Source-detector trajectory optimization in cone-beam computed tomography: a comprehensive review on today's state-of-the-art.

Cone-beam computed tomography (CBCT) imaging is becoming increasingly important for a wide range of applications such as image-guided surgery, image-guided radiation therapy as well as diagnostic imaging such as breast and orthopaedic imaging. The potential benefits of non-circular source-detector trajectories was recognized in early work to improve the completeness of CBCT sampling and extend the field of view (FOV). Another important feature of interventional imaging is that prior knowledge of patient anatomy such as a preoperative CBCT or prior CT is commonly available. This provides the opportunity to integrate such prior information into the image acquisition process by customized CBCT source-detector trajectories. Such customized trajectories can be designed in order to optimize task-specific imaging performance, providing intervention or patient-specific imaging settings. The recently developed robotic CBCT C-arms as well as novel multi-source CBCT imaging systems with additional degrees of freedom provide the possibility to largely expand the scanning geometries beyond the conventional circular source-detector trajectory. This recent development has inspired the research community to innovate enhanced image quality by modifying image geometry, as opposed to hardware or algorithms. The recently proposed techniques in this field facilitate image quality improvement, FOV extension, radiation dose reduction, metal artifact reduction as well as 3D imaging under kinematic constraints. Because of the great practical value and the increasing importance of CBCT imaging in image-guided therapy for clinical and preclinical applications as well as in industry, this paper focuses on the review and discussion of the available literature in the CBCT trajectory optimization field. To the best of our knowledge, this paper is the first study that provides an exhaustive literature review regarding customized CBCT algorithms and tries to update the community with the clarification of in-depth information on the current progress and future trends.

Efficacy of pelvic artery embolisation for severe postpartum hemorrhage.

PURPOSE: The purpose of our study was to evaluate the outcome of selective pelvic arterial embolisation (PAE) in women with severe postpartum hemorrhage (PPH). METHODS: We performed a retrospective, controlled, single-center cohort study. A total of 16 consecutive women with PPH who underwent therapeutic PAE were included. As historical control group, we included 22 women with similar severity of PPH who were managed without PAE. Outcome measures included necessity of surgical interventions such as postpartum hysterectomy and laparotomy after vaginal delivery, the amount of red blood cell transfusions, and hematologic findings after the procedure. RESULTS: PAE was successful in stopping PPH and preserving the uterus in all 16 women in the study group. No woman in the PAE group required a postpartum hysterectomy, whereas postpartum hysterectomy was unavoidable in two women in the control group. Laparotomy after vaginal delivery was necessary in two women of the group without embolisation. Hematologic parameters after the treatment were better in the PAE group than in the control group, although these differences were only in part statistically significant. There were no unwarranted effects of PAE identifiable in the study group. CONCLUSION: This is the first controlled study assessing the efficacy of PAE for the treatment of PPH. Our data suggest that PAE is effective for the treatment of severe PPH. In view of the lack of complications and unwarranted effects, clinical use of PAE in severe PPH seems justified, particularly in view of the life-threatening condition and the potential to preserve fertility in affected patients. Further evidence from well-designed prospective randomized-controlled trials would be nevertheless desirable in the future.

Protective embolization of the gastroduodenal artery with a one-HydroCoil technique in radioembolization procedures.

PURPOSE: Protective occlusion of the gastroduodenal artery (GDA) is required to avoid severe adverse effects and complications in radioembolization procedures. Because of the expandable features of HydroCoils, our goal was to occlude the GDA with only one HydroCoil to provide particle reflux protection. METHODS: Twenty-three subjects with unresectable liver tumors, who were scheduled for protective occlusion of the GDA before radioembolization therapy, were included. The primary end point was to achieve a proximal occlusion of the GDA with only one detachable HydroCoil. Evaluated parameters were duration of deployment, and early (during the intervention) and late (7-21 days) occlusion rates of GDA. Secondary end points included complete duration of the intervention, amount of contrast medium used, fluoroscopy rates, and adverse effects. RESULTS: In all cases, the GDA was successfully occluded with only one HydroCoil. The selected diameter/length range was 4/10 mm in 2 patients, 4/15 mm in 6 patients, and 4/20 mm in 15 patients. HydroCoils were implanted, on average, 3.75 mm from the origin of the GDA (range 1.5-6.8 mm), with an average deployment time of 2:47 (median 2:42, range 2:30-3:07) min. In 21 (91%) of 23 patients, a complete occlusion of the GDA was achieved during the first 30 min after the coil implantation; however, in all patients, a late occlusion of the GDA was present after 6 to 29 days. No clinical or technical complications were reported. CONCLUSION: We demonstrated that occlusion of the GDA with a single HydroCoil is a safe procedure and successfully prevents extrahepatic embolization before radioembolization.

