1-2, respectively). RESULTS: There was no clear evidence that any one technique is superior for imaging on scanner 1. Reader 1 ranked single-segment images the highest for all HRs, but statistically significant differences among the three algorithms were only found for the lowest HRs (< 80 bpm), where reader 1 preferred single-segment over "2-segment fixed end" techniques (p = 0.048). The highest rankings given by reader 2 varied according to HR: single-segment images were superior for lowest HRs, while "2-segment fixed start" images were superior for HRs > 80 bpm; none of these comparisons reached statistical significance. Improved performance of 2-segment reconstruction was found with scanner 2. Both readers ranked "2-segment fixed start" images the highest (p < 0.01). CONCLUSIONS: The added value of 2-segment cardiac reconstruction algorithms for spiral MSCT was not demonstrated for a 4-slice, 500 ms gantry rotation time scanner but shown to be beneficial for a 12-slice, 420 ms gantry rotation time scanner in the crucial HR range of 74-90 bpm.

Adolescent↗

PubMed2005

[Improvements in detection of rectal cancer recurrence by multiplanar reconstruction].

PURPOSE: To evaluate the advantages of multiplanar reconstruction and different axial slice thickness in diagnostic of rectal cancer recurrence after operation and radiotherapy. METHOD: We included 83 patients after operation and radiotherapy of rectal cancer in this study. All patients got a minimum of three CT-examinations in their follow-up program. A total of 294 CT-scans were evaluated. Each examination was reviewed by two experienced radiologists in respect to recurrence. Each examination was presented in axial reconstruction with a slice sickness of 8, 5, and 1.25 mm and in multiplanar reconstruction. The sensitivity, specificity, positive predictive value and accuracy were calculated. RESULTS: Multiplanar reconstructions showed better results for the detection of recurrence than axial reconstruction. A reduced slice thickness did not lead to better results in axial reconstruction. Multiplanar reconstruction showed a sensitivity of 0.88, a specificity of 0.98, an accuracy of 0.96 and a positive predictive value of 0,94, for axial reconstruction we calculated: 0.82, 0.97, 0.94 and 0.88, respectively. Sensitivity and accuracy showed a significant increase after the first and second examination. CONCLUSION: Multiplanar reconstructions allow a significant better detection of rectal cancer recurrence when compared to axial reconstructions. Thinner axial slice thickness shows no diagnostic advantage.

Germany↗

PubMed2004

Improved tolerance to missing data in myocardial perfusion SPET using OSEM reconstruction.

When projection data are incomplete for various technical reasons, artefacts may occur in the reconstructed images. This study examines whether an iterative reconstruction method, the ordered subsets implementation of the EM algorithm (OSEM), can improve reconstruction and minimise the artefacts compared to filtered back-projection (FBP). We varied the number and location of projections removed to investigate when significant artefacts occur, and whether diagnosis is affected. Phantom studies were analysed with sequential orthogonal pairs of projection angles removed (as would typically occur when either data loss or severe motion is detected during acquisition with a right-angled, dual-head cardiac single-photon emission tomography system) and reconstructed with both FBP and OSEM. Twelve normal myocardial perfusion studies were also assessed to study the effect of missing projections on clinical diagnosis. Differences between reconstructions with intact versus missing data were measured. Also, reconstructed images were clinically assessed and scored on a five-point scale based on whether the artefacts would alter clinical interpretation. Although both reconstruction methods showed artefacts, the absolute differences between reconstructed phantom data with intact and missing projection sets were significantly greater (P<0.005) for FBP than for OSEM for all numbers of missing projections. The clinical data showed similar differences between FBP and OSEM reconstructions. The three observers noted superiority of OSEM compared to FBP, with reduced incidence of clinically significant artefacts. However, neither reconstruction method could tolerate six or more missing pairs from 32 projections. There was no significant dependence on the angular location of missing projections. In the absence of any attempt to correct for missing projections, OSEM reduced the influence of artefacts compared to FBP.

Algorithms↗