Treatment of an acute type B dissection with an intramural haematoma in the ascending aorta by percutaneous endovascular stent-graft placement.

Acute type B dissections accompanied by an intramural haematoma in the ascending aorta are rare. However, progression of the intramural haematoma in the ascending aorta poses risks for the patients, which are similar to those of type A dissections, including pericardial effusions and consecutive tamponade. To date, no clear treatment guidelines exist for these patients. We report on successful percutaneous endovascular stent-graft treatment of an acute type B dissection accompanied by an intramural haematoma in the ascending aorta as primary and sole form of treatment.

[PTA and stent placement distal to the superficial femoral artery]. / PTA und Stent distal der AFS.

Although angioplasty and stent applications in the iliac vessels and the superficial femoral artery have become routine procedures, their usefulness for the treatment of lesions of the popliteal artery and the lower leg arteries is still under discussion. For the popliteal artery, limitations are mainly due to the high mechanical stress in this area, causing high traction forces. Moreover, beyond the occlusive atherosclerotic changes, specific pathological entities such as aneurysms, emboli, entrapment syndromes, and cystic adventitial disease have to be differentiated. There is hope that the development of innovative stent designs with high flexibility might overcome the limitations. For lesions of the lower leg arteries treatment with percutaneous transluminal angioplasty (PTA) has become the method of choice. However, stent designs as used for cardiac interventions have been adapted for their application below the knee, and first encouraging results may help to justify their broad use in the future. Regarding PTA, innovative equipment and techniques for the treatment of arterial lesions below the knee include dedicated, long, and very flexible balloons, cutting balloon cryoplasty, and laser angioplasty. Regarding stents, bare metal stents, stents with passive or active coatings, and bioabsorbable stents have all been successfully used.

PTA versus carbofilm-coated stents in infrapopliteal arteries: pilot study.

PURPOSE: To determine the primary success and short-term patency of stent application as a primary treatment modality for high-grade lesions of the infrapopliteal arteries compared with treatment with percutaneous transluminal angioplasty (PTA) in critical limb ischemia in a randomized prospective study. METHODS: Endovascular therapy was performed on 95 lesions in 51 patients (mean age 72.0 years, range 47-80 years) who presented clinically with Fontaine stages III and IV. One patient underwent treatment in both limbs. After angiographic lesion identification, patients were randomized for treatment by PTA (53 lesions in 27 patients) or stent application (42 lesions in 24 patients). Follow-up by clinical investigation and conventional angiography or spiral CT angiography was performed in 37 patients (57 lesions) 6 to 12 months after the procedure, or when clinically indicated. Evaluation was performed by two observers, double-blinded, with thresholds for lesion restenosis of 50% and 70%. Statistical evaluation was performed on a lesion basis by Kaplan-Meier estimated probability rates, and log-rank and Wilcoxon tests. The primary endpoint was the angiographic patency rate of treated lesions. RESULTS: The inter-reader agreement was high (kappa = 0.82). For the stent group the cumulative primary patency at 6 months was 83.7% at the 70% restenosis threshold, and 79.7% at the 50% restenosis threshold. For PTA, the primary patency at 6 months was 61.1% at the 70% restenosis threshold and 45.6% at the 50% restenosis threshold. Both results were statistically significant (p < 0.05). CONCLUSION: Infrapopliteal stent application is an effective treatment modality for high-grade lesions in chronic critical limb ischemia. Compared with PTA, higher patency rates can be expected after 6 months.

Risk analysis and safety assessment in surgical robotics: a case study on a biopsy robot.

One of the most important issues in medical robotics is safety and integration into the clinical workflow. If a robot is not safe and its use is complicated by difficult handling and complex user interfaces physicians would not use a robotic system during clinical patient trials, whatever the other advantages are. However, there are only few publications on this topic, in particular on risk management in developing a robotic prototype (for clinical trials). In this paper risk management and the safety of using robot-assisted surgery equipment are discussed and demonstrated exemplarily in the process of developing a prototype biopsy robot.

[Percutaneous liver biopsy. Overview of different techniques]. / Perkutane Leberbiopsie. Ubersicht über verschiedene Verfahren.

To classify a liver tumor, image-guided percutaneous biopsy of a liver lesion is indicated. Using ultrasound (US) to guide a biopsy needle into a liver lesion has been proven useful and safe. If a lesion cannot be seen on US or the access to a lesion has been complicated by its position, CT-guided biopsy can be performed. If a lesion cannot be delineated on US or CT, MR-guided biopsy is recommended. Using hepatospecific contrast agents, the time span to delineate tumor tissue can be prolonged. To differentiate diffuse liver disease, transvenous biopsy under fluoroscopic control can be performed if a percutaneous biopsy is contraindicated. In recent years fine-needle aspiration biopsy has been increasingly replaced by coaxial 14-20 G core biopsy, which is a safe and efficient technique to classify liver lesions and has a low complication rate.

[MRT of the liver. Clinical significance of nonspecific and liver-specific MRT contrast agents]. / MRT der Leber. Klinische Bedeutung nichtspezifischer und leberspezifischer MRT-Kontrastmittel.

The liver is a common site for various benign and malignant focal lesions. The initial modality for assessing liver lesions is ultrasound or CT. MRI with its superior soft tissue contrast offers multiple advantages over other imaging modalities. Contrast agents have been developed that increase the detection rate and provide more specific information in comparison to unenhanced techniques. In the mean time three classes are available for MR imaging of the liver: extracellular gadolinium chelates, hepatobiliary and reticulo-endothelia, superparamagnetic agents. We describe in this review the most common focal lesions, their diagnostic possibilities, and the imaging protocols. Clinical use of these contrast agents facilitates detection and differential diagnosis of focal liver lesions that may help to avoid invasive procedures such as biopsy for lesion characterization.

[Three-dimensional digital rotation angiography for embolization therapy of uterine leiomyomas: first results]. / Dreidimensionale digitale Rotationsangiographie in der Embolisationstherapie von Uterusmyomen: Erste Erfahrungen.

PURPOSE: To evaluate three-dimensional rotational digital subtraction angiography (3D-RDSA) in the embolization of the uterine artery in the treatment of symptomatic uterine leiomyomas (fibroids). MATERIALS AND METHODS: Eight women with complex pelvic vessel anatomy caused by large fibroids were embolized using 3D-RDSA. The raw data were sent to an external workstation, and video files with a resolution of one image/3 degrees and a scan range of 180 degrees in a surface-shaded display mode were produced. The primary goal was to assess an image intensifier angulation for the optimal visualization of the origin of the uterine artery. In addition, the intervention parameters were compared with those of 48 patients with standard angiography. RESULTS: The analysis revealed no single angulation that can be recommended for standard angiography. No statistical differences were found between both groups concerning fluoroscopy time, dosage area product and amount of administered contrast medium (p > 0.05). CONCLUSION: It can be stated that 3D-RDSA is a feasible method that facilitates the catheterization of the uterine artery even in patients with complex pelvic vessel anatomy, with the potential to reduce the radiation exposure and the amount of administered contrast medium in future embolization therapy of symptomatic uterine fibroids.

Ultrasound-guided percutaneous ethanol ablation of parathyroid hyperplasia: preliminary experience in patients on chronic dialysis.

OBJECTIVE: We report on a 3-year experience using single-shot, ultrasonography-guided, percutaneous ethanol ablation (PEA) of hyperplastic parathyroid glands in chronic dialysis patients suffering from secondary or tertiary hyperparathyroidism. MATERIALS AND METHODS: Seventeen uraemic patients (mean age 52 +/- 14 years) with hypercalcaemia and elevated serum levels of parathyroid hormone were assessed for ethanol ablation. Ten patients did not fulfil the inclusion criteria and underwent surgical parathyroidectomy. Seven patients were treated using PEA. RESULTS: All patients treated with PEA tolerated the procedure well, and no major complications were observed. Three out of seven patients underwent further ethanol ablation due to recurrent symptomatic hyperparathyroidism. Following the procedures, serum values of total calcium and parathyroid hormone remained within target range with concomitant medical therapy in all patients. CONCLUSION: PEA performed as a single-shot therapy can be used as a minimally invasive and safe supplement to medical therapy in the treatment of secondary or tertiary hyperparathyroidism in selected patients. In case of recurrence, treatment can be repeated without any problems.

[Percutaneous radiofrequency ablation of liver cell carcinoma: a current overview]. / Perkutane Radiofrequenzablation von Leberzellkarzinomen: eine aktuelle Ubersicht.

In patients with hepatocellular carcinoma (HCC) surgical resection so far offers potential cure. Due to the frequent association with liver cirrhosis less then 30% of patients with HCC can be resected. In unresectable cases, radiofrequency ablation (RFA) offers an effective treatment alternative. Substantial improvements in the development of powerful generators (up to 250 W) combined with expandable, closed or open-perfused needle electrodes, provide coagulation necroses up to 5 cm in diameter. Most recently primary technical success rates of 85 to 100% were reported. Following RFA of HCC's (diameter up to 2,8 cm) 1-, 2-, 3 and 5-year survival was reported to be 97, 89, 71 and 48%. Low complication rates of 0-12% and a mortality of 0-1% indicate the minimal-invasive character of RFA. Basic principles, technique, indications, contraindications and limitations of percutaneous RFA will be discussed together with a presentation of own cases and a review of literature.

[Percutaneous radiologically-guided vertebroplasty in the treatment of osteoporotic and tumorous spinal body lesions]. / Perkutane, radiologisch gesteuerte Vertebroplastie zur Therapie osteoporotischer und tumoröser Wirbelkörperläsionen.

Vertebroplasty is a radiological intervention for the augmentation of bone lesions with bone cement. Main indications are the treatment of osteoporotic vertebral body fractures, however also the treatment of tumorous lesions becomes more and more established. The indication for vertebroplasty of tumorous lesions is therapy-refractory pain in symptomatic hemangiomas, metastases and myelomas. By minimal invasive therapy stabilization of vertebral bodies and pain reduction may be achieved.

MR imaging-guided focused ultrasound surgery of fibroadenomas in the breast: a feasibility study.

PURPOSE: To test the feasibility of noninvasive magnetic resonance (MR) imaging-guided focused ultrasound surgery (FUS) of benign fibroadenomas in the breast. MATERIALS AND METHODS: Eleven fibroadenomas in nine patients under local anesthesia were treated with MR imaging-guided FUS. Based on a T2-weighted definition of target volumes, sequential sonications were delivered to treat the entire target. Temperature-sensitive phase-difference-based MR imaging was performed during each sonication to monitor focus localization and tissue temperature changes. After the procedure, T2-weighted and contrast material-enhanced T1-weighted MR imaging were performed to evaluate immediate and long-term effects. RESULTS: Thermal imaging sequences were improved over the treatment period, with 82% (279 of 342) of the hot spots visible in the last seven treatments. The MR imager was used to measure temperature elevation (12.8 degrees -49.9 degrees C) from these treatments. Eight of the 11 lesions treated demonstrated complete or partial lack of contrast material uptake on posttherapy T1-weighted images. Three lesions showed no marked decrease of contrast material uptake. This lack of effective treatment was most likely due to a lower acoustic power and/or patient movement that caused misregistration. No adverse effects were detected, except for one case of transient edema in the pectoralis muscle 2 days after therapy. CONCLUSION: MR imaging-guided FUS can be performed to noninvasively coagulate benign breast fibroadenomas.

In-vitro assessment of a registration protocol for image guided implant dentistry.

In this study a computer aided navigation technique for accurate positioning of oral implants was assessed. An optical tracking system with specially designed tools for monitoring the position of surgical instruments relative to the patient was used to register 5 partially or completely edentulous jaw models. Besides the accuracy of the tracking system, the precision of localizing a specific position on 3-dimensional preoperative imagery is governed by the registration algorithm which conveys the coordinate system of the preoperative computed tomography (CT) scan to the actual patient position. Two different point-to-point registration algorithms were compared for their suitability for this application. The accuracy was determined separately for the localization error of the position measurement hardware (fiducial localization error-FLE) and the error as reported by the registration algorithm (fiducial registration error-FRE). The overall error of the navigation procedure was determined as the localization error of additional landmarks (steel spheres, 0.5 mm diameter) after registration (target registration error-TRE). Images of the jaw models were obtained using a high resolution CT scan (1.5 mm slice thickness, 1 mm table feed, incremental scanning, 120 kV, 150 mAs, 512 x 512 matrix, FOV 120 mm). The accuracy of the position measurement probes was 0.69 +/- 0.15 mm (FLE). Using 3 implanted fiducial markers, FRE was 0.71 +/- 0.12 mm on average and 1.00 +/- 0.13 mm maximum. TRE was found to be 1.23 +/- 0.28 mm average and 1.87 +/- 0.47 mm maximum. Increasing the number of fiducial markers to a total of 5 did not significantly improve precision. Furthermore it was found that a registration algorithm based on solving an eigenvalue problem is the superior approach for point-to-point matching in terms of mathematical stability. The experimental results indicate that positioning accuracy of oral implants may benefit from computer aided intraoperative navigation. The accuracy achieved compares well to the resolution of the CT scan used. Further development of point-to-point/point-to-surface registration methods and tracking hardware has the potential to improve the precision of the method even further. Our system has potential to reduce the intraoperative risk of causing damage to critical anatomic structures, to minimize the efforts in prosthetic modelling, and to simplify the task of transferring preoperative planning data precisely to the operating room in general.

[MRI-assisted brachytherapy of nonresectable liver metastases. Preliminary technical and clinical experiences]. / MR-gestützte Brachytherapie nichtresektabler Lebermetastasen. Vorläufige technische und klinische Erfahrungen.

PURPOSE: To evaluate the feasibility and efficacy of MR-guided interstitial brachytherapy of non-resectable liver metastasis. METHODS: Liver metastases (0.8-5.2 cm in diameter) were treated during a prospective phase I/II study using an open 0.2 Tesla MR system (Magnetom Open Viva, Siemens, Erlangen). MR-compatible brachytherapy applicators were placed percutaneously under MR-guidance in an open 0.2 Tesla MR system (Magnetom Open Viva, Siemens, Erlangen) using fast T1-weighted sequences. Pretreatment and follow-up studies were performed using a 1.5 Tesla MR system. RESULTS: Preliminary results of an unpublished prospective study are discussed exemplary on 2 selected patients. The median procedure time was 4.9 h. No major complications were observed and late effects were acceptable. In large symptomatic metastases only a temporary relief of pain was achieved. In smaller metastases (DM 3 cm) a tumor control was observed. CONCLUSION: MR-guided brachytherapy is feasible and has the potential to ablate liver metastases with diameter of less than 3 cm. Further developments are necessary.

Intraluminal 192Ir brachytherapy following transjugular intrahepatic portosystemic shunt revision: long-term results and radiotherapy parameters.

PURPOSE: The stenosis or occlusion of transjugular intrahepatic portosystemic shunt (TIPS) occurs in up to 75% of patients within 12 months after treatment. The aim of our investigation was to evaluate the feasibility, safety and efficacy of intraluminal high-dose rate brachytherapy (HDRBT) with Iridium-192 following TIPS revision to prevent restenosis due to pseudointimal hyperplasia. MATERIALS AND METHODS: Between September and November 1996, intraluminal BT was performed in five patients after TIPS revision. The indications for initial TIPS were a Budd-Chiari syndrome in two female patients and recurrent variceal bleeding by alcoholic liver cirrhosis in three male patients. TIPS was created with Wallstents (10 mm diameter in four patients) and Palmaz stent (10 mm diameter in one patient). The re-dilatation was done in all five patients 6 months after first stenting because of restenosis (>50% stent lumen reduction) or occlusion of the stent. A 5-French closed-tip, noncentered BT delivery catheter was used for subsequent radiotherapy. The whole length of the stent and performed dilatation (interventional length - IL) was taken as clinical target length (CTL). A 10-mm safety margin was added proximal and distal to the CTL due to uncertainties of BT source positioning, so forming the planning target length (PTL). To ensure that prescribed dose covers the whole PTL, the active source length (ASL) was 5 mm longer proximal and distal than PTL, so forming the reference isodose length (RIL). A dose of 12 Gy was prescribed in 3 mm distance from the source axis in the mid-plane of the applicator for three patients and in 5 mm distance for two patients. RESULTS: A normal patency (<50% lumen reduction) of the stent was achieved at 44 months follow-up (duplex sonography+portography) in all three patients with liver cirrhosis, whereas further revisions were necessary in two patients with Budd-Chiari syndrome (after 5.5 and 18 months). No acute, subacute or late brachytherapy (BT)-related side effects were seen until now. CONCLUSIONS: HDRBT following TIPS revision was safe and feasible in all patients. The exact impact of BT on the TIPS patency should be evaluated in larger clinical trials. Moderate dose escalation and use of today's commercially available centering radiation catheters seem to be necessary.

Interventional and intraoperative magnetic resonance imaging.

The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selection. Since 1994, more than 800 of these procedures, including various percutaneous procedures and open surgeries, have been successfully performed at Brigham and Women's Hospital (Boston, MA).

Report generation using digital speech recognition in radiology.

The aim of this study was to evaluate whether the use of a digital continuous speech recognition (CSR) in the field of radiology could lead to relevant time savings in generating a report. A CSR system (SP6000, Philips, Eindhoven, The Netherlands) for German was used to transform fluently spoken sentences into text. Two radiologists dictated a total of 450 reports on five radiological topics. Two typists edited those reports by means of conventional typing using a text editor (WinWord 6.0, Microsoft, Redmond, Wash.) installed on an IBM-compatible personal computer (PC). The same reports were generated using the CSR system and the performance of both systems was then evaluated by comparing the time needed to generate the reports and the error rates of both systems. In addition, the error rate of the CSR system and the time needed to create the reports was evaluated. The mean error rate for the CSR system was 5.5%, and the mean error rate for conventional typing was 0.4%. Reports edited with the CSR, on average, were generated 19% faster compared with the conventional text-editing method. However, the amount of error rates and time savings were different and depended on topics, speakers, and typists. Using CSR the maximum time saving achieved was 28% for the topic sonography. The CSR system was never slower, under any circumstances, than conventional typing on a PC. When compared with a conventional manual typing method, the CSR system proved to be useful in a clinical setting and saved time in generating radiological reports. The amount of time saved, however, greatly depended on the performance of the typist, the speaker, and on stored vocabulary provided by the CSR system.

Assessment of chronic constipation: colon transit time versus defecography.

OBJECTIVE: The aim of this study was to determine the value of radiological colon transit time (CTT) measurements in relation to defecography (DFG) in chronically constipated patients. MATERIALS AND METHODS: In 30 patients with chronic constipation, total and segmental CTT was determined using radiopaque markers. In all of these patients defecography (DFG) was obtained. The patients were divided into three groups: In group I, 11 patients were classified with idiopathic constipation based on low stool frequency, normal DFG, or absence of symptoms of abnormal defecation. In group II, ten patients with rectal intussusception were diagnosed by DFG. In group III, there were nine patients with rectal prolapse or spastic pelvic floor syndrome, based on results of DFG. RESULTS: Group I, idiopathic constipation (n = 11), showed increased total CTT (mean, 93 h) and segmental CTT (right colon, 33 h (36%), left colon, 31 h (33%), rectosigmoid, 29 h (31%)). In group II, intussusception (n = 10), patients had normal mean total CTT (54 h) and a relative decrease in rectosigmoid CTT (mean, 13 h (24%)). In group III (n =9), rectal prolapse (n = 5) or spastic pelvic floor syndrome (n = 4), patients showed elevated total (mean, 167 h) and rectosigmoidal CTT (mean, 95 h (57%)). Mean total CTT was significantly different between groups I and II and between groups II and III, and mean rectosigmoidal CTT was significantly different between all three groups (P < 0.05). CONCLUSION: The use of total and rectosigmoidal CTT helps to identify the underlying pathophysiology of chronic constipation. Furthermore CTT helps to identify patients, who may benefit from DFG.